CN111356419A

CN111356419A - Systems and methods for ankle replacement

Info

Publication number: CN111356419A
Application number: CN201880069415.0A
Authority: CN
Inventors: 查尔兹·萨尔茨曼; 阿尔伯特·H·伯斯汀; 乔纳森·T·德兰
Original assignee: Limacorporate SpA
Current assignee: Limacorporate SpA
Priority date: 2017-08-24
Filing date: 2018-08-24
Publication date: 2020-06-30
Anticipated expiration: 2038-08-24
Also published as: EP3672535A1; AU2018322380A1; CN111356419B; WO2019040865A9; JP2020531166A; WO2019040865A1; KR20200045527A; AU2018322380B2; BR112020003815A2

Abstract

An ankle replacement system (100) may have a talar prosthesis (102) and a tibial prosthesis (104) each having an articular surface (110,120) and a bone engaging surface (112, 122). Each bone engaging surface may have an anterior-posterior curvature and a medial-lateral curvature with a convex shape. A drill (610,800,830,860) having a rotatable cutting element (720,820,850,880) may be used to form a prepared surface on the talus or tibia to accommodate a corresponding prosthesis. The cutting guide may be used to guide the movement of the reamer. The cutting guide may include a base and an arm movably coupled to the base. One of the base and the arm may have a guide surface and the other may have a follower that slides along the guide surface to limit movement of the reamer such that the preparation surface has at least a concave curve and a convex curve.

Description

Systems and methods for ankle replacement

Technical Field

The present disclosure relates to surgical systems and methods. More particularly, the present disclosure relates to implants for ankle replacement surgery and related methods.

Background

Joint replacement (Joint arthroplasty) procedures are surgical procedures in which one or more articular surfaces of a Joint are replaced with a prosthetic articular surface. Such processes are becoming more and more common. Ankle replacement (Ankle arthroplasty) may be required, particularly due to trauma or degeneration of the natural articular surfaces of the tibia and talus.

For a successful ankle replacement it is important that the postoperative motion characteristics of the ankle joint mimic the motion characteristics of the natural ankle joint as closely as possible. Furthermore, it is desirable to keep the ankle implant in place during subsequent functions of the joint. Further, it is desirable that the ankle replacement procedure be performed quickly and smoothly with little margin for error. Many existing ankle replacement implants and methods are biomechanically inaccurate, time consuming to implant, or fail to form adequate attachment to the underlying bone.

Disclosure of Invention

In response to the present state of the art, various systems and methods of the present disclosure have been developed, particularly in response to problems and needs in the art that have not yet been fully solved by existing systems and methods for ankle joint replacement. The systems and methods of the present disclosure may provide ankle implants and instruments, including but not limited to talar and tibial prostheses and instruments, that provide enhanced biomechanics, superior bone fixation, and/or streamlined implantation.

According to some embodiments, the ankle replacement system may be designed to replace the natural talar articular surface on the talus and the natural tibial articular surface on the tibia. The ankle replacement system may have a talar prosthesis and a tibial prosthesis, each having an articular surface and a bone engaging surface. At least one of the bone engaging surfaces may have a first anterior-posterior curvature and a medial-lateral curvature having a convex shape.

The first anterior-posterior curvature may extend in an anterior-posterior direction along substantially an entire length of the bone engaging surface. The bone engaging surface may also have a keel (keel) projecting from the first anterior-posterior curvature and extending in an anterior-posterior direction. The keel may have a base portion fixed to or integrally formed with the selected remainder portion, and a penetrating portion extending from the base portion to penetrate a talar prepared surface (talar prepared surface) or a tibial prepared surface (tibial prepared surface). The penetration portion may have a substantially semicircular periphery.

The talar articular surface may have two convex talar curvatures extending in medial-lateral directions (medial-lateral directions) and a concave talar curvature extending in medial-lateral directions (sagittal curvatures) between the two convex talar curvatures. The tibial articular surface may have two concave tibial curvatures extending in the medial-lateral direction and a convex tibial curvature extending in the medial-lateral direction between the two concave tibial curvatures. The talar articular surface and the tibial articular surface may be further shaped such that the tibial articular prosthesis is centered on the talar articular prosthesis with two concave tibial curvatures substantially flush with two convex talar curvatures.

The bone engaging surface having a first anterior-posterior curvature may be a talar engaging surface, and the first anterior-posterior curvature may be a concave curvature. The talar engaging surface may further have: a second inside-outside bend having a convex shape and extending in the inside-outside direction; and a central expansion portion extending in a substantially straight line in the medial-lateral direction between the first medial-lateral bend and the second medial-lateral bend. The talar engaging surface may also have a keel projecting from the first anterior-posterior curvature and extending in an anterior-posterior direction.

The bone-engaging surface having a first anterior-posterior curvature may be a tibial-engaging surface, and the first anterior-posterior curvature may be a convex curvature. The tibial engaging surface may also have: a second inward-outward bend portion having a convex shape and extending in an inward-outward direction; and a central expansion portion extending in a substantially straight line in the medial-lateral direction between the first medial-lateral bend and the second medial-lateral bend. The tibial engaging surface may also have a keel projecting from the first anterior-posterior curvature and extending in an anterior-posterior direction.

According to some embodiments, a talar joint prosthesis may have a talar articular surface shaped to replace a natural talar articular surface, and a talar engagement surface shaped to engage a talar preparation surface of a talus. The talar engaging surface may have a first anterior-posterior curvature having a concave shape and extending in an anterior-posterior direction; and a first inward-outward bend having a convex shape and extending in an inward-outward direction.

The talar engaging surface may further have a second medial-lateral curvature having a convex shape and extending in a medial-lateral direction; and a central expansion portion extending in a substantially straight line in the medial-lateral direction between the first medial-lateral bend and the second medial-lateral bend. The talar engaging surface may also have a keel projecting from the first anterior-posterior curvature and extending in an anterior-posterior direction. The keel may have a base fixed to or integrally formed with the remainder of the talar engaging surface and a penetrating portion extending from the base to penetrate the talar preparation surface. The penetration portion may have a substantially semicircular periphery.

According to some embodiments, a tibial articular prosthesis may have a tibial articular surface shaped to replace a natural tibial articular surface, and a tibial engaging surface shaped to engage a tibial preparation surface of a tibia. The tibial engaging surface may have a first anterior-posterior curvature having a convex shape and extending in an anterior-posterior direction; and a first inward-outward bend having a convex shape and extending in an inward-outward direction.

The first anterior-posterior curvature may extend in an anterior-posterior direction along substantially an entire length of the tibial engaging surface. The tibial engaging surface may also have: a second inward-outward bend having a convex shape and extending in an inward-outward direction; and a central expansion portion between the first inner and outer portions and the second inner and outer portions extending in a substantially straight line along the inner and outer portions. The tibial engaging surface may also have a keel projecting from the first anterior-posterior curvature and extending in an anterior-posterior direction. The keel may have a base portion fixed to or integrally formed with the remainder of the tibial engaging surface and a penetrating portion extending from the base portion to penetrate the tibial preparation surface. The penetration portion may have a substantially semicircular periphery.

According to some embodiments, a system for preparing a bone for joint replacement may have a reamer with a rotatable cutting element having a shape extending along a length of the rotatable cutting element, the shape selected from a concave shape and a convex shape. The system may further have: a cutting guide having a bone attachment interface securable to bone, a broach attachment interface securable to a broach; and a guide mechanism configured to limit relative movement between the reamer attachment interface and the bone attachment interface to facilitate forming a preparation surface on the bone using the reamer. The preparation surface may have at least one concave curvature or one convex curvature.

The cutting guide may further have a base and a bore holder. The base may have a bone attachment interface and a bore retainer interface. The bore holder may have a reamer attachment interface and a base interface that may be coupled to the bore holder interface.

The guide mechanism may allow movement of the reamer attachment interface in a first direction perpendicular to the length of the rotatable cutting element. The guide mechanism may guide movement of the reamer attachment interface along a line perpendicular to a length of the rotatable cutting element. The shape of the rotatable cutting element may be a convex shape having a maximum radius perpendicular to the length such that the preparation surface has a cross-sectional shape of a first convex curve having a first radius of curvature substantially equal to the maximum radius. The second convex curve has: a second radius of curvature substantially equal to the maximum radius; and a central expansion portion extending in a substantially straight line between the first and second convex curves.

The guide mechanism may further allow movement of the reamer attachment interface along a second direction parallel to the length of the rotatable cutting element. The guide mechanism may allow movement of the reamer attachment interface in the second direction by allowing the reamer attachment interface to rotate about an axis perpendicular to the rotatable cutting element. The shape of the rotatable cutting element may be a concave shape having a maximum radius perpendicular to the length such that the prepared surface has a cross-sectional shape as follows: a first convex curve, wherein a first radius of curvature of the first convex curve is substantially equal to the maximum radius; a second convex curve, wherein the second convex curve has a second radius of curvature that is substantially equal to the maximum radius; and a central enlarged portion extending in a substantially straight line between the first convex curve and the second convex curve. The cross-sectional shape may be swept along a convex curve.

According to some embodiments, a method of preparing a bone for joint replacement may include positioning a cutting guide adjacent the bone. The cutting guide may include a bone attachment interface, a reamer attachment interface, and a guide mechanism. The method may further include securing the bone attachment interface to bone and securing a reamer to the reamer attachment interface. The reamer may have a rotatable cutting element having a shape extending along a length of the rotatable cutting element, the shape selected from a concave shape and a convex shape. The method may further include guiding movement of the reamer relative to the bone with the guide mechanism to facilitate forming a prepared surface on the bone with the reamer. The preparation surface may have at least one concave curvature or one convex curvature.

The cutting guide may also have a base with a bone attachment interface and a bore holder interface. Further, the cutting guide may have a bore holder having a reamer attachment interface and a base interface. The method may further include connecting a base interface of the borehole holder to a borehole holder interface of the base.

The guided movement of the reamer relative to the bone may include allowing movement of the reamer along a first direction perpendicular to the length of the rotatable cutting element by way of a guide mechanism. The guided movement of the broach relative to the bone may further include guiding movement of the broach attachment interface along a line perpendicular to the length of the rotatable cutting element with a guide mechanism. The shape may be a convex shape having a maximum radius perpendicular to the length such that the preparation surface has the following cross-sectional shape: a first convex curve, wherein a first radius of curvature of the first convex curve is substantially equal to the maximum radius; a second convex curve, wherein the second convex curve has a second radius of curvature that is substantially equal to the maximum radius; and a central enlarged portion extending in a substantially straight line between the first convex curve and the second convex curve.

The guided movement of the broach relative to the bone may further include allowing the broach attachment interface to move in a second direction parallel to the length of the rotatable cutting element. The guided movement of the reamer relative to the bone may further comprise allowing the reamer attachment interface to rotate about an axis perpendicular to the rotatable cutting element. The shape may be a concave shape having a maximum radius perpendicular to the length such that the prepared surface has a cross-sectional shape as follows: a first convex curve, wherein a first radius of curvature of the first convex curve is substantially equal to the maximum radius; a second convex curve, wherein the second convex curve has a second radius of curvature that is substantially equal to the maximum radius; and a central enlarged portion extending in a substantially straight line between the first convex curve and the second convex curve. The cross-sectional shape may be swept along a convex curve.

According to some embodiments, a system for preparing an ankle replacement talus or tibia may include a first broach and a first cutting guide. A first reamer may have a first rotatable cutting element having a first shape extending along a length of the first rotatable cutting element. The first shape may be selected from a concave shape and a convex shape. The first cutting guide may include: a first bone attachment interface securable to a talus or a tibia; a first reamer attachment interface securable to a first reamer; and a first guide mechanism limiting relative movement between the first reamer attachment interface and the first bone attachment interface by allowing movement of the first reamer attachment interface in a first direction perpendicular to the first length of the first rotatable cutting element to facilitate formation of a first prepared surface on the tibia or talus with the first reamer. The first preparation surface may have at least one concave curvature or one convex curvature.

The first bone attachment interface may be secured to the talus bone such that the first prepared surface is located on the talus bone. The first guide mechanism may also allow the first reamer attachment interface to move in a second direction along a second direction parallel to the first length of the first rotatable cutting element by allowing the first reamer attachment interface to rotate about an axis perpendicular to the first rotatable cutting element. The first shape may be a concave shape such that the first preparation surface has a cross-sectional shape that sweeps along a convex curve.

The system may further include a second reamer having a convexly shaped second rotatable cutting element and a second cutting guide. The second cutting guide may have: a second bone attachment interface securable to a tibia; a second reamer attachment interface securable to a second reamer; and a second guide mechanism configured to limit relative movement between the second reamer attachment interface and the second bone attachment interface by allowing movement of the second reamer attachment interface in a third direction perpendicular to the second length of the second rotatable cutting element to facilitate the second reamer forming a second prepared surface on the tibia. The second preparation surface may have at least one concave curvature.

The first cutting guide may further have a first base having a first bone attachment interface and a first bore retainer. The first base may further have a first bore retainer interface. The first borehole holder can have a first reamer attachment interface, and a first base interface that can be coupled with the first borehole holder interface. The second cutting guide may further have a second base and a second bore holder. The second base may have a second bone attachment interface and a second bore retainer interface. The second borehole holder can have a second reamer attachment interface and a second base interface coupleable to the second borehole holder interface. The system may further include an alignment block having a third base interface attachable to the first base and a fourth base interface attachable to the second base to facilitate positioning of the second base relative to the first base.

According to some embodiments, a method for performing an ankle replacement may comprise: exposing an anterior side of the ankle joint; securing a first cutting guide to a first bone that is a talus or a tibia; the method includes inserting a first cutting tool into the ankle joint along an anterior path, and guiding movement of the first cutting tool relative to the first bone using a first cutting guide such that the first cutting tool forms a first prepared surface on the first bone. The first preparation surface may have a first front-to-back curve extending front-to-back. The method may further include placing a first prosthesis on the first preparation surface. The first prosthesis may have a first articular surface shaped to replace a first natural articular surface of the first bone.

The first prosthesis may have a keel. The method may further comprise: the second cutting tool is inserted into the ankle joint along an anterior path and movement of the second cutting tool relative to the first bone is guided with the first cutting guide such that a slot is formed in the first bone with the second cutting tool such that the slot is oriented anteroposteriorly. Placing the first prosthesis on the first preparation surface may include inserting a keel into the slot.

The first bone may be a tibia. The first fore-aft bend may be a concave bend extending fore-aft. The first prosthesis may have a convex bone engaging surface. Placing the first prosthesis on the first preparation surface may include inserting the convex bone engaging surface into the concave curvature.

The first bone may be a talus bone. The first fore-aft bend may be a convex bend extending fore-aft. The first prosthesis may have a concave bone engaging surface. Placing the first prosthesis on the first preparation surface may include positioning the convex curve in the concave bone engaging surface.

The method may further comprise: exposing an anterior side of the ankle joint; securing a second cutting guide to the tibia; and inserting the first cutting tool or the second cutting tool into the ankle joint along an anterior path. Further, the method may include guiding movement of the first cutting tool or the second cutting tool relative to the tibia with a second cutting guide such that a second prepared surface is formed on the tibia with the first cutting tool or the second cutting tool such that the second prepared surface has a second anterior-posterior curvature with a concave curvature extending anteroposteriorly. The method may further include placing a second prosthesis on the second preparation surface. The second prosthesis may have: a convexly shaped bone engaging surface; and a second articular surface shaped to replace a second natural articular surface of the tibia. Placing the second prosthesis on the second preparation surface may comprise: the convex bone engaging surface is inserted into the concave curvature.

The first cutting guide may have: a talar base having a talar bone attachment interface and a talar tool holder interface, and a talar tool holder having a talar tool attachment interface and a base interface. Securing the first cutting guide to the first bone may include: the talar attachment interface is secured to the talus. The method may further comprise: the method further includes coupling the talar base to the talar tool holder by coupling the talar tool holder interface to the talar base interface, and attaching the first cutting tool to the talar tool attachment interface prior to guiding movement of the first cutting tool with the first cutting guide.

The method may further comprise placing the trial on the talus bone prior to securing the talus base to the talus bone. The test substance may be attached to the distal end of the column. The method may further comprise: using the post to align the trial with the talus bone prior to securing the talus base to the talus bone by aligning a proximal end of the post with a landmark on a portion of the patient's leg proximal to the talus bone; and aligning the talar base with the trial.

The method may further comprise: the alignment block includes a talar base interface attached to the talar base and a tibial base interface attached to the tibial base. The tibial base may have a tibial attachment interface and a tibial tool holder interface. The method may further comprise: the method includes securing a tibial attachment interface to the tibia, and coupling a tibial tool holder to the tibial base by coupling the tibial tool holder interface to a tibial base interface of the tibial tool holder. The tibial base and tibial tool holder may constitute a second cutting guide.

The method may further comprise: the method includes attaching a first cutting tool or a second cutting tool to a tibial tool attachment interface of a tibial tool holder, inserting the first cutting tool or the second cutting tool into the ankle joint from along an anterior path, and guiding the first cutting tool or the second cutting tool with a second cutting guide in a medial-lateral direction relative to the tibia such that the first cutting tool or the second cutting tool forms a second prepared surface on the tibia. The second preparation surface may have a second front-to-back curve, wherein the second front-to-back curve has a concave curve extending front-to-back.

The guided movement of the first cutting tool relative to the first bone to form the first preparation surface may comprise: moving the first cutting tool in a medial-lateral direction. The guided movement of the first cutting tool relative to the first bone to form the first preparation surface may further comprise: rotating the first cutting tool relative to the first bone about an inwardly and outwardly extending axis to move the first cutting tool back and forth.

According to some embodiments, a method for ankle replacement on an ankle joint having a talus and a tibia may comprise: exposing an anterior side of the ankle joint; securing a talar cutting guide to a talus; and inserting a first cutting tool into the ankle joint along an anterior path. The method may further comprise: the method includes guiding movement of a first cutting tool relative to the talus bone with a talar cutting guide to rotate the first cutting tool relative to the talus bone about a medial-lateral extending axis to move the first cutting tool forward to form a first prepared surface on the talus bone. The first preparation surface may have a first front-to-back curve extending front-to-back. The method may further include placing a talar prosthesis on the first prepared surface. The talar prosthesis may have a talar articular surface shaped to replace a natural talar articular surface of the talus.

The talar prosthesis may have a keel. The method may further comprise: the first or second cutting tool is inserted into the ankle joint along an anterior path and movement of the first or second cutting tool relative to the talus is guided to the ankle joint with the talar cutting guide. Forming a slot on the talus bone with the first cutting tool or the second cutting tool such that the slot is oriented anteroposteriorly. Placing the talar prosthesis on the first preparation surface may comprise: the keel is inserted into the slot.

The guided movement of the first cutting tool relative to the talus to form the first preparation surface may further comprise: moving the first cutting tool in a medial-lateral direction. The method may further comprise: the tibial cutting guide is secured to the tibia and either the first cutting tool or the second cutting tool is inserted into the ankle joint from along an anterior path. The method may further comprise: the method further includes guiding movement of the first cutting tool relative to the tibia with the tibial cutting guide to cause the first cutting tool or the second cutting tool to move in and out to form a second prepared surface on the tibia. The second preparation surface may have a second front-to-back curve extending front-to-back. The method may further comprise: the tibial prosthesis is placed on the second prepared surface. The tibial prosthesis may have a tibial articular surface shaped to replace the natural tibial articular surface of the tibia.

The talar cutting guide may have a talar base and a talar tool holder. The talar base may have a talar attachment interface and a talar toolhead interface. The talar tool holder may have a talar tool attachment interface and a talar base interface. Securing the talar cutting guide to the talus bone may include securing a talar attachment interface to the talus bone. The method may further include coupling the talar base to the talar tool holder by coupling the talar tool holder interface to the talar base interface and attaching the first cutting tool to the talar tool attachment interface prior to guiding movement of the first cutting tool with the talar cutting guide.

The method may further include attaching the talar base interface of the alignment block to the talar base and attaching the tibial base interface of the alignment block to the tibial base. The tibial base may have a tibial attachment interface and a tibial tool holder interface. The method may further include securing the tibial attachment interface to the tibia, and coupling the tibial tool holder to the tibial base by coupling the tibial tool holder interface to a tibial base interface of the tibial tool holder. The tibial base and tibial tool holder may constitute a second cutting guide.

According to some embodiments, a method for ankle replacement on an ankle joint having a talus and a tibia may comprise: exposing an anterior side of the ankle joint; securing a talar cutting guide to a talus; a first cutting tool is inserted into the ankle joint. The method includes guiding movement of a first cutting tool relative to the talus bone along an anterior path using a talar cutting guide such that the first cutting tool forms a first prepared surface on the talus bone. The first preparation surface may have a first front-to-back curve extending front-to-back. The method may further comprise: the method includes securing a tibial cutting guide to the tibia, inserting a first cutting tool or a second cutting tool along an anterior path into the ankle joint, and guiding movement of the first cutting tool or the second cutting tool relative to the tibia through the tibial cutting guide to cause the first cutting tool or the second cutting tool to form a second prepared surface on the tibia. The second preparation surface may have a second front-to-back curve extending front-to-back. The method may further comprise: a talar prosthesis is placed on the first prepared surface, and a tibial prosthesis is placed on the second prepared surface. The talar prosthesis may have a talar articular surface shaped to replace a first natural articular surface of the talus, and the tibial prosthesis may have a tibial articular surface shaped to replace a second natural articular surface of the tibia.

The talar prosthesis may have a talar keel and the tibial prosthesis may have a tibial keel. The method may further comprise: the method further includes guiding movement of the first cutting tool, the second cutting tool, or the third cutting tool relative to the talus bone with a talar cutting guide to form a first slot in the talus bone such that the first slot is anteroposteriorly oriented. The method may further comprise: the method further includes guiding movement of the first cutting tool, the second cutting tool, the third cutting tool, or the fourth cutting tool relative to the tibia with a tibial cutting guide to form a second slot in the tibia such that the second slot is oriented anteroposteriorly. Placing the talar prosthesis on the first preparation surface may comprise: the talar keel is inserted into the first slot. Placing the tibial prosthesis on the second preparation surface may include: the tibial keel is inserted into the second slot.

The talar cutting guide may include a talar base and a talar tool holder. The tibial cutting guide may have a tibial base and a tibial tool holder. Securing the talar cutting guide to the talus may include: the talar base is secured to the talus. The method may further include attaching the talar base interface of the alignment block to the talar base and attaching the tibial base interface of the alignment block to the tibial base prior to guiding movement of the first cutting tool or the second cutting tool with the tibial cutting guide. Securing the tibial cutting guide to the tibia may comprise: the tibial base is secured to the tibia with a talar base interface attached to the talar base and a tibial base interface attached to the tibial base.

According to some embodiments, a system for preparing a bone for joint replacement may have: a cutting tool and guide assembly securable to bone. The introducer assembly may have a base and an arm. The base may have a first coupling feature and a first guide feature. The arm may have a second coupling feature movably coupled to the first coupling feature; a tool attachment interface attachable to a cutting tool; and a second guide feature. One of the first and second guide features may have a guide surface having a predetermined shape. The other of the first and second guide features may include a follower configured to slide along the guide surface to limit movement of the tool attachment interface relative to the base.

The first coupling feature and the second coupling feature may be coupled together to allow the arm to rotate relative to the base about an arm rotation axis. The guide surface may face towards the arm rotation axis or away from the arm rotation axis. The guide surface may have a planar shape configured to prevent movement of a cutting tool shaft of the cutting tool beyond a planar boundary to prevent over-penetration of the cutting tool into the bone. The cutting tool may include a reamer having a cutting element that rotates about an axis of the cutting tool.

The guide surface may be on the base and the follower may be on the arm. The follower may comprise a cylindrical post projecting from the remainder of the arm.

The arm may include: a first arm member having at least a portion of a second coupling feature; and a second arm member slidably coupled to the first arm member, the second arm member having a tool attachment interface and a second guide feature. The system may further include a resilient member that urges the follower toward the guide surface and urges the cutting tool toward the bone.

The guide assembly may further have a base having: a bone attachment interface attachable to a bone, and a base attachment interface (base attachment interface) attachable to a base. The base may further have: a fixation member having a bone attachment interface; and a moving member coupled with the fixed member such that the moving member is rotatable relative to the fixed member about a base axis perpendicular to the arm rotation axis. The mover may have a base attachment interface.

The bone may be a talus or a tibia. The bone attachment interface may be configured to attach the base to the talus or tibia proximate an ankle joint defined by the talus and tibia.

According to some embodiments, a method for preparing a bone for joint replacement may include securing a guide assembly to the bone. The introducer assembly may include a base and an arm. The base may include a first coupling feature and a first guide feature. The arm may include: a second coupling feature movably coupled to the first coupling feature, the tool attachment interface, and the second guide feature. The method may further comprise: the cutting tool is attached to the tool attachment interface and the arm is moved relative to the base to guide movement of the cutting tool relative to the bone such that a prepared surface is formed on the bone with the cutting tool. One of the first and second guide features may include a guide surface having a predetermined shape. The other of the first and second guide features may comprise a follower. Moving the arm relative to the base may include: the follower is slid along the guide surface to limit movement of the tool attachment interface relative to the base.

Moving the arm relative to the base may further comprise: the arm is rotated relative to the base about an arm rotation axis. The guide surface may face towards the arm rotation axis or away from the arm rotation axis.

The guide surface may have a planar shape. The cutting tool may include a reamer having a cutting element that rotates about an axis of the cutting tool. Sliding the follower along the guide surface to limit movement of the tool attachment interface relative to the base may include: the cutting tool shaft is prevented from moving beyond the planar boundary to prevent the drill from over-penetrating the bone.

The arm may include a first arm member having at least a portion of the second coupling feature, and a second arm member slidably coupled to the first arm member, the second arm member having a tool attachment interface and a second guide feature. Sliding the follower along the guide surface to limit movement of the finger tool attachment interface relative to the base may include: relative sliding movement is performed with respect to the first arm member with respect to the second arm member. The introducer assembly may further include a resilient member. Sliding the follower along the guide surface to limit movement of the tool attachment interface relative to the base may further comprise: with the resilient member, the follower is urged towards the guide surface and the cutting tool is urged towards the bone.

The guide assembly may further include a base having a fixation member with a bone attachment interface, and a moving member rotatably coupled to the fixation member. The moving member may have a base attachment interface. Securing the guide assembly to the bone may include: the bone attachment interface is attached to the talus. The method may further comprise: the base attachment interface of the base is attached to the base attachment interface prior to moving the arm relative to the base to guide movement of the cutting tool relative to the bone. Moving the arm relative to the base to guide movement of the cutting tool relative to the bone may further comprise: the moving member is rotated about the base axis relative to the fixed member.

The guide assembly may further have a base having a bone attachment interface and a base attachment interface. Securing the guide assembly to the bone may include: attaching a bone attachment interface to the tibia. The method may further include attaching the base attachment interface of the base to the base attachment interface prior to moving the arm relative to the base to guide movement of the cutting tool relative to the bone.

According to some embodiments, a system for preparing an ankle replacement talus or tibia may comprise: a reamer having a cutting element that rotates about a reamer axis; and a guide assembly securable to the talus or tibia. The guide assembly may have a base having a first coupling feature, a first guide feature, and an arm. The arm may have a first arm member having at least a portion of a second coupling member coupled to the first coupling member to allow the arm to rotate relative to the base about an arm rotation axis. The arm may also have a second arm member slidably coupled to the first arm member. The second arm member may have a tool attachment interface that is attachable to the reamer, the second guide feature, and the resilient member. One of the first and second guide features may include a guide surface having a planar shape configured to prevent movement of the drill shaft beyond a planar boundary to prevent the drill from over penetrating the talus or tibia. The other of the first and second guide features may include a follower configured to slide along the guide surface to limit movement of the tool attachment interface relative to the base. The resilient member may urge the follower toward the guide surface and may urge the reamer toward the talus or tibia.

These and other features and advantages of the present disclosure will become more fully apparent from the following description and appended claims, or may be learned by the practice of the systems and methods as set forth hereinafter.

Drawings

Exemplary embodiments of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only exemplary embodiments and are not therefore to be considered to be limiting of the scope of the appended claims, the exemplary embodiments of the disclosure will be described with additional specificity and detail through use of the accompanying drawings, in which:

FIG. 1 is a perspective view of an ankle replacement system according to one embodiment.

Fig. 2A to 2E are a perspective cephalad view, a perspective caudal view, a side elevational view, a side cross-sectional view, and an anterior cross-sectional view, respectively, of a talar prosthesis.

Fig. 3A to 3E are a cephalad perspective view, a caudal perspective view, a side elevational view, a side sectional view, and an anterior sectional view, respectively, of a tibial prosthesis.

Fig. 4A-4C are perspective cephalad, caudal, and cephalad views, respectively, of a trial that may be assembled with the talus and trial of fig. 4C by positioning the talus base relative to the talus using posts, wherein the talus base and posts are assembled together.

Fig. 5A, 5B and 5C are a posterior, anterior and anterior perspective view, respectively, of the talar base of fig. 4C, with the talar base secured to the talus of fig. 5C.

Fig. 6A and 6B are front and rear perspective views, respectively, of a talar drill holder secured to a talar base to hold a drill relative to the talar.

Fig. 7A to 7C are perspective, side and plan sectional views, respectively, of the reamer of fig. 6A and 6B.

Fig. 8A-8C are side views of a reamer according to various embodiments.

Fig. 9A-9C are perspective cranial and caudal perspective and front sectional views, respectively, of the talar drill holder of fig. 6A and 6B.

Fig. 10A and 10B are front and rear perspective views, respectively, of a talus with a talus base affixed thereto, a talus drill holder affixed thereto, and a drill positioned to cut anterior portions of a natural articular surface of the talus.

Fig. 11A and 11B are a side elevational view, a cross-sectional view, and an enlarged head side elevational view, respectively, of a talus having a talar base, a talar drill holder, and a drill, as in fig. 10A and 10B.

Fig. 12 is a perspective view illustrating the use of a drill to form a slot in a talus preparation surface.

Fig. 13A-13C are posterior-caudal, anterior-elevational, and anterior-cranial perspective views, respectively, of a tibial base, and in fig. 13C are also shown an alignment block and a talar base for securing the tibial base to the tibia.

Fig. 14A, 14B and 14C are, respectively, an anterior perspective view, a side elevation view and an anterior perspective view of a tibial drill holder, in fig. 14C the tibial drill holder is secured to a tibial base and a tibia.

Fig. 15 is a side cross-sectional view of the tibial drill holder and tibial base secured to the tibia.

Fig. 16 is a side cross-sectional view depicting a talus and tibia bone with a talus prosthesis secured to a prepared surface of the talus bone and a tibial prosthesis secured to a prepared surface of the tibia bone.

Figure 17A is a perspective view of a talus having a talar base with a portion of the trial of figures 4A-4C positioned on a concave curve of the talus according to an alternative embodiment.

Fig. 17B is a perspective view of the talar base of fig. 17A with talar base 1710 secured to talus 420.

Fig. 18A and 18B are perspective views of the talar base of fig. 17A and 17B with a talar drill holder secured to a mobile member of the talar base.

Fig. 19 is a side cross-sectional view of the talar base of fig. 17A and 17B with a talar drill holder secured to a mobile member of the talar base.

20A, 20B, 20C, 20D, and 20E are exploded perspective, rear, front, side, and side exploded views, respectively, of an alignment block according to an alternative embodiment.

21A, 21B, 22A, 22B, and 22C are perspective, side, front, perspective, and side cross-sectional views of the talar base of FIGS. 17A and 17B attached to a talus, with the tibial base positioned relative to the tibia using an alignment block and a tibial trial.

Fig. 23 is a perspective view of a tibial drill holder secured to the tibial base of fig. 17A and 17B to hold a drill relative to the tibia.

Fig. 24A, 24B, and 24C are top, bottom, and side views, respectively, of a patient-specific mounting plate that may be used as part of a patient-specific guide mechanism for the talus, according to one embodiment.

Fig. 25A is a perspective view of the patient-specific mounting plate of fig. 24A-24C on the talus.

Fig. 25B is a perspective view of the patient-specific mounting plate and talus of fig. 24A with fixation components secured to the patient-specific mounting plate to define fixation members that function similarly to the fixation members of fig. 5A and 5B and the fixation members of fig. 17A and 17B.

Fig. 26A and 26B are top and side views, respectively, of the talar base of fig. 25A and 25B with the talar drill holder secured to the mobile member defined by the patient-specific mounting plate and the fixed components of fig. 24A-25B.

Detailed Description

Exemplary embodiments of the present disclosure will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. It will be readily understood that the components of the present disclosure, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the apparatus, system, and method, as represented in fig. 1 through 16, is not intended to limit the scope of the claims, as claimed, but is merely a representative example of exemplary embodiments.

The phrases "connected to", "coupled to", and "communicating with … …" refer to any form of interaction between two or more entities, including mechanical, electrical, magnetic, electromagnetic, fluid, and thermal interactions. Two components may be functionally coupled to each other even though they are not in direct contact with each other. The term "abutting" refers to items that are in direct physical contact with each other, although the items need not necessarily be connected together.

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

Figures 1A, 1B, and 1C are perspective, side, and front cross-sectional views, respectively, of an ankle replacement system or system 100 according to one embodiment. The system 100 may be designed to replace the natural articular surface of the ankle joint and, thus, may have a talar prosthesis 102 and a tibial prosthesis 104. In some embodiments, the system 100 may be designed to replace only the talar or tibial articular surface, and thus may include only the talar prosthesis 102 or the tibial prosthesis 104.

The talar prosthesis 102 and the tibial prosthesis 104 may each have an articular surface and a bone-engaging surface. Specifically, talar prosthesis 102 may have: a talar articular surface 110 shaped to replace a natural articular surface of the talus; and a talar engaging surface 112 shaped to engage a talar bone preparation surface of the talus bone, either by direct contact (if talar engaging surface 112 is a porous ingrowth material) or by a layer of adhesive such as polymethacrylate (PMMA or "bone cement"). Similarly, the tibial prosthesis 104 may have: a tibial articular surface 120 shaped to replace the natural articular surface of the tibia; and a tibial engagement surface 122 shaped to engage a tibial preparation surface of the tibia either by direct contact (if talus engagement surface 112 is a porous in-growth material) or by a layer of adhesive such as PMMA.

The system 100 is shown relative to an orientation that would be appropriate when the system 100 is implanted in an ankle joint. These directions may include an anterior-posterior direction (anti-dominant direction)130, a medial-lateral direction (medial-lateral direction)132, and a cephalad-caudal direction (cephalad-caudal direction) 134. In this application, these directions may be referred to as, for example, "in the fore-aft direction 130" or "fore-aft". Direction may refer to movement of an object. For example, an object moving in the fore-aft direction 130 moves in a forward direction and/or a rearward direction. In the alternative, the direction may refer to the direction of an object or feature. For example, an anteroposteriorly extending object or feature is oriented such that its maximum length is substantially parallel to the anteroposterior direction 130.

Talar prosthesis 102 will be shown and described in greater detail in connection with fig. 2A-2E. The tibial prosthesis 104 will be shown and described in greater detail in connection with fig. 3A through 3E.

Fig. 2A-2E are perspective cephalad, perspective caudal, side elevation, and cross-sectional anterior views, respectively, of talar prosthesis 102. The talar articular surface 110 may be shaped to mimic the shape of a natural talar articular surface. In some embodiments, the talar articular surface 110 may have two convex talar curves 200 extending medially and laterally. The convex talar curves 200 may be separated from each other by inwardly and outwardly extending convex talar curves 202. The convex talar curve 200 and the convex talar curve 202 are most easily seen in fig. 2E, where the cross-sectional plane runs medially, laterally, and cranially parallel to the convex talar curve 200 and the convex talar curve 202.

The talar engaging surface 112 may be shaped to provide a secure engagement with a prepared surface of the talar bone using a porous bone ingrowth surface or a surface suitable for bone cement, as will be shown and described later. In some embodiments, the talar engaging surface 112 may have a body portion 210 and a keel 212 extending from the body portion 210. Body portion 210 may have a profile to help it remain securely on the talus while leaving much of the adjacent bone of the talus intact. Thus, talar prosthesis 102 may be a "bone sparing" prosthesis.

In some embodiments, the body portion 210 may have two medial-lateral curvatures 220 located at the edges of the talar engaging surface 112, and a central flare 222 extending substantially medially and laterally between the two medial-lateral curvatures 220. The medial-lateral curve 220 and the central flare 222 are most easily seen in FIG. 2E, with a cross-sectional plane extending medial-lateral and cephalad-caudal parallel to the medial-lateral curve 220 and the central flare 222. The central expansion 222 may optionally be slightly concave relative to the medial-lateral curvature 220, thereby defining a wall 224 facing the keel 212. The wall 224 may be circumferentially disposed and may serve as a retaining wall for bone cement when implanting the talar prosthesis 102. The wall 224 may be used to house a porous material if the talar prosthesis 102 is secured to bone using a porous interface.

The body portion 210 may also have a front-to-back bend 230 extending forward-to-back. Thus, as shown in fig. 2C, the cross-sectional shape of the body portion 210 may be generally arcuate, having a concave shape, when viewed from the side. As shown in fig. 2E, the cross-sectional shape of the body portion 210 may be substantially linear when viewed from the front. The body portion 210 may be described as a surface formed when the cross-sectional shape defined by the medial-lateral curve 220, the central flare 222, and optionally the wall 224 sweeps along an arcuate path of the anterior-posterior curve 230. Similarly, the talar articular surface 110 may be described as the surface that is formed when the cross-sectional shape defined by the medial-lateral bend 220 and the anterior-posterior bend 230 sweeps along a similar arcuate path, as also shown in fig. 2E.

Keel 212 may also have a bone-sparing shape. Specifically, the keel 212 may have a base 240 integrally formed with the remainder of the talar prosthesis 102, and a penetration 242 extending from the base 240 to penetrate the bone of the talar. The penetrating portion 242 may have a generally semi-circular periphery 244 at its head end. The generally semi-circular perimeter 244 may help retain the bone by presenting medial and lateral surface areas that resist medial and lateral movement of the talar prosthesis 102 relative to the bone. The resistance to medial-lateral movement can be equal to that provided by a keel having a rectangular cross-sectional shape without removing as much bone as the rectangular perimeter.

In some alternative embodiments (not shown), staples may be used in addition to or in place of the keel 212. Such staples may be of any size or shape known in the art. In some embodiments, the fixation pegs may be permanently fixed to the remainder of the talar engaging surface 112. In other embodiments, the fixation pegs may be modular and may, for example, attach to receiving features in the bone engaging surface, such as mounting holes. In other embodiments, the fixation pegs may be deployed in situ and may be moved from a retracted position to a deployed position to facilitate placement of the talar prosthesis and/or reduce the amount of distraction of the ankle joint required for implantation.

Fig. 3A-3E are a cephalad perspective view, a caudal perspective view, a lateral cross-sectional view, and an anterior cross-sectional view, respectively, of the tibial prosthesis 104. The tibial articular surface 120 may be shaped to mimic the shape of a natural tibial articular surface. In some embodiments, the tibial articular surface 120 may have two concave tibial curvatures 300 extending medially and laterally. The concave tibial curvatures 300 may be separated from one another by convex tibial curvatures 302 that extend medially and laterally. The concave tibial curvature 300 and the convex tibial curvature 302 are most easily seen in fig. 3E, where the cross-sectional plane extends medially, and cephaladly, parallel to the concave tibial curvature 300 and the convex tibial curvature 302.

After the joint replacement is complete, in the central position of the ankle joint, the convex talar curve 200 of the talar prosthesis 102 may be located in the concave tibial curve 300 of the tibial prosthesis 104, while the convex tibial curve 302 of the tibial prosthesis 104 may be placed in the concave talar curve 202 of the talar prosthesis 102. This is the arrangement shown in fig. 1C. As the tibia rotates medially and laterally relative to the talus, a concave tibial curvature 300 may slide along an adjacent convex talar curvature 200, thereby moving another tibial curvature 300 away from an adjacent convex talar curvature 200. The configurations and operations of talar articular surface 110 and tibial articular surface 120 set forth herein are merely exemplary; the invention is not limited to the disclosed embodiments. In alternate embodiments, any arrangement of articulation surfaces and motion paths known in the art may be used.

The tibial engaging surface 122 may be shaped to provide a secure engagement with a prepared surface of a tibia, as will be shown and described later. In some embodiments, the tibial engaging surface 122 may have a body portion 310 and a keel 312 extending from the body portion 310. The body portion 310 may have a profile that helps it to remain securely on the tibia while leaving many of the adjacent bones of the tibia intact. Thus, the tibial prosthesis 104 may be a "bone backup" prosthesis.

In some embodiments, the body portion 310 may have two medial-lateral curvatures 320 located at the edges of the tibial engaging surface 122, and a central expansion 322 extending substantially medially and laterally between the two medial-lateral curvatures 320. The medial-lateral curve 320 and the central flare 322 are most easily seen in FIG. 3E, where the cross-sectional plane extends medial-lateral and cephalad-caudal parallel to the medial-lateral curve 320 and the central flare 322. The central flared portion 322 may be slightly concave relative to the medial-lateral bend 320 to define a wall 324 facing the keel 312. The wall 324 may be circumferentially disposed and may serve as a retaining wall for bone cement during implantation of the tibial prosthesis 104. If a porous interface is to be used to secure the tibial component to the bone, the wall 324 may be used to contain the porous material.

The body portion 310 may also have a front-to-back bend 330 extending forward-to-back. Thus, as shown in fig. 3C, the cross-sectional shape of the body portion 310 may be generally arcuate, having a convex shape, when viewed from the side. As shown in fig. 3E, the cross-section of the body portion 310 may be substantially linear when viewed from a front view. The main portion 310 may be described as a surface formed as the cross-sectional shape defined by the medial-lateral curve 320, the central flare 322, and optionally the wall 324 sweeps along the arcuate path of the anterior-posterior curve 330. Similarly, the tibial articular surface 120 may be described as the surface that is formed when the cross-sectional shape defined by the medial-lateral curvature 320 and the central augment 322 sweeps along a similar arcuate path, as also shown in fig. 2E.

The keel 312 may also have a bone-sparing shape similar to keel 212. In particular, the keel 312 may have a base 340 integrally formed with the remainder of the tibial prosthesis 104, and a penetrating portion 342 extending from the base 340 to penetrate the bone of the talus. The penetrator 342 may have a generally semi-circular perimeter 344 at a head end thereof. In some embodiments, fixation pegs may be used to anchor the tibial prosthesis 104 to the adjoining bone, as described above in connection with the talar prosthesis 102.

Various instruments and methods may be used to prepare the receiving surfaces of the talus and tibia to receive the talus prosthesis 102 and tibial prosthesis 104, respectively. An exemplary kit of instruments and an exemplary method will be shown and described in connection with fig. 4-15. One skilled in the art will recognize that each of the implants, instruments, and methods set forth herein may be used independently of the other implants, and/or with alternative implants, instruments, or methods.

In some embodiments, it may be beneficial to prepare the talus and/or tibia from a procedure that follows an anterior approach (i.e., a procedure that inserts the instrument into the joint space from an anterior direction toward the joint space). The less invasive anterior approach procedure minimizes trauma and thus speeds recovery time. In some known procedures, a transverse approach is used to create an anterior-posterior curvature in the prepared talus and/or tibial surfaces to retain more bone underlying the implant. However, known instruments are generally not capable of producing a back-and-forth bend from other methods, such as an anterior approach.

According to some embodiments, the surgeon may initiate an arthroplasty procedure that enables access to the anterior portion of the ankle joint. This may be accomplished, for example, by cutting and retracting tissue located in front of the joint space (i.e., on the anterior surface of the ankle). The joint space may then be exposed. The surgeon may then attach one or more guide assemblies to the talus and/or tibia to guide the movement of one or more cutting tools.

In some examples, the talar guide assembly may be first secured to the talus bone and used to guide the movement of a cutting tool to prepare the talus bone to receive talar prosthesis 102. This will be shown and described in connection with fig. 4A to 12. The anterior half of the talar guide assembly can then be used to properly position the tibial guide assembly, which can be registered on the talar guide assembly and then secured to the tibia. This will be shown and described in connection with fig. 13A to 13C. The tibial guide assembly may be used to guide the movement of a cutting tool to prepare the tibia to receive the tibial prosthesis 104. This will be shown and described in connection with fig. 14A to 15. The talar prosthesis 102 and tibial prosthesis 104 may then be inserted and secured to the talus and tibia, respectively. After completion of the ankle replacement surgery, the resulting joint space will be shown and described in connection with fig. 16.

Fig. 4A-4C are a perspective cephalad, caudal, and cephalad view, respectively, of trial 400. trial 400 may be used to position talus base 410 relative to talus 420 by using posts 430, where talus base 410 is assembled with talus 420 and trial 400 of fig. 4C with posts 430. The talus 420 may have a natural articular surface 422, which natural articular surface 422 is to be replaced by an arthroplasty procedure.

As shown, trial 400 may have a cephalad side 440 and a caudal side 442. The head side 440 may have post mounting features 444 that interface with corresponding features (not shown) on the post 430. As shown, the post mounting feature 444 may have an oval shape with an aperture that may interface with a corresponding oval notch and/or boss on the post 430. Caudal side 442 may have a talar base alignment feature 446 that mates talar base 410 with talar base 410 to temporarily couple trial 400 to talar base 410 such that rotation of trial 400 causes talar base 410 to also rotate. Talar base alignment feature 446 may have a hole 448 and a rectangular boss 450 surrounding the hole 448.

In addition, trial 400 can have a front end 460 and a back end 462. When trial 400 is positioned on talus 420, anterior end 460 may extend over talus 420 and the anterior portion of the metacarpal. The posterior end 462 may rest on the natural articular surface 422 of the talus 420. The anterior end 460 may have an anterior window 464 that may be used to visually align the anterior end 460 with the talus 420 and/or metacarpal bones. The posterior end 462 may have a posterior window 456 that facilitates visualization of the natural articular surface 422 and/or alignment of the posterior end 462 with the natural articular surface 422. The posterior end 462 may also have a concave curvature 458 sized to allow the posterior end 462 to fit relatively snugly against the natural articular surface 422.

The post 430 may have a proximal end (not shown) and a distal end 470. The distal end 470 may have a trial receiver 472 with a trial mounting feature (not shown) that may be secured to the post mounting feature 444 of the trial 400. Trial receiver 472 may also have holes 474, and when post 430 is attached to trial 400, holes 474 align with holes 448 of talar base alignment feature 446, providing access to holes 448. The proximal end of post 430 may have alignment features, such as pins, holes, or markings, that may be easily aligned with landmarks on the patient's leg proximal to the talus. In some embodiments, the landmark may be a tibial tubercle on the proximal tibia. Thus, the post 430 may have a length sufficient to span substantially the entire length of the patient's tibia.

When the proximal end of post 430 is rotated into desired alignment with the tibial tubercle, the distal end may also be rotated, thereby rotating trial 400 on talus 420. The rotation may also cause talar base 410 to rotate to a desired orientation relative to talus 420. Talar base 410 may then be fixed relative to talus 420, for example, by using pin 480 inserted through talar base 410 and driven into talus 420. Talar bases 410 may be obliquely oriented with respect to one another such that talar bases 410 cannot slide along pins 480 toward or away from talus 420. After talar base 410 is fixed in position relative to talus 420, trial 400 and post 430 may be removed from talar base 410.

Fig. 5A, 5B, and 5C are, respectively, a posterior perspective view, an anterior perspective view, and an anterior perspective view of the talar base 410 of fig. 4C, wherein the talar base 410 is secured to the talus 420 of fig. 5C. Talar base 410 may be designed as a stable attachment point to position and/or move other instruments relative to talus 420 and/or tibia. Talar base 410 may have a fixation member 500 and a moving member 502 movably coupled to fixation member 500.

Fixation member 500 may have a bone attachment interface that facilitates attachment of fixation member 500 to talus 420. In the embodiment of fig. 5A-5C, the bone attachment interface may take the form of a series of channels 510 into which pins 480 are inserted. The channels 510 may be oriented obliquely with respect to one another such that the pins 480 are not parallel to one another. Thus, when pin 480 is in place, the position and orientation of talus base 410 may be substantially fixed relative to talus 420. The number of channels 510 may be more than necessary for fixation of the talar base 410; thus, the surgeon may only insert the pin 480 through the channel 510, the channel 510 being positioned to optimally secure the pin 480 in the talus 420.

The stationary member 500 may also have a moving member interface that provides a movable coupling of the moving member 502 to the stationary member 500. As shown in fig. 5A to 5C, the moving member 502 rotates relative to the fixed member 500. In an alternative embodiment (not shown), instead of pure rotation, the base may have a moving member that translates relative to a stationary member and/or undergoes some combination of translation and rotation. Any movable coupling known in the art may be used, including but not limited to pin joints, sliding joints, links, and the like.

In fig. 5A-5C, the moving member interface may take the form of a pair of arcuate slots 512, the arcuate slots 512 extending fore and aft. The arcuate slot 512 may be centered on an axis 514 that extends inward and outward. As shown in fig. 5C, the shaft 514 may be located aft and rearward of the arcuate slot 512. From the outward facing side of the fixation member 500, the arcuate slot 512 may be recessed within an arcuate groove 516, the arcuate groove 516 following the same arcuate path as the arcuate slot 512. Two or more sets of detents 518 may be formed on each side of the fixation member 500. The stop 518 may extend generally inward and outward and may help control the range of motion of the moving member 502 relative to the stationary member 500, as will be discussed later.

Further, the fixing member 500 may have a test object interface coupling the fixing member 500 to the test object 400. For a trial interface, it is desirable to provide a fixed attachment between fixation member 500 and trial 400, such that the position and orientation of trial 400 determines the position and orientation of fixation member 500, and the position of talar base 410.

As shown in fig. 5A-5C, the test interface can be an aperture 520 located in a rectangular recess 522. A fastener such as a screw or bolt may be inserted through talar pedestal alignment feature 446 of trial 400. A fastener may be inserted through hole 474 of trial receiver 472 and through hole 448 of talar base alignment feature 446, and may be anchored in hole 520. Rectangular recess 522 may receive rectangular boss 450 of talar pedestal alignment feature 446 to ensure that fixation member 500 cannot rotate relative to trial 400 or post 430 with post 430 and trial 400 attached to fixation member 500.

The moving member 502 may have a fixed member interface that cooperates with a moving member interface of the fixed member 500 to provide a movable coupling between the fixed member 500 and the moving member 502. The stationary member interface may be selected to provide a rotatable coupling between the stationary member 500 and the moving member 502.

In fig. 5A-5C, the fixed member interface can include a roller 530, the roller 530 residing in an arcuate groove 516 and being rotatably anchored to the body of the moving member 502 by an arcuate slot 512. There may be two rollers 530 in each arcuate groove 516 to ensure that the moving member 502 is not free to rotate relative to the fixed member 500, but is constrained to rotate predictably relative to the fixed member 500 as the rollers move along the arcuate grooves 516. Thus, the moving member 502 may be constrained to rotate relative to the stationary member 500 about the axis 514.

In addition to the roller 530, the moving member 502 may have a guide knob 540 protruding from the inner or outer side of the moving member 502. In some embodiments, the guide knob 540 may be rotated relative to the remainder of the moving member 502 such that the guide knob 540 may be tightened to frictionally engage the fixed member 500 to prevent relative rotation between the fixed member 500 and the moving member 502, or loosened to allow the moving member 502 to rotate relative to the fixed member 500. Thus, prior to disengaging the guide knob 540 to move the moving member 502 to a new position and orientation, the surgeon may engage the guide knob 540 to temporarily fix the moving member 502 in position relative to the fixed member 500 to make a cut with the moving member 502 in its current position and orientation.

The moving member 502 may also have abutments (not shown) facing the fixed member 500 such that the abutments engage the pawl 518 when the moving member 502 is in two or more predetermined positions relative to the fixed member 500. The predetermined position may be, for example, a desired fore-aft limit of movement of the moving member 502 relative to the stationary member 500. For example, when the moving member 502 is positioned such that the abutments engage the detents 518 on the front of the fixed member 500, the engagement of the abutments with the detents 518 may prevent the moving member 502 from moving further forward relative to the fixed member 500. This may be the position depicted in fig. 5A-5C. Similarly, when the moving member 502 is positioned such that the abutments engage the stops 518 on the rear portion of the fixed member 500, the engagement of the abutments with the stops 518 may prevent the moving member 502 from moving further rearward relative to the fixed member 500.

In the alternative, the engagement of the abutment with the pawl 518 may not establish a limit of motion, but may provide a tactile response indicating to the surgeon that the moving member 502 has reached a front or rear reference position relative to the stationary member 500. Specifically, the surgeon may hear and/or feel the engagement of the abutment with the pawl 518 when the abutment snaps or clicks into the pawl 518. Thus, the surgeon may appreciate that further forward or rearward movement of the moving member 502 relative to the fixed member 500 may cause the moving member 502 to pass a predetermined reference point.

The moving member 502 may also have a tool holder attachment interface, or more specifically, a talar drill holder interface attachable to a talar drill holder that holds a cutting tool in the form of a drill. The talar bore holder may have a base attachable to the talar bore holder interface. Thus, the talar drill holder interface may also be referred to as a base attachment interface. The base attachment interface may be designed to fix the base relative to the moving member 502 such that the moving member 502 carries the base when the moving member 502 moves relative to the fixed member 500. As will be described later, the base attachment interface may also be used to attach the alignment block to the mobile member 502 to facilitate positioning of the tibial base relative to the tibia.

In fig. 5A-5C, the base attachment interface may take the form of a pair of threaded holes 550 in the moving member 502. The threaded holes 550 may receive fasteners, such as screws or bolts, which may be used to secure the base in place on the moving member 502. The configuration and operation of the talar drill holder will be shown and described in connection with fig. 6A through 11B.

Fig. 6A and 6B are front and rear perspective views, respectively, of talar drill holder 600 secured to talar base 410 to hold drill 610 relative to talus 420. Taken together, talar base 410 and talar bore holder 600 may define a talar guide assembly that guides movement of drill 610 relative to talus 420 to form a prepared surface 620 on talus 420 shaped to receive a prosthesis, as shown for talar prosthesis 102 of fig. 1A-2E.

Specifically, talar bore holder 600 may be fixed to moving member 502 of talar base 410 such that talar bore holder 600 is pivotable with moving member 502 relative to fixation member 500 and talus 420. Talar drill holder 600 may also move reamer 610 further (e.g., inside-out and cranio-caudal) to create a desired profile of preparation surface 620. The use of reamer 610 is exemplary only. One skilled in the art will recognize that a wide variety of cutting tools may be used to form the prepared surface 620. Such cutting tools may include rotating and/or translating tools, such as reamers, reciprocating saws, and the like.

As shown, talar drill holder 600 may have: a base 630 fixedly secured to the mobile member 502 of the talar base 410; and an arm 640 that moves relative to the base 630. In addition to the back and forth rotation provided by the movement of the mobile member 502 relative to the talus 420, the movement of the arm 640 relative to the base 630 may enable the drill 610 to move in and out on the talus 420. Reamer 610, as well as other reamers that may be used in connection with joint replacement, will be described in more detail in connection with fig. 7A-8C.

Fig. 7A to 7C are perspective, side and plan sectional views, respectively, of a drill 610. Reamer 610 may have a body 700, a shaft 710, and a cutting element 720. Adapter 730 may be used to couple reamer 610 to talar drill holder 600. The body 700 may be generally cylindrical in shape and may contain a rotary motor (not shown). The rotation motor may cause the shaft 710 to rotate relative to the body 700. The shaft 710 may also be cylindrical. Cutting element 720 may be carried by shaft 710. Thus, rotation of the shaft 710 may drive rotation of the cutting element 720.

Cutting element 720 and shaft 710 may rotate about a cutting tool shaft 740 that is parallel to the length of cutting element 720. Cutting elements 720 may have a concave shape that facilitates forming a convex front-to-back curve from the forward path. Specifically, cutting element 720 may have a proximal end 750, a distal end 760, and an intermediate portion 770 between proximal end 750 and distal end 760. Both proximal end 750 and distal end 760 may be enlarged relative to intermediate portion 770 and may share a maximum radius 780 that is perpendicular to cutting tool axis 740. The radius of the middle section 770 may be much smaller. Maximum radius 780 may be the same as the radius of the medial-lateral curvature present in prepared surface 620 to be formed on talus 420 by cutting element 720. .

In-plane with the cutting tool shaft 740, the cutting element 720 may have an arcuate concave profile with a radius 782 defined by the change in diameter of the cutting element 720 from the proximal end 750 to the intermediate portion 770 and then to the distal end 760. Radius 782 may be the same as the radius of the anterior-posterior curvature present in preparation surface 620, which preparation surface 620 will be formed on talus 420 by cutting element 720.

Adapter 730 may have a flared proximal end 790, a cylindrical distal end 792, a pair of body attachment holes 794 and a pair of bore retainer attachment bosses 796. Proximal end 790 may be hollow and may be sized to receive body 700 of reamer 610. Cylindrical distal end 792 is sized to similarly receive shaft 710 and/or surrounding material of reamer 610. Body attachment hole 794 may facilitate adapter 730 to be securely attached to drill 610. According to some examples, a fastener, such as a set screw, may be inserted into body attachment hole 794 to anchor adapter 730 to drill 610. Bore holder attachment boss 796 may be used to facilitate attachment of adapter 730 and, thus, attachment of drill 610 to talar bore holder 600 and/or tibial bore holder, as will be shown and described later.

According to some examples, the body 700 may be the body of a standard orthopedic drill or reamer. Cutting element 720 and adapter 730 may be used to customize such a standard orthopedic reamer or reamer for use in forming preparation surface 620 from a forward path.

In addition to or in lieu of cutting element 720, a variety of different cutting elements may be used. Such cutting elements may have a convex shape or a linear shape. Examples will be shown and described in connection with fig. 8A to 8C.

Fig. 8A-8C are side views of reamer 800, reamer 830, and reamer 860, respectively, according to various embodiments. Reamer 800, reamer 830, and reamer 860 may each be used in conjunction with adapter 730, as shown in fig. 7A-7C, and may have components similar to reamer 610, including body 700 and shaft 710. Each of reamer 800, reamer 830, and reamer 860 may be configured to rotate about cutting tool axis 740 like reamer 610. However, the cutting elements of reamer 800, reamer 830 and reamer 860 may be configured differently.

Specifically, reamer 800 may have cutting element 820 with a straight, substantially cylindrical shape. Cutting element 820 may have a diameter 822 suitable for cutting the space of keel 212 of talar prosthesis 102 in preparation surface 620. The diameter of the cutting element 820 may also be adapted to cut the space of the keel 312 of the tibial prosthesis 104.

Reamer 830 may also have cutting element 850 with a straight, generally cylindrical shape. Cutting element 850 may have a diameter 852 suitable for cutting a space for shaft 710 in preparation surface 620, such as a shaft of reamer 610, reamer 800, and/or reamer 860. Thus, reamer 830 may serve as a lead-in to provide space for shaft 710 to move during future bone removal procedures.

The drill 860 may be used to form a concave anterior posterior curvature in the tibia. Thus, reamer 860 may have a generally convex shape of cutting element 880. In particular, cutting member 880 may have a proximal end 882, a distal end 884, and an intermediate portion 886 between proximal end 882 and distal end 884. The intermediate portion 886 may be enlarged relative to the proximal and

distal ends

882, 884 and may have a maximum radius 888 perpendicular to the cutting tool axis 740. The radii of the proximal and

distal ends

882, 884 may be much smaller. The maximum radius 888 may be substantially the same as the radius of the medial-lateral curvature present in the surface that is to be formed on the tibia by the cutting element 880.

In-plane with the cutting tool shaft 740, the cutting element 880 may have an arcuate convex profile with a radius 890 defined by the change in diameter of the cutting element 880 from the proximal end 882 to the intermediate portion 886 and then to the intermediate portion 886. Radius 890 may be the same as the radius of the anterior-posterior curvature present in the prepared surface that will be formed on the tibia by cutting element 880.

Fig. 9A-9C are a perspective cephalad view, a perspective caudal view, and a cross-sectional frontal view, respectively, of talar drill holder 600 of fig. 6A and 6B. Talar bore holder 600 may be designed to hold one or more cutting tools to facilitate forming prepared surface 620 in talus 420.

Specifically, talar drill holder 600 may be used to hold drill 830 to remove the anterior portion of natural articular surface 422, thereby providing space for shaft 710 of drill 610 and shaft 710 of drill 800. Talar drill holder 600 may then be used to hold drill 610 to remove the remainder of natural articular surface 422 of talus 420, thereby creating a convex anterior-posterior curvature of prepared surface 620. Talar drill holder 600 may also be used to form a slot generally in the shape of keel 212 of talar prosthesis 102. Thus, after talar drill holder 600 is used in conjunction with drill 830, drill 610, and drill 800, preparation surface 620 may be shaped to receive talar engaging surface 112 of talar prosthesis 102. These steps may be reordered and will be described in more detail later.

Base 630 of talar drill holder 600 may have a base interface that may be used to attach base 630 to talar base 410. The base interface may have any structure suitable for securing the base 630 to the talar base 410. As embodied in fig. 9A-9C, the base interface may include two holes 900, the two holes 900 being spaced apart similarly to the threaded holes 550 of the moving member 502 of the talar base 410. The hole 900 may be smooth. Thus, a fastener 902, which may be a screw, bolt, or the like, may be inserted through the hole 900 and rotated into engagement with the threaded hole 550 of the moving member 502 of the talar base 410. To secure the base 630 to the moving member 502.

The base 630 may also have an arm coupling feature by which the arm 640 is coupled to the base 630. The base 630 and the arm 640 may be movably coupled together by any combination of rotational and/or sliding joints. According to some embodiments, the arm coupling feature provides a rotatable coupling between the base 630 and the arm 640.

As shown in fig. 9A-9C, the arm coupling feature may include a pin 910 with the arm 640 rotatably mounted about the pin 910. The pin 910 may have a head 912 and a shank 914 with male threads that may engage corresponding female threads in a bore 916 in the base 630. Head 912 may have an interface that allows head 912 to be rotated with a tool, such as a screwdriver, to facilitate assembly of talar drill holder 600. The head 912 may be located within a bore 918 in the base 630. The portion of the handle 914 adjacent to the head 912 may be smooth so that the arm 640 may engage and smoothly rotate thereon. The base 630 may further have two parallel plates, a front plate 920 and a rear plate 922, between which the proximal portions of the arms 640 are captured. The hole 918 in which the head 912 resides may be formed in the front plate 920, while the hole 916 in which the stem 914 is anchored may be formed in the rear plate 922. Thus, the pin 910 may be inserted rearwardly through the hole 918 in the front plate 920 to anchor in the hole 916 in the rear plate 922.

In addition, the base 630 may have base guide features that facilitate movement of the guide arms 640 relative to the base 630. The base guide features may cooperate with corresponding arm guide features of the arm 640 to limit the range of motion of the arm 640, thereby limiting the attached cutting tool, such as drill 610, drill 800, or drill 830 relative to the talus 420. As embodied in fig. 9A-9C, the base guide feature may include a rectangular window 930 with four guide surfaces 932. The caudal-positioned guide surface 932 (facing in the cephalad direction) may limit movement of the cutting tool in the caudal direction toward the talus 420, as described below.

As shown in fig. 9C, the arm 640 may be divided into a first arm member 950 and a second arm member 952. The second arm member 952 may be nested within the first arm member 950 such that the second arm member 952 may slide within the first arm member 950 such that the arm 640 effectively has an adjustable reach relative to the pin 910. The resilient member may be used to separate the first arm member 950 from the second arm member 952, thereby urging the arm 640 to its maximum length. The resilient member may take the form of a linear spring 954 that is normally held in compression. The linear spring 954 may be partially located in a cavity in the distal end of the second arm member 952.

The arm 640 may have a base coupling feature by which the arm 640 is coupled to the base 630. The base coupling features may be configured in a variety of ways and may be designed to mate with the arm coupling features of the base 630. In fig. 9A-9C, the base coupling feature may include a slot 960 formed in the proximal end of the first arm member 950, and a bracket 962 formed in the proximal end of the second arm member 952. The slot 960 may be fore-aft elongated and may receive the pin 910 to allow the first arm member 950 to move up or down relative to the pin 910. The bracket 962 may be concave and semi-circular such that the proximal end of the second arm member 952 abuts and slides relatively smoothly with respect to the pin 910 while allowing the proximal end of the second arm member 952 to push up against the pin 910, thereby pushing the first arm member 950 down.

The arm 640 may further have a tool attachment interface to which a cutting tool may be attached. Where the cutting tool is a reamer, such as reamer 610, reamer 800, reamer 830, and/or reamer 860, the tool attachment interface may be referred to as a reamer attachment interface. The reamer attachment interface may be designed to hold any one of reamer 610, reamer 800 and reamer 830 in a fixed relationship with first arm member 950. More precisely, the reamer attachment interface may be designed to receive and secure an adapter 730, said adapter 730 being secured to one of reamer 610, reamer 800 and reamer 830.

As shown in fig. 9A-9C, the reamer attachment interface may take the form of an attachment sleeve 970, the attachment sleeve 970 having an aperture 972 sized to receive the cylindrical distal end 792 of the adapter 730. The attachment sleeve 970 may also have one or more locking features. The adapter 730 may be selectively locked in place relative to the attachment sleeve 970. Thus, they may take the form of slots 974 that extend axially and then circumferentially on the attachment sleeve. Each slot 974 may be sized to receive one of the bore retainer attachment bosses 796 of adapter 730.

Specifically, the adapter 730 may be attached to a corresponding cutting tool and then inserted back into the attachment sleeve 970 such that the bore retainer attachment boss 796 enters the axial extension of the slot 974. Once the bore holder attachment boss 796 has reached the end of the axially extending portion, the adapter 730 may be rotated about the axis of the attachment sleeve 970, which may be collinear with the cutting tool axis 740 of the cutting tool, such that the bore holder attachment boss 796 slides along the circumferentially extending portion of the slot 974. One or more snap features (not shown) may optionally snap adapter 730 in place in attachment sleeve 970. In any event, the combination of axial translation and rotation required to attach the adapter 730 to the attachment sleeve 970 may ensure that the cutting tool is securely held relative to the first arm member 950 until insertion movement is reversed.

Still further, the arm 640 may have an arm guide feature that cooperates with a base guide feature to constrain movement of the arm 640 relative to the base 630. The arm guide feature may be any member that can interact with the base guide feature to help limit relative movement between the base 630 and the arm 640. Where the base guide feature comprises a guide surface, the arm guide feature may advantageously be a follower which may abut and/or abut such a guide surface.

Specifically, the base guide feature may be a post 980 protruding from the first arm member 950 between the pin 910 and the attachment sleeve 970. The posts 980 may protrude forward such that the posts 980 are located in the rectangular windows 930 of the base 630. The interaction of the post 980 with the guide surface 932 of the rectangular window 930 may limit the movement of the attachment sleeve 970, and thus the movement of the cutting tool, to a substantially rectangular area. In particular, the guide surface 932 on the bottom of the rectangular window 930 may limit the movement of the cutting tool toward the talus 420, thereby controlling the depth of the resection.

More specifically, guide surface 932 on the bottom of rectangular window 930 may prevent cutting tool axis 740 of drill 610, drill 800, or drill 830 from moving closer to talus 420 than the planar boundary. Similarly, guide surfaces 932 on the sides of rectangular window 930 may prevent further inward or outward movement of drill 610, drill 800, or cutting tool axis 740 of drill 830 than the additional planar boundaries. Thus, the posts 980 of the arms 640 may mate with the rectangular windows 930 of the base 630 to ensure that the preparation surface 620 has a desired depth, width, and overall shape.

The action of linear spring 954 may also help to ensure that preparation surface 620 has a desired shape. In particular, the pressure exerted by linear spring 954 may help ensure that the cut made to talus 420 extends to the entire desired depth, thereby ensuring that preparation surface 620 has the depth and consistency needed to provide continuous bone to support talar prosthesis 102. However, the linear spring 954 may be adjusted to provide a force that the surgeon can easily resist in order to remove bone with a shallower cut before expanding the cutting tool to the maximum depth allowed by the interaction of the post 980 with the rectangular window 930. The manner in which a talar cutting guide including talar base 410 and talar drill holder 600 may be used to control resection of talus 420 will be shown and described in more detail in connection with fig. 6A, 6B, and 10A through 12.

Turning briefly to fig. 6A and 6B, in some embodiments, talar base 410 and talar drill holder 600 may be used to form a prepared surface 620 starting from a posterior side of prepared surface 620. Specifically, with base 630 secured to mobile member 502 of talar base 410 and reamer 830 secured to arm 640, mobile member 502 may be pivoted relative to fixed member 500 toward its rearward position. This may position cutting element 850 of reamer 830 over the posterior portion of natural articular surface 422 of talus 420. The surgeon may hold reamer 830 over natural articular surface 422 against the force of linear spring 954 with post 980 moving away from guide surface 932 at the bottom of rectangular window 930 until he or she is ready to begin resecting natural articular surface 422.

The surgeon may then lower reamer 830, allowing linear springs 954 to press on reamer 830 to engage natural articular surface 422 until post 980 rests on guide surface 932 at the bottom of rectangular window 930. The reamer 830 can then be moved in and out (i.e., side to side) by moving the attachment sleeve 970 in and out, thereby sliding the post 980 in and out along the guide surface 932 at the bottom of the rectangular window 930. The posts 980 may abut the guide surfaces 932 on the left and right sides of the rectangular window 930 to control the degree of in-out movement of the reamer 830.

Once reamer 830 has passed beyond the inner and outer extent of natural articular surface 422, mobile member 502 may be rotated forward relative to fixation member 500 to move reamer 830 toward the anterior portion of natural articular surface 422. The in-out motion of reamer 830 may be repeated as needed to remove material from the anterior portion of natural articular surface 422. If desired, medial-lateral movement of the reamer 830 may also be performed during forward rotation of the moving member 502 to remove material from the entire anterior-posterior curvature of the natural articular surface 422.

As previously described, the purpose of reamer 830 may simply be to remove enough material to allow reamer 610 and reamer 800 to engage talus 420 without obstruction, particularly by removing bone from where shaft 710 of reamer 610 and shaft 710 of reamer 800 are located in future cutting steps. Thus, reamer 830 need not be used to resect the entire natural articular surface 422.

Once reamer 830 has passed beyond the medial-lateral and anterior-posterior extent of natural articular surface 422, reamer 830 may be removed from attachment sleeve 970 and reamer 610 may be secured to attachment sleeve 970. The reamer 610 may then be positioned over the posterior portion of the natural articular surface 422. The surgeon may hold reamer 610 over natural articular surface 422, which has now been partially resected, against the force of linear spring 954. Again, the post 980 may be moved away from the guide surface 932 at the bottom of the rectangular window until the surgeon is ready to begin cutting the natural articular surface 422 with the broach 610.

The surgeon may then lower reamer 610, allowing linear springs 954 to press on reamer 610 to engage natural articular surface 422 until posts 980 rest on guide surfaces 932 at the bottom of rectangular window 930. This is the position depicted in fig. 6A and 6B. Reamer 610 may then be moved in and out (i.e., side to side) by moving attachment sleeve 970 in and out, causing post 980 to again slide in and out along guide surface 932 at the bottom of rectangular window 930. The posts 980 may abut the guide surfaces 932 on the left and right sides of the rectangular window 930 to control the degree of in-out movement of the drill 610.

Once reamer 610 has passed beyond the inner and outer extent of natural articular surface 422, mobile member 502 may be rotated forward relative to fixation member 500 to move reamer 610 toward the anterior portion of natural articular surface 422. This is the position depicted in fig. 10A and 10B.

Fig. 10A and 10B are front and rear perspective views, respectively, of a talus 420, a talus base 410 attached to the talus 420, a talus drill holder 600 attached to the talus base 410, and a drill 610 positioned to cut an anterior portion of a natural articular surface 422 of the talus 420. The medial-lateral motion of reamer 610 may be repeated to remove material from the anterior portion of natural articular surface 422 as desired. If desired, medial-lateral movement of the reamer 610 may also be performed during forward rotation of the moving member 502 to remove material from the entire anterior-posterior curvature of the natural articular surface 422.

The result may be the formation of a prepared surface 620 as shown in fig. 6B and 10B. Preparation surface 620 is further shown and described in connection with fig. 11A and 11B.

Fig. 11A and 11B are side elevational, cross-sectional and enlarged head side elevational views, respectively, of talus 420 with talar base 410, talar drill holder 600 and drill 610 positioned as shown in fig. 10A and 10B. The shape of the preparation surface 620 is shown in more detail, in addition to the slot for the keel 212 of the talar prosthesis 102.

As shown in fig. 11A, the prepared surface 620 may have a side cross-sectional shape in a plane located in the anterior-posterior direction 130 and the cranial-caudal direction 134 that closely matches the side view of the talar prosthesis 102 shown in fig. 2C. The preparation surface 620 may have a convex anterior-posterior curvature 1100 with a radius substantially the same as the anterior-posterior curvature 230 of the talar engaging surface 112 of the talar prosthesis 102. Anterior and posterior to the convex anterior-posterior curvature 1100, the preparation surface 620 may have two convex anterior-posterior curvatures 1110, which may have the same radius as the portions of the talar engaging surface 112 anterior and posterior to the anterior-posterior curvature 230.

As shown in fig. 11B, preparation surface 620 may have a cross-sectional shape in a plane located in medial-lateral direction 132 and cranio-caudal direction 134 that closely matches the cross-sectional shape of talar engaging surface 112 of talar prosthesis 102, as depicted in fig. 2E, except that no slot is formed for keel 212 of talar prosthesis 102. The preparation surface 620 may have a central flare 1120 that is generally linear in shape (in cross section), and two concave inward-outward curves 1130 on either side of the central flare 1120. The central augment 1120 may have a width that is substantially equal to the central augment 222 of the talar engaging surface 112 of the talar prosthesis 102, and the concave medial-lateral curve 1130 has a radius that is generally equal to the radius of the medial-lateral curve 220 of the talar engaging surface 112 of the talar prosthesis 102.

The shape of cutting elements 720 of reamer 610 may determine parameters for various compositional shapes of preparation surface 620. Specifically, a radius 782 along the length of the cutting tool axis 740 of the cutting element 720 of the reamer 610 may be substantially the same as the radius of the convex front-to-back curve 1100. Similarly, the maximum radius 780 of cutting tool axis 740 perpendicular to cutting element 720 of reamer 610 may be substantially the same as the radius of concave inner-outer curve 1130.

As previously discussed, it may be desirable to form a slot in the prepared surface 620 so that the surface 620 may securely receive the keel 212 of the talar prosthesis 102. The formation of the slot is optional; in some embodiments, the ankle prosthesis may not have a keel or may have a keel with an internal cutting element that forms a slot in response to pressure of the keel against the bone. Further, in some embodiments, the slots may be formed prior to forming the remainder of preparation surface 620. Thus, for example, reamer 800 may be used to form a slot prior to use of reamer 610 to form preparation surface 620 shown in fig. 11A and 11B, and may even be used to form a slot prior to use of reamer 830. The formation of the slits will be depicted in fig. 12 under the assumption that the preparation surface 620 has been formed as shown in fig. 11A and 11B.

Fig. 12 is a perspective view illustrating the use of drill 800 to form a slot 1200 in a prepared surface 620 of talus 420. After the previous bone removal steps are completed (or alternatively, as described above, before these steps are performed), reamer 800 may be attached to attachment sleeve 970 of talar drill holder 600, and talar drill holder 600 is secured to moving member 502 of talar base 410. Reamer 800 may then be positioned over a central portion of preparation surface 620. The surgeon may hold reamer 800 above preparation surface 620 against the force of linear spring 954. Likewise, post 980 may be moved away from guide surface 932 at the bottom of rectangular window 930 until the surgeon is ready to begin forming a slot in preparation surface 620 with drill 800.

The surgeon may then hold reamer 800 in a central position inside and outside and lower reamer 800, allowing linear spring 954 to press reamer 800 to engage preparation surface 620 until post 980 rests on guide surface 932 at the bottom of rectangular window 930. This is the position depicted in fig. 12. When cutting element 820 of reamer 800 is lowered into preparation surface 620, cutting element 820 may form slot 1200 substantially in the center of preparation surface 620. Diameter 822 of cutting element 820 may be substantially equal to the width of keel 212 of talar prosthesis 102. The slot 1200 may have a trailing end (not visible) having a generally hemispherical concave cross-sectional shape that closely receives the semi-circular periphery 244 of the penetrating portion 242 of the keel 212.

Keel 212 may engage slot 1200 in a manner that helps prevent medial and lateral movement of talar prosthesis 102 relative to preparation surface 620 and further promotes secure adhesion of talar prosthesis 102 to preparation surface 620. The keel 212 and/or the remainder of the talar engaging surface 112 of the talar prosthesis 102 may optionally have a porous and/or coated surface designed to promote bone ingrowth and adhesion. Additionally or alternatively, talar prosthesis 102 may be designed for use with bone cement that forms a bond between talus 420 and talar prosthesis 102.

Once preparation surface 620 (including slot 1200) has been fully formed, talar drill holder 600, along with any attached cutting tools, may be removed from talar base 410. Talar base 410 may be held in place on talus 420 as shown in fig. 5C. The talar base 410 may then be used to facilitate attachment of the tibial cutting guide to the tibia, as shown in fig. 13A-13C.

Fig. 13A-13C are rear-to-rear, front-to-front and front-to-front perspective views, respectively, of the tibial base 1300, and also illustrate an alignment block 1310 for securing the tibial base 1300 to the tibia 1320 in fig. 13C. As shown, the talar base 410 may remain fixed to the talus 420, and the alignment block 1310 may be attached to the talar base 410 and the tibial base 1300 such that the tibial base 1300 is properly positioned relative to the joint.

Like the bone base 410, the tibial base 1300 may be part of a cutting guide that helps guide a cutting tool relative to the bone. A cutting tool holder, such as a tibial drill holder, may be attached to the tibial base 1300 as will be shown and described later.

The tibial base 1300 may have a bone attachment interface that facilitates attachment of the tibial base 1300 to the tibia 1320. Any bone attachment feature known in the art may be used. In the embodiment of fig. 13A-13C, the bone attachment interface may take the form of a series of channels 1330 through which pins 480 are inserted. As in talar base 410, channels 1330 may be oriented obliquely with respect to each other such that pins 480 are not parallel to each other. Thus, when the pin 480 is in place, the position and orientation of the tibial base 1300 relative to the tibia 1320 may be substantially fixed. The channel 1330 may be more than necessary to secure the tibial base 1300; the channel 1330 may be more secure than the tibial base 1300. Thus, the surgeon can only insert the pin 480 through the channel 1330 that is positioned to optimally anchor the pin 480 in the tibia 1320.

The tibial base 1300 may also have a tool holder attachment interface, or more specifically, a tibial drill holder interface attachable to a tibial drill holder that holds a cutting tool in the form of a drill. The tibial drill holder may have a base connectable to the talar drill holder interface. Accordingly, the tibial drill holder interface may also be referred to as a base attachment interface. The base attachment interface may be designed to secure the base relative to the tibial base 1300. Unlike the talar base 410, the tibial base 1300 may not have a fixed component and a moving component; and the tibial base 1300 may not have a fixation member. Instead, the entire tibial base may serve as the fixed base for the tibial drill holder. As depicted in fig. 13C, the base attachment interface may also be used to attach the tibial base 1300 to the alignment block 1310 to facilitate positioning of the tibial base 1300 relative to the tibia 1320.

In fig. 13A-13C, the base attachment interface may take the form of a button 1340 with a threaded hole 1342 that can receive a threaded tip of a fastener to attach the tibial drill holder or alignment block to the button 1340. The button 1340 can also have a leading edge 1344 and a trailing edge 1346, the leading edge 1344 and the trailing edge 1346 cooperating to engage the slot 1350. More precisely, the slot 1350 may have a ledge 1352 defining a keyhole shape (keyhole shape) of the slot 1350. The ledge 1352 may be located between the leading edge 1344 and the trailing edge 1346 such that the button 1340 may slide up or down within the slot 1350. The slot 1350 may have a head end 1354 with the ledge 1352 not present. The head end 1354 may thus provide a circular opening through which the front edge 1344 and the rear edge 1346 may be inserted to allow the buttons to be assembled into the plate 1360 having the slots 1350 formed therein.

As shown in fig. 13C, the alignment block 1310 may have a body 1370 with a talar base interface connectable to the talar base 410 and a tibial base interface connectable to the tibial base 1300. Each base interface may provide secure securement with a corresponding base. Thus, the talar base 410 and the tibial base 1300 may be fixed together in a predictable relative position.

As shown in fig. 13C, the talar base interface may include two holes 1380 configured similar to the two holes 900 of talar drill holder 600. The holes 1380 may be spaced in a similar manner to the threaded holes 550 of the moving member 502 of the talar base 410 and may be smoothly drilled. Thus, a fastener, such as fastener 902 of talar drill holder 600, which may be a screw, bolt, or the like, may be inserted through hole 1380 and rotated to engage it with threaded hole 550 of moving member 502 of talar base 410 to secure alignment block 1310 to moving member 502.

The tibial base interface may include a hole 1390, which may be smoothly drilled like hole 1380. Fasteners such as the fastener 902 of the talar drill holder 600, which may be screws, bolts, or the like, may be inserted through the holes 1390 and rotated to engage the holes 1342 of the tibial base 1300 to secure the tibial base 1300 to the alignment block 1310.

Alignment block 1310 may first be secured to talar base 410, for example, by securing holes 1380 to threaded holes 550 of moving member 502 with fasteners 902. When the alignment block 1310 is attached thereto, the moving member 502 may be positioned in a predictable location, such as relative to the front of the range of motion of the stationary member 500. If desired, the moving member 502 may be locked in place relative to the fixed member 500, for example, by using a guide knob 540.

The tibial base 1300 may then be secured to the alignment block 1310 by, for example, securing the holes 1390 to the holes 1342 of the tibial base 1300 using fasteners such as screws or bolts. In an alternative embodiment, the alignment block 1310 may be secured to the tibial base 1300 first, and then to the talar base 410.

In either case, after attaching the alignment block 1310 to the talar base 410 and the tibial base 1300, the tibial base 1300 may be in a predictable position relative to the talar base 410 and thus relative to the ankle joint. Thus, the tibial base 1300 may be used to guide resection of the tibia 1320. As shown, the tibial base 1300 can be secured to the tibia 1320 by inserting the pin 480 through the passage 1330 of the tibial base 1300 and anchoring the distal end of the pin 480 in the bone of the tibia 1320, as shown. Once the tibial base 1300 has been anchored to the tibia 1320, the alignment block 1310 may be separated from the talar base 410 and the tibial base 1300. Talar base 410 may also be separated from talus 420 by withdrawing pin 480 from talus 420.

The tibial base 1300 can then be used in conjunction with a tibial drill holder to define a tibial guide assembly relative to a tibial guide drill. This will be described in more detail in connection with fig. 14A to 14C.

Fig. 14A, 14B and 14C are, respectively, an anterior perspective, a side elevation and an anterior perspective of a tibial drill holder 1400, wherein the tibial drill holder 1400 is secured to the tibial base 1300 and tibia 1320 of fig. 14C. The combined tibial base 1300 and tibial drill holder 1400 may define a tibial guide assembly that guides movement of the drill 860 relative to the tibia 1320 to form a prepared surface on the tibia 1320 that is shaped to receive a prosthesis, such as the tibial prosthesis 104 of fig. 1A-1C and 3A-3E. Additionally, fig. 15 is a side cutaway view of the tibial drill holder 1400 and tibial base 1300 secured to the tibia 1320. The construction and operation of the tibial drill holder will be explained in connection with fig. 14A-15.

Specifically, the tibial drill holder 1400 may be secured to the aperture 1390 of the tibial base 1300. The tibial drill holder 1400 may move (e.g., medio-lateral and cranio-caudal) the drill 860 to produce a desired contour of the prepared surface 1420 (shown in fig. 15) of the tibia 1320. The use of reamer 860 is exemplary only; one skilled in the art will recognize that a wide variety of cutting tools may be used to form the prepared surface 1420. Such cutting tools may include rotating and/or translating tools, such as reamers, reciprocating saws, and the like.

As shown, the tibial drill holder 1400 may have a base 1430 fixedly secured to the tibial base 1300 and an arm 1440 that moves relative to the base 1430. The movement of the arm 1440 relative to the base 1430 may enable the drill 860 to move in and out on the tibia 1320. The base 1430 and the arm 1440 may cooperate to provide limited movement of the cutting tool relative to the tibia 1320 in a manner similar to that of the talar drill holder 600, as described below.

The base 1430 of the tibial drill holder 1400 may have a base interface that may be used to attach the base 1430 to the tibial base 1300. The base interface may have any structure suitable for securing the base 1430 to the tibial base 1300. As shown in fig. 14A-15, the base interface can include an aperture 1450 that can be aligned with the aperture 1342 of the button 1340 of the tibial base 1300. Accordingly, a fastener 1452, such as a screw or bolt, can be inserted through the hole 1450 and rotated into engagement with the hole 1342 of the button 1340 of the tibial base 1300 to secure the base 1430 to the tibial base 1300.

The base 1430 may also have an arm coupling feature by which the arm 1440 is coupled to the base 1430. The base 1430 and the arm 1440 may be movably coupled together by any combination of rotational and/or sliding joints. According to some embodiments, the arm coupling feature provides a rotatable coupling between the base 1430 and the arm 1440.

As shown in fig. 14A-15, the arm coupling feature may include a pin 1460 about which the arm 1440 is rotatably mounted. The pin 1460 may have a head 1462 and shank 1464 with male threads that may engage corresponding female threads in a hole 1466 in the bottom 1430. The head 1462 may have an interface that allows the head 1462 to be rotated by a tool, such as a screwdriver, to facilitate assembly of the tibial drill holder 1400. The head 1462 may be located within a hole 1468 in the base 1430. A portion of stem 1464 adjacent head 1462 may be smooth so that arm 1440 may engage and rotate smoothly thereon. The base 1430 may further have two front plates 1470 and a rear plate 1472 between which the arm 1440 is generally captured. The hole 1468 in which the head 1462 is located may be formed at the topmost portion of the front plate 1470, while the hole 1466 in which the stem 1464 is anchored may be formed in the rear plate 1472. Thus, the pins 1460 may be inserted rearwardly through the holes 1468 in the topmost portion of the front plate 1470 to anchor in the holes 1466 in the rear plate 1472.

In addition, the base 1430 can have base guide features that facilitate movement of the guide arm 1440 relative to the base 1430. The base guide features may cooperate with corresponding arm guide features of the arm 1440 to limit the range of motion of the arm 1440, thereby limiting the range of motion of an attached cutting tool (e.g., drill 860, drill 800, or drill 830) relative to the tibia 1320. As embodied in fig. 14A-15, the base guide feature may include a notch 1480 with a plurality of guide surfaces 1482. One of the guide surfaces 1482 may be oriented in a caudal direction to limit movement of the cutting tool in a cephalad direction toward the tibia 1320 of the head, as will be described later. The remaining guide surfaces 1482 may be oriented inward and outward to limit movement of the cutting tool in and out.

As shown in fig. 15, the arm 1440 may be divided into a first arm member 1500 and a second arm member 1502. The second arm member 1502 may be nested within the first arm member 1500 such that the second arm member 1502 may slide within the first arm member 1500 such that the arm 1440 effectively has an adjustable range relative to the pin 1460. A resilient member may be used to separate the first arm member 1500 from the second arm member 1502, thereby urging the arm 1440 to its maximum length. The resilient member may take the form of a linear spring 1504 that is normally held under compression. The linear spring 1504 may be partially located in a cavity at the distal end of the second arm member 1502. The first arm member 1500 can have a hole 1506, and a fastener 1452 can be accessed from the front of the tibial drill holder 1400 through the hole 1506.

The arm 1440 may have a base coupling feature by which the arm 1440 is coupled to the base 1430. The base coupling features can be configured in a variety of ways and can be designed to mate with the arm coupling features of the base 1430. In fig. 15, the base coupling feature may include a slot 1510 formed in the first arm member 1500 and a bracket 1512 formed in the top end of the second arm member 1502. The slot 1510 may be elongated fore-aft and may receive the pin 1460 to allow the first arm member 1500 to move up or down relative to the pin 1460. The bracket 1512 may be concave and semi-circular such that the tip of the second arm member 1502 abuts and slides relatively smoothly relative to the pin 1460, while allowing the end of the second arm member 1502 to push down against the pin 1460, pushing the first arm member 1500 upward.

The arm 1440 may further have a tool attachment interface to which a cutting tool may be attached. Where the cutting tool is a reamer, such as reamer 610, reamer 800, reamer 830, and/or reamer 860, the tool attachment interface may be referred to as a reamer attachment interface. The reamer attachment interface may be designed to hold any one of reamer 860, reamer 800 and reamer 830 in a fixed relationship with first arm member 1500. More precisely, the reamer attachment interface may be designed to receive and secure an adapter 730, said adapter 730 being secured to one of reamer 860, reamer 800 and reamer 830.

As shown in fig. 14A-15, the reamer attachment interface may take the form of an attachment sleeve 970 that is substantially identical to the attachment sleeve 970 of the talar drill holder 600. Thus, the attachment sleeve 970 of the tibial burr holder 1400 may have an aperture 972 sized to receive the cylindrical distal end 792 of the adapter 730. The attachment sleeve 970 may also have one or more locking features that may selectively lock the adapter 730 in place relative to the attachment sleeve 970. Thus, they may take the form of slots 974 that extend axially and then circumferentially on the attachment sleeve. Each slot 974 may be sized to receive one of the bore retainer attachment bosses 796 of adapter 730. As described in connection with talar drill holder 600, the adapter may be received in attachment sleeve 970 and interlock with attachment sleeve 970.

Still further, the arm 1440 may have arm guide features that cooperate with the base guide features to constrain the motion of the arm 1440 relative to the base 1430. The arm guide feature can be any member that can interact with the base guide feature to help limit relative movement between the base 1430 and the arm 1440. Where the base guide feature comprises a guide surface, the arm guide feature may advantageously be a follower which may abut and/or bear against such a guide surface.

In particular, the base guide feature may be a post 1490 protruding from the first arm member 1500 between the pin 1460 and the attachment sleeve 970. The pillar 1490 may protrude forward such that the pillar 1490 is located in a notch 1480. The interaction of the posts 1490 with the guide surfaces 1482 of the notches 1480 may limit the movement of the attachment sleeve 970, and thus the movement of the cutting tool, to a generally rectangular region. In particular, a guide surface 1482 on the top of the notch 1480 may limit movement of the cutting tool toward the tibia 1320, thereby controlling the depth of resection.

More specifically, guide surface 1482 on top of notch 1480 may prevent drill 860, drill 800 or cutting tool axis 740 of drill 830 from moving closer to tibia 1320 than the planar boundary. Similarly, guide surfaces 1482 on the sides of notch 1480 may prevent further inward or outward movement of drill 860, drill 800, or cutting tool axis 740 of drill 830 than the additional planar boundaries. Thus, the posts 1490 of the arms 1440 can mate with the notches 1480 of the base 1430 to ensure that the prepared surface 1420 has a desired depth, width, and overall shape.

The action of the linear spring 1504 may also help ensure that the preparation surface 1420 has a desired shape. In particular, the pressure exerted by the linear spring 1504 may help ensure that the cuts made to the tibia 1320 extend to the full desired depth, thereby ensuring that the preparation surface 1420 has the desired depth and consistency to provide continuous bone to support the tibial prosthesis 104. However, the linear spring 1504 may be adjusted to provide a force that can be easily resisted by the surgeon to remove bone with a shallower cut before expanding the cutting tool to the full depth allowed by the interaction of the strut 1490 with the notch 1480.

The tibial drill holder 1400 may be used in a manner similar to the talar drill holder 600 to form a prepared surface 1420 on the distal end of the tibia 1320, except that the tibial drill holder 1400 has no moving components and therefore does not require moving a cutting tool back and forth. Instead, the cuts may all be made at the same front to back datum. The cut may optionally begin with reamer 830 to remove enough bone head to make room for shaft 710 of reamer 860, and then the cut may continue using reamer 860 to create the contour of preparation surface 1420, except for the slot for keel 312 of tibial prosthesis 104. Drill 800 may be used to form such a slot.

As with talar drill holder 600, linear spring 1504 may be used to help ensure that the proper cutting depth is obtained. Specifically, the surgeon may position cutting element 850 of reamer 830 below the natural articular surface of tibia 1320. The surgeon may hold drill 830 below the natural articular surface against the force of linear spring 1504 with posts 1490 displaced below guide surface 1482 at the top of notch 1480 until he or she is ready to begin resecting the natural articular surface.

The surgeon may then allow drill 830 to be raised, allowing linear spring 1504 to depress drill 830 to engage the natural articular surface until post 1490 rests on guide surface 1482 at the top of notch 1480. Reamer 830 may then be moved in and out (i.e., side to side) by moving attachment sleeve 970 in and out, thereby sliding posts 1490 in and out along guide surfaces 1482 at the top of notches 1480. The posts 1490 may abut the guide surface 1482 on the left and right sides of the recess 1480 to control the degree of in-out motion of the drill 830.

Once reamer 830 has passed beyond the inner and outer extent of the natural articular surface, reamer 830 may be removed from attachment sleeve 970 and reamer 860 may be secured to attachment sleeve 970. The drill 860 may then be positioned below the natural articular surface of the tibia 1320. The surgeon may hold reamer 860 against the force of linear spring 1504 below the natural articular surface, which has now been partially resected. Again, the struts 1490 may be displaced from the guide surface 1482 at the top of the notch 1480 until the surgeon is ready to begin resecting the natural articular surface with the reamer 860.

The surgeon may then lift the reamer 860, allowing the linear spring 1504 to press the reamer 860 to engage the natural articular surface until the posts 1490 rest on the guide surface 1482 at the top of the notches 1480. Drill 860 may then be moved in and out (i.e., side to side) by moving attachment sleeve 970 in and out, thereby sliding post 1490 in and out again along guide surface 1482 at the top of notch 1480. Posts 1490 may abut guide surface 1482 on the left and right sides of notch 1480 to control the degree of in-out motion of reamer 860.

Preparation surface 1420 may then have a shape similar to preparation surface 620 of talus 420, but with concave anterior posterior curvature 1592 in place of convex anterior posterior curvature 1100. A portion of the concave front-to-back curve 1592 is shown in fig. 15. Returning briefly to fig. 11B, the preparation surface 1420 may have, in addition to the concave front-to-back bend 1592, two convex front-to-back bends 1110 located before and after the concave front-to-back bend 1592 in a plane parallel to the front-to-back direction 130 and the cranio-caudal direction 134. Further, in a plane parallel to the medial-lateral direction 132 and the cranial-caudal direction 134, the preparation surface 1420 may have a central expansion 1120 and two concave medial-lateral curves 1130 located on either side of the central expansion 1120. Thus, once the slot for the keel 312 is formed, the preparation surface 1420 can have a shape that is substantially complementary to the shape of the tibial engagement surface 122 of the tibial prosthesis 104, as shown in fig. 3A-3E.

Once reamer 860 has passed beyond the inner and outer extent of the natural articular surface, reamer 860 may be removed from attachment sleeve 970 and reamer 800 may be secured thereto. The drill 800 may then be positioned below a central portion of the preparation surface 1420. The surgeon may hold reamer 800 below preparation surface 1420 against the force of linear spring 1504. Likewise, the posts 1490 may be displaced from the guide surface 1482 at the top of the notch 1480 until the surgeon is ready to begin forming slots in the preparation surface 1420 using the drill 800.

The surgeon may then hold drill 800 in a central position inside and outside and raise drill 800 to allow linear spring 1504 to depress drill 800 to engage preparation surface 1420 until posts 1490 abut guide surface 1482 at the top of notches 1480. When cutting element 820 of reamer 800 is raised into preparation surface 1420, cutting element 820 may form a slot 1598 substantially in the center of preparation surface 1420. The diameter 822 of the cutting element 820 may be substantially equal to the width of the keel 312 of the tibial prosthesis 104. The slot 1598 may have a head end with a generally hemispherical concave cross-sectional shape that closely accommodates the semi-circular perimeter 344 of the penetration 342 of the keel 312.

The keel 312 may interface with the slot 1598 in a manner that helps prevent medial-lateral movement of the tibial prosthesis 104 relative to the preparation surface 1420, and further promotes secure adhesion of the tibial prosthesis 104 to the preparation surface 1420. The keel 312 and/or the remainder of the tibial engagement surface 122 of the tibial prosthesis 104 may optionally have a porous surface and/or a coated surface designed to promote bone ingrowth and adhesion. Additionally or alternatively, the tibial prosthesis 104 may be designed for use with bone cement that forms a bond between the tibia 1320 and the tibial prosthesis 104.

Once the preparation surface 1420, including the slot 1598, has been fully formed, the tibial base 1300, along with any attached cutting tools, may be removed from the tibial base 1300. The tibial base 1300 may also be removed from the tibia 1320 in order to clear any obstructions from the joint space. The talar prosthesis 102 and tibial prosthesis 104 may then be positioned on the prepared surface 620 of the talus 420 and the prepared surface 1420 of the tibia 1320, respectively. The final configuration will be shown and described in connection with fig. 16.

Fig. 16 is a side cross-sectional view depicting a talus 420 and a tibia 1320, with the talar prosthesis 102 secured to a prepared surface 620 of the talus 420, and the tibial prosthesis 104 secured to a prepared surface 1420 of the tibia 1320. Talar articular surface 110 may engage tibial articular surface 120 in a manner that generally mimics the engagement (articulation) of a natural ankle joint. The various curvatures of preparation surfaces 620 and 1420, as well as the matching curvatures of talar and tibial engagement surfaces 112 and 122, may help hold talar and

tibial prostheses

102 and 104 in place while retaining sufficient healthy bone to withstand the stresses generated during use of the joint.

In some embodiments (not shown), preparation of the talus 420 and/or tibia 1320 may be facilitated using surgical navigation and/or surgical robotic systems. Some of the steps described above may be automated. Surgical navigation systems, surface mapping systems, and/or the like may be used to determine the location and size of the cut to be made. In addition to or in place of elements of the talus guide assembly and/or tibial guide assembly, the path of motion to the cuts of the talus 420 and tibia 1320 may optionally be mechanized, for example, using a motorized system. Such a motorized system may optionally mimic the motion limits of the talar guide assembly and/or tibial guide assembly, and thus may access and prepare the articular surface from an anterior approach as disclosed herein.

In alternative embodiments, a number of different features may be included in the ankle replacement system. According to some exemplary embodiments, one or more of the following features may be included: (1) the ability to slide the tibial base proximally to enable a more proximal (i.e., deeper) cut in the tibia; (2) a tibial base that can swing in an arc for enhancing the anterior/posterior resection of the tibia; (3) adjusting the ability of the tibial cutting guide to resect varus/valgus and/or medio-lateral position of the tibia; (4) use of a set screws (set screens) to facilitate securing the tibial cutting guide to the tibia; (5) using a talar trial to promote correct placement of tibial resection; (6) patient-specific bone attachment interfaces are used for the talus and/or tibia. These features are shown and described in connection with fig. 17A through 26B.

Figure 17A is a perspective view of talus 420 with talar base 1710 with a portion of trial 400 of figures 4A-4C positioned on concave curve 458 of talus 420 according to an alternative embodiment. Trial 400 may be used to position talar base 1710 relative to talus 420 in much the same manner as described in connection with figures 4A-4C.

Fig. 17B is a perspective view of talar base 1710 of fig. 17A, with talar base 1710 secured to talus 420. Talar base 1710 may have a similar configuration as talar base 410. However, talar base 1710 may have fixation member 1700 and mobile member 1702 configured somewhat differently than their counterparts to talar base 410.

Specifically, fixation member 1700 may also be secured to talus 420 by a pin 480 passing through a channel 510 of fixation member 1700. The fixation member 1700 may also have an arcuate slot 1712 centered on the shaft 514. However, arcuate slot 1712 may not have arcuate groove 516 of arcuate slot 512 of fig. 5C. Further, the securing member 1700 may be absent the pawl 518. Alternatively, the fixation member 1700 may have a detent 1718 in the form of a circular groove positioned in the center of each arcuate slot 1712. Detent 1718 may be used to fix the position of moving member 1702 relative to fixed member 1700 at the center point of arcuate slot 1712, for example, when the tibial base is positioned relative to talar base 1710. A circular fastener (not shown) may be coupled to moving member 1702 and may reside within detent 1718 to lock moving member 1702 in place relative to stationary member 1700.

Moving member 1702 may have a roller 530 that rolls within an arcuate slot 1712 to allow moving member 1702 to pivot about axis 514. Instead of threaded bore 550 of moving member 502, moving member 1702 may have two receiving slots 1750 that extend proximally and open at their proximal ends to receive corresponding features of a talar drill holder, as will be shown and described in connection with fig. 18A and 18B. The moving member 1702 may further have a threaded bore 1760, the threaded bore 1760 receiving a fastener of a talar drill holder.

Referring to fig. 18A, fig. 18B, and fig. 19 in perspective and side views, a cross-sectional view illustrates talar base 1710 of fig. 17A and 17B, talar drill holder 1800 is secured to mobile member 1702 of talar base 1710. Talar bore holder 1800 may have a similar configuration to talar bore holder 600 of fig. 6A and 6B, except that talar bore holder 1800 may be configured to attach to moving member 1702 instead of moving member 502 of fig. 5A-5C.

Specifically, talar drill holder 1800 may have a base 1830 fixed to moving member 1702. The base 1830 may have a pair of flanges 1840 at the inboard and outboard edges that slide into receiving slots 1750 of the moving member 1702. The base 1830 may have a hole 1850 that aligns with a threaded hole 1760 of the moving member 1702. The hole 1850 can receive a bolt 1860 having a threaded end that engages the threads of the threaded hole 1760 to secure the base 1830 to the moving member 1702. The hole 1850 may be vertically elongated to allow for some proximal/distal adjustment of the position of the base 1830 relative to the moving member 1702, thereby allowing the surgeon to adjust the depth of the incision on the talus 420.

Talar base 1710 and talar drill holder 1800 may cooperate to function in a manner similar to talar base 410 and talar drill holder 600 described previously. Talar drill holder 1800 may have arms 640 that move relative to bases 1830, with the connection between arms 640 and bases 1830 providing a constraint. Arm 640 may be coupled to reamer 610 (or any other type of reamer previously described) to guide the motion of reamer 610 to resect talus 420 to form prepared surface 620.

With the talar base 1710 in place, the tibial cutting guide may be referenced on the talar base 1710 and then secured to the tibia. The alignment block may be used for this purpose as will be shown and described in connection with fig. 20A to 22C.

Referring to fig. 20A through 20E, an alignment block 2010 is shown in accordance with an alternative embodiment. The alignment block 2010 may be similar in function to the alignment block 1310, but with some modifications to the additional functionality.

As shown, alignment block 2010 may include mount 2020, adjustment arm 2022, and alignment bar 2024. Fixture 2020 may be secured to mobile member 1702 of talar base 1710 in a manner that allows for in/out adjustment of the position of alignment block 2010 relative to mobile member 1702. Adjustment arm 2022 may be coupled to mount 2020 in a manner that allows for in/out adjustment of the position of alignment block 2010 relative to moving member 1702. The adjustment arm 2022 may also be coupled to a tibial resection guide (shown in subsequent figures) in a manner that allows the position of the tibial resection guide to be adjusted distally/proximally relative to the adjustment arm 2022.

More specifically, the mount 2020 may have two attachment slots 2030 that receive a set screw 2032. The set screw 2032 may have a threaded end that engages threads within the threaded bore 1760 of the moving member 1702. Attachment slot 2030 may be long enough to allow horizontal adjustment of the position of mount 2020 with respect to moving member 1702. If desired, mount 2020 may be fixed in position relative to moving member 1702 by tightening screw 2032, then adjusted by loosening screw 2032, moving mount 2020, and then tightening screw 2032 with mount 2020 in the new position.

Mount 2020 may also have a boss 2034 protruding from the body of mount 2020 toward adjustment arm 2022. The boss 2034 may have a threaded bore 2036. Additionally, mount 2020 may have a threaded bore 2038, with threaded bore 2038 positioned above boss 2034 having threaded bore 2036. The mount 2020 may also have a cover 2040 located over the attachment slot 2030.

Adjustment arm 2022 may have a hole 2050 at its lower end through which bolt 2052 may be inserted and threadably engaged with threaded hole 2036 in boss 2034 of fixture 2020. The bolt 2052 may rotatably reside in the bore 2050 such that the adjustment arm 2022 may pivot about the axis of the bolt 2052 until the adjustment arm 2022 is locked in place relative to the mount 2020. The bolt 2052 may optionally be tightenable to press against the adjustment arm 2022 to lock the adjustment arm 2022 for further rotation relative to the mount 2020.

In addition, the adjustment arm 2022 may have an adjustment slot 2054 above the hole 2050 that has an elongated arcuate shape centered on the center of the hole 2050. Adjustment slot 2054 may receive a bolt 2056 that may be threaded to engage bore 2038 of fixture 2020. The bolt 2056 may reside relatively loosely within the adjustment slot 2054 such that engagement of the bolt 2056 with the adjustment slot 2054 allows the adjustment arm 2022 to rotate relative to the fixture 2020, but abutment of the bolt 2056 with the end of the adjustment slot 2054 limits the degree of rotation of the adjustment arm 2022 relative to the fixture 2020. This relative rotation between the adjustment arm 2022 and the fixture 2020 may allow for adjustment of the medial/lateral position of the resected surface of the tibia at the location where the tibial prosthesis 104 is placed. The bolt 2056 may optionally be tightenable to press against the adjustment arm 2022 to lock the adjustment arm 2022 against further rotation relative to the mount 2020.

The adjustment arm 2022 may also have a tibial base attachment hole 2058 through which the tibial base attachment bolt 2060 may be inserted such that the threaded end of the tibial base attachment bolt 2060 engages a corresponding threaded hole on the tibial base (shown later). As in the tibial base 1300 of fig. 13A and 13B, a threaded hole may optionally be on the vertically moving member with a hole 1342 formed in the button 1340 that slides vertically within the slot 1350. Thus, the tibial base attachment hole 2058 and the tibial base attachment bolt 2060 may couple the adjustment arm 2022 to the tibial base in a manner that allows the vertical (i.e., proximal/distal) position of the tibial base on the tibia to be adjusted, such that the proximal/distal depth of the resected tibia may be adjusted.

The tibial base attachment bolt 2060 may optionally be tightenable to press against the adjustment arm 2022 to lock further rotation of the adjustment arm 2022 relative to the fixture 2020 and/or to lock proximal/distal movement of the tibial cutting guide relative to the adjustment arm 2022. In some embodiments, tightening the tibial base attachment bolt 2060 can lock both further rotation of the adjustment arm 2022 relative to the fixture 2020 and further proximal/distal sliding movement of the tibial base relative to the adjustment arm 2022. Thus, the tibial base attachment bolt 2060 may optionally be tightenable to fix the position of the tibial base relative to the fixture 2020. As previously described, the inward/outward position of mount 2020 with respect to moving member 1702 may be fixed by set screw 2032.

The adjustment arm 2022 may also have a rod bore 2062 that receives the alignment rod 2024. More specifically, the alignment rod 2024 may have a proximal end 2070 and a distal end 2072. The distal end 2072 may be received within the rod bore 2062 such that the alignment rod 2024 is fixed in position relative to the adjustment arm 2022. The alignment rod 2024 may then be used to help adjust the position and/or orientation of the adjustment arm 2022 relative to the moving member 1702. In some examples, the distal end 2072 of the alignment rod 2024 may be aligned with the knee, tibial tubercle, or another anatomical feature to ensure that the adjustment arm 2022 is properly positioned medially/laterally and properly oriented for varus/valgus adjustment. Optionally, the alignment rod 2024 may also be used to facilitate proper anterior/posterior positioning of the tibial base relative to the talar base 1710, as will be discussed later.

Fig. 21A, 21B, 22A, 22B, and 22C are perspective, side, front, perspective, and side cross-sectional views of a talar base 1710 attached to a talus 420, wherein the tibial base 1710 is positioned relative to the tibia 420 using an alignment block 2010 and a tibial trial 2120. Fig. 21A shows the tibial base 2110 secured to the tibia 1320 and fig. 22B shows the isolated tibial trial 2120. As in the previous embodiments, the "tibial cutting guide" may include a tibial base 2110 attachable to the tibia 1320, and a tibial drill holder (shown later) attachable to the tibial base 2110.

Tibial base 2110 may have a structure similar to talar base 1710. Thus, the tibial base 2110 may have a stationary member 2100 and a moveable member 2102. Fixation member 2100 may have two arcuate slots 1712, similar to arcuate slots 1712 of fixation member 1700 of talar base 1710. The moving member 2102 can have two sidewalls 2150, with the rollers 530 extending inwardly and outwardly from the sidewalls 2150 to reside within the arcuate slots 1712 of the fixed member 2100. Thus, the moving member 2102 may rotate about the axis 2114 relative to the stationary member 2100.

The moving member 2102 of the tibial base 2110 can also have buttons 1340 and slots 1350, which can be configured similarly to those of the tibial base 1300 of fig. 13A and 13B. Accordingly, the button 1340 and the slot 1350 can provide proximal/distal adjustment of the position of the tibial base 2110 relative to the adjustment arm 2022 of the alignment block 2010. As best shown in fig. 22C, the button 1340 can receive a threaded end of a tibial base attachment bolt 2060 that secures the adjustment arm 2022 to the moving member 2102 of the tibial base 2110.

Alignment block 2010 may be first secured to mobile member 1702 of talar base 1710 by inserting the threaded end of set screw 2032 into threaded bore 1760 of mobile member 1702 of talar base 1710 and the shank of set screw 2032 is located in attachment slot 2030 of fixture 2020, and then tightening fixture 2020 with respect to mobile member 1702 set screw 2032 in the desired medial/lateral position. Set screw 2032 can be loosened, if desired, and the medial/lateral position of fixture 2020 can be adjusted relative to moving member 1702. Set screw 2032 may then be tightened again to secure mount 2020 to moving member 1702. If desired, the alignment rod 2024 of the alignment block 2010 may be aligned with an anatomical feature, such as a tibial tubercle, to facilitate the medial/lateral positioning.

The adjustment arm 2022 may then be pivotably coupled to the mount 2020. This may be accomplished by inserting the threaded end of bolt 2052 through hole 2050 of adjustment arm 2022 and threading the threaded end into hole 2036 of boss 2034 of fixture 2020. As previously described, some clearance may remain between the shank of bolt 2052 and hole 2050 such that adjustment arm 2022 may be rotated relative to fixture 2020 to allow varus/valgus to adjust the orientation of the tibial prepared surface relative to the talar prepared surface.

The threaded end of bolt 2056 may then be inserted through adjustment slot 2054 and into bore 2038 of fixture 2020 and tightened within bore 2038. As previously described, sufficient clearance may be left between the shank of bolt 2056 and the walls of adjustment slot 2054 to allow the shank of bolt 2056 to slide along the arcuate path between the ends of adjustment slot 2054. This interaction may limit the range of pivotal movement of the adjustment arm 2022 relative to the mount 2020, thereby limiting varus/valgus adjustability between the mount 2020 and the adjustment arm 2022 to an acceptable predetermined range. If desired, the alignment rod 2024 of the alignment block 2010 may be aligned with an anatomical feature, such as a tibial tubercle, to facilitate the varus/valgus positioning.

The tibial base 2110 can then be secured to the adjustment arm 2022. As previously mentioned, this can be accomplished by: the threaded end of the tibial base attachment bolt 2060 is passed through the hole 2050 of the adjustment arm 2022 and the threaded end of the tibial base attachment bolt 2060 is then threaded into position to engage the hole 1342 of the button 1340 in the movable member 2102 of the tibial base 2110. Until the head of the tibial base attachment bolt 2060 is tightened against the adjustment arm 2022, the button 1340 can be slid proximally/distally within the slot 1350, allowing proximal/distal adjustment of the position of the tibial base 2110 relative to the alignment block 2010 and the talar base 1710. This proximal/distal adjustment may allow the surgeon to adjust the depth to which the tibia 1320 is resected. The tibial base attachment bolt 2060 may be tightened so that the head of the tibial base attachment bolt 2060 is tightly against the adjustment arm 2022 to lock the button 1340 from further movement within the slot 1350, thereby preventing further proximal/distal adjustment.

Further adjustment of the position of the tibial base 2110 relative to the talar base 1710 in the anterior/posterior direction may be facilitated through the use of a tibial trial 2120. As best shown in fig. 22B and 22C, tibial trial 2120 may have a simulated talar bearing component 2200 and a tibial adjustment component 2202.

Prior to attaching alignment block 2010 and tibial base 2110 to talar base 1710, simulated talar bearing component 2200 may be shaped to sit on prepared surface 620 of talus 420, which may be formed as previously described. Accordingly, the simulated talar bearing component 2200 may have a bone placement surface 2210 that is the same shape as the talar engaging surface 112 of the talar prosthesis 102. The simulated talar bearing component 2200 may also have an anterior/posterior groove 2220 that generally follows the shape of the talar articular surface 110 of the talar prosthesis 102.

The tibial adjustment component 2202 may have a curved bearing portion 2230 and an anterior tongue 2240. The curved bearing portion 2230 may have an arcuate shape with a radius of curvature that matches the radius of curvature of the anterior/posterior groove 2220 of the simulated talar bearing component 2200. Accordingly, the curved bearing portion 2230 can slide forward and backward within the front/rear groove 2220. As best shown in fig. 22C, a front tongue 2240 may project forward to engage the alignment block 2010. More specifically, the front tongue 2240 may have a rear protrusion 2250 and a front protrusion 2260. The rear protrusion 2250 and the front protrusion 2260 may be spaced apart such that the bottom of the fixture 2020 of the alignment block 2010 is located therebetween, as shown in fig. 22C.

The tibial adjustment component 2202 also may have a pair of indicia 2270 positionable at predetermined anterior-posterior locations on the flexure bearing portion 2230. The markers 2270 may be used by the surgeon to visualize the anterior/posterior position of the curved bearing portion 2230 relative to the talar bearing component 2200. Markers 2270 can be radiopaque, if desired, so that they can be easily detected and viewed by using surgical imaging, such as fluoroscopy.

In operation, the tibial trial 2120 may be positioned such that the anterior tongue 2240 engages the fixture 2020, and the fixture 2020 is between the posterior protrusion 2250 and the anterior protrusion 2260, as best shown in fig. 22C. The tibial base 2110 can be locked such that the mobile member 2102 is in a neutral position relative to the stationary member 2100, as best shown in fig. 21B. This can be achieved by the following steps: the moving member 2102 is moved to an intermediate position relative to the fixed member 2100, and the roller 530 of the moving member 2102 is then locked in the center of the arcuate slot 512, for example, by using a fastener (not shown) that couples the roller 530 to a detent 1718 of the arcuate slot 512.

Talar pedestal 1710 may be initially in an anterior position with roller 530 of translating member 1702 near the bottom of arcuate slot 512 of stationary member 1700. This is also best seen in fig. 21B. From this position, moving member 1702 can move anteriorly, causing alignment block 2010, tibial adjustment component 2202 of tibial trial 2120 (which is coupled to fixture 2020 of alignment block 2010) and tibial base 2110 (which is not yet coupled to tibia 1320) to rotate anteriorly. Once the markings 2270 indicate that the curved bearing portion 2230 is in a generally neutral position relative to the anterior/posterior groove 2220 of the talar bearing assembly 2200 (i.e., antero/posteriorly centered within the anterior/posterior groove 2220), the tibial base 2110 may be considered in the proper anterior/posterior position relative to the talar base 1710.

As described above, once the tibial base 2110 has been properly positioned medially/laterally, varus/valgus, proximally/distally and anteriorly/posteriorly, the tibial base 2110 may be secured to the tibia 1320. Fixation member 2100 may have a channel 510 that receives a pin 480, such as pin 480, that attaches talar base 1710 to talus 420.

To ensure that the process of anchoring the tibial base 2110 to the tibia 1320 using the pin 480 does not shift the position of the tibial base 2110, a hex screw (standoff screw)2180 may be used. The hex screw 2180 may have a threaded shank that is inserted through a threaded hole in the fixation member 2100 of the tibial base 2110 and a blunt end (not shown) that abuts the tibia 1320. Before anchoring the tibial base 2110 to the tibia 1320 by the pin 480, a hex screw 2180 may be inserted into a corresponding hole in the fixation member 2100 and advanced until the blunt end engages the tibia 1320 without significantly penetrating the tibia 1320. Thus, when the pin 480 is driven into the bone, the hex screw 2180 may prevent the fixation member 2100 from moving closer to the tibia 1320. A similar hex screw (not shown) may optionally be used in conjunction with one or more talar components, such as talar base 1710.

Once the tibial base 2110 is secured to the tibia 1320, the alignment block 2010 and the talar base 1710 may be separated from each other, from the tibial base 2110, and from the talus 420, and the alignment block 2010 and the talar base 1710 may be removed to make room for resecting the tibia 1320. This may be accomplished by using tibial drill retainer 2300, which may be similar in function and configuration to talar drill retainer 600 of fig. 6A and 6B. Tibial drill retainer 2300 is shown in greater detail in fig. 23.

Referring to fig. 23, a perspective view illustrates a tibial drill holder 2300 secured to a tibial base 2110 for holding a drill 860 relative to a tibia 1320. The combined tibial base 2110 and tibial drill retainer 2300 may define a tibial guide assembly that guides movement of the drill 860 relative to the tibia 1320 to form a prepared surface on the tibia 1320 that is shaped to receive a prosthesis, such as the tibial prosthesis 104 of fig. 1A-2E.

Specifically, tibial drill holder 2300 may be secured to a mobile member 2102 of tibial base 2110 such that tibial drill holder 2300 is pivotable with mobile member 2102 relative to fixed member 2100 and tibia 1320. The tibial burr holder 2300 may also enable further movement (e.g., medio-lateral and cranio-caudal) of the reamer 860 to produce a desired contour of the prepared surface of the tibia 1320. The use of reamer 860 is exemplary only. One skilled in the art will recognize that a variety of cutting tools may be used to form the prepared surface on the tibia 1320. Such cutting tools may include rotating and/or translating tools, such as reamers, reciprocating saws, and the like.

As shown, tibial drill retainer 2300 may have: a base 2330 fixedly secured to the mobile member 2102 of the tibial base 2110; and an arm 2340 that moves relative to base 2330. In addition to the anteroposterior rotation provided by the movement of the mobile member 2102 relative to the tibia 1320, the movement of the arm 2340 relative to the base 2330 can enable movement of the drill 860 in and out on the tibia 1320.

The base 2330 can also have an arm coupling feature by which the arm 2340 is coupled to the base 2330. Base 2330 and arm 2340 may be movably coupled together by any combination of rotational and/or sliding joints. According to some embodiments, the arm coupling feature provides a rotatable coupling between the base 2330 and the arm 2340.

As shown in fig. 23, the arm coupling feature may include a pin 2310, with the arm 640 rotatably mounted about the pin 2310. The pin 2310 may have a head and a shank (not visible) with male threads that may engage with corresponding female threads in a hole (not visible) in the base 2330. The head may have an interface that allows the head to be rotated with a tool, such as a screwdriver, to facilitate assembly of tibial drill retainer 2300. The head may be located within a hole 2318 in base 2330. A portion of the handle adjacent the head may be smooth so that the arm 2340 may engage and rotate smoothly thereon. The base 2330 can further have two parallel plates, a front plate 2320 and a rear plate 2322, between which the proximal portions of the arms 2340 are captured. A hole 2318 in which the head is located may be formed in the front plate 2320 and a hole in which the shank is anchored may be formed in the rear plate 2322. Thus, the pin 2310 may be inserted rearwardly through the hole 2318 in the front plate 2320 to anchor in the hole in the rear plate 2322.

In addition, base 2330 can have base guide features that facilitate guiding movement of arm 2340 relative to base 2330. The base guide features may cooperate with corresponding arm guide features of the arm 2340 to limit the range of motion of the arm 2340, thereby limiting the attachment of a cutting tool, such as the drill 860, the drill 800, or the drill 830, relative to the tibia 1320. As shown in fig. 23, the base guide feature may include a rectangular recess 2328 with three guide surfaces 2332. A leading surface 2332 for cephalad placement (oriented in a caudal direction, or downward in the view of fig. 23) may be used to limit the movement of the cutting tool in a cephalad direction to the tibia 1320. The inboard and outboard facing guide surfaces 2332 may limit the inboard/outboard movement of the cutting tool, as will be explained in more detail below.

Like arm 640 of calcaneus drill holder 600, arm 2340 may be divided into a first arm member 2350 and a second arm member (not visible). The second arm member may be nested within the first arm member 2350 such that the second arm member may slide within the first arm member 2350 such that the arm 2340 effectively has an adjustable range relative to the pin 2310. A resilient member (not visible) may be used to bias the first arm member 2350 away from the second arm member, thereby urging the arm 2340 to its maximum length. The resilient member may take the form of a linear spring (not visible) which is normally held under compression.

The arm 2340 may have a base coupling feature through which the arm 2340 is coupled to the base 2330. The base coupling features can be configured in a variety of ways and can be designed to mate with the arm coupling features of the base 2330. The base coupling feature may optionally include a slot and bracket, such as slot 960 and bracket 962 of fig. 9A-9C.

The arm 2340 may further have a tool attachment interface to which a cutting tool may be attached. Where the cutting tool is a reamer, such as reamer 860, reamer 800, reamer 830, and/or reamer 610, the tool attachment interface may be referred to as a reamer attachment interface. The reamer attachment interface may be designed to hold any one of reamer 860, reamer 800, and reamer 830 in a fixed relationship with the first arm member 2350. More precisely, the reamer attachment interface may be designed to receive and secure an adapter 730, said adapter 730 being secured to one of reamer 860, reamer 800 and reamer 830.

As in fig. 9A-9C, the reamer attachment interface of fig. 23 may take the form of an attachment sleeve 970, the attachment sleeve 970 having a bore (not visible) sized to receive the cylindrical distal end of adapter 730. The attachment sleeve 970 may also have one or more locking features that may selectively lock the adapter 730 in place relative to the attachment sleeve 970. The locking feature may operate as a bayonet fitting (bayonet fittings) as in fig. 9A to 9C.

Still further, the arm 2340 may have an arm guide feature that cooperates with a base guide feature to limit movement of the arm 2340 relative to the base 2330. The arm guide feature may be any member that can interact with the base guide feature to help limit relative movement between the base 2330 and the arm 2340. Where the base guide feature comprises a guide surface, the arm guide feature may advantageously be a follower which may abut and/or bear against such a guide surface.

In particular, the base guide feature may be a post 2380 protruding from the first arm member 2350 between the pin 2310 and the attachment sleeve 970. The strut 2380 may protrude forward such that the strut 2380 is located in the rectangular recess 2328 of the base 2330. The interaction of the struts 2380 with the guide surfaces 2332 of the rectangular recess 2328 may limit the movement of the attachment sleeve 970 (and thus the cutting tool) to an area having a generally rectangular head boundary. In particular, the guide surface 932 on the top of the rectangular recess 2328 may limit the movement of the cutting tool toward the tibia 1320, thereby controlling the depth of the resection.

More specifically, the guide surface 2332 on the top of the rectangular recess 2328 may prevent the cutter axis 740 of the drill 860, drill 800 or drill 830 from moving closer to the tibia 1320 than the planar boundary. Similarly, guide surfaces 2332 on the sides of rectangular recess 2328 may prevent drill 860, drill 800 or cutting tool axis 740 of drill 830 from moving further inward or outward than the additional planar boundary. Thus, the post 2380 of the arm 2340 may mate with the rectangular recess 2328 of the base 2330 to ensure that the prepared surface of the tibia 1320 has the desired depth, width, and overall shape.

The action of the linear spring within the arm 2340 may also help ensure that the prepared surface of the tibia 1320 has the desired shape. In particular, the pressure exerted by the linear spring may help ensure that the cuts made to the tibia 1320 extend to the entire desired depth, thereby ensuring that the prepared surface has the depth and consistency needed to provide continuous bone to support the tibial prosthesis 104. However, the linear spring may be adjusted to provide a force that may be easily resisted by the surgeon to remove bone with a shallower cut before extending the cutting tool to the full depth allowed by the interaction of the post 2380 and the rectangular recess 2328. Thus, a tibial cutting guide comprising a tibial base 2110 and tibial drill holder 2300 may be used to control resection of the tibia 1320.

With the tibial drill holder 2300 secured to the tibial base 2110, the tibial base 2110 can be used to guide the movement of the tibial drill holder 2300 to resect the tibia 1320, thereby creating a prepared surface on the tibia 1320 to receive the tibial prosthesis 104. The mobile member 2102 of the tibial base 2110 can be unlocked from the neutral position shown in fig. 21B to allow the mobile member 2102, and thus the tibial drill holder 2300 and drill 860, to pivot forward/backward relative to the stationary member 2100 as the tibia 1320 is reamed. The anterior/posterior motion may cause the tibial preparation surface to have a longer anterior/posterior curvature than the length of the cutting element 880 of the broach 860.

Tibial base 2110 may be used to guide the movement of drill 830, drill 860, and/or drill 800 in the same manner that talar base 1710 or talar base 410 guides the movement of drill 610, drill 830, and/or drill 800. The prepared surface on the tibia 1320 may be formed from the posterior or anterior side of the prepared surface. In some embodiments, drill 830 may be first applied to make a relatively shallow cut to tibia 1320, thereby clearing the path for drill 860 and/or drill 800 to enter the joint cavity and/or joint cavity, as well as making deeper cuts to accommodate the shape of tibial engagement surface 122 of tibial prosthesis 104.

More specifically, as with talar base 1710 and talar base 410, the surgeon may hold reamer 830 below the natural articular surface of tibia 1320 against the force of the linear spring within arm 2340, with strut 2380 displaced from guide surface 2332 at the top of rectangular recess 2328 until he or she is ready to begin resecting the natural articular surface of tibia 1320.

The surgeon may then lift drill 830, allowing the linear spring to press drill 830 to engage the natural articular surface of tibia 1320 until post 2380 rests on guide surface 2332 at the top of rectangular recess 2328. The reamer 830 can then be moved inboard and outboard (i.e., side to side) by moving the attachment sleeve 970 inboard and outboard, thereby sliding the strut 2380 inboard and outboard along the guide surface 2332 at the top of the rectangular recess 2328. Struts 2380 may abut guide surfaces 2332 on the left and right sides of rectangular recess 2328 to control the degree of in-out movement of reamer 830.

Once drill 830 has passed beyond the medial-lateral extent of the natural articular surface of tibia 1320, moving member 2102 can be rotated anteriorly or posteriorly relative to stationary member 2100 to move drill 830 toward the opposite (i.e., posterior or anterior) portion of the natural articular surface of tibia 1320. The medial-lateral motion of drill 830 may be repeated to remove material from the opposite portion of the natural articular surface of tibia 1320 as desired. If desired, medial-lateral movement of drill 830 may also be performed during forward or backward rotation of mobile member 2102 to remove material from the entire anterior-posterior curvature of the natural articular surface of tibia 1320.

As previously described, the purpose of reamer 830 may simply be to remove enough material to allow reamer 860 and/or reamer 800 to engage tibia 1320 without obstruction, particularly by removing bone from where shaft 710 of reamer 860 and shaft 710 of reamer 800 are located in future cutting steps. Thus, reamer 830 need not be used to resect the entire natural articular surface of tibia 1320.

Once reamer 830 has passed over the medial-lateral and anterior-posterior extent of the natural articular surface of tibia 1320, reamer 830 may be removed from attachment sleeve 970 and reamer 860 may be alternatively secured to attachment sleeve 970. The drill 860 may then be positioned on the anterior or posterior portion of the natural articular surface of the tibia 1320. The surgeon may hold drill 860 against the force of the linear spring in arm 2340 below the natural articular surface of tibia 1320, which has now been partially resected. Again, the strut 2380 may be displaced from the guide surface 2332 at the top of the rectangular recess 2328 until the surgeon is ready to begin resecting the natural articular surface of the tibia 1320 with the broach 860.

The surgeon may then raise the broach 860, allowing the linear spring in the arm 2340 to press the broach 860 to engage the natural articular surface of the tibia 1320 until the strut 2380 rests on the guide surface 2332 at the top of the rectangular recess 2328. The broach 860 may then be moved inboard and outboard (i.e., side to side) by moving the attachment sleeve 970 inboard and outboard, thereby sliding the strut 2380 inboard and outboard again along the guide surface 2332 at the top of the rectangular recess 2328. Struts 2380 may abut guide surfaces 2332 on the left and right sides of rectangular recess 2328 to control the degree of in-out movement of reamer 860.

Once reamer 860 has passed the medial-lateral extent of the natural articular surface of tibia 1320, if applicable, moving member 2102 can be rotated anteriorly or posteriorly relative to stationary member 2100 to move reamer 860 toward the anterior or posterior portion of the natural articular surface of tibia 1320. During the anterior-posterior motion, the reamer 860 may move in/out to ensure that the prepared surface of the tibia 1320 is fully formed.

As with the prepared surface 620 of the talus 420, it may be desirable to form a slot in the prepared surface of the tibia 1320 so that the preparation may securely receive the keel 312 of the tibial prosthesis 104. The formation of the slot is optional; in some embodiments, the ankle prosthesis may not have a keel or may have a keel with an internal cutting element that forms a slot in response to pressure of the keel against the bone. Further, in some embodiments, the slot may be formed prior to forming the remainder of the prepared surface of the tibia 1320. Thus, for example, drill 800 may be used to form a slot prior to using drill 860 to form a prepared surface of tibia 1320, and drill 800 may be used to form a slot even prior to using drill 830.

After the previous bone removal step is completed (or alternatively, before the above-described steps are performed, as described above), drill 800 may be attached to attachment sleeve 970 of tibial drill holder 2300, with tibial drill holder 2300 secured to mobile member 2102 of tibial base 2110. The drill 800 may then be positioned below a central portion of the prepared surface of the tibia 1320. The surgeon may hold drill 800 below the prepared surface of tibia 1320 against the force of a linear spring in arm 2340. Again, the strut 2380 may be displaced from the guide surface 2332 at the bottom of the rectangular recess 2328 until the surgeon is ready to begin forming a slot in the prepared surface of the tibia 1320 with the drill 800.

The surgeon may then hold drill 800 in a medial-lateral central position and raise drill 800, allowing the linear spring in arm 2340 to compress drill 800 to engage the prepared surface of tibia 1320 until post 2380 rests on guide surface 2332 at the top of rectangular recess 2328. When the cutting element 820 of the drill 800 is raised into the prepared surface of the tibia 1320, the cutting element 820 may form a slot corresponding to the slot 1200 of fig. 12, substantially in the center of the prepared surface of the tibia 1320. The diameter 822 of the cutting element 820 may be substantially equal to the width of the keel 312 of the tibial prosthesis 104. The slot may have a head end with a generally hemispherical concave cross-sectional shape that closely accommodates the semi-circular perimeter 344 of the penetration 342 of the keel 312.

Thus, a prepared surface of the tibia 1320 can be formed that has a shape that is appropriate for the shape of the tibial engagement surface 122 of the tibial prosthesis 104. Once the prepared surface of the tibia 1320 is completely formed, the tibial drill retainer 2300 may be separated from the tibial base 2110 and removed, and the tibial base 2110 may be separated from the tibia 1320 and removed. The joint space may then be prepared to accept the talar prosthesis 102 and the tibial prosthesis 104.

In some embodiments, the talar prosthesis 102 and the tibial prosthesis 104 may be inserted in a generally posterior direction such that the keel 212 of the talar prosthesis 102 slides posteriorly into the slot 1200 of the surface 620 of the talus 420 and the keel 312 of the tibial prosthesis 104 slides posteriorly into the corresponding slot of the prepared tibial surface 1320. Notably, some incidental head/tail movement and/or rotation of the talar prosthesis 102 and/or tibial prosthesis 104 may be applied to fully seat the talar prosthesis 102 and tibial prosthesis 104 in their respective prepared surfaces. However, it is advantageous to minimize the distraction force required in the joint space. Thus, the insertion vectors (insertion vectors) of the talar prosthesis 102 and the tibial prosthesis 104 may advantageously be predominantly posterior.

Furthermore, advantageously, there may be no features protruding into the talus 420 or tibia 1320 that have an anterior or posterior facing surface that would otherwise need to be inserted into the bone along an insertion vector of the head or tail (i.e., proximal or distal). Such insertion vectors may require excessive distraction of the joint space and thus cause injury to the joint tissue as the joint space is expanded to accommodate the necessary cephalad or caudal motion required to place the talar prosthesis 102 or tibial prosthesis 104.

In some embodiments, the guide mechanism may have patient-specific components that are custom manufactured to conform to a portion of the patient's anatomy. Such a guide mechanism may be made for the talus and/or tibia. One example of such a guide mechanism will be shown and described below in connection with fig. 24A through 26B.

Fig. 24A, 24B, and 24C are top, bottom, and side views, respectively, of a patient-specific mounting plate 2400 that can be used as part of a patient-specific guide mechanism for a talus, according to one embodiment. As shown, the patient-specific mounting plate 2400 may have an outward-facing side 2410 that faces away from the bone and an bone-facing side 2420.

The patient-specific mounting plate 2400 may have a bone attachment interface in the form of a bone attachment hole 2430, which may be located on either side of the patient-specific mounting plate 2400, between the lateral-facing side 2410 and the bone-facing side 2420. The bone attachment holes 2430 may receive screws (shown later) that secure the patient-specific mounting plate 2400 to the talus 420. The bone attachment hole 2430 can optionally have a countersink 2460, as shown, that receives the head of the bone screw.

The patient-specific mounting plate 2400 may also have an interface at which the remainder of the fixation members of the talar base may be fixed to the patient-specific mounting plate 2400. In fig. 24A and 24B, the interface consists of a pair of component attachment holes 2440 that extend from an outward facing side 2410 to a bone facing side 2420. The component attachment holes 2440 can accommodate fasteners that attach the patient-specific mounting plate 2400 to another component, as will be shown and described later. The component attachment hole 2440 can optionally be threaded to receive a threaded end of a fastener for securing another component to the patient-specific mounting plate 2400.

As shown in fig. 24B, the bone-facing side 2420 may have a contoured surface 2470 that is shaped to match the contour of the portion of the patient-specific mounting plate 2400 to which the talus 420 is to be attached. The talus 420 may be a portion of the talus 420 in front of and/or around the natural articular surface 422. The contoured surface 2470 can be fabricated by using any process known in the art. In some examples, contoured surface 2470 may be made by exposing an adjoining portion of talus 420, taking a mold of the talus, and then making a model similar to the adjoining portion of talus 420. A pattern may be embossed into the malleable blocks to form the contoured surface.

In an alternative embodiment, CT scan data or other images of the talus 420 may be used to custom manufacture a patient-specific mounting plate 2400 having a contoured surface 2470. For example, the CT scan data may be used in a milling machine to form the contoured surface 2470 in a block of metal, plastic, or other material. In the alternative, such CT scan data may be used during additive manufacturing to customize the patient-specific mounting plate 2400 with a contoured surface 2470 of the patient-specific mounting plate 2400 that precisely matches the shape of the abutment surface of the talus 420.

In any event, the shape of the contoured surface 2470 matches the shape of the adjacent portion of the talus 420. Therefore, with no doubt as to the attachment location of the patient-specific mounting plate 2400, the patient-specific mounting plate 2400 can fit tightly and securely on the talus 420. The process of aligning the patient specific mounting plate 2400 to the talus 420 can be performed while planning the contoured surface 2470. If desired, prior to creating the contoured surface 2470, measurements can be made to determine not only the shape of the contoured surface 2470, but also the exact location and orientation of the contoured surface 2470 in the patient-specific mounting plate 2400, which will result in the creation of a prepared surface at the appropriate location and orientation on the talus 420.

Fig. 25A is a perspective view of a patient specific mounting plate 2400 on talus 420. As shown, lateral side 2410 faces upward, while bone-facing side 2420 faces talus 420, and contoured surface 2470 is positioned against the area of talus 420 that abuts natural articular surface 422. The shape of the contoured surface 2470 may exactly match the shape of the talus 420 in which it is located, and thus the patient-specific mounting plate 2400 may only fit over the talus 420 in one position and orientation. The patient-specific mounting plate 2400 may be secured to the talus 420 using bone screws 2590.

Fig. 25B is a perspective view of the patient-specific mounting plate 2400 and talus 420 of fig. 24A, with a fixation component 2500 secured to the patient-specific mounting plate 2400 to define a fixation member that functions similarly to the fixation component 500 of fig. 5A and 5B, and to the fixation member 1700 of fig. 17A and 17B. The fixing component 2500 may be fixed to the patient-specific mounting plate 2400 by using screws (shown later).

The patient-specific mounting plate 2400 and the fixed component 2500 can cooperate with the moving member to define a talar pedestal 2510. As shown, the moving member may be similar or identical to moving member 1702 of talar base 1710 of fig. 17A and 17B. Once assembled, the talar base 2510 of fig. 25B may be similar in operation to talar base 1710 of fig. 17A and 17B, and may guide rotation of the reamer about axis 2114.

Fig. 26A and 26B are top and side views, respectively, of talar base 2510 of fig. 25A and 25B with talar drill holder 1800 secured to the moving member defined by patient-specific mounting plate 2400 and fixed component 2500. As shown, the patient-specific mounting plate 2400 is secured to the fixation component 2500 using screws 2600. Talar base 2510 may function in a manner similar to talar base 1710 to guide the movement of talar drill holder 1800 to cause reamer 610, reamer 800 and/or reamer 830 to resect natural articular surface 422 to form prepared surface 620 on talar 420.

Fig. 24A-26B depict the use of a patient-specific talar assembly. One skilled in the art will recognize how to form a patient-specific tibial component by using the same principles. Such components may be incorporated into a tibial base, which may function similarly to the tibial base 1300 of fig. 13A-15, or may function similarly to the tibial base 2110 of fig. 21A-21C.

Those skilled in the art will recognize that the previously proposed systems and methods represent only a few of the systems and methods that may be used to perform ankle replacement. Alternative methods, cutting tools, guide assemblies, and implants may be used within the scope of the present disclosure.

Any methods disclosed herein comprise one or more steps or actions for performing the described method. Method steps and/or actions may be interchanged with one another. In other words, unless a specific order of steps or actions is required for proper operation of the embodiment, the order and/or use of specific steps and/or actions may be modified.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the recitation of reference phrases or variations thereof throughout this specification is not necessarily all referring to the same embodiment.

Similarly, it should be appreciated that in the foregoing description of embodiments, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure. However, the methods of the present disclosure should not be construed as reflecting the intent: any claim requires more features than are expressly recited in that claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of any single foregoing disclosed embodiment. Thus, the claims following this detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment. The present disclosure includes all permutations of the independent claims and their dependent claims.

Recitation in the claims of the term "first" with respect to a feature or element does not necessarily imply the presence of a second or additional such feature or element. It will be apparent to those skilled in the art that changes can be made in the details of the above-described embodiments without departing from the underlying principles set forth herein.

While particular embodiments and applications of the present disclosure have been illustrated and described, it is to be understood that the scope of the appended claims is not limited to the precise configuration and components disclosed herein. Various modifications, changes, and variations apparent to those skilled in the art may be made in the arrangement, operation, and details of the methods and systems disclosed herein.

Claims

1. An ankle replacement system comprising: the ankle replacement system comprises:

a talar joint prosthesis comprising:

a talar articular surface shaped to replace a natural talar articular surface; and

a talar engaging surface shaped to engage a talar preparation surface of a talus;

a tibial prosthesis, comprising:

a tibial articular surface configured to replace a natural tibial articular surface and articulate with the talar articular surface; and

a tibial engaging surface configured to engage a tibial preparation surface of a tibia;

wherein the selection of at least one of the talar and tibial engaging surfaces comprises:

a first front-to-back bend extending in a front-to-back direction; and

a first inward-outward bend having a convex shape and extending in an inward-outward direction.

2. The ankle replacement system according to claim 1, wherein: the first front-to-back bend extends in a front-to-back direction along substantially the entire length of the selection.

3. The ankle replacement system according to claim 1, wherein: the option further includes a keel projecting from the first anterior-posterior curvature and extending in the anterior-posterior direction, wherein the keel comprises:

a base portion fixed to or integrally formed with the remainder of the selection; and

a penetration portion extending from the base portion to penetrate the talus preparation surface or the tibial preparation surface, the penetration portion having a generally semi-circular perimeter.

4. The ankle replacement system according to claim 1, wherein:

the talar articular surface comprising:

two convex talar curves extending in the medial-lateral direction; and

a concave talar curvature extending in said medial-lateral direction between said two convex talar curvatures;

the tibial articular surface comprises:

two concave tibial curvatures extending along the medial-lateral direction; and

a convex tibial curvature extending in the medial-lateral direction between the two concave tibial curvatures; and

the talar articular surface and the tibial articular surface are further shaped such that the tibial articular prosthesis is centered on the talar articular prosthesis and the two concave tibial curvatures are substantially flush with the two convex talar curvatures.

5. The ankle replacement system according to claim 1, wherein:

the selection is the talus engaging surface; and

the first front-to-back curve comprises a concave curve.

6. The ankle replacement system according to claim 5, wherein: the talar engaging surface further comprises:

a second inward-outward bend having a convex shape and extending in the inward-outward direction; and

a central flared portion extending in a substantially straight line along the medial-lateral direction between the first medial-lateral bend and the second medial-lateral bend.

7. The ankle replacement system according to claim 6, wherein: the talar engaging surface further includes a keel projecting from the first antero-posterior curvature and extending in the anterior-posterior direction.

8. The ankle replacement system according to claim 1, wherein:

the selection is the tibial engagement surface; and

the first front-to-back bend comprises a convex bend.

9. The ankle replacement system according to claim 8, wherein: the tibial engaging surface further comprises:

10. The ankle replacement system according to claim 9, wherein: the tibial engaging surface further includes a keel projecting from the first anterior-posterior curvature and extending in the anterior-posterior direction.

11. A talar joint prosthesis, comprising: the talar joint prosthesis comprises:

a talar engaging surface shaped to engage a talar preparation surface of a talus, said talar engaging surface comprising:

a first front-to-back bend having a concave shape and extending in a front-to-back direction; and

12. The talar joint prosthesis of claim 11, wherein: the first anterior-posterior curvature extends substantially along an entire length in an anterior-posterior direction of the talar engaging surface.

13. The talar joint prosthesis of claim 12, wherein: the talar engaging surface further comprises:

14. The talar joint prosthesis of claim 13, wherein: the talar engaging surface further comprises: the talar engaging surface further includes a keel projecting from the first antero-posterior curvature and extending in the anterior-posterior direction.

15. The talar joint prosthesis of claim 14, wherein: the keel comprises:

a base fixed to or integrally formed with the remaining talar engaging surface; and

a penetration portion extending from the base portion to penetrate the talus preparation surface, the penetration portion having a substantially semi-circular perimeter.

16. A tibial articular prosthesis characterized by: the tibial joint prosthesis comprises:

a tibial articular surface shaped to replace a natural tibial articular surface; and

a tibial engaging surface configured to engage a tibial preparation surface of a tibia, the tibial engaging surface comprising:

a first front-rear bend having a convex shape and extending in a front-rear direction; and

a first inward-outward bend having a convex shape and extending in the inward-outward direction.

17. A tibial articular prosthesis according to claim 16, wherein: the first anterior-posterior curvature extends along substantially the entire length in the anterior-posterior direction of the tibial engaging surface.

18. A tibial articular prosthesis according to claim 17, wherein: the tibial engaging surface further comprises:

19. A tibial articular prosthesis according to claim 18, wherein: the tibial engaging surface further includes a keel projecting from the first anterior-posterior curvature and extending in the anterior-posterior direction.

20. A tibial articular prosthesis according to claim 18, wherein: the keel comprises:

a base portion fixed to or integrally formed with the remaining tibial engaging surface; and

a penetrating portion extending from the base portion to penetrate the tibial preparation surface, the penetrating portion having a substantially semi-circular periphery.

21. A system for preparing bone for joint replacement, comprising: the system comprises:

a reamer comprising a rotatable cutting element having a shape extending along a length of the rotatable cutting element, the shape selected from a concave shape and a convex shape; and

a cutting guide, comprising:

a bone attachment interface securable to said bone;

a reamer attachment interface securable to the reamer; and

a guide mechanism configured to limit relative movement between the broach attachment interface and the bone attachment interface to facilitate formation of a prepared surface on the bone with the broach, the prepared surface having at least one concave curvature or one convex curvature.

22. The system of claim 21, wherein: the cutting guide further comprises:

a base comprising said bone attachment interface, said base further comprising a bore retainer interface; and

a borehole holder including the reamer attachment interface, the borehole holder further including a base interface coupleable to the borehole holder interface.

23. The system of claim 21, wherein: the guide mechanism allows the reamer attachment interface to move in a first direction perpendicular to the length of the rotatable cutting element.

24. The system of claim 23, wherein: the guide mechanism guides movement of the reamer attachment interface along a line perpendicular to a length of the rotatable cutting element.

25. The system of claim 24, wherein: the shape of the rotatable cutting element is a convex shape including a maximum radius perpendicular to the length such that the preparation surface has a cross-sectional shape including:

a first convex curve having a first radius of curvature substantially equal to the maximum radius;

a second convex curve having a second radius of curvature substantially equal to the maximum radius; and

a central expansion portion extending in a substantially straight line between the first and second convex curves.

26. The system of claim 23, wherein: the guide mechanism also allows the reamer attachment interface to move in a second direction parallel to the length of the rotatable cutting element.

27. The system of claim 26, wherein: the guide mechanism allows the reamer attachment interface to move in the second direction by allowing the reamer attachment interface to rotate about an axis perpendicular to the rotatable cutting element.

28. The system of claim 27, wherein:

the shape of the rotatable cutting element is a concave shape comprising a maximum radius perpendicular to the length such that the preparation surface has a cross-sectional shape comprising:

a central expansion portion extending in a substantially straight line between the first and second convex curves; and

the cross-sectional shape is swept along a convex curve.

29. A method of preparing bone for joint replacement, comprising: the method comprises the following steps:

positioning a cutting guide adjacent the bone, the cutting guide comprising:

a bone attachment interface;

a drill attachment interface; and

a guide mechanism;

securing the bone attachment interface to the bone;

securing the reamer to the reamer attachment interface, the reamer including a rotatable cutting element having a shape extending along a length of the rotatable cutting element, the shape selected from a concave shape and a convex shape; and

guiding movement of the broach relative to the bone with the guide mechanism to facilitate forming a prepared surface on the bone with the broach, the prepared surface having at least one concave curvature or one convex curvature.

30. The method of claim 29, wherein: the cutting guide further comprises:

a drill holder including the drill attachment interface, the drill holder further including a base interface; and

the method also includes connecting a base interface of the borehole holder to a borehole holder interface of the base.

31. The method of claim 29, wherein: guiding the movement of the reamer relative to the bone comprises: with the guide mechanism, the reamer is allowed to move in a first direction perpendicular to the length of the rotatable cutting element.

32. The method of claim 31, wherein: guiding the movement of the reamer relative to the bone further comprises: with the guide mechanism, movement of the reamer attachment interface is guided along a line perpendicular to a length of the rotatable cutting element.

33. The method of claim 32, wherein: the shape is a convex shape including a maximum radius perpendicular to the length such that the preparation surface has a cross-sectional shape including:

34. The method of claim 31, wherein: guiding the movement of the reamer relative to the bone further comprises: allowing the reamer attachment interface to move along a second direction parallel to the length of the rotatable cutting element.

35. The method of claim 34, wherein: guiding the movement of the reamer relative to the bone further comprises: allowing the reamer attachment interface to rotate about an axis perpendicular to the rotatable cutting element.

36. The method of claim 35, wherein:

the shape is a concave shape including a maximum radius perpendicular to the length such that the preparation surface has a cross-sectional shape including:

the cross-sectional shape is swept along a convex curve.

37. A system for preparing an ankle replacement talus or tibia, comprising: the system comprises:

a first reamer comprising a first rotatable cutting element having a first shape, the first rotatable cutting element extending along a length of the first rotatable cutting element, the first shape selected from a concave shape and a convex shape; and

a first cutting guide, comprising:

a first bone attachment interface securable to the talus or the tibia;

a first reamer attachment interface securable to the first reamer; and

a first guide mechanism configured to limit relative movement between the first drill attachment interface and the first bone attachment interface by allowing movement of the first drill attachment interface in a first direction perpendicular to a first length of the first rotatable cutting element to facilitate formation of a first prepared surface on a tibia or talus with the first drill, the first prepared surface having at least one concave curvature or a convex curvature.

38. The system of claim 37, wherein:

the first bone attachment interface may be secured to the talus bone such that the first preparation surface is on the talus bone;

the first guide mechanism also allows movement of the first reamer attachment interface in a second direction parallel to the first length of the first rotatable cutting element by allowing rotation of the first reamer attachment interface about an axis perpendicular to the first rotatable cutting element; and

the first shape is a concave shape such that the first preparation surface has a cross-sectional shape that sweeps along a convex curve.

39. The system of claim 38, wherein: the system further comprises:

a second reamer including a second rotatable cutting element having a convex shape; and

a second cutting guide, comprising:

a second bone attachment interface securable to the tibia;

a second reamer attachment interface securable to the second reamer; and

a second guide mechanism configured to limit relative movement between the second reamer attachment interface and the second bone attachment interface by allowing movement of the second reamer attachment interface in a third direction perpendicular to a second length of the second rotatable cutting element to facilitate formation of a second prepared surface on a tibia utilizing the second reamer, the second prepared surface having at least a concave curvature.

40. The system of claim 39, wherein:

the first cutting guide further comprises:

a first base comprising the first bone attachment interface, the first base further comprising a first bore retainer interface; and

a first borehole holder including the first borehole attachment interface, the first borehole holder further including a first base interface, the first base interface being coupleable to the first borehole holder interface;

the second cutting guide further comprises:

a second base comprising the second bone attachment interface, the second base further comprising a second bore retainer interface; and

a second borehole holder including the second borehole attachment interface, the second borehole holder further including a second base interface, the second base interface being coupleable to the second borehole holder interface; and

the system also includes an alignment block, the alignment block comprising:

a third base interface attachable to the first base; and

a fourth base interface attachable to the second base to facilitate positioning of the second base relative to the first base.

41. A method of performing an ankle joint replacement on an ankle joint comprising a talus and a tibia, comprising: the method comprises the following steps:

exposing an anterior side of the ankle joint;

securing a first cutting guide to a first bone comprising the talus or the tibia;

inserting a first cutting tool into the ankle joint along an anterior path;

guiding movement of said first cutting tool relative to said first bone using said first cutting guide such that said first cutting tool forms a first prepared surface on said first bone, said first prepared surface including a first anterior-posterior curve extending anteroposteriorly; and

placing a first prosthesis on the first prepared surface, the first prosthesis including a first articular surface shaped to replace a first natural articular surface of the first bone.

42. The method of claim 41, wherein:

the first prosthesis comprises a keel;

the method further comprises the following steps:

inserting a second cutting tool into the ankle joint along an anterior path; and

guiding movement of the second cutting tool relative to a first bone with the first cutting guide such that the second cutting tool forms a slot in the first bone, wherein the slot is oriented anteriorly and posteriorly; and

placing the first prosthesis on the first preparation surface comprises: inserting the keel into the slot.

43. The method of claim 41, wherein:

the first bone comprises the tibia;

the first fore-aft bend comprises a concave bend extending fore-aft;

said first prosthesis comprising a convex bone engaging surface; and

placing the first prosthesis on the first preparation surface comprises: inserting the convex bone engaging surface into the concave curvature.

44. The method of claim 41, wherein:

the first bone comprises the talus;

said first anterior-posterior curvature comprises a convex curvature extending antero-posteriorly;

said first prosthesis comprising a concave bone engaging surface; and

placing the first prosthesis on a first preparation surface comprises: positioning the convex curvature in the concave bone engaging surface.

45. The method of claim 44, wherein: the method further comprises the following steps:

exposing an anterior side of the ankle joint;

securing a second cutting guide to the tibia;

inserting the first cutting tool or a second cutting tool into the ankle joint along an anterior path;

guiding movement of the first cutting tool or the second cutting tool relative to the tibia with the second cutting guide such that the first cutting tool or the second cutting tool forms a second prepared surface on the tibia, the second prepared surface including a second anterior-posterior curvature, the second anterior-posterior curvature including a concave curvature extending anteriorly-posteriorly; and

placing a second prosthesis on the second preparation surface, the second prosthesis comprising:

a convex bone engaging surface; and

a second articular surface shaped to replace a second natural articular surface of the tibia;

wherein placing the second prosthesis on the second preparation surface comprises: inserting the convex bone engaging surface into the concave curvature.

46. The method of claim 44, wherein:

the first cutting guide includes:

a talar base including a talar attachment interface and a talar tool holder interface; and

a talar tool holder including a talar tool attachment interface and a talar base interface;

securing the first cutting guide to the first bone comprises: securing the talus attachment interface to the talus;

the method further comprises, prior to guiding movement of the first cutting tool with the first cutting guide:

coupling the talus base to the talus tool holder by coupling the talus tool holder interface to the talus base interface; and

attaching the first cutting tool to the talar tool attachment interface.

47. The method of claim 46, wherein: the method further comprises, prior to securing the talus base to the talus: placing a trial on the talus, wherein the trial is coupled to a distal end of a post; using the post to align the trial with the talus bone by aligning a proximal end of the post with a landmark on a portion of a patient's leg proximal to the talus bone; and aligning the talar base with the trial.

48. The method of claim 46, wherein: the method further comprises the following steps:

interfacing a talar base of an alignment block to the talar base;

connecting a tibial base interface of the alignment block to a tibial base, the tibial base including a tibial attachment interface and a tibial tool holder interface;

securing the tibial attachment interface to the tibia; and

connecting the tibial tool holder to the tibial base by connecting the tibial tool holder interface to a tibial base interface of the tibial tool holder, wherein the tibial base and the tibial tool holder constitute a second cutting guide.

49. The method of claim 48, wherein: the method further comprises the following steps:

a tibial tool attachment interface to attach the first cutting tool or a second cutting tool to a tibial tool holder;

inserting the first cutting tool or the second cutting tool into the ankle joint along an anterior path; and

guiding movement of the first cutting tool or the second cutting tool in a medial-lateral direction relative to the tibia with the second cutting guide such that the first cutting tool or the second cutting tool forms a second prepared surface on the tibia, the second prepared surface including a second anterior-posterior curvature, the second anterior-posterior curvature including a concave curvature extending anteriorly.

50. The method of claim 44, wherein: the step of guiding the first cutting tool in motion relative to the first bone to form the first prepared surface includes moving the first cutting tool in a medial-lateral direction.

51. The method of claim 50, wherein: the step of guiding the first cutting tool to move relative to the first bone to form the first prepared surface further comprises: rotating the first cutting tool about a medially and laterally extending axis relative to the first bone to move the first cutting tool fore and aft.

52. A method of performing an ankle joint replacement on an ankle joint comprising a talus and a tibia, comprising: the method comprises the following steps:

exposing an anterior side of the ankle joint;

securing a talar cutting guide to the talus;

inserting a first cutting tool into the ankle joint along an anterior path;

guiding movement of the first cutting tool relative to the talus bone with the talar bone cutting guide such that the first cutting tool rotates about a medially and laterally extending axis relative to the talus bone to move the first cutting tool anteriorly and posteriorly to form a first prepared surface on the talus bone, the first prepared surface including a first anteroposterior curve extending anteroposteriorly; and

placing the talar prosthesis on the first prepared surface, the talar prosthesis including a talar articular surface shaped to replace a natural talar articular surface of the talus.

53. The method of claim 52, wherein:

the talar prosthesis includes a keel;

the method further comprises the following steps:

guiding movement of the first cutting tool or the second cutting tool relative to the talus bone with the talar cutting guide to cause the first cutting tool or the second cutting tool to form a slot in the talus bone, wherein the slot is oriented anteroposteriorly; and

placing the talar prosthesis on the first preparation surface comprises: inserting the keel into the slot.

54. The method of claim 52, wherein: the step of guiding the first cutting tool to move relative to the talus to form a first prepared surface further comprises: moving the first cutting tool in an inner-outer direction.

55. The method of claim 54, wherein: the method comprises the following steps:

securing a tibial cutting guide to the tibia;

guiding movement of the first cutting tool relative to the tibia with the tibial cutting guide to cause the first cutting tool or the second cutting tool to move in and out to form a second prepared surface on the tibia, the second prepared surface including a second anterior-posterior curve extending anteroposteriorly; and

placing a tibial prosthesis on the second prepared surface, the tibial prosthesis including a tibial articular surface shaped to replace a natural tibial articular surface of the tibia.

56. The method of claim 52, wherein: the method comprises the following steps:

the talar cutting guide comprises:

securing the talar cutting guide to the talus comprises: securing the talus attachment interface to the talus;

the method further comprises, prior to guiding movement of the first cutting tool with the talar cutting guide:

connecting the first cutting tool to the talar tool attachment interface.

57. The method of claim 56, wherein: the method comprises the following steps:

interfacing a talar base of an alignment block to the talar base;

securing the tibial attachment interface to the tibia; and

connecting the tibial tool holder to the tibial base by connecting the tibial tool holder interface to a tibial base interface of a tibial tool holder, wherein the tibial base and the tibial tool holder comprise a second cutting guide.

58. A method of performing an ankle joint replacement on an ankle joint comprising a talus and a tibia, comprising: the method comprises the following steps:

exposing an anterior side of the ankle joint;

securing a talar cutting guide to the talus;

inserting a first cutting tool into the ankle joint along an anterior path;

guiding movement of the first cutting tool relative to the talus bone with the talar cutting guide such that the first cutting tool forms a first prepared surface on the talus bone, the first prepared surface including a first anterior-posterior curve extending anteroposteriorly;

securing a tibial cutting guide to the tibia;

inserting the first cutting tool or a second cutting tool into the ankle joint along the anterior path;

guiding movement of the first cutting tool or the second cutting tool relative to the tibia with the tibial cutting guide such that the first cutting tool or the second cutting tool forms a second prepared surface on the tibia, the second prepared surface including a second anterior-posterior curvature extending anteroposteriorly;

placing a talar prosthesis on the first prepared surface, the talar prosthesis including a talar articular surface shaped to replace a first natural articular surface of the talar; and

placing a tibial prosthesis on the second prepared surface, the tibial prosthesis including a tibial articular surface shaped to replace a second natural articular surface of the tibia.

59. The method of claim 58, wherein: the method comprises the following steps:

the talar prosthesis comprises a talar keel;

the tibial prosthesis comprises a talar keel;

the method further comprises the following steps:

guiding movement of the first cutting tool, the second cutting tool, or a third cutting tool relative to the talus bone with the talus bone cutting guide to form a first slot in the talus bone, wherein the first slot is oriented anteroposteriorly;

guiding movement of the first cutting tool, the second cutting tool, the third cutting tool, or a fourth cutting tool relative to the tibia with the tibial cutting guide to form a second slot in the tibia, wherein the second slot is oriented anteroposteriorly;

placing the talar prosthesis on the first preparation surface comprises: inserting the talus keel into the first slot; and

placing the tibial prosthesis on the second preparation surface comprises: inserting the tibial keel into the second slot.

60. The method of claim 58, wherein: the method comprises the following steps:

the talar cutting guide comprises:

a talus base; and

a talar tool holder;

the tibial cutting guide comprises:

a tibial base; and

a tibial tool holder;

securing the talar cutting guide to the talus comprises: securing the talus base to the talus;

the method further comprises, prior to guiding movement of the first cutting tool or the second cutting tool with the tibial cutting guide:

interfacing a talar base of an alignment block to the talar base; and

coupling a tibial base interface of the alignment block to a tibial base; and

securing the tibial cutting guide to the tibia comprises: securing the tibial base to the tibia by attaching the talar base interface to the talar base and attaching the tibial base interface to the tibial base.

61. A system for preparing bone for joint replacement, comprising: the system comprises:

a cutting tool;

a guide assembly securable to the bone, the guide assembly comprising:

a base, comprising:

a first coupling feature; and

a first guide feature; and

an arm, comprising:

a second coupling feature movably coupled to the first coupling feature;

a tool attachment interface attachable to the cutting tool; and

a second guide feature;

wherein:

one of the first and second guide features comprises: a guide surface having a predetermined shape; and

the other of the first and second guide features comprises: a follower configured to slide along the guide surface to limit movement of the tool attachment interface relative to the base.

62. The system of claim 61, wherein: the first and second coupling features are coupled together to allow rotation of the arm relative to the base about an arm rotation axis.

63. The system of claim 62, wherein: the guide surface faces the arm rotation axis or faces away from the arm rotation axis.

64. The system of claim 63, wherein: the guide surface has a planar shape configured to prevent movement of a cutting tool shaft of the cutting tool beyond a planar boundary to prevent over-penetration of the bone by the cutting tool.

65. The system of claim 64, wherein: the cutting tool includes a reamer having a cutting element that rotates about the cutting tool axis.

66. The system of claim 63, wherein: the guide surface is on the base and the follower is on the arm.

67. The system of claim 66, wherein: the follower comprises a cylindrical post projecting from the remainder of the arm.

68. The system of claim 63, wherein: the arm includes:

a first arm member having at least a portion of the second coupling feature; and

a second arm member slidably coupled to the first arm member having the tool attachment interface and the second guide feature.

69. The system of claim 68, wherein: the system further includes a resilient member urging the follower toward the guide surface and the cutting tool toward the bone.

70. The system of claim 63, wherein: the introducer assembly further includes a base, the base including:

a bone attachment interface attachable to the bone; and

a base attachment interface attachable to a base attachment interface of the base.

71. The system of claim 70, wherein: the base further includes:

a fixation member having the bone attachment interface; and

a moving member coupled to the fixed member such that the moving member is rotatable relative to the fixed member about a base axis perpendicular to the arm rotation axis, the moving member having the base attachment interface.

72. The system of claim 70, wherein:

the bone comprises a talus or a tibia; and

the bone attachment interface is configured to attach the base to the talus or the tibia proximate an ankle joint defined by the talus and the tibia.

73. A method of preparing bone for joint replacement, comprising: the method comprises the following steps:

securing a guide assembly to the bone, the guide assembly comprising:

a base, comprising:

a first coupling feature; and

a first guide feature; and

an arm, comprising:

a second coupling feature movably coupled to the first coupling feature;

a tool attachment interface; and

a second guide feature;

attaching a cutting tool to the tool attachment interface; and

moving the arm relative to the base to guide movement of the cutting tool relative to the bone such that the cutting tool forms a prepared surface on the bone;

wherein:

the other of the first and second guide features comprises: a driven member; and

the step of moving the arm relative to the base comprises: sliding the follower along the guide surface to limit movement of the tool attachment interface relative to the base.

74. The method of claim 73, wherein:

the step of moving the arm relative to the base comprises: rotating the arm relative to the base about an arm rotation axis; and

the guide surface faces the arm rotation axis or faces away from the arm rotation axis.

75. The method of claim 73, wherein:

the guide surface has a planar shape;

the cutting tool includes a reamer having a cutting element that rotates about a cutting tool axis; and

sliding the follower along the guide surface to limit movement of the tool attachment interface relative to the base comprises: preventing movement of the cutting tool shaft beyond a planar boundary to prevent over-penetration of the bone by the reamer.

76. The method of claim 73, wherein:

the arm includes:

a second arm member slidably coupled to the first arm member, having the tool attachment interface and the second guide feature;

sliding the follower along the guide surface to limit movement of the tool attachment interface relative to the base comprises: sliding the second arm member relative to the first arm member.

77. The method of claim 76, wherein:

the introducer assembly further comprises a resilient member; and

sliding the follower along the guide surface to limit movement of the tool attachment interface relative to the base further comprises: with the resilient member, the follower is urged towards the guide surface and the cutting tool is urged towards the bone.

78. The method of claim 73, wherein:

the introducer assembly further includes a base, the base including:

a fixation member having a bone attachment interface; and

a moving member rotatably coupled to the stationary member, the moving member having a base attachment interface;

the step of securing the guide assembly to the bone comprises: attaching the bone attachment interface to a talus;

the method further comprises the following steps: attaching a base attachment interface of the base to the base attachment interface prior to moving the arm relative to the base to guide movement of the cutting tool relative to the bone; and

moving the arm relative to the base to guide movement of the cutting tool relative to the bone further comprises: rotating the moving member relative to the fixed member about a base axis.

79. The method of claim 73, wherein:

the introducer assembly further includes a base, the base including:

a bone attachment interface; and

a base accessory interface;

securing the guide assembly to the bone comprises: attaching the bone connection interface to the tibia; and

the method further comprises the following steps: attaching a base attachment interface of the base to the base attachment interface prior to moving the arm relative to the base to guide movement of the cutting tool relative to the bone.

80. A system for preparing a talus or tibia for ankle replacement, comprising: the system comprises:

a drill including a cutting element rotatable about a drill axis; and

a guide assembly securable to the talus or the tibia, the guide assembly comprising:

a base, comprising:

a first coupling feature; and

a first guide feature; and

an arm, comprising:

a first arm member including at least a portion of a second coupling feature coupled to the first coupling feature to allow the arm to rotate relative to the base about an arm rotation axis; and

a second arm member slidably coupled to the first arm member, comprising:

a tool attachment interface attachable to the reamer; and

a second guide feature; and

an elastic member;

wherein:

one of the first and second guide features comprises: a guide surface having a predetermined shape configured to prevent movement of the reamer shaft beyond a planar boundary to prevent excessive penetration of the reamer into the talus or the tibia;

the other of the first guide feature and the second guide feature comprises a follower configured to slide along the guide surface to limit movement of the tool attachment interface relative to the base; and

the resilient member urges the follower toward the guide surface and urges the reamer toward the talus or the tibia.