WO2016026007A1

WO2016026007A1 - Knee prosthesis apparatus and methods and instrumentation for implantation thereof

Info

Publication number: WO2016026007A1
Application number: PCT/AU2015/050482
Authority: WO
Inventors: Frederick HOE
Original assignee: Hoe Frederick
Priority date: 2014-08-21
Filing date: 2015-08-21
Publication date: 2016-02-25

Abstract

Knee prosthesis apparatus is disclosed in which a bearing and a tibial component are interconnected by receipt of anterior and posterior buttresses in anterior and posterior recesses wherein, after interconnection, a filler member is used to fill a gap between first and second surfaces of the apparatus. Knee prosthesis apparatus is also disclosed in which a bearing and a tibial component comprise a plurality of pegs and holes, wherein the bearing and tibial component are releasably engaged by location of at least some of the plurality of pegs in at least some of the plurality of holes. A femoral component for a knee prosthesis is also disclosed that includes a patella flange having a trochlear groove surface, wherein a lateral transition between a lateral flank of the trochlear groove surface and a lateral surface of the patella flange is a substantially smooth transition and a medial transition between a medial flank of the trochlear groove surface and a medial surface of the patella flange is a substantially angular transition. Methods and instrumentation for rotationally orienting a first prosthetic component of a knee prosthesis at a resected surface of a first bone are also disclosed.

Description

Knee prosthesis apparatus and methods and instrumentation for implantation thereof

Cross-Reference to Related Applications

[0001] The present application claims priority from Australian provisional patent application no. 2014903294 filed on 21 August 2014, Australian provisional patent application no. 2014904897 filed on 3 December 2014, Australian provisional patent application no. 2015900678 filed on 26 February 2015, and Australian provisional patent application no. 2015903360 filed on 19 August 2015, the contents of which provisional patent applications are incorporated herein by reference.

Technical Field

[0002] The present disclosure relates to knee prosthesis apparatus used in knee replacement surgery.

Background

[0003] Knee replacement surgery is a surgical procedure performed to replace weight -bearing surfaces of a knee joint.

[0004] The surgical procedure commonly involves implantation of a knee prosthesis that includes a femoral component that replaces the distal end of the femur, a bearing and a tibial component that replace the proximal end of the tibia and the menisci. A tibial tray is commonly used as the tibial component, the tray being attached to the tibia and defining a recess that receives the bearing. The bearing provides a surface against which condyle surfaces of the femoral component articulate during use. The femoral component includes a trochlear or patella flange including a trochlear groove (sulcus) that an articular surface of the native patella, or of a modified version of the native patella, bears against and articulates along during use-.

[0005] Forces applied to the bearing by the femoral component during articulation are complex, and adequate retention of the bearing by the tibial component must therefore be provided to avoid undesirable displacement. Typically, this is achieved by providing a bearing that has a size and shape corresponding to the size and shape of the recess in which it is received, thus ensuring a secure fit between the two components.

[0006] However, due to the wide range of sizes of knee prostheses and their components required for the general population, it is desirable to have a knee prosthesis system which allows broad interchangeability between bearings and tibial components of different sizing, without compromising secure engagement therebetween.

[0007] One attempt at introducing interchangeability between differently sized tibial components and bearings is described in US Patent No. 8,128,703. A tibial component is provided that has elongate buttresses along a surface thereof, the buttresses including a number of undercut portions. A bearing is provided that has interconnected, elongate recesses, the recesses including tabs. To secure the bearing to the tibial component, the buttresses are received in the recesses and tabs are snap-fitted in the undercuts.

[0008] Although commonly considered as a single joint, a knee joint or a knee prosthesis includes two separate articulations. The first articulation is between the femoral and the tibial components (the tibio-femoral articulation). The second articulation is between the femoral component and the patella component or native patella (the patello-femoral articulation).

[0009] Patello-femoral articulation has been a common source of complications following total knee replacement surgery due to, among other factors, the complexity of the surfaces of the patella and the femur. Patients can experience considerable pain due to inappropriate surface topography or support for the patella. Dislocation of the patella from the trochlear groove can also take place. Further, more limited flexion properties for the knee post-operation is commonplace. Moreover, excessive wear of the prosthesis regularly occurs.

[0010] When modified, the native patella is typically resurfaced by inclusion of a prosthetic patella component. The patella component includes an articular surface adapted to replace the native articular surface of the patella. In the process of resurfacing the native patella, the surgeon typically everts the patella such that the native articular surface of the patella faces towards the surgeon. A portion of the patella including the native articular surface of the patella is then resected, leaving a resected bone surface on the patella. Typically, holes are drilled in the resected surface of the patella to receive protrusions such as pegs that extend from an engagement surface of the patella component. The engagement surface of the patella component is located on an opposite side of the patella component to the articular surface of the patella component.

[0011] The pegs of the patella component are inserted in the drill holes in the resected surface of the patella to attach the patella component to the patella. Bone cement may also be applied. The positioning of the drill holes in the resected surface of the patella therefore determines the rotational orientation of the patella component about an axis perpendicular to the resected surface.

[0012] A prosthetic patella component can be provided in a symmetrical or non-symmetrical configuration. Generally, a symmetrical patella component has an apex on its articular surface, with the surface profile of the articular surface being consistent in all radial directions from the apex. On the other hand, a non-symmetrical patella component can have an apex on its articular surface with the surface profile of the articular surface being non-consistent in all radial directions from the apex.

[0013] A symmetrical patella is therefore easy to orientate on the resected surface of the patella as the rotational orientation of its articular surface relative to the resected surface is not important. However, symmetrical patella components may not provide an optimal shape for articulating with the trochlear groove surface. [0014] Non-symmetrical patella components can provide a more optimal shape for articulating with the trochlear groove surface. When a non-symmetrical patella component is used, however, the rotational orientation of the articular surface of the patella component relative to the resected surface is critical to ensure congruent contact of the articular surface with the trochlear groove surface. It can be difficult to determine the orientation of the patella once it has been everted and once landmarks of the patella have been resected, and therefore difficult to determine an appropriate rotational orientation of the patella component relative to the resected surface of the patella.

[0015] In addition to appropriately orienting the patella component, another goal at the end of knee replacement surgery is to have the rotational orientation of the femoral and tibial components matching each other in a plane perpendicular to the long axis of the leg, with the knee in the extended position. When this goal is achieved, twisting of the soft tissues and ligaments surrounding the knee is reduced. There is evidence that, if a tibial tray is implanted in a mal- rotated position, it may lead to pain, patella maltracking, tibial tray loosening and patient dissatisfaction.

[0016] During a total knee replacement procedure the surgeon has to determine the correct rotational position of the tibial component on a planar resected surface at the proximal end of the tibia. One method is to position the tibial component using various landmarks on the tibia as points of reference. However, these landmarks tend to be unreliable due to variations in anatomy and difficulty of visualisation. Another method to position the tibial component is to allow the femoral component to determine the position of the tibial component. In this method, the tibial component is loosely placed on the resected proximal surface of the tibia and allowed to slide and/or rotate ("float") into a position where it registers against a distal surface of the femoral component. To facilitate this method, most current knee replacement systems provide marks on the periphery of the tibial component which the surgeon can use to make corresponding mark(s) on the periphery of the tibia bone while the tibial tray is registered against the femur, with the knee in the extended position. The mark(s) on the bone can be used in a later step to define the position of a tibial drilling template and therefore the ultimate position of the fixed tibial component. However, one or two marks on the periphery of the tibia can have limited ability in accurately defining appropriate positioning of the tibial component.

Summary

Bearing and tibial component engagement using filler member

[0017] According to one aspect, the present disclosure provides knee prosthesis apparatus, comprising:

a bearing comprising a first engagement surface, the first engagement surface comprising an anterior edge and a posterior edge, the bearing further comprising an anterior recess adjacent the anterior edge of the first engagement surface and a posterior recess adjacent the posterior edge of the first engagement surface;

a tibial component comprising a second engagement surface, the second engagement surface comprising an anterior edge and a posterior edge, the tibial component further comprising an anterior buttress adjacent the anterior edge of the second engagement surface and a posterior buttress adjacent the posterior edge of the second engagement surface,

wherein the anterior buttress is locatable at a position in the anterior recess, and the posterior buttress is locatable at a position in the posterior buttress, to interconnect the bearing and the tibial component;

wherein, when the bearing and tibial component are interconnected, a gap is provided between a first gap surface and a second gap surface of the apparatus, the first gap surface being a posterior surface of the anterior buttress and the second gap surface being a posterior surface of the anterior recess; and

wherein the apparatus further comprises:

one or more filler members configured to locate in and fill the gap between the first and second gap surfaces.

[0018] According to one aspect, the present disclosure provides a method of implanting a knee prosthesis, comprising:

interconnecting a bearing and a tibial component,

wherein the bearing comprises:

a first engagement surface, the first engagement surface comprising an anterior edge and a posterior edge, the bearing further comprising an anterior recess adjacent the anterior edge of the first engagement surface and a posterior recess adjacent the posterior edge of the first engagement surface;

wherein the tibial component comprises:

a second engagement surface, the second engagement surface comprising an anterior edge and a posterior edge, the tibial component further comprising an anterior buttress adjacent the anterior edge of the second engagement surface and a posterior buttress adjacent the posterior edge of the second engagement surface,

wherein the interconnecting of the bearing and a tibial component comprises locating the anterior buttress at a position in the anterior recess and locating the posterior buttress at a position in the posterior buttress;

wherein, when the bearing and tibial component are interconnected, a gap is provided between a first gap surface and a second gap surface, the first gap surface being a posterior surface of the anterior buttress and the second gap surface being a posterior surface of the anterior recess; the method further comprising locating one or more filler members in the gap between the first and second gap surfaces to fill the gap.

[0019] In the above aspects, after location in the gap, the one or more filler members may fill the gap by extending between and engaging both the first and second gap surfaces. The one or more filler members may prevent relative movement of the first and second gap surfaces at least towards each other, in an anterior/posterior direction. By locating in the gap, the one or more filler members may provide for secure interconnection between the bearing and the tibial component. For example, it may not be possible or it may be very difficult, manually or otherwise, to release the interconnection between the bearing and tibial component when the one or more filler members are located in the gap.

[0020] The one or more filler members may be releasable from the gap. Alternatively, the one or more filler members may be configured to remain substantially fixed in the gap.

[0021] Configuring the bearing and tibial component such that a gap is present between the first and second surfaces after interconnection between the bearing and the tibial component may be necessary or desirable in view of the manner in which the bearing and tibial component may move relative to each other in order to achieve the interconnection. The gap may result from providing an anterior recess that is large enough to both accommodate the anterior buttress and allow relative movement between the bearing and tibial component in an anterior/posterior direction while the anterior buttress is located in the anterior recess. Such relative movement in an anterior/posterior direction between the bearing and the tibial component, when the anterior buttress is located in the anterior recess, may be necessary to achieve the interconnection between the bearing and the tibial component. For example, the interconnection may rely on this relative movement to cause engagement between locking elements of the bearing and tibial component. The locking elements may restrict movement of the bearing and tibial component at least in a super/inferior direction, for example.

[0022] As an example of a locking element, the posterior buttress may comprise one or more anterior tabs that project in an anterior direction from an anterior surface of the posterior buttress. The anterior tabs may define one or more anterior grooves of the posterior buttress that are located between the anterior tabs and the second engagement surface of the bearing. As another example of a locking element, an anterior surface of the posterior recess may comprise one or more anterior tabs that project in a posterior direction from the anterior surface of the posterior recess. The anterior tabs of the posterior recess may define one or more anterior grooves of the posterior recess that are located between a bottom surface of the recess and the anterior tabs.

[0023] In use of the apparatus, the first and second engagement surfaces may be moved substantially in a superior/inferior direction towards each other so that they are brought into abutment at a first position of the apparatus. As they are brought into abutment, the anterior buttress may locate in the anterior recess and the posterior buttress may locate in the posterior recess. While the apparatus is in the first position, with the anterior buttress located in the anterior recess and the posterior buttress located in the posterior recess, the first and second gap surfaces may be touching or relatively close to each other such that the gap between the first and second gap surfaces is substantially not present or is relatively small.

[0024] The apparatus may then be moved from the first position to a second position to achieve the interconnection between the bearing and the tibial component. When the apparatus is moved from the first to the second position, the bearing and the tibial component, and therefore the first and second engagement surfaces, may be caused to move (e.g., slide) relative to each other substantially in an anterior/posterior direction, at which point the one or more anterior tabs of the posterior buttress may travel towards and locate in the one of more anterior grooves of the posterior recess and the one or more anterior tabs of the posterior recess may travel towards and locate in the one or more anterior grooves of the posterior buttress. While this happens, the anterior buttress may also move substantially in an anterior/posterior direction within the anterior recess. The movement of the anterior buttress within the anterior recess may cause the first and second gap surfaces to move apart such that the gap between the first and second gap surfaces is created or enlarged.

[0025] Once the apparatus is in the second position and the bearing and tibial component are interconnected, the one or more filler members may be positioned in the gap between the first and second gap surfaces. The one or more filler members when positioned in the gap may restrict or substantially prevent relative movement of first and second gap surfaces in the anterior/posterior direction, and therefore also prevent relative movement of the bearing and tibial component in the anterior/posterior direction. Accordingly, secure engagement between the anterior tabs and grooves can be maintained, which in turn can restrict or substantially prevent relative movement of the first and second surfaces in the superior/inferior direction. Thus, it may not be possible to release interconnection between the bearing and the tibial component, at least without first releasing one or more of the filler members from the gap.

[0026] While two separate movements are described above, in particular relative movement between the bearing and tibial component in a superior/inferior direction to arrive at the first position substantially followed by relative movement between the bearing and the tibial component in an anterior/posterior direction to arrive at the second position, the movements may not be mutually exclusive. In some instances a portion of the two movements may occur concurrently. For example, some relative movement of the bearing and tibial component in the anterior/posterior direction may commence prior to completion of movement of the bearing and tibial component in the inferior/superior direction. [0027] The posterior buttress of the tibial component may have a V-shape. For example, the posterior buttress may comprise two substantially straight sidewalls that project from the second engagement surface and extend at an angle to each other to form the V-shape. The angle may be between about 20° and 90°, for example. Surfaces of the two sidewalls may in combination provide the anterior surface of the posterior buttress. The one or more anterior tabs that project in an anterior direction from the anterior surface of the posterior buttress, and that define the anterior grooves, may be formed in the two sidewalls. The two sidewalls may extend on respective sides of a posterior notch in the tibial component that is adapted to receive the posterior cruciate ligament (PCL) of the knee joint when the apparatus is implanted.

[0028] The posterior recess may have a V-shape that is reciprocal to the V-shape of the posterior buttress. For example, the posterior recess may have two substantially straight surfaces that extend at an angle to each other to at least partially define the V-shape. The angle may be between about 20° and 90°, for example. The two surfaces may in combination provide the anterior surface of the posterior recess. The two surfaces may extend on respective sides of a posterior notch in the bearing that is adapted to receive the posterior cruciate ligament (PCL) of the knee joint when the apparatus is implanted, and that is adapted to align with the posterior notch of the tibial component when the bearing and tibial component are interconnected.

[0029] The one or more filler members may have an anterior surface and a posterior surface. The one or more filler members may be advanced into the gap substantially in a lateral/medial direction. The first and second gap surfaces may not only define the gap but may also serve to guide or channel the one or more filler members into the gap.

[0030] The one or more filler members may be in the form of a wedge. For example, a single filler member in the form of a wedge, or multiple filler members that combine to form a wedge, may be wedged between the first and second gap surfaces. The wedge may taper towards a leading end, the leading end being introduced first into the gap. The wedge may have a taper of between about 2° and 7°, for example.

[0031] As the one or more filler members are advanced into the gap, the anterior surface of the one or more filler members may move into engagement with the first gap surface and the posterior surface of the one or more filler members may move into engagement with the second gap surface. As the one or more filler members are further advanced, a pressure between the anterior and posterior surfaces and the first and second gap surfaces may increase such that they are held firmly in place by a frictional force.

[0032] The one or more filler members may be curved. For example, the anterior and/or posterior surface of the one or more filler members may be curved. The first and/or second gap surfaces gap may be curved. The first and second gap surfaces may have a curvature conforming to a curvature of the anterior and posterior surfaces, respectively, of the one or more filler members. For example, the first gap surface may have a curvature of a first radius and the anterior surface of the one or more filler members may also have a curvature of the first radius. Similarly, the second gap surface may have a curvature of a second radius and the posterior surface of the one or more filler members may also have a curvature of the second radius. Where the one or more filler members have a wedge shape, the first radius and second radius may be different.

[0033] Whether or not the one or more filler members are wedge-shaped and/or curved, the first and/or second gap surfaces may comprise a plurality of first teeth and the anterior and/or posterior surfaces of the one or more filler members may comprise a plurality of second teeth adapted to engage the first teeth when the one or more filler members are moved into the gap. The engagement between the first and second teeth may be such that, at least after the one or more filler members are advanced into the gap to a position where they engage both the first and second gap surfaces, the one or more filler members may be substantially non-removable from the gap, e.g., at least in an opposite direction to the direction in which they were advanced into the gap. The teeth may provide for a locking mechanism between the one or more filler members and the bearing/tibial component. Other locking mechanisms may be provided, however. For example, any one of more of the first and second gap surfaces and the anterior and posterior surfaces of the one or more filler members may be roughened or include other surfaces features to provide for frictional lock therebetween. As another example, a fixation element such as a screw or pin may be employed.

[0034] The one or more filler members may have a variety of different sizes, e.g. due to having different lengths and/or widths. For example, filler members of greater length may be provided when used with tibial components of greater size.

[0035] In any of the aspects described herein, the manner in which the tibial component and bearing are interconnected, and the use of the one or more filler members, may prevent relative translation, rotation and/or tilting between the bearing and the tibial component when subjected to forces during use.

[0036] In the present disclosure, the arrangements of buttresses, recesses and filler members may enable broad interchangeability between bearings and tibial components of different sizes to be achieved without compromising secure engagement therebetween. For example, bearings of different sizes may be securely engaged with the same tibial component or tibial components of different sizes may be securely engaged with the same bearing.

[0037] The tibial component may substantially have no peripheral wall or lip around the second engagement surface. The tibial component of the present disclosure may differ in this regard from a tibial tray that relies on peripheral registration between the tibial tray and a bearing, where the tibial tray has peripheral walls that define a recess in which the bearing is received in a snug -fit manner. Instead, the tibial component of the present disclosure may rely on a substantially central registration between the tibial component and the bearing, the registration being central at least in a lateral/medial direction. Accordingly, bearings that have different widths (i.e. different dimensions in a lateral/medial direction) may be engaged with the same tibial component configured as described and/or bearings with different depths (i.e. dimensions in the

anterior/posterior direction) may be engaged with the same tibial component configured as described. Similarly, tibial components with different widths (i.e. different dimensions in a lateral/medial direction) may be engaged with the same bearing as described and/or tibial components with different depths (i.e. dimensions in the anterior/posterior direction) may be engaged with the same bearing configured as described. Thus, the central registration may provide for broader interchangeability between bearings and tibial components of different sizes.

[0038] Where the bearings or tibial components with different depths are used, one or more filler members of different sizes may be provided to accommodate difference in the size of the gap that may result. Nevertheless, the gap size need not necessarily change with different sizes of bearings and tibial components. In this regard, the distance between the posterior surface of anterior buttress and anterior surface of posterior buttress, and the surface profiles thereof, and the distance between the posterior surface of the anterior recess and the anterior surface of the posterior recess, and the surface profiles thereof, may be kept substantially constant for tibial components and bearings having different sizes, ensuring that the same-sized one or more filler members may be used with any combination of differently sized bearings and tibial components.

[0039] The bearing, the tibial component and the filler members may each be formed, respectively, in one piece or in multiple pieces. The femoral component, bearing, tibial component and filler members may be formed from material commonly used for components of knee prostheses. For example, the femoral component and/or the tibial component may be formed from a surgical grade metal, e.g. cobalt chromium alloy, titanium alloy, or ceramic. The bearing may be formed from a plastic/polymer, e.g. high density polyethylene. The filler members may be formed from metal e.g. cobalt chromium alloy, titanium alloy, or plastic/polymer e.g., high density polyethylene, or polyetheretherketone (PEEK).

[0040] In accordance with features of the present disclosure, the bearing may be engaged directly with the tibial component without undue force, whether the tibial component is already implanted in the knee (in situ) or externally located. Further, at least where the one or more filler members are releasable from the gap between the first and second gap surfaces, the bearing may be removed and replaced with an identical bearing, or replaced with another bearing of different size, without compromise to any component of the prosthesis or without causing trauma to the knee. [0041] Once engaged with a the tibial component, a bearing of a variety of different sizes can be positively retained against displacement relative to the tibial component, e.g., when the bearing is subjected to contact with a femoral component in any foreseeable presentation. This retention can be enduring and robust throughout the service life of the prosthesis.

[0042] Particularly in scenarios where there is considerable mismatch in size between femoral and tibial components, the surface area of the engagement surfaces of the bearing and tibial component may differ (e.g., the first engagement surface of the bearing may be substantially smaller than the second engagement surface of the tibial component, or the periphery of the first engagement surface extend beyond (overhang) the periphery of the second engagement surface, etc.). However, through the interconnection according to the present disclosure, the bearing and tibial component may still be adequately restrained against relative displacement.

Bearing and tibial component engagement using pegs and holes

[0043] According to one aspect, the present disclosure provides knee prosthesis apparatus, comprising:

a bearing having a first engagement surface; and

a tibial component having a second engagement surface configured to releasably engage the first engagement surface of the bearing;

wherein a plurality of pegs are provided on one of the first and second engagement surfaces and a plurality of holes are provided on the other of the first and second engagement surfaces, and wherein at least some of the plurality of pegs locate in at least some of the plurality of holes to effect releasable engagement between the bearing and the tibial component.

[0044] In another aspect, the present disclosure provides a bearing for a knee prosthesis, the bearing comprising a first engagement surface configured to releasably engage a second engagement surface of a tibial component, wherein the bearing further comprises at least one of:

(i) a plurality of pegs provided on the first engagement surface, at least some of the plurality of pegs being configured to locate in at least some of a plurality of holes provided on the second engagement surface to effect releasable engagement between the bearing and the tibial component; and

(ii) a plurality of holes provided on the first engagement surface, at least some of the plurality of holes being configured to receive at least some of a plurality of pegs provided on the second engagement surface to effect releasable engagement between the bearing and the tibial component.

[0045] In another aspect, the present disclosure provides a tibial component for a knee prosthesis, the tibial component comprising a second engagement surface adapted to releasably engage a first bearing surface of a bearing, wherein the tibial component further comprises at least one of: (i) a plurality of pegs provided on the second engagement surface, at least some of the plurality of pegs being configured to locate in at least some of a plurality of holes provided on the first engagement surface to effect releasable engagement between the tibial component and the bearing; and

(ii) a plurality of holes provided on the second engagement surface, at least some of the plurality of holes being configured to receive at least some of a plurality of pegs provided on the first engagement surface to effect releasable engagement between the tibial component and the bearing.

[0046] In yet another aspect, the present disclosure provides a method of implanting a knee prosthesis, comprising:

releasably engaging a bearing having a first engagement surface with a tibial component having a second engagement surface by locating at least some of a plurality of pegs provided on one of the first and second engagement surfaces in at least some of a plurality of holes provided on the other of the first and second engagement surfaces.

[0047] The bearing may include a first bearing surface, the first bearing surface configured to articulate with a second bearing surface of a femoral component. The first bearing surface may be on a substantially opposite side of the bearing to the first engagement surface. The apparatus may comprise a femoral component having a second bearing surface configured to articulate with the first bearing surface of the bearing.

[0048] In any of the aspects, location of the pegs in the holes may prevent relative translation, rotation and/or tilting between the bearing and the tibial component when the bearing and tibial component are engaged and subjected to forces during use.

[0049] The tibial component may have no peripheral wall or lip around the second engagement surface. A majority of the pegs and holes may be positioned inwardly from the peripheral edge of the respective engagement surfaces. The tibial component of the present disclosure may differ in this regard from a tibial tray that relies on peripheral registration between the tibial tray and a bearing, the tibial tray having peripheral walls that define a recess in which an entire engagement surface of a bearing is received. In the present disclosure, through use of inwardly located pegs and holes to effect engagement, broader interchangeability between bearings and tibial components of different sizes can be achieved without compromising secure engagement therebetween.

[0050] Thus, in one aspect, the present disclosure provides a knee prosthesis system, comprising:

a plurality of bearings, each bearing having a first engagement surface, and each bearing having a size that is different from at least some of the other bearings; and

a tibial component having a second engagement surface that is separately and selectively engageable with the first engagement surface of every one of the plurality of bearings;

wherein a plurality of pegs are provided on one of the first and second engagement surfaces and a plurality of holes are provided on the other of the first and second engagement surfaces, and wherein at least some of the plurality of pegs locate in at least some of the plurality of holes to effect releasable engagement between the selected bearing and the tibial component.

[0051] Further, in another aspect, the present disclosure provides a knee prosthesis system, comprising:

a bearing having a first engagement surface;

a plurality of tibial components, each tibial component having a second engagement surface and each tibial component having a size that is different from at least some of the other of the plurality of tibial components,

wherein the first bearing surface of the bearing is separately and selectively engageable with the second engagement surface of every one of the plurality of tibial components;

wherein a plurality of pegs are provided on one of the first and second engagement surfaces and a plurality of holes are provided on the other of the first and second engagement surfaces, and wherein at least some of the plurality of pegs locate in at least some of the plurality of holes to effect releasable engagement between the bearing and the selected tibial component.

[0052] In any of the above aspects, for any combination of bearing and tibial component, the total number of pegs may be the same as, or may be different from, the total number of holes. In some embodiments, to effect engagement between the bearing and the tibial component, only a subset of the plurality of pegs may locate in the holes and/or only a subset of the plurality of holes may receive pegs. Since only a subset of pegs or holes may need be utilised to effect the releasable engagement, the apparatus is further adaptable for use with bearings and tibial components of different sizes. For example, even if the engagement surface of one of the bearing and the tibial component is smaller than the engagement surface of the other of the bearing and tibial component to such an extent that the smaller engagement surface cannot support one or more a pegs or holes that could interface with one or more holes or pegs provided on the other of the engagement surfaces, the ability for the bearing and the tibial component to securely engage each other may not be compromised. The total number of pegs and holes may vary depending on the size of the engagement surface on which they are provided. Where multiple bearings of different sizes or multiple tibial components of different sizes are provided, each bearing or tibial component may incorporate the same core group of pegs and/or holes. The smallest bearing or tibial component may incorporate the core group of pegs and/or holes only, whereas larger bearings or tibial components may incorporate the core group of pegs and/or holes along with additional pegs and/or holes.

[0053] The bearing and the tibial component may be releasably engageable with each other at one relative position and orientation only. This can ensure that an inappropriate relative positioning and orientation of the bearing and tibial component is avoided. This may be achieved at least in part through a particular distribution, size and/or shape of the pegs and holes such that, for any bearing and tibial component combination, there is only one hole into which each peg is locatable.

[0054] The pegs may project in a direction substantially perpendicular to the engagement surface on which they are provided. The pegs may be elongated in the direction substantially perpendicular to the engagement surface on which they are provided. When the knee prosthesis is implanted, the pegs may be elongated in a direction substantially parallel to the mechanical and anatomical axes of the tibia and/or to the mechanical axis of the leg. The pegs may be elongated in a direction that extends no more than 10°, or no more than 5°, from the mechanical and anatomical axes of the tibia and/or from the mechanical axis of the leg.

[0055] The pegs may take a variety of different forms. Pegs may have a uniform or nonuniform cross-section along their length. Pegs may taper towards their distal ends, include rounded distal ends or otherwise. By tapering towards their distal ends or by having rounded distal ends, it may be easier to position the pegs in openings of corresponding holes in a process of locating the pegs in the holes. Across a plane perpendicular to their direction of elongation, pegs may have a cross-sectional shape that is circular, elliptical, square, rectangular, irregular or otherwise. In one embodiment, one of more of the pegs are substantially frustoconical. In another embodiment, one or more pegs are cylindrical with rounded distal ends.

[0056] All of the pegs may have identical length and/or may extend from the engagement surface on which they are provided to substantially the same height. Alternatively, some or all of the pegs may have different lengths and/or may extend from the engagement surface on which they are provided to different heights. In one embodiment, pegs are provided on the second engagement surface of the tibial component and the lengths of the pegs are generally proportional to the depth of the bearing at the region of the bearing where the hole is located in which the peg is to locate. At relatively thick regions of the bearing, longer pegs can be accommodated.

[0057] The holes may extend in a direction substantially perpendicular to the engagement surface on which they are provided. The holes may extend into the bearing or tibial component on which they are provided. The holes may be elongated in the direction substantially perpendicular to the engagement surface on which they are provided. When the knee prosthesis is implanted, the holes may be elongated in a direction substantially parallel to the mechanical and anatomical axes of the tibia and/or to the mechanical axis of the leg. The holes may be elongated in a direction that extends no more than 10°, or no more than 5°, from the mechanical and anatomical axes of the tibia and/or from the mechanical axis of the leg.

[0058] The holes may take a variety of different forms. Holes may have a uniform cross-section along their length or they may taper towards bottom surfaces. Across a plane perpendicular to their direction of elongation, holes may have a cross-sectional shape that is circular, elliptical, square, rectangular, irregular or otherwise. In one embodiment, one or more of the holes are substantially frustoconical. In another embodiment, one or more of the holes are substantially cylindrical.

[0059] One or more of the holes may be blind holes or recesses. Additionally or alternatively, one or more of the holes may extend all the way through the component on which they are provided.

[0060] Openings of the holes through which pegs enter the holes may be flush with the engagement surface on which they are provided. When pegs are fully located in the holes, the first and second engagement surfaces may abut each other. The first and second engagement surfaces may have corresponding profiles to ensure abutment between a major part, or all, of the first and second engagement surfaces. In some embodiments, both the first and second engagement surfaces are flat. However, other surface profiles can be employed.

[0061] The pegs and holes may be sized to ensure a tight frictional fit with each other. Through provision of a frictional fit between the pegs and holes, a moderate or strong separation force may need to be applied to the bearing and tibial component to effect release of the engagement, ensuring that release does not occur at the time of implantation or at other inopportune moments.

[0062] In one embodiment, the plurality of pegs are provided on the first engagement surface and the plurality of holes are provided on the second engagement surface. In another

embodiment, the plurality of pegs are provided on the second engagement surface and the plurality of holes are provided on the first engagement surface. In one embodiment, a plurality of pegs are provided on only one of the first and second engagement surfaces and a plurality of holes are provided on only the other of the first and second engagement surfaces. However, in an alternative embodiment, both pegs and holes are provided on each one of the first and second engagement surfaces.

[0063] Between the first bearing surface and the first engagement surface of the bearing, the bearing may have varying depth. Where the holes are provided on the first engagement surface of the bearing, the holes may be provided at regions of the bearing that have relatively greater depth to other regions of the bearing.

[0064] At least one post may be provided on one of the first and second engagement surfaces and at least one cavity may be provided on the other of the first and second engagement surfaces, wherein the post locates in the cavity in the process of engaging the bearing and the tibial component. The post and cavity may be located at a central region of the surface on which they are provided. Pegs and/or holes may be distributed around the post and the cavity. [0065] The post may project in a direction substantially perpendicular to the engagement surface on which it is provided. The post may be elongated in a direction substantially perpendicular to the engagement surface on which it is provided. When the knee prosthesis is implanted, the post may be elongated in a direction substantially parallel to the mechanical and anatomical axes of the tibia and/or to the mechanical axis of the leg. The post may be elongated in a direction that extends no more than 10°, or no more than 5°, from the mechanical and anatomical axes of the tibia and/or from the mechanical axis of the leg. The post may have a greater cross-sectional area than the pegs. The post may be longer than some or all of the pegs. The post may have a length that is at least 1.5 times, at least 2 times or at least 10 times the length of the pegs. Accordingly, in the process of effecting releasable engagement between the bearing and the tibial component, the post may enter the cavity prior to pegs entering holes. The post may therefore provide for initial registration of the bearing with the tibial component, making it more straightforward to subsequently align pegs with corresponding holes. Once the post enters the cavity, only relative rotation of the bearing and tibial component may need to be carried out to align pegs with the corresponding holes. Further, by having a greater length than the pegs, the post may provide for greater restraint against relative tilting of the bearing and the tibial component, when the bearing and tibial component are engaged and subjected to forces during use. The post can provide a journal about which the tibial component rotates.

[0066] The post may take a variety of different forms. The post may have a uniform cross- section along its length. The post may taper towards its distal end and/or may have a rounded distal end. By tapering towards its distal end or by having a rounded distal end, it can be easier to position the distal end of the post in the opening of the cavity in the process of locating the post in the cavity. Across a plane perpendicular to its direction of elongation, the post may have a cross- sectional shape that is circular, elliptical, square, rectangular, irregular or otherwise. In one embodiment, the post is frustoconical in shape.

[0067] The cavity may project in a direction substantially perpendicular to the engagement surface on which it is provided. The cavity may be elongated in a direction substantially perpendicular to the engagement surface on which it is provided. When the knee prosthesis is implanted, the cavity may be elongated in a direction substantially parallel to the mechanical and anatomical axes of the tibia and/or to the mechanical axis of the leg. The cavity may be elongated in a direction that extends no more than 10°, or no more than 5°, from the mechanical and anatomical axes of the tibia and/or from the mechanical axis of the leg. The cavity may have a greater cross-sectional area than the holes. The cavity may be deeper than the holes. The cavity may have a depth that is at least 1.5 times, at least 2 times or at least 2.5 times the depth of the holes.

[0068] The cavity may take a variety of different forms. The cavity may have a uniform cross- section along its length or may taper towards its bottom surface. Across a plane perpendicular to its direction of elongation, the cavity may have a cross-sectional shape that is circular, elliptical, square, rectangular, irregular or otherwise. In one embodiment, the cavity is frustoconical in shape.

[0069] In one embodiment, the post is provided on an opposite one of the first and second engagement surfaces to the surface on which the pegs are provided, and the cavity is provided on an opposite one of the first and second engagement surfaces to the surface on which the holes are provided. In one embodiment, the post is provided on the first engagement surface and the cavity is provided on the second engagement surface. In one embodiment, the post and the holes are provided on the first engagement surface and the cavity and the pegs are provided on the second engagement surface.

[0070] The tibial component may comprise a tibia mating surface on a substantially opposite side of the tibial component from the second engagement surface. A stem may be provided on the tibia mating surface. The stem may project from the tibia mating surface. The stem may be adapted to extend into the intramedullary canal of the tibia when the tibial component is fixed to the tibia.

[0071] The cavity may be provided on the second engagement surface, and may extend from the second engagement surface, through the tibial component, and at least partially into the stem. The stem may provide a region of increased depth to the tibial component in which to partially accommodate the cavity.

[0072] Any one of the femoral component, the bearing and the tibial component may be formed in one piece or otherwise. The pegs may be integrally formed with the surface on which they are provided and/or the holes (e.g., walls or surfaces delineating the holes) may be integrally formed with the surface on which they are provided. The post may be integrally formed with the surface on which it is provided and/or the cavity (e.g., walls or surfaces delineating the cavity) may be integrally formed with the surface on which it is provided. The femoral component, the bearing and the tibial component may be formed from material commonly used for components of knee prostheses. For example, the femoral component and/or the tibial component may be formed from a surgical grade metal, e.g. cobalt chromium alloy or titanium, and the bearing may be formed from plastic.

[0073] In accordance with features of the present disclosure, the bearing may be engaged directly with the tibial component without undue force, whether the tibial component is already implanted in the knee (in situ) or externally located. Further, the bearing may be removed and replaced with an identical bearing, or replaced with another bearing of different size, without compromise to any component of the prosthesis or without causing trauma to the knee.

[0074] Once engaged with a compatible tibial component, a bearing of a variety of different sizes can be positively retained against displacement relative to the tibial component, e.g., when the bearing is subjected to contact with the femoral component in any foreseeable presentation. This retention can be enduring and robust throughout the service life of the prosthesis.

[0075] Particularly in scenarios where there is considerable mismatch in size between femoral and tibial components, the surface area of the engagement surfaces of the bearing and tibial component may differ (e.g., the first engagement surface of the bearing may be substantially smaller than the second engagement surface of the tibial component, or the periphery of the first engagement surface extend beyond (overhang) the periphery of the second engagement surface, etc.). However, through the releasable engagement according to the present disclosure, the bearing and tibial component can still be adequately restrained against relative displacement.

Configuration of surfaces of knee prosthesis apparatus

[0076] According to one aspect, the present disclosure provides a femoral component for a knee prosthesis, comprising:

a patella flange comprising first and second opposite ends and a trochlear groove extending between the first and second ends;

a lateral condyle and a medial condyle each projecting from the first end of the patella flange and separated by an intercondylar notch;

wherein the patella flange comprises a lateral surface, a medial surface and a trochlear groove surface, the trochlear groove surface being located between the lateral and medial surfaces and recessed relative to the lateral and medial surfaces;

the trochlear groove surface comprising a lateral flank and a medial flank, the lateral flank adjoining the lateral surface and the medial flank adjoining the medial surface, wherein a lateral transition between the lateral flank and the lateral surface is a substantially smooth transition and a medial transition between the medial flank and the medial surface is a

substantially angular transition.

[0077] The lateral and medial flanks of the trochlear groove surface may extend along the trochlear groove surface, between the first and second ends of the patella flange, on either side of a notional bottom line of the trochlear groove surface. The notional bottom line extends through the lowest points of the trochlear groove surface along the path of the trochlear groove surface between the first and second ends of the patella flange.

[0078] The lateral and medial surfaces may each extend between the first and second ends of the patella flange. In a transverse (lateral-medial) direction of the femoral component, the lateral and medial surfaces may extend from the trochlear groove surface to lateral and medial edges, respectively, of the patella flange.

[0079] At least a portion of the lateral flank may be substantially flat and at least a portion of the medial flank may be substantially curved. [0080] According to one aspect, the present disclosure provides a femoral component for a knee prosthesis, comprising:

wherein the patella flange comprises a lateral surface, a medial surface and a trochlear groove surface, the trochlear groove surface being located between the lateral and medial surfaces in a transverse direction of the femoral component and recessed relative to the lateral and medial surfaces;

the trochlear groove surface comprising a lateral flank and a medial flank, the lateral flank adjoining the lateral surface and the medial flank adjoining the medial surface, wherein at least a portion of the lateral flank is substantially flat.

[0081] In aspects disclosed herein, a major portion, i.e. more than 50%, of the lateral flank may be substantially flat, for example.

[0082] All or part of the lateral flank may follow a substantially straight line as the lateral flank extends from the notional bottom line of the trochlear groove surface to the lateral surface in the transverse direction of the femoral component.

[0083] At least a portion of the medial flank may be substantially curved. For example, a major portion of the medial flank may be substantially curved. In one embodiment, the medial flank is curved across its entire length. In another embodiment, the medial flank has both curved and straight portions. All or part of the medial flank may follow a substantially curved line as the medial flank extends from the notional bottom line of the trochlear groove surface to the medial surface in the transverse direction of the femoral component. Any curved portion of the medial flank may follow a circular arc or otherwise.

[0084] The outer surface of patella flange, including the trochlear groove surface, may provide a bearing surface for a native patella, or a prosthetic patella component mounted to a resected surface of a native patella, to enable articulation of the native patella/patella component relative to the femoral component. For simplicity, subsequent discussions make reference predominantly to use of a patella component. However, it should be recognised that an unmodified native patella can be used where appropriate, e.g., if the native patella is in good condition.

[0085] A bearing surface of the patella component may bear against and track along the trochlear groove surface during articulation of the knee prosthesis. The bearing surface of the patella component may include a lateral facet and a medial facet positioned on either side of an apex of the bearing surface. When the patella component articulates with the femoral component, the lateral facet may bear against the lateral flank of the trochlear groove surface and the medial facet may bear against the medial flank of the trochlear groove surface. The apex of the bearing surface may align with and track along the notional bottom line of the trochlear groove surface.

[0086] A close fit may exist between the bearing surface of the patella component and the trochlear groove surface. To achieve a close fit, the bearing surface of the patella component may have a profile corresponding to the profile of the trochlear groove surface. For example, at least a portion of the lateral facet may be substantially flat and at least a portion of the medial facet may be substantially curved.

[0087] According to one aspect, the present disclosure provides a patella component, comprising:

a bearing surface for bearing against a trochlear groove surface of a femoral component of a knee prosthesis,

wherein the bearing surface comprises a lateral facet and a medial facet on substantially opposites of an apex of the bearing surface,

wherein at least a portion of the lateral facet is substantially flat and at least a portion of the medial facet is substantially curved.

[0088] In aspects disclosed herein, a major portion of the lateral facet may be substantially flat, for example.

[0089] All or part of the lateral facet may follow a substantially straight line as the lateral facet extends from the apex to a lateral edge of the patella component. The lateral facet may extend at an angle relative to a substantially flat anterior surface of the patella component, on an opposite side of the patella component to the bearing surface of the patella component, of between 15 and 30 degrees for example.

[0090] At least a portion of the medial facet may be substantially curved. For example, a major portion of the medical facet may be substantially curved. In one embodiment, the medial facet is curved across its entire length. In another embodiment, the medial facet has both curved and straight portions. All or part of the medial facet may follow a substantially curved line as it extends from the apex to a medial edge of the patella component. Any curved portion of the medial facet may follow a circular arc or otherwise.

[0091] When the patella component bears against and articulates with the femoral component, the lateral and medial facets of the patella component may extend beyond the lateral and medial flanks of the trochlear groove surface, across the respective lateral and medial transitions, such as to partially overhang or contact the lateral and medial surfaces. Compressive loads on a patella component can reach 2 to 3 times body weight when performing certain activities such as climbing stairs. Moreover, greater compressive load can be taken by the lateral facet of a patella component compared to a medial facet. By providing a smooth lateral transition between the lateral flank of the trochlear groove surface and the lateral surface in aspects of the present disclosure, forces are more evenly distributed at this region, enabling contact stresses between the lateral facet of the patella component and the patella flange to be reduced. This can provide numerous benefits including increase reliability of the knee prosthesis and user comfort.

[0092] Since the compressive load taken by the medial facet of the patella component may be significantly lower than the load taken by the lateral facet, providing a medial transition between the medial flank and medial surface of the femoral component that is angular (e.g., a stepped transition and/or a transition where a ridge is identifiable) can present a lower stress risk for the medial facet of the patella component when bearing against this region. Further, through providing the angular transition rather than a smooth transition, a trochlear groove with substantially increased depth may be achieved. The depth of the groove can be substantially increased by virtue of the medial flank extending more steeply from the medial transition than would generally be possible if it were adjoined to the medial surface by virtue of a smooth transition. By providing a deeper trochlear groove, the likelihood of dislocation or displacement of the patella component from the trochlear groove may be substantially reduced.

[0093] The lateral flank of the trochlear groove surface may have a width in the transverse direction of the femoral component that is greater than the width of the medial flank of the trochlear groove surface. Similarly, the lateral facet of the patella component may be wider in the transverse direction than the medial facet.

[0094] According to one aspect, the present disclosure provides a femoral component for a knee prosthesis, comprising:

the trochlear groove surface comprising a lateral flank and a medial flank, the lateral flank adjoining the lateral surface and the medial flank adjoining the medial surface, wherein the lateral flank is wider than the medial flank in the transverse direction of the femoral component.

[0095] Further, according to one aspect, the present disclosure provides a patella component, comprising:

wherein the bearing surface comprises a lateral facet and a medial facet on substantially opposites of an apex of the bearing surface in a transverse direction of the patella component, wherein the lateral facet is wider than the medial facet in the transverse direction.

[0096] In aspects disclosed herein, the contact between the lateral flank of the trochlear groove surface and the lateral facet of the patella component may therefore take place over a larger area than the contact between the medial flank of the trochlear groove surface and the medial facet of the patella component. Accordingly, the knee prosthesis may be more capable of distributing higher forces that occur at the lateral side of the patello -femoral articulation, further reducing stress and increasing reliability and comfort.

[0097] The depth of the trochlear groove may increase towards the first end of the patella flange.

[0098] According to one aspect, the present disclosure provides a femoral component for a knee prosthesis, comprising:

the trochlear groove surface comprising a lateral flank and a medial flank, the lateral flank adjoining the lateral surface and the medial flank adjoining the medial surface,

wherein the depth of the trochlear groove increases towards the first end of the patella flange.

[0099] In aspects disclosed herein, the increase in depth of the trochlear groove may occur in a gradual fashion and may allow the patella component to lie more deeply in the trochlear groove when the knee prosthesis is in a flexion state, reducing potential obstruction by the patella to adjacent elastic soft tissue structures (e.g. the patella retinaculum) that stretch over patella and patella flange during flexion of the knee prosthesis.

[0100] The angle of the lateral flank of the trochlear groove surface may increase towards the first end of the patella flange. In particular, the lateral flank may rotate such that it faces in a more medial direction as it extends along the path of the trochlear groove surface from the second to the first end of the patella flange.

[0101] Related to this, according to one aspect, the present disclosure provides a femoral component for a knee prosthesis, comprising:

wherein a notional bottom line extends through the lowest points of the trochlear groove surface along the path of the trochlear groove surface between the first and second ends of the patella flange, the lateral and medial flanks being located on opposite sides of the notional bottom line,

wherein the lateral flank rotates as it extends along the path of the trochlear groove surface between the first and second ends of the patella flange.

[0102] The total rotation may be in the range of 2 to 7 degrees, for example. The rotation of the lateral flank may be such that the lateral flank faces in a more medial direction as it extends along the path of the trochlear groove surface towards the first end of the patella flange.

[0103] Due to engagement between the lateral facet of the patella component and the lateral flank, the rotation of the lateral flank may cause a corresponding rotation of the patella component as the patella component tracks along the trochlear groove during articulation. The rotation of the patella component can be considered a progressive "internal rotation" of the patella component ("internal rotation" being as defined in ISO 14243-4), as the patella component moves towards the first end of the patella flange and the knee moves towards flexion. The rotation may be such that a substantially flat anterior surface of the patella component, on an opposite side of the patella component to the bearing surface of the patella component, faces in a more medial direction as the patella component moves towards the first end of the patella flange and the knee moves towards flexion.

[0104] The rotation of the lateral flank angle may cause the lateral flank to extend at a progressively steeper angle from the bottom of the trochlear groove surface as the trochlear groove extends from the second end towards the first end of the patella flange.

[0105] According to one aspect, the present disclosure provides a femoral component for a knee prosthesis, comprising:

wherein the lateral flank extends at a progressively steeper angle from the bottom of the trochlear groove surface as the trochlear groove extends from the second end towards the first end of the patella flange.

[0106] In aspects disclosed herein, by varying the depth of the trochlear groove, a patella component tracking along the groove may more closely emulate the tracking behaviour of a patella in a native knee. Further, by having the lateral flank extending at a steeper angle from the bottom of the trochlear groove, an increased slope is provided for the patella component to climb before dislocation of the patella component from the trochlear groove can occur, which dislocation can otherwise be particularly prevalent towards the lateral side of the femoral component. Even though the flank angle is changing, the patella component may maintain a close/congruent fit with the trochlear groove surface by virtue of rotation of the patella component within the trochlear groove.

[0107] The profile of the patella flange in the transverse direction may be partially replicated in the condyle region of the femoral component where the lateral and medial condyles and the intercondylar notch are provided. The outer, bearing surface of the lateral condyle may include a lateral surface extension that is an extension of the lateral surface of the patella flange. Further, the outer surface of the lateral condyle may include a lateral flank extension that is an extension of the lateral flank of the trochlear groove surface of the patella flange. The lateral transition between the lateral flank extension and the lateral surface extension in the transverse direction of the femoral component may be a substantially smooth transition. Further, the lateral flank extension may be substantially flat, the lateral flank extension following a substantially straight line as it extends from the intercondylar notch to the lateral surface extension in the transverse direction of the femoral component. The outer, bearing surface of the medial condyle may include a medial surface extension that is an extension of the medial surface of the patella flange. Both the lateral and medial surface extensions may follow curved lines in the transverse direction of the femoral component. The curvatures of the lateral and medial surface extensions may be convex and may follow a substantially circular arc or otherwise.

[0108] The surface profiles of the lateral and medial condyles as described above may provide the condylar region of the femoral component with asymmetry. While the entire surface of the medial condyle can follow a substantially circular arc in the transverse direction of the femoral component, the surface of the lateral condyle may be divided up in the transverse direction into the substantially flat region of the lateral flank extension and the substantially circular arc region of the lateral surface extension.

Rotational alignment of knee prosthesis components

[0109] According to one aspect of the present disclosure there is provided a method of rotationally orienting a first prosthetic component of a knee prosthesis at a resected surface of a first bone, the method comprising:

attaching a marking jig to the resected surface of the bone, the marking jig comprising: an engagement surface, a marking jig pin protruding from the engagement surface; an articular surface opposite to the engagement surface; and

at least one marker guide at a position spaced from the marking jig pin;

wherein the attaching comprises locating the marking jig pin in a pin hole in the resected surface; the method further comprising:

engaging the articular surface of the attached marking jig with an articular surface of a second prosthetic component, the second prosthetic component being fixed to a second bone; rotating the marking jig about the axis of the marking jig pin to place the articular surface of the marking jig into registration with the articular surface of the second prosthetic component;

placing a mark on the first bone, wherein the marker guide is used to guide location of the mark on the first bone;

positioning one of more recesses in the first bone to receive one or more protrusions that extend from an engagement surface of the first prosthetic component, wherein the positions of the one or more recesses are determined based on the position of the pin hole in the resected surface and the position of the mark; and

attaching the first prosthetic component to the first bone by locating the one or more protrusions in the one or more recesses.

[0110] According to another aspect of the present disclosure there is provided a marking jig for use in a method of rotationally orienting a first prosthetic component of a knee prosthesis at a resected surface of a first bone, the marking jig comprising:

an engagement surface for engaging the resected surface of the first bone;

a marking jig pin protruding from the engagement surface for locating in a pin hole in the resected surface;

an articular surface opposite to the engagement surface, the articular surface of the marking jig being registrable with an articular surface of a second prosthetic component, the second prosthetic component being fixed to a second bone; and

at least one marker guide at a spaced position from the marking jig pin. [0111] In the above aspects, locating the marking jig pin in the pin hole of the resected surface may comprise pushing the pin into the resected surface, wherein the pushing of the pin into the resected surface forms the pin hole. Alternatively, the pin hole may be pre-formed in the resected surface, e.g. by drilling, punching or otherwise, prior to locating of the marking jig pin into the pin hole.

[0112] The marking jig pin may be permanently attached or integrally formed with the engagement surface of the marking jig. Alternatively, the marking jig pin may be attached by being inserted into a hole which may be provided through the marking jig between its articular and engagement surfaces. Prior to insertion of the marking jig pin in the hole of the marking jig, the hole may be used to guide a tool (e.g., a drill or punch) that forms the pin hole in the resected surface.

[0113] The marker guide may comprise a notch, line, spot, bump or other identifying feature. The marker guide may be adjacent a periphery of the marking jig. The marker guide may therefore be easily visible to a surgeon and may be locatable directly adjacent the resected surface to assist in marking of the resected surface. The marking jig may comprise a side wall extending between its engagement surface and its articular surface and the marker guide may be at least partially disposed on the sidewalk

[0114] In one embodiment, the marker guide comprises a notch in the side wall which notch has an open end at the engagement surface of the marking jig. The mark may be placed on the resected surface of the first bone via the open end of the notch. The mark may be placed on the first bone by applying additional matter to the first bone, e.g., ink or paint, and/or by altering the structure of the first bone, e.g., by scribing, engraving or scoring the first bone. The mark may be formed using a sterile pen, electrocautery tool or otherwise.

[0115] The articular surface of the marking jig may have a shape that is a reciprocal of a shape of the articular surface of the second prosthetic component. The shape of the articular surface of the marking jig may be such that it can be positioned with a snug, congruent fit with the articular surface of the second prosthetic component. This may be such that there is only one clearly identifiable position of registration between the articular surface of the marking jig and the articular surface of the second prosthetic component. Upon engaging the articular surface of the marking jig with the articular surface of the second prosthetic component, rotation of the marking jig about the axis of the marking jig pin may occur partially or entirely automatically in some embodiments. In this regard, the articular surface of the marking jig may be predisposed to rotating and sliding into the registration with the articular surface of the second prosthetic component. When the articular surface of the marking jig registers with the articular surface of the second prosthetic component, the resistance to further relative rotation of the two articular surfaces may be at its greatest. In one embodiment, when the articular surface of the marking jig registers with the articular surface of the second prosthetic component, there may be substantially no further relative rotation possible between the two articular surfaces.

[0116] To form the recesses, e.g., holes, in the resected surface, a drill guide may be used. The drill guide may be attached to the resected surface after removal of the marking jig. The drill guide may comprise a bone contact surface and an opposite, outer surface. Drill guide holes may extend between the contact surface and the outer surface.

[0117] A drill guide pin may protrude from the contact surface of the drill guide. The drill guide pin may be adapted to locate in the pin hole in the resected surface of the first bone, which pin hole has previously received the marking jig pin. The drill guide may further comprise a drill guide marker.

[0118] According to one aspect of the present disclosure there is provided a drill guide for use in a method of rotationally orienting a first prosthetic component of a knee prosthesis at a resected surface of a first bone, the drill guide comprising:

a contact surface for engaging the resected surface of the first bone; a drill guide pin protruding from the contact surface for locating in a pin hole of the resected surface;

an outer surface opposite to the contact surface;

one or more drill guide holes extending between the contact surface and the outer surface; and

at least one drill guide marker.

[0119] In the above aspects, upon location of the drill guide pin in the pin hole, the drill guide may be rotated about the axis of the drill guide pin so that the drill guide marker aligns with the mark placed on the first bone using the marking jig. When the drill guide marker is aligned with the mark, the drill guide can be considered to be in an aligned position.

[0120] Alternatively, the drill guide may be rotated about the axis of the drill guide pin so that the drill guide marker aligns with an identifier on the first bone that is different to the mark placed on the first bone, but which different identifier has been placed of the first bone based on the positioning of the mark. For example, after the mark is placed on the first bone, a straight line may be drawn or scored in the resected surface between the pin hole and the mark (and optionally beyond the mark). Thus, upon location of the drill guide pin in the pin hole, the drill guide may be rotated about the axis of the drill guide pin so that the drill guide marker aligns with the line, again placing the drill guide into the aligned position.

[0121] The drill guide holes are in a fixed positioned relative to the drill guide pin and the drill guide marker such that, when the drill guide is rotated to the aligned position, the drill guide holes are in a correct orientation for guiding a drill or other tool, such as a punch or spike, to form holes in the resected surface of the first bone. The correct orientation of the holes in the resected surface is such that, when the protrusions of the first prosthetic component are located in the recesses, the first prosthetic component is correctly rotationally oriented relative to the resected surface of the first bone. The correct rotational orientation of first prosthetic component may be such that when an articular surface of the first prosthetic component is brought into engagement with the articular surface of the second prosthetic component, the two articular surfaces are in an optimal orientation for articulation during normal use of the knee prosthesis.

[0122] When the drill guide is placed into the aligned position, the rotational orientation of the marking jig is effectively transferred to the drill guide, i.e. the rotational orientation of the drill guide is identical to that of the marking jig when the articular surface of the marking jig was registered with the articular surface of the second prosthetic component. Similarly, when first prosthetic component is attached to the first bone based on the position of the holes formed using the drill guide, the rotational orientation of the marking jig is effectively transferred to the first prosthetic component.

[0123] Recesses in the resected surface of the first bone need not necessarily be formed using a drill guide. Other types of guides or tools may be used. Nevertheless, these other guides or tools may include a contact surface for engaging the resected surface of the first bone, a pin protruding from the contact surface for locating in a pin hole of the resected surface; an outer surface opposite to the contact surface, and a guide marker, and may be orientated relative to the resected surface in substantially the same manner as described above with respect to the drill guide. In some instances, these other guides or tools may incorporate an instrument for forming recesses in the resected surface, such as a punch or otherwise, rather than be used in conjunction with a separate instrument.

[0124] The marking jig and the first prosthetic component may have a similar shape and size. Nevertheless, since the marking jig does not form part of the knee prosthesis itself, the shape of the articular surface of the marking jig can be exaggerated to ensure absolute congruence with the articular surface of the second prosthetic component for the purpose of finding the rotational alignment. For example, as indicated above, the articular surface of the marking jig can have a shape that is substantially a reciprocal of the shape of the articular surface of the second prosthetic component. This can ensure that registration between the articular surface of the marking jig and the articular surface of the second prosthetic component is more exact, when rotational alignment occurs, than would be possible if the articular surface of the marking jig was identical to the articular surface of the first prosthetic component.

[0125] The second prosthetic component against which the marking jig articulates may be a component of the knee prosthesis, which component may remain implanted, along with the first prosthetic component, following surgery. Alternatively, the second prosthetic component may be a trial or temporary component, and may be used for the purpose of orienting the first prosthetic component only. The second prosthetic component may be removed from the second bone after orientation is complete.

[0126] In any of the above aspects, the drill guide marker may comprise a notch, line, spot, bump or other identifying feature adjacent the periphery of the drill guide.

[0127] In any of the above aspects, the contact surface of the drill guide may comprise one or more peripheral pins. The peripheral pins may be shorter than the drill guide pin and therefore the drill guide pin may project from the contact surface of the drill guide to a greater degree than the peripheral pins. The peripheral pins, in combination with the drill guide pin, may assist in maintaining the drill guide in the aligned position prior to it guiding formation of the holes in the resected surface. For example, the surgeon may only partially locate the drill guide pin in the pin hole of the resected surface while the drill guide is rotated to the aligned position. Once the drill guide reaches the aligned position, the surgeon may press on the drill guide such that the drill guide pin is fully inserted into the pin hole and the peripheral pins are pressed into the resected surface, preventing further rotation of the drill guide.

[0128] According to one aspect, the present disclosure provides a kit for use in a method of rotationally orienting a first prosthetic component of a knee prosthesis at a resected surface of a first bone, the kit comprising the marking jig and the drill guide according to any of the preceding aspects.

[0129] In one embodiment, the marking jig comprises a drill guide component. For example, the marking jig may comprise two parts releasably engaged with each other. The first part of the marking jig may comprise the articular surface of the marking jig. The second part of the marking jig may comprise the engagement surface for contacting the resected surface of the bone and may comprise all or part of the at least one marker guide. The second part may further comprise drill guide holes. When used to form the mark on the resected surface in a manner as described above, the first and second parts may be engaged. Once the mark is formed, however, rather than remove the entire marking jig and replace it with a separate drill guide, the first part of the marking jig may be removed only. Removing the first part of the marking jig may expose openings to the drill guide holes in the second part of the marking jig for use in forming recesses in the resected surface. Prior to forming the recesses, the second part of the drill guide may be stabilised manually or by other means.

[0130] In one embodiment, the first prosthetic component is a patella component and the first bone is a native patella with a resected articular surface. Moreover, the second prosthetic component is a femoral component fixed to the femur, the articular surface of the femoral component being a patella surface including a trochlear groove surface.

[0131] In this embodiment, the method therefore comprises:

attaching the marking jig to the resected surface of the patella by locating the marking jig pin in a pin hole in the resected surface of the patella:

engaging the articular surface of the attached marking jig with the femoral component, rotating the marking jig about the axis of the marking jig pin to place the articular surface of the marking jig into registration with the trochlear groove surface of the femoral component;

placing a mark on the patella, wherein the marker guide is used to guide location of the mark on the patella;

positioning holes in the patella to receive protrusions that extend from an engagement surface of the prosthetic patella component, wherein the positions of the holes are determined based on the position of the pin hole in the resected surface and the position of the mark; and attaching the prosthetic patella component to the first bone by locating the protrusions in the holes.

[0132] In another embodiment, the first prosthetic component is a tibial component and the first bone is a tibia having a resected proximal surface. Moreover, the second prosthetic component is a femoral component fixed to the distal surface of the femur, the articular surface of the femoral component being a distal surface of the femoral component.

[0133] In this embodiment, the method therefore comprises:

attaching the marking jig to the resected surface of the tibia by locating the marking jig pin in a pin hole in the resected surface of the tibia:

engaging the articular surface of the attached marking jig with the distal surface of the femoral component,

rotating the marking jig about the axis of the marking jig pin to place the articular surface of the marking jig into registration with the distal surface of the femoral component; placing a mark on the tibia, wherein the marker guide is used to guide location of the mark on the tibia;

positioning one or more recesses in the tibia to receive one or more protrusions that extend from an engagement surface of the tibial component, wherein the positions of the one or more recesses are determined based on the position of the pin hole in the resected surface and the position of the mark; and

attaching the tibial component to the tibia by locating the one or more protrusions in the one or more recesses.

[0134] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Brief Description of Drawings [0135] By way of example only, embodiments of the present disclosure are now discussed with reference to the drawings in which:

[0136] Fig. 1 shows an exploded view of a knee prosthesis;

[0137] Fig. 2 shows an exploded view of a bearing, a tibial component and a filler member of a knee prosthesis according to an embodiment of the present disclosure;

[0138] Figs. 3a, 3b and 3c show a posterior oblique view, an anterior oblique view and an inferior view, respectively, of the bearing of Fig. 2;

[0139] Figs. 4a, 4b, 4c and 4d show a posterior view, a superior view, a lateral view and an oblique view, respectively, of the tibial component of Fig. 2;

[0140] Fig. 5 shows a schematic superior view of the bearing and tibial component of Fig. 2 in an interconnected state, and the filler member of Fig. 2 located between first and second gap surfaces of the bearing and tibial component;

[0141] Fig. 6a shows a cross-sectional view along line A— A of Fig. 5 and Fig. 6b shows an enlarged view of area B of Fig. 5;

[0142] Fig. 7 illustrates different sizes of different tibial components usable in an embodiment of the present disclosure;

[0143] Fig. 8 illustrates different sizes of different bearings usable in an embodiment of the present disclosure.

[0144] Fig. 9 shows an exploded view of a bearing and a tibial component of a knee prosthesis according to an embodiment of the present disclosure;

[0145] Fig. 10 shows a top view of the tibial component of Fig. 9;

[0146] Fig. 11 shows a cross-sectional view of the tibial component along line A— A of Fig. 10;

[0147] Fig. 12 shows a top view of the tibial component of Fig. 9 with example bearings of different sizes, selectively and separately usable with tibial component, indicated thereon;

[0148] Fig. 13 shows a top view of a tibial component according to another embodiment of the present disclosure;

[0149] Fig. 14 shows a side view of the tibial component of Fig. 13;

[0150] Fig. 15 shows an anterior view of a knee prosthesis according to an embodiment of the present disclosure;

[0151] Fig. 16 shows a posterior view of the knee prosthesis of Fig. 15;

[0152] Fig. 17 shows a medial view of the knee prosthesis of Fig. 15; [0153] Fig. 18 shows a cross-sectional view of a patella flange of the femoral component of the knee prosthesis of Fig. 15;

[0154] Fig. 19 shows an oblique view of a patella component of the knee prosthesis of Fig. 15;

[0155] Fig. 20 shows a cross-sectional view of the patella component of Fig. 19;

[0156] Fig. 21 shows a medial view of the femoral component of the knee prosthesis of Fig. 15;

[0157] Figs. 22a to 22d show cross-sectional views of the femoral component along lines a— a, b— b, c— c, and d— d, respectively, of Fig. 21;

[0158] Fig. 23 shows a flowchart representing steps in a method of orienting a prosthetic component of a knee prosthesis according to an embodiment of the present disclosure;

[0159] Figs. 24a and 24b show top and bottom oblique views, respectively, of a marking jig according to an embodiment of the present disclosure;

[0160] Fig. 25 shows an oblique view of the marking jig of Figs. 24a and 24b registered with a trochlear groove surface of a femoral component;

[0161] Fig. 26a shows an anterior view of the marking jig of Figs. 24a and 24b registered with a trochlear groove surface of a femoral component, and Fig. 26b shows a cross-sectional view of the marking jig and femoral component along line A— A of Fig. 26a; Fig. 26c shows a lateral view of the marking jig of Figs. 24a and 24b registered with a trochlear groove surface of a femoral component, and Fig. 26d shows a cross-sectional view of the marking jig and femoral component along line B— B of Fig. 26c;

[0162] Fig. 27a to 27f illustrate steps in a method of orienting a prosthetic component at a resected surface of a patella according to an embodiment of the present disclosure;

[0163] Fig. 28 shows an anterior view of a marking jig registered with a trochlear groove surface of a femoral component in accordance with the method illustrated in Fig. 27a to 27f;

[0164] Figs. 29a and 29b show top and bottom oblique views, respectively, of a drill guide according to an embodiment of the present disclosure;

[0165] Figs. 30a and 30b show top and bottom oblique views, respectively, of a marking jig according to another embodiment of the present disclosure;

[0166] Fig. 31 shows an oblique view of the marking jig of Figs. 30a and 30b registered with a distal surface of a femoral component;

[0167] Fig. 32a shows a lateral view of the marking jig of Figs. 30a and 30b registered with a distal surface of a femoral component, and Fig. 32b shows a cross-sectional view of the marking jig and femoral component along line C— C of Fig. 32a; Fig. 32c shows an anterior view of the marking jig of Figs. 30a and 30b registered with a distal surface of a femoral component, and Fig. 32d shows a cross-sectional view of the marking jig and femoral component along line D— D of Fig. 32c;

[0168] Fig. 33a to 33f illustrate steps in a method of orienting a tibial component at a resected surface of a tibia according to an embodiment of the present disclosure;

[0169] Fig. 34 shows a bottom oblique view of a drill guide according to another embodiment of the present disclosure; and

[0170] Fig. 35a and 35b show anterior views of a marking jig according to another embodiment of the present disclosure.

Description of Embodiments

[0171] An exploded view of a knee prosthesis 100 is illustrated generally in Fig. 1. The knee prosthesis includes a femoral component 110, a bearing 120, a tibial component 130 and a patella component 140. The femoral component 110 is implanted at a distal end of a femur 150. The tibial component 130 is implanted at a proximal end of a tibia 160. The bearing 120 locates between the femoral and tibial components 110, 130.

[0172] The bearing 120 has a first bearing surface 121 and a first engagement surface 122 on substantially opposite sides of the bearing 120. The femoral component 110 has second bearing surface 111 and a femur mating surface 112 on substantially opposite sides of the femoral component 110. The tibial component 130 has a second engagement surface 132 and a tibia mating surface 131 on substantially opposite sides of the tibial component 130.

[0173] When implanted at the knee, the femur mating surface 112 of the femoral component 110 is fixed to the femur 150, the tibia mating surface 131 of the tibial component 130 is fixed to the tibia 160, the second bearing surface 111 of the femoral component 110 bears against and articulates with the first bearing surface 121 of the bearing 120 and with a bearing surface of the patella component 140, and the first engagement surface 122 of the bearing 120 is interconnected with the second engagement surface 132 of the tibial component.

Bearing and tibial component engagement using filler member

[0174] A bearing 210, tibial component 220 and filler member 230 of a knee prosthesis 200 according to an embodiment of the present disclosure are illustrated in detail in Figs. 2 to 6b.

[0175] Fig. 2 shows an exploded view of the bearing 210, tibial component 220and filler member 230, which components are connected together when the knee prosthesis is implanted in a patient. Fig. 2 also includes an indication of three perpendicular axes of the apparatus 200, indicative of the relative anatomical positioning of features of the apparatus when correctly implanted in the patient. The axes include specifically a superior/inferior axis S, I, an

anterior/posterior axis A, P and a lateral/medial axis L, M. [0176] As most easily seen in Figs. 3a to 3c, a first engagement surface 211 of the bearing 210 has a posterior edge 212 and an anterior edge 213. A posterior recess 214 of the bearing 210 is provided adjacent the posterior edge 212 of the bearing 210 and an anterior recess 215 of the bearing 210 is provided adjacent the anterior edge 213 of the bearing 210.

[0177] The posterior recess 214 of the bearing 210 is partially defined by two substantially straight surfaces 2141, 2142 that extend at an angle a to each other (see Fig. 3 c) such as to provide the posterior recess 214 with substantially a V-shape. The surfaces 2141, 2142 diverge in the posterior direction and are oriented substantially symmetrically either side of a sagittal plane that extends centrally through the bearing 210. The angle a between the surfaces 2141, 2142 is approximately 40° in this embodiment, although the angle may be anywhere between about 20° and 90° in other embodiments, for example. The two angled surfaces 2141, 2142 form part of an anterior surface of the posterior recess 214 and are adapted to extend on respective sides of a posterior notch 216 in the bearing 210 that receives the posterior cruciate ligament (PCL) of the knee joint when the apparatus is implanted in the patient.

[0178] The anterior surface of the posterior recess 214 includes a locking element in the form of an anterior tab 2143 that extends along the two angled surfaces 2141, 2142 and projects from the angled surfaces 2141, 2142, including in a posterior direction. The anterior tab 2143 defines a further locking element in the form of an anterior groove 2144 that also extends along the two angled surfaces 2141, 2142, and between the anterior tab 2143 and a superior surface 2145 of the posterior recess 214.

[0179] The anterior recess 215 of the bearing 210 is provided by a cut-out in the first engagement surface 211 adjacent the anterior edge 213. The cut-out has a generally bi-convex shape, being defined on a posterior side by a curved posterior surface 2151 of the anterior recess 215 and extending to a curved portion of the anterior edge 213.

[0180] As most easily seen in Figs. 2 and 4a to 4d, a second engagement surface 221 of the tibial component 220 has a posterior edge 222 and an anterior edge 223. A posterior buttress 224 of the tibial component 220 is provided adjacent the posterior edge 222 of the tibial component 220 and an anterior buttress 225 of the tibial component 220 is provided adjacent the anterior edge 223 of the tibial component 220.

[0181] The posterior buttress 224 has two substantially straight sidewalls 2241, 2242 that project from the second engagement surface 221 and extend at an angle a to each other such as to provide the posterior buttress 224 with substantially a V-shape, which shape is the substantially a reciprocal of the shape of the posterior recess 214. The sidewalls 2241, 2242 diverge in the posterior direction and are oriented substantially symmetrically either side of a sagittal plane that extends centrally through the tibial component 220. The angle a between the sidewalls 2241, 2242 is approximately 40° in this embodiment (see Fig. 4b) although the angle may be anywhere between about 20° and 90° in other embodiments, for example. Surfaces of the two sidewalls 2241, 2242 form part of an anterior surface of the posterior buttress 224 and are adapted to extend on respective sides of a posterior notch 226 in the tibial component 220 that is adapted to receive the posterior cruciate ligament (PCL) of the knee joint when the apparatus is implanted in the patient. The anterior surface of the posterior buttress 224 includes a locking element in the form of an anterior tab 2243 that extends along the surfaces of the angled sidewalls 2241, 2242 and projects from the angled sidewalls 2241, 2242, including in an anterior direction. The anterior tab 2143 defines a locking element in the form of an anterior groove 2244 that also extends along the surfaces of the two angled sidewalls 2241, 2242, and between the anterior tab 2243 and the second engagement surface 221 of the tibial component 220.

[0182] The anterior buttress 225 of the tibial component 220 is provided adjacent the anterior edge 223 of the second engagement surface 221 of the tibial component 220. The anterior buttress 225 also has a generally bi-convex shape, including a posterior sidewall providing a curved posterior surface 2251 of the anterior buttress 225 and an anterior sidewall providing a curved anterior surface 2252, the anterior surface 2252 being substantially congruent with the anterior edge 223. The anterior buttress 225 has a width in the anterior/posterior direction (i.e. in a direction substantially parallel to the anterior/posterior axis A,P generally as indicated in Fig. 2), that is smaller than the width of the anterior recess 215 in the same direction.

[0183] The posterior buttress 224 is locatable at a position in the posterior recess 214, and the anterior buttress 225 is locatable at a position in the anterior recess 215, to interconnect the bearing 210 and the tibial component 220. The interconnection is achieved through relative movement of the bearing 210 and tibial component 220 substantially in two directions.

[0184] In more detail, prior to or during implantation of the apparatus, the first and second engagement surfaces 211, 221 of the bearing 210 and tibial component 220 are moved towards each other, substantially in a superior/inferior direction (i.e. in a direction substantially parallel to the superior/inferior axis S, I generally as indicated in Fig. 2), so that the first and second engagement surfaces 211, 221 are brought into abutment at a first position of the apparatus. The surfaces 211, 221 are brought into abutment at the first position so that the posterior buttress 224 locates in the posterior recess 214 and the anterior buttress 225 locates in the anterior recess 215. In the first position, the posterior surface 2151 of the anterior recess 215 and the posterior surface 2251 of the anterior buttress 225 may be touching or relatively close to each other.

[0185] The apparatus is then moved from the first position to a second position to achieve the interconnection between the bearing 210 and the tibial component 220. When the apparatus is moved from the first to the second position, the bearing 210 and the tibial component 220, and therefore the first and second engagement surfaces 211, 221, slide relative to each other substantially in the anterior/posterior direction in a manner that causes the anterior tab 2143 of the posterior recess 214 to travel towards and locate in the anterior groove 2244 of the posterior buttress 224, and that causes the anterior tab 2243 of the posterior buttress 224 to travel towards and locate in the anterior groove 2144 of the posterior recess 214. This interconnection is represented in Fig. 6a, for example, and substantially prevents relative movement of the bearing 210 and the tibial component 220 in the superior/inferior direction.

[0186] While the apparatus is moved from the first position to the second position, the anterior buttress 225 also moves substantially in an anterior/posterior direction, within the anterior recess 215, causing the posterior surface 2151 of the anterior recess 215 and the posterior surface 2251 of the anterior buttress 225 to move apart or further apart such that a gap 240 is created or enlarged between the surfaces 2151, 2251. The posterior surface 2251 of the anterior buttress 225 and the posterior surface 2151 of the anterior recess 215 are considered to provide first and second gap surfaces 2251, 2151 of the apparatus, respectively.

[0187] Fig. 5 shows a schematic superior view of the bearing 210 and tibial component 220 in the interconnected state, with an anterior portion of the bearing 210 omitted to aid understanding. An arrow is provided to indicate the gap 240 between the first and second gap surfaces 2251 , 2151.

[0188] In this embodiment, the gap 240 is a by-product of the manner in which the bearing and tibial component 210, 220 move relative to each other in order to achieve the interconnection. The gap 240 results from providing an anterior recess 215 that is large enough to both

accommodate the anterior buttress 225, and allow relative movement between the bearing 210 and tibial component 220 in the anterior/posterior direction while the anterior buttress 225 is located in the anterior recess 215.

[0189] To maintain the bearing 210 and the tibial component 220 in the interconnected state, the filler member 230 is located in the gap 240 at a position where it extends between and engages both the first and second gap surfaces 2251, 2151. Since the filler member 230 is substantially rigid and incompressible, it prevents the first and second gap surfaces 2251, 2151 from moving back towards each other in the anterior/posterior direction, and therefore retains the bearing 210 and tibial component 220 in the interconnected state. The filler member 230 therefore provides for secure interconnection between the bearing 210 and the tibial component 220. Generally, it is not possible or very difficult, manually or otherwise, to release the interconnection between the bearing 210 and tibial component 220 when the filler member 230 is located in the gap 240. In other embodiments, multiple filler members may be provided that locate in the gap 240 and in combination can be used to achieve the same effect.

[0190] The filler member 230 has a posterior surface 231 and an anterior surface 232. The filler member 230 is advanced into the gap 240 substantially in a lateral/medial direction (i.e. in a direction substantially parallel to the lateral/medial axis L, M generally as indicated in Fig. 2). The direction of movement of the filler member 230 is indicated by arrow 233 in Fig. 5. A tool (not shown) can be used to advance the filler member 230, which tool can engage an indent 234 at a rear end 235 of the filler member 230. The first and second gap surfaces 2251, 2151 not only define the gap 240 but also serve to guide the filler member 230 into the gap 240.

[0191] The filler member 230 in this embodiment is a wedge. The wedge tapers towards a leading end 236 of the filler member 230, the leading end 236 being opposite to the rear end 235 and being introduced first into the gap 240. As the filler member 230 is advanced into the gap 240, its anterior surface 232 moves into engagement with the first gap surface 2251 and its posterior surface 231 moves into engagement with the second gap surface 2151. As the filler member is further advanced, pressure between the anterior and posterior surfaces 232, 231 of the filler member 230 and the first and second gap surfaces 2251, 2151 increases such that filler member 230 is held firmly in the gap 240 by frictional force. In this embodiment, the wedge- shape of the filler member tapers at an angle of between about 2° and 7°.

[0192] The filler member 230 is curved through the provision of curved anterior and posterior surfaces 232, 231. The first and second gap surfaces 2251, 2151 are also curved in a manner that conforms to the curvature of the anterior and posterior surfaces 232, 231 , respectively, of the filler member. The first gap surface 2251 has a curvature of a first radius and the anterior surface 232 of the filler member 230 also has a curvature of the first radius. Similarly, the second gap surface 2151 has a curvature of a second radius and the posterior surface 231 of the filler member 230 has a curvature of the second radius. The first and second radii are different. The first radius is larger than the second radius in this embodiment.

[0193] As can be seen in Fig. 5, and in more detail in Fig. 6b, the second gap surface 2151 comprises a plurality of first teeth 2152 and the posterior surface 231 of the filler member 230 comprises a plurality of second teeth 2311 adapted to engage the first teeth 2152 when the filler member 230 is moved into the gap 240. The engagement between the first and second teeth 2152, 2311 is such that, at least after the filler member 230 is advanced into the gap 240 to a position where it engages both the first and second gap surfaces 2251, 2151, the filler member 230 is substantially non-removable from the gap 240, e.g., at least in an opposite direction to the direction 233 in which it was advanced into the gap 240.

[0194] The manner in which the bearing 210 and the tibial component 220 are interconnected, and the use of the filler member 230, substantially prevents relative translation, rotation and/or tilting between the bearing 210 and the tibial component 220 when subjected to forces during use.

[0195] The arrangements of centrally located buttresses 224, 225 and recesses 214, 215, along with the use of the filler member 230, enable broad interchangeability between bearings and tibial components of different sizes to be achieved without compromising secure engagement therebetween. For example, as represented schematically in Fig. 7, in one embodiment tibial components 220, 220a, 220b, 220c of a variety of different sizes are provided, which can be independently selected for use with a variety of differently sized tibial bones. Since the profiles of, and distances between, the anterior surface of the posterior buttress 224 and the posterior surface 2251 of the anterior buttress 225 are kept substantially constant across all of the tibial components 220, 220a, 220b, 220c, one bearing 210 can be securely engaged with any one of these tibial components. As another example, as represented schematically in Fig. 8, in one embodiment bearings 210, 210a, 210b, 210c of a variety of different sizes are provided, which can be selected for use with a variety of differently sized femoral components. Since the profiles of, and distances between, the anterior surface of the posterior recess 214 and the posterior surface 2151 of the anterior recess 215 are kept substantially constant across all of the bearings 210, 210a, 210b, 210c, one tibial component 220 can be securely engaged with any one of these bearings. Moreover, in general, any one of the bearings 210, 210a, 210b, 210c sized as depicted in Fig. 8 may be used with any one of the tibial components 220, 220a, 220b, 220c sized as depicted in Fig. 7.

[0196] In alternative embodiments, rather than retain substantially constant profiles and distances between the surfaces of the buttresses and recesses, filler members of different sizes may be used, particularly for bearing and tibial components that have different depths (i.e.

different dimensions in an anterior/posterior direction).

[0197] In this embodiment, the bearing 210, the tibial component 220 and the filler member 230 are each be formed in one piece. In alternative embodiments, they may be formed in multiple pieces.

Bearing and tibial component engagement using pegs and holes

[0198] With reference to Figs. 9 to 11, in a knee prosthesis 300 according to another

embodiment of the present disclosure, a releasable engagement between a bearing 310 and a tibial component 320 is achieved at least in part using a plurality of pegs 323 provided on one of the first and second engagement surfaces 312, 322 and using a plurality of holes 313 provided on the other of the first and second engagement surfaces 312, 322, wherein at least some of the plurality of pegs 323 locate in at least some of the plurality of holes 313 to effect engagement between the bearing 310 and the tibial component 320. In this embodiment as illustrated in Fig. 9, the plurality of pegs 323 are provided on the second engagement surface 322 of the tibial component 320 and the plurality of holes 313 are provided on the first engagement surface 312 of the bearing 310. However, in alternative embodiments, the pegs and holes can be provided on the opposite engagement surfaces 312, 322, or a plurality of pegs and holes can be provided on both engagement surfaces 312, 322. The positioning of the pegs and holes may be selected in consideration of the size and shape of the bearing and/or tibial component. For example, if the bearing is relatively thin (i.e. has a relatively shallow depth between the first bearing surface and the first engagement surface), it may not be possible to provide sufficiently deep holes in the bearing to accommodate pegs of a desired length. In this instance or otherwise, it may be desirable to provide some or all of the plurality of holes on the second engagement surface 322 of the tibial component 320.

[0199] In this embodiment, the tibial component 320 has no peripheral wall or lip around the second engagement surface 322. A majority of the pegs 323 and holes 313 are positioned inwardly from the peripheral edges 324, 314 of the respective engagement surfaces 322, 312. The tibial component 320 differs in this regard from a tibial tray that relies on peripheral registration between the tibial tray and a bearing, the tibial tray having peripheral walls that define a recess in which an entire engagement surface of a bearing is received. Through use instead of inwardly located pegs 323 and holes 313 to effect engagement between the bearing 310 and tibial component 320, knee prosthesis systems with broader interchangeability between bearings and tibial components of different sizes can be achieved by the present disclosure.

[0200] An example of this interchangeability is illustrated in Fig. 12, where a plurality of bearings 310a-d are provided in a knee prosthesis system according to an embodiment of the present disclosure, which bearings 310a-d have a variety of different sizes (represented using broken lines in Fig. 12), and which bearings 310a-310d can be selectively and separately used with a single tibial component 320 (represented using unbroken lines). As can be seen in Fig. 12, one of the bearings 310a can be selected for use with the tibial component 320, which bearing 310a has a first engagement surface with a substantially smaller area than the area of the second engagement surface 322 of the tibial component 320. As can also be seen in Fig. 12, a different one of the bearings 310d can be selected separately for use with that tibial component 320, which bearing 310d has a first engagement surface with substantially the same area (or an area slightly larger than) the area of the second engagement surface 322 of the tibial component 320. In this instance, the bearing 310d may overhang the tibial component 320. Knee prosthesis systems according to alternative embodiments of the present disclosure can include a plurality of tibial components of different sizes, which can be selectively and separately used with a single bearing. Knee prosthesis systems according to yet further alternative embodiments of the present disclosure can include a plurality of tibial components of different sizes, which can be selectively and separately used with a plurality of bearings of different sizes.

[0201] While the total number of pegs 323 and the total number of holes 313 in the embodiment represented in Figs. 9 to 11 are identical (one of the holes is obscured by a post 315 in Fig. 9), a combination of a bearing and a tibial component may be provided in accordance with the present disclosure in which the total number of pegs is different from the total number of holes. In general, to effect engagement between the bearing and tibial component, it is possible to have only a subset of the plurality of pegs (a core group of pegs) locating in the holes and/or only a subset of the plurality of holes (a core group of holes) receiving pegs. This makes the knee prosthesis system further adaptable for use with bearings and tibial components of different sizes and/or shapes. For example, even if the engagement surface of the bearing is smaller than the engagement surface of the tibial component to such an extent that it cannot support one or more a pegs or holes that could interface with one or more holes or pegs of the tibial component, the ability for the bearing and the tibial component to securely engage each other may not be compromised. To provide an example of this, reference should again be made to Fig. 12, where it can be seen that the two smallest bearings 310a, 310b that are illustrated are unable to support a complete hole to receive the most peripherally located peg 323' that is provided on the tibial component 320.

[0202] Thus, in general, where multiple bearings of different sizes and/or multiple tibial components of different sizes are provided, each bearing or tibial component may incorporate the same core group of pegs and/or holes. The smallest bearing or tibial component may incorporate the core group of pegs and/or holes only, whereas larger bearings or tibial components may incorporate the core group of pegs and/or holes along with additional pegs and/or holes.

[0203] As can be seen most clearly in Fig. 11, each of the pegs 323 projects in a direction, as indicated by arrow 3231 in Fig. 11, that is substantially perpendicular to the second engagement surface 322 of the tibial component 320. The pegs 323 are elongated in this direction 3231.

When the tibial component 320 is implanted, the direction 3231 is substantially parallel to the mechanical and anatomical axes of the tibia and/or to the mechanical axis of the leg.

[0204] In this embodiment, each peg 323 is substantially identical in size and has a substantially frustoconical shape. Each peg 323 tapers towards its distal end 3232. Similarly, each hole 313 has a corresponding substantially frustoconical shape (as delineated by surfaces defining the recess). Since the pegs 323 taper towards their distal ends 3232, it is easier to position the pegs 323 in openings of respective holes 313 in a process of locating the pegs 323 in the holes 313. However, a variety of differently shaped pegs and holes may be employed in alternative embodiments. Pegs may have a cross-sectional shape that is circular, elliptical, square, rectangular, irregular or otherwise and all pegs may or may not be same size and/or shape as one another. In general, however, it may be expected that each hole will have size and shape corresponding to a peg that is to be located in that recess.

[0205] Openings of the holes 313 through which pegs 323 enter the holes 313 are flush with the first engagement surface 312 of the bearing 310. The holes 313 extend from the first engagement surface 312 into the bearing 310. When the pegs 323 are fully located in the respective holes 313, the first and second engagement surfaces 312, 322 abut each other. Except at positions where the pegs 323 and holes 313 are provided, the first and second engagement surfaces 312, 323 have conforming flat profiles such that the abutment between the first and second engagement surfaces occur across a major part of each engagement surface 312, 323. Other conforming surface profiles may be employed, however.

[0206] The pegs 323 and holes 313 are sized to ensure a reasonably tight frictional fit with each other. While the bearing 310 and tibial component 320 are releasably rather than fixedly engaged, through the provision of a frictional fit between the pegs 323 and holes 313, a moderate or strong separation force may need to be applied to the bearing 310 and tibial component 320, e.g., by hand, to effect release. This can ensure that release does not occur undesirably during

implantation of the components or at other inopportune moments.

[0207] In this embodiment, across a first bearing surface 311 of the bearing, the distance between the first bearing surface 311 and the first engagement surface 312 varies. This is a result of the undulating profile of the first bearing surface 311 in contrast to the flat profile of the first engagement surface 312. Thus, the bearing 310 has varying depth. To ensure that holes 313 (of depths sufficient large to accommodate the pegs 323) can be provided in the bearing 310, the holes 313 are distributed over regions of the bearing 310 that have a relatively greater depth to other regions of the bearing 310.

[0208] Referring to Fig. 9, a post 315 is provided on one of the first and second engagement surfaces, in particular the first engagement surface 312 in this embodiment, and a cavity 325 is provided on the other of the first and second engagement surfaces, in particular the second engagement surface 322 in this embodiment. To effect releasable engagement between the bearing 310 and the tibial component 320, the post 315 locates in the cavity 325 in addition to the pegs 323 locating in the holes 313. The post 315 and cavity 325 are provided at a central region of first and second engagement surfaces 312, 322, respectively. The holes 313 and pegs 323 are distributed substantially around the post 315 and cavity 325, respectively.

[0209] The post 315 projects in a direction, indicated by arrow 3151 in Fig. 9, that is substantially perpendicular to the plane of the first engagement surface 312 of the bearing 310. The post 315 is elongated in this direction 3151. When the bearing is implanted, the direction 3151 is substantially parallel to the mechanical and anatomical axes of the tibia and/or to the mechanical axis of the leg.

[0210] The post 315 is longer than each one of the pegs 323, which pegs 323 are of substantially the same length in this embodiment. The post 315 is about twice as long as the pegs in this embodiment. In general, however, the post 315 may be at least 1.5 times, at least 2 times or at least 2.5 times the length of the pegs, or otherwise. The post 315 also has a larger cross-sectional area than each one of the pegs.

[0211] By providing a post 315 that is substantially longer than the pegs 323, in the process of effecting engagement between the bearing 310 and the tibial component 320, the post 315 can enter the cavity 325 prior to the pegs 323 entering the holes 313. The post 315 can provide for an initial registration of the bearing 310 with the tibial component 320, making it more

straightforward to subsequently align pegs 323 with corresponding holes 313. Once the post 315 enters the cavity 325, only relative rotation of the bearing 310 and tibial component 320 may need to be performed to align the pegs 323 with the corresponding holes 313. The post 315 can provide a journal about which the tibial component 320 rotates. Further, by providing the post 315 with a greater length than the pegs 323, the post can provide for greater restraint against relative tilting between the bearing 310 and the tibial component 320 when the bearing 310 and tibial component 320 are releasably engaged and subjected to forces during use.

[0212] In this embodiment, the post 315 has a substantially frustoconical shape. The post 315 tapers towards its distal end. Similarly, the cavity 325 has a corresponding substantially frustoconical shape (as delineated by surfaces defining the cavity 325). By tapering towards its distal end, it is easier to position the post 315 through the opening of the cavity 325 in the process of locating the post 315 in the cavity 325. However, a variety of differently shaped posts and cavities may be employed in alternative embodiments. Posts may have a cross -sectional shape that is circular, elliptical, square, rectangular, irregular or otherwise. In general, however, it may be expected that each cavity will have size and shape corresponding to the post.

[0213] A substantially hollow stem 326 is provided on the tibia mating surface 321. The stem 326 projects from the tibia mating surface 321. The stem 326 is adapted to extend into the intramedullary canal of the tibia when the tibial component 320 is fixed to the tibia. The cavity 325 provided on the second engagement surface 322 extends from the second engagement surface 322, through the tibial component 320, partially into the stem 326. The stem 326 provides a region of increased depth to the tibial component 320 in which to partially accommodate the cavity 325 (and the post 315 when located in the cavity 325).

[0214] The bearing 310 and the tibial component 320 can be releasably engaged at one relative position and orientation only. This ensures that an inappropriate relative positioning and orientation of the bearing 310 and tibial component 320 is avoided. In this embodiment, this is achieved through distribution of the pegs 323 in a non-circularly-symmetrical pattern about the cavity 325.

[0215] In this embodiment, the femoral component 110, the bearing 310 and the tibial component 320 are each formed in one piece. As such, the pegs are integrally formed with the second engagement surface and the holes (or at least surfaces delineating the holes) are integrally formed with the first engagement surface. The femoral component and tibial component are formed from a surgical grade metal and the bearing is formed from surgical grade plastic.

[0216] The bearing 310 in this embodiment is engaged directly with the tibial component 320 without undue force, whether the tibial component 320 is already implanted in the knee (in situ) or externally located. Further, the bearing 310 is releasable from the tibial component 320 so that it can be replaced as necessary with an identical bearing, or replaced with another bearing of different size, without compromising any component of the prosthesis or causing trauma to the knee.

[0217] Bearings 310a-d of a variety of different sizes can be separately selected to be releasably engaged and positively retained against displacement relative to the tibial component 320, e.g., when subjected to contact with the femoral component 11 in any foreseeable presentation. This retention can be enduring and robust throughout the service life of the prosthesis.

[0218] A tibial component 430 according to another embodiment is illustrated in Figs. 13 and 14. The tibial component 430 is substantially identical to the tibial component 320 discussed above with reference to Figs. 9 to 12, except for the distribution of the pegs and the shapes of the pegs. In this embodiment, pegs 433 are provided that each have a substantially cylindrical body with a rounded distal end. The pegs 433 have differing lengths. The lengths of the pegs 433 are generally proportional to the depth of the bearing at the region of the bearing where a hole is located in which the peg is to locate. In general, longer pegs 433 are provided where the bearing is thicker. Since longer pegs 433 offer better restraint against relating movement of the tibial component and bearing (most notably tilting), the restraining effect of the pegs 433 can be maximised. In this embodiment, the pegs 433 are provided on the second engagement surface 432 of the tibial component, at an inner region of the second engagement surface 432 only. The pegs 433 again surround a cavity 435, the cavity receiving a post provided on the bearing.

Configuration of surfaces of knee prosthesis components

[0219] A knee prosthesis 500 comprising a femoral component 510, bearing 520 and tibial component 530 according to another embodiment of the present disclosure is illustrated in Figs. 15 to 17. The knee prosthesis 500 illustrated in the Figures is a right knee prosthesis. However, the teaching herein is equally applicable to a left knee prosthesis.

[0220] The femoral component 510 includes a patella flange 511 comprising first and second opposite ends 512, 513 and a trochlear groove 514 extending between the first and second ends 512, 513. The second end 513 is a free end of the flange 511 that locates anteriorly of the first end 512 upon implantation. The first end 512 is located where the patella flange 511 transitions into condyles. In particular, a lateral condyle 515 and a medial condyle 516 each project from the first end 512 of the patella flange 511 and are separated by an intercondylar notch 5110. As can be seen in Fig. 17, for example, the femoral component 510 has a generally u-shaped

configuration across a sagittal plane, with the patella flange 511 and the medial and lateral condyles 515, 516 having curved outer surfaces.

[0221] Referring to Fig. 15, the outer curved bearing surface of the patella flange 511 includes a lateral surface 517, a medial surface 518 and a trochlear groove surface 519, the trochlear groove surface defining the trochlear groove514 and being located between the lateral and medial surfaces 517, 518. The trochlear groove surface 519 is recessed relative to the lateral and medial surfaces 517, 518. Each of the lateral, medial and trochlear groove surfaces, 517, 518, 519 extend substantially up to and between the first and second ends 512, 513 of the patella flange 511 and are located side -by-side in a transverse (medial -lateral) direction of the femoral component 510, the transverse direction being indicated by a line 501 in the Figures.

[0222] The trochlear groove surface 519 includes a lateral flank 5191 and a medial flank 5192 located on a lateral side and a medial side, respectively, of a notional bottom line 5193 of the trochlear groove surface 519, the notional bottom line 5193 of the trochlear groove surface 519 extending through the lowest (most recessed) points of the trochlear groove surface 519 along the path of the trochlear groove surface 519 between the first and second ends 512, 513 of the patella flange 511. The lateral flank 5191 adjoins the lateral surface 517 and the medial flank 5192 adjoins the medial surface 518.

[0223] An example surface profile of the lateral and medial surfaces 517, 518, and the lateral and medial flanks 5191, 5192 of the trochlear groove surface 519, in the transverse direction 501 of the femoral component 510, is represented in Fig. 18. As can be seen, the lateral transition 5191a between the lateral flank 5191 and the lateral surface 517 in the transverse direction 501 is a substantially smooth transition, whereas the medial transition 5192a between the medial flank 5192 and the medial surface 518 in the transverse direction 501 is a substantially angular transition.

[0224] A major portion of the lateral flank 5191 is substantially flat, the lateral flank 5191 following a substantially straight line 502 as it extends from the notional bottom line 5193 of the trochlear groove surface 519 to the lateral surface 517 in the transverse direction 501 of the femoral component 510. In contrast, the medial flank 5192 is entirely curved, the medial flank 5192 following a substantially curved line 503 as it extends from the notional bottom line 5193 of the trochlear groove surface 519 to the medial surface 518 in the transverse direction 501 of the femoral component 510. The curvature of the medial flank 5192 is generally concave and follows a substantially circular arc. Nevertheless, in alternative embodiments, the medial flank 5192 can comprise both flat and curved portions.

[0225] As can be seen in Fig. 18, both the lateral and medial surfaces 517, 518 follow curved lines 504, 505 from their transitions 5191a, 5192a with the lateral and medial flanks 5191, 5192 to lateral and medial edges 5111, 5112 of the femoral component 510. The curvatures of the lateral and medial surfaces 517, 518 are convex and follow a substantially circular arc.

[0226] The outer surface of patella flange 511, including the trochlear groove surface 519, provides a bearing surface for a patella component 540. In this embodiment, the patella component 540 is a prosthetic patella component adapted to be mounted on a resected surface of a native patella, although an unmodified native patella may be used in alternative embodiments according to the present disclosure. The patella component 540 is illustrated in more detail in Figs. 19 and 20. The patella component 540 includes a bearing surface 547 comprising a lateral facet 541 and a medial facet 542 positioned on either side of an apex 543 of the bearing surface 547. First and second side-facets 5471, 5472 are positioned between the lateral and medial facets 541, 542, on opposite sides of the apex 543, providing connecting surfaces that blend (e.g., based on CAD surface modelling) into the topology of the lateral and medial facets 541, 542. As discussed further below with reference to Figs. 22a to 22c, the bearing surface 547 is adapted to bear against and track along the trochlear groove surface 519 of the femoral component 510 during articulation of the knee prosthesis. During this articulation, the lateral facet 541 bears against the lateral flank 5191 of the trochlear groove surface 519, the medial facet 542 bears against the medial flank 5192 of the trochlear groove surface 519 and the apex 543 aligns with and tracks along the notional bottom line 5193 of the trochlear groove surface 519. To ensure a close fit between the bearing surface 547 of the patella component 540 and the trochlear groove surface 519, the lateral facet 541 has a surface profile substantially identical to that of the lateral flank 5191 of the trochlear groove surface 519 and the medial facet 542 has a surface profile substantially identical to that of the medial flank 5192 of the trochlear groove surface 519. In this regard, a major portion of the lateral facet 541 is substantially flat, the lateral flank 541 following a substantially straight line 502 as it extends from the apex 543 to a lateral edge 544 of the patella component 540 in the transverse direction 501. The lateral facet 541 extends at an angle relative to a flat anterior surface 548 of the patella component 540, located on an opposite side of the patella component to the bearing surface, of between about 15 and 30 degrees. Further, the medial facet 542 is substantially curved, the medial facet 542 following a substantially curved line 503 as it extends from the apex 543 to a medial edge 545 of the patella component 540 in the transverse direction 501. The curvature of the medial facet 542 is generally convex and follows a substantially circular arc. Nevertheless, in alternative embodiments, where the medial flank comprises both flat and curved portions, the medial facet may also comprise both flat and curved portions.

[0227] The manner in which the patella component 540 bears against and articulates with the femoral component 510 is illustrated in Figs. 22a to 22c, which show cross-sections of the femoral component 510 along lines a— a, b— b and c— c, respectively, of Fig. 21, in addition to a cross-section of the patella component 540, the patella component 540 bearing against and articulating with the femoral component 510. Line a— a is the line closest to the second end 513 of the patella flange 511, line c— c is the line closest to the first end 512 of the patella flange 511 and line b— b is located between lines a— a and line c— c. For each cross-section, the profile of the patella flange 511 is generally as described above with reference to Fig. 18. However, the lateral and medial surfaces 517, 518 and the lateral and medial flanks 5191, 5192 widen towards the first end 512 of the patella flange 511, the depth of the trochlear groove 514 as defined by the lateral and medial flanks 5191, 5192 of the trochlear groove surface 519 increases towards the first end 512 of the patella flange 511, and the angle of the lateral flank 5191 changes towards the first end 512 of the patella flange 511.

[0228] As can be seen in Figs. 22a to 22c, when the patella component 540 bears against and articulates with the femoral component 510, the lateral and medial facets 541, 542 of the patella component 540 extend beyond the lateral and medial flanks 5191, 5192 of the trochlear groove surface 519 such as to partially overhang or contact the lateral and medial surfaces 517, 518. By providing a smooth lateral transition 5191a between the lateral flank 5191 of the trochlear groove surface 519 and the lateral surface 517, contract stresses between the lateral facet 541 of the patella component 540 and the patella flange 511 can be reduced. It has been determined that compressive loads on the patella component can reach 2 to 3 times body weight when performing certain activities such as climbing stairs. Moreover, greater compressive load is taken by the lateral facet 541 of the patella component 540 compared to the medial facet 542. Since the lateral transition 5191a between the lateral surface 517 and the lateral flank 5191 is a smooth transition, the potential for increased stress to form on the lateral facet 541 of the patella component 540 when bearing against this transition region 5191a can be reduced. By reducing stress, reliability and comfort associated with use of the knee prosthesis can be substantially increased.

[0229] Since the compressive load taken by the medial facet 542 of the patella component 540 can be significantly lower than the load taken by the lateral facet 541, the angular medial transition 5192a between the medial flank 5192 and medial surface 518 of the femoral component 510 can present a lower stress risk for the medial facet 542 of the patella component 540 when bearing against this region. Further, through providing the angular transition 5192a rather than a smooth transition, a trochlear groove 514 with substantially increased depth can be achieved. The depth of the groove 514 can be substantially increased by virtue of the medial flank 5192 extending more steeply from the medial surface 518 than would generally be possible if it were connected to the medial surface 518 by virtue of a smooth transition. By providing a deeper trochlear groove 514, the likelihood of dislocation or displacement of the patella component 540 from the trochlear groove 514 can be substantially reduced.

[0230] At any point along the path of the trochlear groove between the first and second ends 512, 513 of the patella flange 511, the lateral flank 5191 of the trochlear groove surface 519 has a width in the transverse direction 501 of the femoral component that is greater than the width of the medial flank 5192 of the trochlear groove surface 519. Similarly, the lateral facet 541 of the patella component is wider in the transverse direction 501 than the medial facet 542. Contact between the lateral flank 5191 of the trochlear groove surface 519 and the lateral facet 541 of the patella component 540 therefore takes place over a larger area than contact between the medial flank 5192 of the trochlear groove surface 519 and the medial facet 542 of the patella component 540. Accordingly, the knee prosthesis is capable of distributing the higher forces that occur at the patella-femoral articulation of the knee prosthesis over a greater surface area of the prosthesis, further reducing stress and increasing reliability and comfort.

[0231] As indicated above, the depth of the trochlear groove 514 in this embodiment increases towards the first (posterior) end 512 of the patella flange 511. The increase in depth occurs in a gradual fashion and allows the patella component 540 to lie more deeply in the groove 514 when the knee prosthesis is in a flexion state, reducing potential obstruction by the patella component 540 to adjacent elastic soft tissue structures (e.g. the patella retinaculum) that stretch over patella component 540 and patella flange 511 during flexion of the knee prosthesis.

[0232] As also indicated above, the angle of the lateral flank 5191 of the trochlear groove surface 519 changes towards the first end 512 of the patella flange 511. In particular, the lateral flank 5191 rotates such that it faces in a more medial direction as it extends towards the first end 512 of the patella flange. In this embodiment the rotation of the lateral flank 5191 is about an axis of rotation 5000 that is positioned on a lateral dwell plane 507 of the femoral component. The axis of rotation 5000 follows the curvature of the lateral surface of the patella flange 511 on the lateral dwell plane 507, the axis 5000 being spaced proximally of the lateral surface 517 by a distance corresponding to the radius of the arc of curvature of the lateral surface 517 such that, in any transverse cross-section (e.g. , a— a, b— b, c— c) of the patella flange 511, the axis of rotation 5000 passes through the center of arc of lateral surface 517. In general, by virtue of the rotation, the lateral flank 5191 extends at a steeper angle from the bottom of the trochlear groove as the trochlear groove extends from the second end towards the first end of the patella flange. The rotation may be in the range of 2 to 7 degrees, for example. Due to the engagement between the lateral facet 541 of the patella component and the lateral flank 5191, the rotation of the lateral flank 5191 causes a rotation of the patella component 540 as the patella component 540 moves along the trochlear groove 514 during articulation between the patella component 540 and the patella flange 511. The rotation can be considered a progressive "internal rotation" of the patella component ("internal rotation" being e.g., as defined in ISO 14243-4), as the knee moves towards flexion.

[0233] The rotation of the patella component and the increase in depth of the trochlear groove 514 as described above enables the patella component to more closely emulate the tracking behaviour of a patella in a native knee. Further, since lateral flank 5191 extends at a steeper angle from the bottom of the trochlear groove 514 an increased slope is provided for the patella component to climb before dislocation of the patella component 540 from the trochlear groove 514 can occur, which dislocation can otherwise be particularly prevalent towards the lateral side of the femoral component. Even though the patella component 540 rotates, the patella component 540 maintains a close/congruent fit with the trochlear groove surface 519. [0234] With reference to Fig. 22d, which shows a cross-section of the femoral component 510 along line d— d of Fig. 21, the profile of the patella flange 511 in the transverse direction is partially replicated in the condyle region of the femoral component 510, i.e., the region of the femoral component where the lateral and medial condyles 515, 516 and the intercondylar notch 5110 are provided. The outer, bearing surface of the lateral condyle 515 includes a lateral surface extension 517' that is an extension of the lateral surface 517 of the patella flange 511. Further, the outer surface of the lateral condyle 515 includes a lateral flank extension 519 that is an extension of the lateral flank 5191 of the trochlear groove surface 519 of the patella flange. The lateral transition 5191a' between the lateral flank extension 519 and the lateral surface extension 517' in the transverse direction 501 is a substantially smooth transition. Further, the lateral flank extension 519 is substantially flat, the lateral flank extension 519 following a substantially straight line as it extends from the intercondylar notch 5110 to the lateral surface extension 517' in the transverse direction 501. The outer, bearing surface of the medial condyle 516 includes a medial surface extension 518' that is an extension of the medial surface 518 of the patella flange 511. Both the lateral and medial surface extensions 517', 518' follow curved lines in the transverse direction. The curvatures of the lateral and medial surface extensions 517', 518' are convex and follow a substantially circular arc.

[0235] The surface profiles of the lateral and medial condyles 515, 516 as described above provide the condylar region of the femoral component with asymmetry. While the entire surface of the medial condyle can follow a substantially circular arc in the transverse direction 501, the surface of the lateral condyle is divided up in the transverse direction into the substantially flat region of the lateral flank extension 519 and the substantially circular arc region of the lateral surface extension 517'.

Rotational alignment of knee prosthesis components

[0236] Further embodiments of the present disclosure relate to methods of rotationally orienting components of a knee prosthesis in an implantation procedure, and relate to instrumentation used in those methods. Common to these embodiments is a method in which a first prosthetic component of a knee prosthesis is rotationally oriented at a resected surface of a first bone. A marking jig is used that includes an engagement surface, a marking jig pin protruding from the engagement surface, an articular surface opposite to the engagement surface, and at least one marker guide at a position spaced from the marking jig pin.

[0237] As illustrated in Fig. 23, the method can include: attaching the marking jig to the resected surface of the first bone including locating the marking jig pin in a pin hole in the resected surface (item 601); engaging the articular surface of the attached marking jig with an articular surface of a second prosthetic component fixed to a second bone (item 602), rotating the marking jig about the axis of the marking jig pin to place the articular surface of the marking jig into registration with the articular surface of the second prosthetic component (item 603); placing a mark on the first bone, wherein the marker guide is used to guide location of the mark on the first bone (item 604); positioning one or more recesses in the first bone to receive one of more protrusions that extend from an engagement surface of the first prosthetic component, the positions of the holes being determined based on the position of the pin hole in the resected surface and the position of the mark (item 605); and attaching the first prosthetic component to the first bone by locating the one or more protrusions in the one or more recesses (item 606).

[0238] In one embodiment, the first prosthetic component is a patella component and the first bone is a native patella with a resected surface. Moreover, the second prosthetic component is a femoral component fixed to the femur, the articular surface of the femoral component being the patella flange surface including the trochlear groove surface.

[0239] In another embodiment, the first prosthetic component is a tibial component and the first bone is the tibia with a resected proximal surface. Moreover, the second prosthetic component is a prosthetic femoral component fixed to the femur, the articular surface of the femoral component being a distal surface of the femoral component.

[0240] A marking jig 710 according to an embodiment of the present disclosure, for use in conjunction with a knee prosthesis, is illustrated in Figs. 24a and 24b. Specifically, the marking jig 710 is configured for use in a method of rotationally orienting a prosthetic patella component of the knee prosthesis at a resected surface of a native patella, the patella component being configured to articulate with a trochlear groove surface at a patella flange of a femoral component 720 of the knee prosthesis.

[0241] The marking jig 710 comprises an engagement surface 711 for engaging the resected surface of the patella, an articular surface 712 at an opposite side of the marking jig 710 from the engagement surface 711, and a side wall 713 extending between the engagement surface 711 and the articular surface 712 and around the periphery of the marking jig 710. The marking jig 710 further comprises a marking jig pin 714 that protrudes from a central region of the engagement surface 711 in a direction substantially perpendicular to the plane of the engagement surface 711. The axial direction of the marking jig pin 714 defines an axis of rotation 7141 of the marking jig 710. The making jig 710 further comprises a marker guide in the form of a notch 715 at the periphery of the marking jig 710, the notch 715 being spaced from the marking jig pin 714.

[0242] The engagement surface 711 of the marking jig 710 is substantially flat so that it can coapt with the (substantially flat) resected surface of the patella while the marking jig pin 714 is located in a pin hole in the resected surface. Nevertheless, when the marking jig pin 714 is located in the pin hole, the marking jig can rotate relative to the resected surface of the patella, about the axis of rotation 7141 of the marking jig 710. In this embodiment, the marking jig pin 714 is approximately 2 mm in diameter, so that it is relatively small in dimension relative to the resected surface of the patella, and so that there is minimal frictional torque to resist free rotation of the marking jig pin 714 within the bone. Moreover, the pin may be small enough so that it can be pressed into the bone by thumb pressure, without the need for drilling. In this embodiment, the marking jig pin is also approximately 3-7 mm in length with a pointed tip.

[0243] The marking jig pin is rigidly secured to the body of the marking jig 710 in this embodiment. However, alternatively, it may be constructed so that it is free to rotate relative to the body of the marking jig 710. The marking jig pin can be made from surgical grade metal, for example, with the body of the marking jig 710 being made from surgical grade metal or surgical grade plastic, polymer or composite material.

[0244] The articular surface 712 of the marking jig is curved, and more particularly saddle- shaped, such that it can engage with and register with a trochlear groove surface 722 at a patella flange 721 of a femoral component 720, generally as illustrated in Fig. 25. Figs. 26a to 26d provide further illustration of registration between the articular surface 712 of the marking jig 710 and the trochlear groove surface 722. In general, the articular surface 712 of the marking jig 710 has a shape that is substantially a reciprocal of the shape of the trochlear groove surface 722 at a particular location along the trochlear groove, the location corresponding to the location at which the patella locates when the patient's knee is in flexion, e.g., at 90 degrees.

[0245] The reciprocal shape of the articular surface 712 of the marking jig 710 enables it to achieve a snug, congruent fit with the trochlear groove surface 722. Indeed, in this embodiment, the closeness of the fit is such that there is one clearly identifiable position of registration between the articular surface 712 of the marking jig 710 and the trochlear groove surface 722. The position of registration is reached by rotating the marking jig 710 relative to both the resected surface of the patella and the trochlear groove surface 722, about the axis 7141 of the marking jig pin 714. Rotation can occur automatically to some extent. In particular, when the articular surface 712 of the marking jig 710 and the patella flange 721 are pressed together, the articular surface 712 of the marking jig 710 is predisposed to sliding and rotating into registration with the trochlear groove surface 722. When registered, there is substantially no further relative rotation possible between the articular surface 712 of the marking jig 710 and the trochlear groove surface 722. Thus, the alignment of the trochlear groove surface 722 can determine the appropriate rotational orientation of the marking jig 710.

[0246] As best seen in Figs. 24a and 24b, the notch 715 is located in the side wall 713 of the marking jig 710, which notch 715 has a first open end 7151 at the periphery of the engagement surface 711 and a second open end 7152 at the periphery of the articular surface 712. The notch tapers in size from the second open end 7152 towards the first open end 7151, the second open end 7152 therefore being larger than the first open end 7151. The notch 715 can receive the tip of an instrument, such as a sterile pen or electrocautery tool. The tip of the instrument can enter the notch 715 and be directed by the notch 715 towards the first open end 7151. The instrument is used to mark the resected surface of the patella, as discussed in more detail below. The notch 715 is provided at a medial side of the marking jig 710 so that it is easily accessible by the surgeon.

[0247] A method of rotationally orienting a patella component at a resected surface of a patella using the marking jig 710 is now discussed in more detail with reference to Figs. 27a to 27f. To prepare the native patella for resection, the surgeon everts the patella such that its native articular surface faces towards the surgeon and away from the femoral component of the knee prosthesis. A portion of the patella including the native articular surface is then resected. The resected native patella including its resected surface are represented as items 731 and 732, respectively, in Figs. 27a to 27f.

[0248] Before or after resection, an appropriately sized marking jig 710 is selected by the surgeon that corresponds to the chosen size of the femoral component and the shape of the trochlea groove surface. While the resected patella 731 is in the everted state, the surgeon temporarily secures the marking jig 710 to the resected surface 732 by manually pushing the marking jig pin 714 into a central region of soft bone at the resected surface 732, whereupon the engagement surface 711 of the marking jig 710 rests gently against the resected surface. An illustration of the marking jig 710 attached to the resected patella is provided in Fig. 27a with the position of the marking jig pin 714 underneath the marking jig 710 being shown using dotted lines. Pushing of the pin 714 into the resected surface forms a pin hole 734 in the resected surface 732. As an alternative, the pin hole 734 may be formed prior to locating of the marking jig pin 714 into the pin hole 734, e.g. by drilling, punching or otherwise.

[0249] In Fig. 27a, the marking jig 710 is in a non-optimal rotational orientation relative to the resected surface 732 of the patella 731. While in this orientation, the surgeon returns the patella 731 from its everted position (i.e. turns the patella and the marking jig 710 over) so that the articular surface 712 of the marking jig 710 is brought into engagement with the patella flange 721 of the femoral component 720 and the knee is flexed and extended. By virtue of contact between the articular surface 712 of the marking jig 710 and the patella flange 721, and/or through manipulation by the surgeon, the marking jig 710 is rotated relative to both the resected surface 732 of the patella 731 and relative to the patella flange 721, whereupon it registers with the trochlear groove surface 722 of the patella flange as illustrated in Fig. 28 (see also Figs. 26a to 26d and discussions above).

[0250] Fig. 27b illustrates the rotational orientation of the of the marking jig 710 relative to the resected surface 732 of the patella 731 when the marking jig 710 is registered with the trochlear groove surface 722 of the patella flange 721 of the femoral component 720. When in this registered state, the surgeon places a mark 733 on the resected surface 732 of the patella 731 adjacent the notch 715 of the marking jig 710. The mark 733 can be made using a sterile pen, electrocautery tool or other instrument that can cause an observable mark to be left on the resected surface 732.

[0251] Following placement of the mark 733, the patella 731 is everted once again and the marking jig 710 is removed from the resected surface 732 of the patella 731, as illustrated in Fig. 27c. Through use of the marking jig 710, however, the mark 733, along with the pin hole 734 of the marking jig pin 714, remain visible on the resected surface 732. Optionally, as shown in Fig. 27d, an orientation line 735 can be drawn on the resected surface 732 between the pin hole 734 and the mark 733.

[0252] The pin hole 734, mark 733 and optional line 735, are used to guide positioning of recesses, e.g., holes, in the resected surface of the patella. The holes are to receive protrusions, specifically pegs in this embodiment, which protrude from an engagement surface of the patella component.

[0253] To guide location of the holes in the resected surface 732, a drill guide 740 as illustrated in Figs. 29a and 29b can be used. The drill guide 740 comprises a patella contact surface 741, an opposite, outer surface 742, and a side wall 743 extending between the contact surface 741 and the outer surface 742 and around the periphery of the drill guide 740. Drill guide holes 744 extend between the contact surface 741 and the outer surface 742, through the drill guide 740.

[0254] The drill guide 740 further comprises a drill guide pin 745 that protrudes from a central region of the contact surface 741 in a direction substantially perpendicular to the plane of the contact surface 741. The axial direction of the drill guide pin 745 defines an axis of rotation 7451 of the drill guide 740. The drill guide pin 745 is adapted to locate in the same pin hole 734 in the resected surface 732 of the patella 731 that previously accommodated the marking jig pin 714. The contact surface 741 of the drill guide also comprises a plurality of peripheral pins 747. The peripheral pins 747 are shorter than the drill guide pin 745 and therefore the drill guide pin 745 projects from the contact surface of the drill guide to a greater degree than the peripheral pins 747.

[0255] The drill guide 740 further comprises a drill guide marker in the form of a notch 746 at the periphery of the drill guide 740, the notch 746 being spaced from the drill guide pin 745. The notch 746 has a first open end 7461 at the periphery of the contact surface 741 and a second open end 7462 at the periphery of the outer surface 742. The notch tapers in size from the second open end 7462 towards the first open end 7461, the second open end 7462 therefore being larger than the first open end 7461.

[0256] The contact surface 741 of the drill guide 740 is substantially flat so that it can coapt with the (substantially flat) resected surface 732 of the patella 731 when the drill guide pin 745 is located in the pin hole 734 in the resected surface. Nevertheless, when the drill guide pin 745 is located in the pin hole 734, the drill guide 740 can rotate relative to the resected surface 732 of the patella 731, about the axis of rotation 7451 of the drill guide 740. [0257] With reference to Fig. 27e, while the patella 731 remains in the everted state, the surgeon attaches the drill guide 740 to the resected surface 732 by partially locating the drill guide pin 745 in the pin hole 734 in the resected surface 732. In Fig. 27e, the position of the drill guide pin 745 underneath the drill guide 740 is shown using dotted lines. The drill guide pin 745 is only inserted in the pin hole 734 to a point where tips of the peripheral pins 747 rest gently against the resected surface 732.

[0258] In Fig. 27e, the drill guide 740 is in a non-optimal rotational orientation relative to the resected surface 732 of the patella 731. Through manipulation by the surgeon, however, the drill guide 740 is rotated about the axis of rotation 7451, relative to the resected surface 732 of the patella 731, to a position where its marker, i.e. the notch 746, aligns with the marker 733 (and optionally also the line 735). This places the drill guide 740 into an aligned position as shown in Fig. 27 f. When the aligned position is reached, the surgeon presses on the drill guide 740 such that the drill guide pin 745 becomes fully inserted into the pin hole 734 and the peripheral pins 747 are pressed into the soft bone of the resected surface 732, preventing further rotation of the drill guide 740.

[0259] The drill guide holes 744 are in a fixed position relative to the drill guide pin 745 and the drill guide marker 746 such that, when the drill guide 740 is rotated to and fixed in the aligned position, the drill guide holes are in a correct orientation for guiding a drill or other tool, such as a punch or spike, to form recesses, e.g., holes, in the resected surface 732 of the patella 731. The correct orientation of the holes in the resected surface is such that, when the pegs of the patella component are located in the holes, the patella component is correctly rotationally oriented relative to the resected surface 732 of the patella 731. The correct rotational orientation of the patella component in this embodiment is such that, when an articular surface of the patella component is brought into engagement with trochlear groove surface of the femoral component, it is in an optimal orientation for articulation during normal use of the knee prosthesis.

[0260] The marking jig 710 and the drill guide 740 can be provided as part of a kit for use in a method of rotationally orienting a patella component of a knee prosthesis at a resected surface of the patella. Moreover, the marking jig 710, and optionally also the drill guide 740, may be supplied with the femoral component 720, particularly since the marking jig 710 has an articular surface 712 that matches the trochlear groove surface 722 of the femoral component 720.

[0261] Methods and apparatus similar to those described above in relation to rotational alignment of a patella component can also be used to rotationally align a prosthetic tibial component, such as a tibial tray, relative to a resected surface of a tibia.

[0262] Following from this, a marking jig 810 according to another embodiment of the present disclosure, for use in conjunction with a knee prosthesis, is illustrated in Figs. 30a and 30b.

Specifically, the marking jig 810 is configured for use in a method of rotationally orienting a prosthetic tibial component of the knee prosthesis (e.g. a tibial tray) at a resected proximal surface of the native tibia, the tibial component being configured to articulate with a distal surface of the femoral component of the knee prosthesis.

[0263] The marking jig 810 comprises an engagement surface 811 for engaging the resected surface of the tibia, an articular surface 812 at an opposite side of the marking jig 810 from the engagement surface 811, and a side wall 813 extending between the engagement surface 811 and the articular surface 812 and around the periphery of the marking jig 810. The marking jig 810 further comprises a marking jig pin 814 that protrudes from a central region of the engagement surface 811 in a direction substantially perpendicular to the plane of the engagement surface 811. The axial direction of the marking jig pin 814 defines an axis of rotation 8141 of the marking jig 810. The making jig 810 further comprises two marker guides in the form of notches 815a, 815b at the periphery of the marking jig 810, the notches 815a, 815b each being spaced from the marking jig pin 814 and spaced from each other.

[0264] The engagement surface 811 of the marking jig 810 is substantially flat so that it can coapt with the (substantially flat) resected surface of the tibia while the marking jig pin 814 is located in a pin hole in the resected surface. Nevertheless, when the marking jig pin 810 is located in the pin hole, the marking jig 810 can rotate relative to the resected surface of the tibia, about the axis of rotation 8141 of the marking jig 810. In this embodiment, the marking jig pin 814 is approximately 2-5 mm in diameter, so that it is relatively small in dimension relative to the resected surface of the tibia, and so that there is minimal frictional torque to resist free rotation of the marking jig pin 814 within the bone. Moreover, the pin 814 may be small enough so that it can be pressed into the bone by thumb pressure, without the need for drilling. In this

embodiment, the marking jig pin 814 is also approximately 5-15 mm in length with a pointed tip.

[0265] The marking jig pin 814 is rigidly secured to the body of the marking jig 810 in this embodiment. However, alternatively, it may be constructed so that it is free to rotate relative to the body of the marking jig 810 and/or so that it is introduced to the marking jig 810 by extending through a hole in the marking jig, which hole may also be used to guide a tool to form the pin hole. The marking jig pin 814 can be made from surgical grade metal, for example, with the body of the marking jig 810 being made from surgical grade metal or surgical grade plastic, polymer or composite material.

[0266] The articular surface 812 of the marking jig 810 includes two, curved bearing regions 8121, 8122 against which lateral and medial condyles 723, 724 of the femoral component 720 of the knee prosthesis articulate. The bearing regions 8121, 8122 are generally dish-shaped and are provided on opposite sides, in a transverse direction of the marking jig 810, of a ridge 8123 of the articular surface 812. The marking jig 810 includes a posterior cruciate ligament (PCL) relief notch 816 that is located adjacent a posterior edge of the marking jig 810. [0267] The shape of the articular surface 812 of the marking jig 810 is such that it can engage with and register with a portion of the articular surface of the femoral component 720, and specifically, in this embodiment, a distal surface of the femoral component, generally as illustrated in Fig. 31. The femoral component need not be a femoral component that will remain implanted in the patient. In some embodiments, the femoral component may be a trial femoral component, specifically for use in orienting the tibial component.

[0268] Figs. 32a to 32d provide further illustration of registration between the articular surface 812 of the marking jig 810 and the femoral component 720. In general, the articular surface 812 of the marking jig 810 has a shape that is substantially a reciprocal of the shape of the distal surface of the femoral component, corresponding to a surface of patella flange 721, adjacent the condyles 723, 724, where the tibial component engages the femoral component when the patient's leg is at full extension.

[0269] The reciprocal shape of the articular surface 812 of the marking jig 810 enables it to achieve a snug, congruent fit with the distal surface of the femoral component 720. Indeed, in this embodiment, the closeness of the fit is such that there is a clearly identifiable position of registration between the articular surface 812 of the marking jig 810 and the distal surface of the femoral component 720. The position of registration is reached by rotating the marking jig 810 relative to both the resected surface of the tibia and the distal surface of the femoral component, about the axis of rotation 8141 of the marking jig pin 814. Rotation can occur automatically to some extent. In particular, when the articular surface 812 of the marking jig 810 and the distal surface of the femoral component 720 are pressed together, the articular surface 812 of the marking jig 810 is predisposed to sliding and rotating into registration with the distal surface of the femoral component 720. When registered, there is substantially no further relative rotation possible between the articular surface 812 of the marking jig 810 and the distal surface of the femoral component 720. Thus, the configuration of the distal surface of the femoral component 720 can determine the appropriate rotational orientation of the marking jig 810.

[0270] As best seen in Figs. 30a and 30b, the marker guide of the marking jig 810 comprises notches 815a, 815b in the side wall 813 of the marking jig, which notches 815a, 815b each have a first open end 8151a, 8151b at the periphery of the engagement surface 811. The notches 815a, 815b can each receive the tip of an instrument, such as a sterile pen or electrocautory tool. The tip of the instrument can enter the notch 815a, 815b and be directed by the notch 815a, 815b towards the first open end 8151a, 8151b. The instrument is used to mark the resected surface of the tibia, as discussed in more detail below. In general, circumstances during surgery may dictate that a surgeon may see the periphery of the marking jig 810 over an arc of about 90 degrees, for example. Accordingly, the provision of two notches 815a, 815b means that at least one notch 815a, 815b should be available for easy access by the surgeon at any time. [0271] A method of rotationally orienting a tibial component at the resected surface 821 of a tibia 820 using the marking jig 810 is now discussed in more detail with reference to Figs. 33a to 33f. The proximal end of the tibia 820 is resected using common surgical procedures for knee prosthesis surgery, resulting in the resected proximal surface 821. After resection, an

appropriately sized marking jig 810 is selected by the surgeon that has a footprint that best covers the resected surface 821. The surgeon temporarily secures the marking jig 810 to the resected surface 821 by manually pushing the marking jig pin 814 into a central region of soft bone at the resected surface 821, whereupon the engagement surface 811 of the marking jig 810 rests substantially flush against the resected surface 821. An illustration of the marking jig 810 attached to the resected surface 821 is provided in Fig. 33a with the position of the marking jig pin 814 underneath the marking jig 810 being shown using dotted lines. Pushing of the pin 814 into the resected surface forms a pin hole in the resected surface 821. As an alternative, the pin hole may be formed prior to locating of the marking jig pin 814 into the pin hole, e.g. by drilling, punching or otherwise.

[0272] In Fig. 33a, the marking jig 810 is in a non-optimal rotational orientation relative to the resected surface 821 of the tibia 820. While attached to the tibia in this orientation, the surgeon brings the articular surface 812 of the marking jig 810 into engagement with the distal surface of the femoral component 720 with the knee in full extension, the femoral component 720 (e.g. trial femoral component) having been assembled on a previously prepared distal end of the femur. By virtue of contact between the articular surface 812 of the making jig 810 and the femoral component 720, the marking jig 810 is rotated relative to both the resected surface 821 of the tibia 820 and the distal surface of the femoral component 720.

[0273] Fig. 33b illustrates the rotational orientation of the of the marking jig 810 relative to the resected surface 821 of the tibia 820 when the marking jig 810 is registered with the distal surface of the femoral component 720. When in this registered state, the surgeon places a mark 822 on the resected surface 821 of the tibia adjacent either one of the notches 815a, 815b of the marking jig 810. The mark 822 can be made using a sterile pen, electrocautery tool or other instrument that can cause an observable mark to be left on the resected surface 821.

[0274] Following placement of the mark 822, the marking jig 810 is removed from the resected surface 821 of the tibia 820, as illustrated in Fig. 33c. Through use of the marking jig 810, however, the mark 822, along with the pin hole 823 of the marking jig pin 814, remain visible on the resected surface 821. Optionally, as shown in Fig. 33d, an orientation line 824 can be drawn on the resected surface 821 between the pin hole 823 and the mark 822.

[0275] The pin hole 823, mark 822 and optional line 824, are used to guide positioning of one or more recesses, e.g., holes, in the resected surface of the tibia. The holes are to receive protrusions, specifically pegs in this embodiment, which protrude from an engagement surface of the tibial component. In alternative embodiments, positioning of a recess adapted to receive a non-circular stem of the tibial component may be carried out. The non-circular stem may have cruciform shape, for example.

[0276] To guide location of the holes in the resected surface 821, a drill guide 830 as illustrated in Figs. 33e, 33f and 34 can be used. The drill guide 830 comprises a tibia contact surface 831, an opposite, outer surface 832, and a side wall 833 extending between the contact surface 831 and the outer surface 832 and around the periphery of the drill guide 830. Drill guide holes 834 extend between the contact surface 831 and the outer surface 832, through the drill guide 830.

[0277] The drill guide 830 further comprises a drill guide pin 835 that protrudes from a central region of the contact surface 831 in a direction substantially perpendicular to the plane of the contact surface 831. The axial direction of the drill guide pin 835 defines an axis of rotation 8351 of the drill guide 830. The drill guide pin 835 is adapted to locate in the same pin hole 823 in the resected surface 821 of the tibia 820 that previously accommodated the marking jig pin 814. The contact surface 831 of the drill guide also comprises a plurality of peripheral pins 837. The peripheral pins 837 are shorter than the drill guide pin 835 and therefore the drill guide pin 835 projects from the contact surface of the drill guide to a greater degree than the peripheral pins 837.

[0278] The drill guide 830 further comprises drill guide markers in the form of notches 838a, 838b at the periphery of the drill guide 830, the notches 838a, 838b each being spaced from the drill guide pin 835. The notches 838a, 838b each have a first open end 8381a, 8381b at the periphery of the contact surface 831. Each notch 838a, 838b tapers in size towards the first open end 8381a, 8381b.

[0279] The contact surface 831 of the drill guide 830 is substantially flat so that it can coapt with the (substantially flat) resected surface 821 of the tibia 820 when the drill guide pin 834 is located in the pin hole 823 in the resected surface 821. Nevertheless, when the drill guide pin 835 is located in the pin hole 823, the drill guide 830 can rotate relative to the resected surface 821 of the tibia, about the axis of rotation 8351 of the drill guide 830.

[0280] With reference to Fig. 33e, the surgeon attaches the drill guide 830 to the resected surface 821 by partially locating the drill guide pin 835 in the pin hole 823 in the resected surface 821. In Fig. 33e, the position of the drill guide pin 835 underneath the drill guide 830 is shown using dotted lines. The drill guide pin 835 is only inserted in the pin hole 823 to a point where tips of peripheral pins 837 rest gently against the resected surface 821.

[0281] In Fig. 33e, the drill guide 830 is in a non-optimal rotational orientation relative to the resected surface 821 of the tibia 820. Through manipulation by the surgeon, however, the drill guide 830 is rotated about the axis of rotation 8351, relative to the resected surface 821 of the tibia 820, to a position where a respective one of its markers, i.e. the notches 838a, 838b, aligns with the mark 822 or the optional line 824. This places the drill guide 830 into an aligned position as shown in Fig. 33f. When the aligned position is reached, the surgeon presses on the drill guide 830 such that the drill guide pin 835 is then fully inserted into the pin hole 823 and the peripheral pins 837 are pressed into the soft bone of the resected surface 821, preventing further rotation of the drill guide 830.

[0282] The drill guide holes 834 are in a fixed position relative to the drill guide pin 835 and the drill guide marker 838a, 838b such that, when the drill guide 830 is rotated to and fixed in the aligned position, the drill guide holes 834 are in a correct orientation for guiding a drill or other tool, such as a punch or spike, to form recesses such as holes in the resected surface 821 of the tibia 820. The correct orientation of the holes in the resected surface 821 is such that, when the pegs of the tibia component are located in the holes, the tibial component is correctly rotationally oriented relative to the resected surface of the tibia. The correct rotational orientation of the tibial component in this embodiment is such that, when an articular surface of the tibial component is brought into engagement with femoral component, it is in an optimal orientation for articulation during normal use of the knee prosthesis.

[0283] The marking jig 810 and the drill guide 830 can be provided as part of a kit for use in a method of rotationally orienting a tibial component of a knee prosthesis at a resected surface of the tibia. Moreover, the marking jig 810, and optionally also the drill guide 830, may be supplied with the femoral component 720, particularly since the marking jig 810 has an articular surface 812 that matches a distal surface of the femoral component 720.

[0284] While drill guides 740, 830 are described in embodiments above to guide formation of recesses in respective resected surfaces, in alternative embodiments, other types of guides or tools may be used. These other guides or tools may include a contact surface for engaging the resected surface of the bone, a pin protruding from the contact surface for locating in a pin hole of the resected surface; an outer surface opposite to the contact surface, and a guide marker, and may be orientated relative to the resected surface in substantially the same manner as described above with respect to the drill guide. In some instances, these other guides or tools may incorporate an instrument for forming recesses in the resected surface, such as a punch or otherwise, rather than be used in conjunction with a separate instrument. The recesses formed need not necessarily be circular holes, but may be grooves, cruciform shaped recesses or take other forms.

[0285] With reference to Figs. 35a and 35b, in one embodiment of the present disclosure a tibial marking jig 900 is provided that has a surface configuration that is substantially identical to the marking jig 810 described above, but which is formed from two parts releasably engaged with each other, one of the parts effectively providing a drill guide component. In particular, the marking jig 900 includes a first part 910 and a second part 920 releasably engaged with each other. The first part 910 includes the articular surface 911 for engaging the femoral component and the second part 920 includes the engagement surface 921 for engaging the resected surface of the bone. The second part 920 also includes the two marker guide notches 922a, 922b, the marking jig pin 923 on the engagement surface 921 and drill guide holes 924.

[0286] The marking jig 900 is used to form the mark on the resected surface in substantially the same manner as described above with reference to Figs. 33a to 33f, for example, while the first and second parts 910, 920 remain engaged (e.g. mechanically interlocked) so that no relative movement of the parts 910, 920 is possible. Once the mark is formed, however, rather than remove the entire marking jig 900 and replace it with a separate drill guide, the first part 910 of the marking jig is removed only, as represented in Fig. 35b. Removing the first part 910 of the marking jig 900 exposes openings to the drill guide holes 924 in the second part 920. With one of the notches 922a, 922b aligned with the mark on the resected surface, the drill guide holes can be used to guide forming of recesses in the resected surface. Prior to forming the recesses, the second part 920 of the marking jig 900 may be stabilised manually or by other means.

[0287] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above -described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. Knee prosthesis apparatus, comprising:

wherein the apparatus further comprises:

2. The apparatus of claim 1 , wherein the bearing and the tibial component are configured to move relative to each other in an anterior/posterior direction to effect the interconnection between the bearing and the tibial component.

3. The apparatus of claim 2, wherein the one or more filler members, when located in and filling the gap, substantially prevent further relative movement of the bearing and the tibial component in the anterior/posterior direction.

4. The apparatus of claim 1, 2 or 3, wherein the bearing and tibial component each comprise one or more locking elements.

5. The apparatus of claim 4, wherein, when the bearing and the tibial component are interconnected, the one or more locking elements substantially prevent relative movement of the bearing and tibial component in a super/inferior direction.

6. The apparatus of claim 4 or 5, wherein the one or more locking elements of the tibial component comprise one or more anterior tabs on an anterior surface of the posterior buttress and the one or more locking elements of the bearing comprise one or more anterior grooves in an anterior surface of the posterior recess, wherein the one or more anterior tabs of the posterior buttress locate in the one or more anterior grooves of the posterior recess when the bearing and tibial component are interconnected.

7. The apparatus of claim 4, 5 or 6, wherein the one or more locking elements of the bearing comprise one or more anterior tabs on an anterior surface of the posterior recess and the one or more locking elements of the tibial component comprise one or more anterior grooves in an anterior surface of the posterior buttress, wherein the one or more anterior tabs of the posterior recess locate in the one or more anterior grooves of the posterior buttress when the bearing and tibial component are interconnected.

8. The apparatus of any one of the preceding claims, wherein the posterior buttress and the posterior recess each have substantially a V-shape.

9. The apparatus of any one of the preceding claims, wherein the one or more filler members have an anterior surface and a posterior surface, and wherein, when the one or more filler members locate in and fill the gap between the first and second gap surfaces, the anterior surface of the one or more filler members engages the first gap surface and the posterior surface of the one or more filler members engages the second gap surface.

10. The apparatus of claim 9, wherein the anterior surface of the one or more filler members is curved and has a curvature conforming to a curvature of the first gap surface and/or the posterior surface of the one or more filler members is curved and has a curvature conforming to a curvature of the second gap surface.

11. The apparatus of claim 9 or 10, wherein the anterior surface of the one or more filler members has a plurality of first teeth and the first gap surface has a plurality of second teeth adapted to engage the first teeth.

12. The apparatus of claim 9, 10 or 11, wherein the posterior surface of the one or more filler members has a plurality of first teeth and the second gap surface has a plurality of second teeth adapted to engage the first teeth.

13. The apparatus of claim 9 or 10, wherein one or more of the anterior surface of the one or more filler members, the posterior surface of the one or more filler members, the first gap surface and the second gap surface comprises a surface roughening.

14. The apparatus of any one of the preceding claims, wherein the one or more filler members are in the form of a wedge.

15. Knee prosthesis apparatus, comprising:

a bearing having a first engagement surface;

16. The apparatus of claim 15, wherein the plurality of pegs are provided on the second engagement surface of the tibial component and the plurality of holes are provided on the first engagement surface of the bearing.

17. The apparatus of claim 15 or 16, wherein the pegs project in a direction substantially perpendicular to the engagement surface on which they are provided.

18. The apparatus of claim 17, wherein pegs are elongated in the direction substantially perpendicular to the engagement surface on which they are provided.

19. The apparatus of claim 18, wherein upon implantation of the apparatus, the pegs are elongated in a direction substantially parallel to the mechanical and anatomical axes of the tibia and/or to the mechanical axis of the leg.

20. The apparatus of any one of claims 15 to 19, wherein upon implantation of the apparatus, the first and/or second engagement surface extends across a plane substantially perpendicular to mechanical and anatomical axes of the tibia and/or to the mechanical axis of the leg.

21. The apparatus of any one of claims 15 to 20, wherein some or all of the plurality of pegs are frustoconical.

22. The apparatus of any one of claims 15 to 21, wherein some or all of the pegs are cylindrical.

23. The apparatus of any one of claims 15 to 22, wherein some or all of the pegs have rounded distal ends.

24. The apparatus of any one of claims 15 to 23, wherein the engagement between the bearing and the tibial component is possible at one relative position and orientation only of the bearing and tibial component only.

25. The apparatus of claim 24, wherein there is only one respective hole in which each peg is locatable.

26. The apparatus of any one of claims 15 to 25, wherein openings of the holes, through which pegs are located in the holes, are flush with the engagement surface on which the holes are provided.

27. The apparatus of claim 26, wherein, when the pegs are fully located in the holes, the first and second engagement surfaces abut each other.

28. The apparatus of any one of claims 15 to 27, wherein, between the first engagement surface of the bearing and an opposite first bearing surface of the bearing, the bearing has varying depth.

29. The apparatus of claim 28, wherein holes are provided on the first engagement surface of the bearing and wherein the holes are provided at regions of the bearing that have greater depth than other regions of the bearing.

30. The apparatus of claim 28 or 29, wherein holes are provided on the first engagement surface of the bearing and pegs are provided on the second engagement surface of the tibial component; and wherein the length of each peg is proportional to the depth of the bearing at the region of the bearing where the hole is located in which the peg is to locate.

31. The apparatus of any one of claims 15 to 30 comprising at least one post provided on one of the first and second engagement surfaces and at least one cavity provided on the other of the first and second engagement surfaces, wherein the post locates in the cavity in the process of releasably engaging the bearing and the tibial component.

32. The apparatus of claim 31, wherein the post and cavity are located at a central region of the respective surface on which they are provided.

33. The apparatus of claim 32, wherein some or all of the pegs and/or the holes are distributed around the post and some or all of the pegs and/or the holes are distributed around the cavity.

34. The apparatus of any one of claims 31 to 33, wherein the post projects in a direction substantially perpendicular to the engagement surface on which it is provided.

35. The apparatus of claim 34, wherein post is elongated in the direction substantially perpendicular to the engagement surface on which it is provided.

36. The apparatus of claim 35, wherein upon implantation of the apparatus, the post is elongated in a direction substantially parallel to the mechanical and anatomical axes of the tibia and/or to the mechanical axis of the leg.

37. The apparatus of any one of claims 31 to 36, wherein the post is frustoconical.

38. The apparatus of any one of claims 31 to 37, wherein the post is longer than each one of the pegs.

39. The apparatus of any one of claim 38, wherein the post is at least 1.5 times, at least 2 times or at least 10 times the length of each one of the pegs.

40. The apparatus of claim 38 or 39, wherein the post is provided on the first engagement surface of the bearing and the post provides a journal about which the tibial component is rotatable to align the pegs with the holes.

41. A femoral component for a knee prosthesis, comprising:

the trochlear groove surface comprising a lateral flank and a medial flank, the lateral flank adjoining the lateral surface and the medial flank adjoining the medial surface, wherein a lateral transition between the lateral flank and the lateral surface is a substantially smooth transition and a medial transition between the medial flank and the medial surface is a substantially angular transition.

42. The femoral component of claim 41, wherein, in the transverse direction of the femoral component, at least a portion of the lateral flank is substantially flat and at least a portion of the medial flank is substantially curved.

43. The femoral component of claim 42, wherein, in the transverse direction of the femoral component, a major portion of the lateral flank is substantially flat.

44. The femoral component of any one of claims 41 to 43, wherein, in the transverse direction of the femoral component, the width of the lateral flank of the trochlear groove surface is greater than the width of the medial flank of the trochlear groove surface.

45. The femoral component of claim 44, wherein, in the transverse direction of the femoral component, the width of the lateral flank of the trochlear groove surface is at least 1 mm greater than the width of the medial flank of the trochlear groove surface.

46. The femoral component of claim 44, wherein, in the transverse direction of the femoral component, the width of the lateral flank of the trochlear groove surface is between 1 mm and 4 mm greater than the width of the medial flank of the trochlear groove surface.

47. The femoral component of any one of claims 41 to 46, wherein the depth of the trochlear groove increases towards the first end of the patella flange.

48. The femoral component of any one of claims 41 to 47, wherein the lateral flank rotates as it extends along the path of the trochlear groove surface between the first and second ends of the patella flange.

49. The femoral component of claim 48, wherein the rotation of the lateral flank is such that the lateral flank faces in a more medial direction as the lateral flank extends along the path of the trochlear groove surface from the second end towards the first end of the patella flange.

50. The femoral component of claim 49, wherein the total rotation is in the range of 2 to 7 degrees.

51. The femoral component of any one of claims 41 to 50, wherein the lateral flank extends at a progressively steeper angle from the bottom of the trochlear groove surface as the trochlear groove extends from the second end towards the first end of the patella flange.

52. The femoral component of any one claims 41 to 51, wherein the outer surface of the lateral condyle comprises a lateral surface extension that is an extension of the lateral surface of the patella flange, a lateral flank extension that is an extension of the lateral flank of the trochlear groove surface of the patella flange, and a medial surface extension that is an extension of the medial surface of the patella flange.

53. The femoral component of claim 52, wherein a lateral transition between the lateral flank extension and the lateral surface extension in the transverse direction of the femoral component is a substantially smooth transition.

54. The femoral component of claim 52 or 53, wherein, in the transverse direction of the femoral component, at least a portion of the lateral flank extension is substantially flat and at least a portion of the medial flank extension is substantially curved.

55. The femoral component of claim 54, wherein, in the transverse direction of the femoral component, a major portion of the lateral flank extension is substantially flat and a major portion of the medial flank extension is substantially curved.

56. A method of rotationally orienting a first prosthetic component of a knee prosthesis at a resected surface of a first bone, the method comprising:

at least one marker guide at a position spaced from the marking jig pin;

engaging the articular surface of the attached marking jig with an articular surface of a second prosthetic component fixed to a second bone;

rotating the marking jig about the axis of the marking jig pin to place the articular surface of the marking jig into registration with the articular surface of the second prosthetic component;

57. The method of claim 56, wherein the first prosthetic component is a patella component and the first bone is a patella with a resected articular surface.

58. The method of claim 57, wherein the second prosthetic component is a femoral component fixed to the femur, the articular surface of the second prosthetic component comprising a trochlear groove surface.

59. The method of claim 56, wherein the first prosthetic component is a tibial component and the first bone is a tibia having a resected proximal surface.

60. The method of claim 59, wherein the second prosthetic component is a femoral component fixed to the distal surface of the femur, the articular surface of the second prosthetic component comprising a distal surface of the femoral component.

61. The method of any one of claims 56 to 60, wherein the articular surface of the marking jig has a shape that is a reciprocal of a shape of the articular surface of the second prosthetic component.

62. The method of any one of claims 56 to 61, wherein the articular surface of the marking jig has a shape that achieves a snug, congruent fit with the articular surface of the second prosthetic component upon the registration.

63. The method of any one of claims 56 to 62, wherein there is only one identifiable position of registration between the articular surface of the marking jig and the articular surface of the second prosthetic component.

64. The method of any one of the claims 56 to 63, wherein, upon engaging the articular surface of the marking jig with the articular surface of the second prosthetic component, rotation of the marking jig about the axis of the marking jig pin occurs partially or entirely automatically.

65. The method of any one of claims 56 to 64, wherein, when the articular surface of the marking jig registers with the articular surface of the second prosthetic component, substantially no further relative rotation is possible between the two articular surfaces.

66. The method of any one of claims 56 to 65 comprising:

removing the marking jig from the resected surface after placement of the mark, attaching a drill guide to the resected surface; and

using the drill guide to form the one or more recesses in the resected surface.

67. The method of claim 66, wherein the drill guide comprises: a bone contact surface and an opposite, outer surface;

one or more guide holes that extend between the contact surface and the outer surface; a drill guide pin protruding from the contact surface for locating in the pin hole of the resected surface; and

a drill guide marker.

68. The method of claim 67, comprising:

locating the drill guide pin in the pin hole;

rotating the drill guide about the axis of the drill guide pin so that the drill guide marker aligns with the mark placed on the first bone using the marking jig, placing the drill guide in an aligned position; and

using the drill guide to form the one or more recesses in the resected surface when the drill guide is in the aligned position.

69. The method of claim 68, wherein the contact surface of the drill guide comprises one or more peripheral pins, the peripheral pins being shorter than the drill guide pin.

70. The method of claim 69, wherein the drill guide pin is partially located in the pin hole of the resected surface while the drill guide is rotated to the aligned position and, once the drill guide reaches the aligned position, the method comprises pressing the drill guide such that the drill guide pin is fully inserted into the pin hole and the peripheral pins are pressed into the resected surface, preventing further rotation of the drill guide.

71. The method of any one of claims 66 to 70, wherein the drill guide marker comprises a notch, line, spot or bump.

72. The method of any one of claims 56 to 71, wherein the marker guide comprises a notch, line, spot or bump.

73. The method of any one of claims 56 to 65, wherein the marking jig comprises first and second parts releasably engaged together, the first part comprising the articular surface, the second part comprising the engagement surface, the marking jig pin protruding from the engagement surface, and one of more guide holes.

74. A marking jig for use in a method of rotationally orienting a first prosthetic component of a knee prosthesis at a resected surface of a first bone, the marking jig comprising:

an engagement surface for engaging the resected surface of the first bone;

an articular surface opposite to the engagement surface, the articular surface of the marking jig being registrable with an articular surface of a second prosthetic component; the second prosthetic component being fixed to a second bone; and

at least one marker guide at a spaced position from the marking jig pin.

75. A drill guide for use in a method of rotationally orienting a first prosthetic component of a knee prosthesis at a resected surface of a first bone, the drill guide comprising:

an outer surface opposite to the contact surface;

drill guide holes extending between the contact surface and the outer surface; and a drill guide marker.