WO2020056386A1

WO2020056386A1 - Tooling for a pivotal bone anchor assembly with modular receiver and universal shank head

Info

Publication number: WO2020056386A1
Application number: PCT/US2019/051190
Authority: WO
Inventors: Roger P. Jackson; James L. Surber; Nathaniel D. Ginzton
Original assignee: Jackson Roger P
Priority date: 2018-09-13
Filing date: 2019-09-13
Publication date: 2020-03-19

Abstract

A deployment tool for securing a receiver assembly to a head of a bone anchor includes an outer support tube having end effectors at a distal end for coupling to the exterior of the receiver assembly having an actuatable contact surface for operably engaging the head of a bone anchor with a friction fit upon deployment with an applied force. The deployment tool also includes an inner locking tube that is slidably movable within the outer support tube and engageable with the end effectors in a downwardly locked position so as to the lock the distal end of the outer support tube around the receiver assembly. The deployment tool further includes a central bayonet drive shaft downwardly movable within the inner locking tube when the inner locking tube is in the locked position, so as to engage the actuatable deployment surface within the receiver assembly with the applied force and secure the receiver assembly to the bone anchor head with a friction fit.

Description

TOOLING FOR PIVOTAL BONE ANCHOR

ASSEMBLY WITH MODULAR RECEIVER AND UNIVERSAL SHANK HEAD

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No.

62/731 ,059, filed September 13, 2018, which provisional application is incorporated by reference in its entirety herein, and for all purposes.

FIELD OF THE INVENTION

[0002] The present invention generally relates to tools or tooling for preparing, assembling, and/or deploying bone screws and pivotal bone anchor assemblies during bone surgery, particularly spinal surgery.

BACKGROUND

[0003] Bone screws are utilized in many types of spinal surgery in order to secure various implants to vertebrae along the spinal column for the purpose of stabilizing and/or adjusting spinal alignment. Although both closed-ended and open-ended bone screws are known, open-ended screws are particularly well suited for connections to rods and connector arms, because such rods or arms do not need to be passed through a closed bore, but rather can be laid or urged into an open channel within a receiver or head of such a screw.

[0004] Typical open-ended bone screws include a threaded shank with a pair of parallel projecting branches or arms which form a yoke with a U-shaped slot or channel to receive a rod. Hooks and other types of connectors, as are used in spinal fixation techniques, may also include open ends for receiving rods or portions of other structure.

[0005] A common mechanism for providing vertebral support is to implant bone screws into certain bones which then in turn support a longitudinal structure such as an elongate rod, or are supported by such a rod. Bone screws of this type may have a fixed head or receiver relative to a shank thereof. In the fixed bone screws, the rod receiver head cannot be moved relative to the shank and the rod must be favorably positioned in order for it to be placed within the receiver head. This is sometimes very difficult or impossible to do. Therefore, pivotal or polyaxial bone screws are commonly preferred. Open-ended pivotal or polyaxial bone screws typically allow for pivoting and rotation of the separate receiver about the shank in one or more planes until a desired rotational position of the receiver is achieved by fixing such position relative to the shank during a final stage of a medical procedure when an elongate rod or other longitudinal connecting member is inserted into the receiver, followed by a locking screw or other closure.

SUMMARY

[0006] Briefly described, one embodiment of the present disclosure comprises a deployment tool for securing a receiver assembly to a head of a bone anchor with a friction fit. The deployment tool includes an outer support tube having end effectors at a distal end for coupling to the exterior of a receiver assembly, with the receiver assembly having an actuatable contact surface for operably engaging the head of a bone anchor with a friction fit upon deployment with an applied force. The deployment tool also includes an inner locking tube that is slidably movable within the outer support tube and engageable with the end effectors in a downwardly locked position so as to the lock the distal end of the outer support tube around the receiver assembly. The deployment tool further includes a central bayonet drive shaft insertable through the inner locking tube. The central bayonet drive shaft is downwardly movable within the inner locking tube when the inner locking tube is in the locked position to engage the actuatable deployment surface within the receiver assembly with the applied force, so as to secure the receiver assembly to the bone anchor head with a friction fit.

[0007] In one aspect of the present disclosure the applied force is greater than or about

200 pounds force. [0008] The invention will be better understood upon review of the detailed description set forth below taken in conjunction with the accompanying drawing figures, which are briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is an exploded perspective view of a pivotal bone anchor assembly having components that are engageable by one or more tools for the preparation, assembly, and/or deployment of the pivotal bone anchor assembly during spinal surgery.

[0010] FIG. 2 is an exploded perspective view of the bone anchor and capture recess protection sleeve of the pivotal bone anchor assembly of FIG. 1.

[0011] FIG. 3 is a cross-sectional perspective view of the universal shank head of the bone anchor of FIG. 2.

[0012] FIG. 4. is a schematic side view of the bone anchor of FIGS. 1-3 embedded in a bone or substrate.

[0013] FIG. 5 is a perspective view of reamer tool for preparing the shank head of the bone anchor for coupling with a receiver assembly, in accordance with one representative embodiment of the present disclosure.

[0014] FIG. 6 is a cross-sectional schematic side view of the embedded bone anchor of

FIG. 4 and the reamer tool of FIG. 5, prior to engagement of the shank head by the reamer tool.

[0015] FIG. 7 is a cross-sectional schematic side view of the embedded bone anchor of and the reamer tool of FIG. 6 during engagement of the shank head by the reamer tool.

[0016] FIG. 8 is a cross-sectional schematic side view of the embedded bone anchor of and the reamer tool of FIG. 6 after engagement of the shank head by the reamer tool.

[0017] FIG. 9 is a schematic perspective view of the bone anchor of FIG. 4 after engagement by the reamer tool of FIG. 5.

[0018] FIG. 10 is a partially cut-away side view of a pre-assembled receiver assembly of the pivotal bone anchor assembly of FIG. 1 that is engageable by one or more tools for the assembly and/or deployment of the receiver assembly to the shank head of a bone anchor.

[0019] FIG. 11 is a sectioned perspective view of the pre-assembled receiver assembly and bone anchor of FIG. 10.

[0020] FIG. 12 is a side view of a deployment tool for use with the pre-assembled receiver assembly of FIGS. 10-11 , in accordance with another representative embodiment of the present disclosure.

[0021] FIG. 13 is a perspective view of an outer support tube of the deployment tool of

FIG. 12 without installed end effectors.

[0022] FIG. 14 is a close-up perspective view of the distal end of the outer support tube of FIG. 13 with an installed end effector.

[0023] FIGS. 15a and 15b are perspective views of the inside face and the outside face of an end effector.

[0024] FIG. 16 is a perspective view of a pair of end effectors.

[0025] FIG. 17 is a partially cut-away perspective view of a pair of end effectors engaged with the pre-assembled receiver assembly of FIGS. 10-11.

[0026] FIG. 18 is a perspective view of the outer support tube and inner locking tube of the deployment tool of FIG. 12.

[0027] FIGS. 19a and 19b are perspective and close-up perspective views of the outer support tube and inner locking tube of the deployment tool of FIG. 12, respectively, with the inner locking tube withdrawn and spaced from the end effectors.

[0028] FIGS. 20a and 20b are perspective and close-up perspective views of the outer support tube and inner locking tube of the deployment tool of FIG. 12, respectively, with the inner locking tube engaging the end effectors.

[0029] FIG. 21 is a perspective view of the outer support tube, the inner locking tube, and the lower shaft handle of the deployment tool of FIG. 12 forming an engagement assembly. [0030] FIG. 22 is a cross-sectional side view of the lower shaft handle portion of the engagement assembly of FIG. 21 , with the inner locking tube in the upper retracted position.

[0031] FIG. 23 is a cross-sectional side view of the lower shaft handle portion of the engagement assembly of FIG. 21 , with the inner locking tube in the downward locking position.

[0032] FIGS. 24a and 24b are perspective and close-up perspective views of the central bayonet drive shaft of the deployment tool of FIG. 12, respectively, showing a shaped deployment tip.

[0033] FIG. 25 is a cross-sectional side view of the shaft handle portion of the assembled deployment tool of FIG. 12, with the upper shaft handle of the central bayonet drive shaft in the inserted but non-engaged position.

[0034] FIG. 26 is a cross-sectional side view of the shaft handle portion of the assembled deployment tool of FIG. 12, with the upper shaft handle of the central bayonet drive shaft in the inserted and engaged position.

[0035] FIGS. 27a and 27b are cross-sectional side views of the shaft handle and distal tip portions, respectively, of the assembled deployment tool of FIG. 12, without a captured receiver assembly, and with the shaped deployment tip in a withdrawn position.

[0036] FIGS. 28a and 28b are cross-sectional side views of the shaft handle and distal tip portions, respectively, of the assembled deployment tool of FIG. 12, with a captured receiver assembly, and with the shaped deployment tip in an extended position.

[0037] FIG. 29 is a partially cut-away perspective view of the distal end of the engagement assembly of FIG. 21 , prior to engagement with a receiver assembly.

[0038] FIG. 30 is a partially cut-away perspective view of the distal end of the engagement assembly of FIG. 21 , during engagement with a receiver assembly.

[0039] FIG. 31 is another partially cut-away perspective view of the distal end of the engagement assembly of FIG. 21 , during engagement with the receiver assembly. [0040] FIG. 32 is another partially cut-away perspective view of the distal end of the engagement assembly of FIG. 21 , during engagement with the receiver assembly.

[0041] FIG. 33 is a partially cut-away perspective view of the distal end of the assembled deployment tool of FIG. 12, upon locking with the inner locking tube to complete engagement with the receiver assembly.

[0042] FIG. 34 is a partially cut-away perspective view of the distal end of the deployment tool of FIG. 33, prior to coupling the receiver assembly to a shank head.

[0043] FIG. 35 is a partially cut-away perspective view of the distal end of the deployment tool of FIG. 33, during coupling of the receiver assembly to a shank head.

[0044] FIG. 36 is another partially cut-away perspective view of the distal end of the deployment tool of FIG. 33, during coupling of the receiver assembly to a shank head.

[0045] FIG. 37 is a partially cut-away perspective view of the distal end of the deployment tool of FIG. 33, during deployment of the pressure insert within the receiver assembly to establish a friction fit with the shank head.

[0046] FIG. 38 is a partially cut-away side view of the receiver assembly of FIG. 37.

[0047] FIG. 39 is a partially cut-away perspective view of the distal end of the deployment tool of FIG. 33 after deployment of the pressure insert within the receiver assembly to establish a friction fit with the shank head.

[0048] FIG. 40 is a partially cut-away side view of the receiver assembly of FIG. 39.

[0049] FIG. 41 is a partially cut-away perspective view of the distal end of the deployment tool of FIGS. 39-40, during disengagement of the deployment tool from the pivotal bone anchor assembly.

[0050] FIG. 42 is another partially cut-away perspective view of the distal end of the deployment tool of FIGS. 39-40, during disengagement of the deployment tool from the pivotal bone anchor assembly.

[0051] FIG. 43 is another partially cut-away perspective view of the distal end of the deployment tool of FIGS. 39-40, during disengagement of the deployment tool from the pivotal bone anchor assembly. [0052] FIG. 44 is a partially cut-away perspective view of the distal end of the deployment tool of FIGS. 39-40, after disengagement of the deployment tool from the pivotal bone anchor assembly.

[0053] FIG. 45 is a partially cut-away and sectioned perspective view of the pivotal bone anchor assembly of FIG. 44, with the bone anchor being pivoted relative to the receiver.

[0054] FIG. 46 is another partially cut-away and sectioned perspective view of the pivotal bone anchor assembly of FIG. 44, with the bone anchor being pivoted relative to the receiver.

[0055] FIG. 47 is a partially cut-away side view of an assembled deployment tool configured for rod reduction, in accordance with another representative embodiment of the present disclosure.

[0056] FIG. 48 is a partially cut-away and sectioned perspective view of the pivotal bone anchor assembly with an elongate rod and closure in a fully locked configuration and with the bone anchor being pivoted relative to the receiver.

[0057] FIG. 49 is a partially cut-away side view of an engagement assembly of the deployment tool having ramp and bump features for automatic disengagement from a receiver assembly, in accordance with another representative embodiment of the present disclosure.

[0058] FIG. 50a is a partially cut-away front view and FIG. 50b is a close-up cross- sectional side view of the engagement assembly of FIG. 49 prior to engagement with a pre-assembled receiver assembly.

[0059] FIG. 51 is a partially cut-away front view of the engagement assembly of FIG.

50a during engagement with the pre-assembled receiver assembly.

[0060] FIG. 52a is a partially cut-away front view and FIG. 52b is a close-up cross- sectional side view of the engagement assembly of FIG. 51 after engagement with the pre-assembled receiver assembly. [0061] FIG. 53 is a partially cut-away front view of the engagement assembly and receiver assembly of FIG. 52a after the receiver assembly has been coupled to a shank head to form a pivotal bone anchor assembly.

[0062] FIG. 54a is a partially cut-away front view and FIG. 54b is a close-up cross- sectional side view of the engagement assembly and receiver assembly of FIG. 53 after the engagement assembly has been released and withdrawn from the pivotal bone anchor assembly.

[0063] Those skilled in the art will appreciate and understand that, according to common practice, various features and elements of the drawings described above are not necessarily drawn to scale, and that the dimensions and relative positions between the features or elements may be expanded, reduced or otherwise altered to more clearly illustrate the various embodiments of the present disclosure depicted therein.

DETAILED DESCRIPTION

[0064] The following description, in conjunction with the accompanying drawings described above, is provided as an enabling teaching of exemplary embodiments of tools or tooling for preparing, assembling, and/or deploying bone screws and pivotal bone anchor assemblies or components thereof during spinal surgery. As described below, the tools or tooling and their methods of use can provide several significant advantages and benefits over other tools or tooling known in the art. However, the recited advantages are not meant to be limiting in any way, as one skilled in the art will appreciate that other advantages may also be realized upon practicing the present disclosure

[0065] Furthermore, those skilled in the relevant art will recognize that changes can be made to the described tooling or tool embodiments while still obtaining the beneficial results. It will also be apparent that some of the advantages and benefits of the described embodiments can be obtained by selecting some of the features of the embodiments without utilizing other features, and that features from one embodiment may be combined with features from other embodiments in any appropriate combination. For example, any individual or collective features of method embodiments may be applied to apparatus, product or system embodiments, and vice versa. Accordingly, those who work in the art will recognize that many modifications and adaptations to the embodiments described are possible and may even be desirable in certain circumstances, and are a part of the disclosure. Thus, the present disclosure is provided as an illustration of the principles of the embodiments and not in limitation thereof, since the scope of the invention is to be defined by the claims.

[0066] Referring now in more detail to the drawing figures, wherein like parts are identified with like reference numerals throughout the several views, FIG. 1 illustrates a pivotal bone anchor apparatus or assembly 10 having components that are engageable by one or more tools for the preparation, assembly, and/or deployment of the pivotal bone anchor assembly during spinal surgery. As known in the art, the pivotal bone anchor assembly 10 includes some form of bone anchor, such as a shank 20, having a capture portion at a proximal end and an anchor portion extending distally from the capture portion for securement to patient bone. In embodiments where the bone anchor is a shank 20, such as the shank 20 shown in FIGS. 1-3, the capture portion can further comprise a universal shank head 22 and the anchor portion can be a shank body 40.

[0067] The pivotal bone anchor assembly 10 generally includes a receiver 100 having an internal cavity 126 in a base portion 134 and two upright arms 104 extending upwardly from the base portion to define a rod channel 106 for receiving an elongate rod 90. The receiver 100 can be initially pivotably secured to the shank head 22 with a number of separate internal components that have been pre-assembled into the internal cavity 126 and the rod channel 106 to form a receiver assembly 14. In one aspect these components can include a resilient open retainer 70, a pressure insert 150, and a multi-piece positioner 170 that may secured within the internal cavity 126 of the base portion 134 with positioner pins 190. After an elongate rod 90 has been positioned within a lower portion of the rod channel 106, a closure 80 can be threadably secured into an upper portion of the rod channel to apply pressure to an upper surface of the elongate rod, thereby locking both the elongate rod 90 and the assembly 10 into a final locked position. The pivotal bone anchor assembly 10 can be configured for multi-planar pivotal motion or uni-planar pivotal motion relative to the universal shank head 22.

[0068] Additional details and disclosure regarding the structure, assembly, and operation of the various components making up the pivotal bone anchor assembly described above, including the receiver assembly and the bone anchor or shank having a universal shank head, can be found in co-pending Patent Cooperation Treaty (PCT) Application PCT/US2019/051189, filed the same day as the present application on September 13, 2019, and claiming the benefit of U.S. Provisional Application No. 62/731 ,023, filed September 13, 2018, and U.S. Provisional Application No. 62/810,361 , filed February 25, 2019, with each of the above-referenced applications being incorporated by reference in its entirety herein and for all purposes.

[0069] With reference to FIGS. 2-3, the shank 20 generally comprises shank head 22 at a proximal end 23 having a universal shank head structure, and a shank body 40 extending distally from the shank head 22 toward a tip 48 at a distal end 49. The shank 20 is elongate, with the shank body 40 having a helically wound bone implantable thread 44 (single or dual lead thread form) extending from near a neck 42 located adjacent to the shank head 22, to the distal tip 48 of the body 40 and extending radially outwardly therefrom. During use, the shank body 40 utilizing the thread 44 for gripping and advancement is implanted into the vertebra (not shown) of a patient leading with the tip 48 and driven down into the vertebra with an installation or driving tool (also not shown), so as to be implanted in the vertebra to near the neck 42 of the shank 20, as more fully described in the paragraphs below. The shank 20 has a central longitudinal axis, or axis of rotation, that is generally identified by the reference numeral 21.

[0070] The neck 42 extends axially upward from the shank body 40. The neck 42 may be of the same or is typically of a slightly reduced radius as compared to an adjacent upper end of the shank body 40 where the thread 44 terminates. In one aspect the threaded shank body 44 and the neck 42 can together define an anchor portion of the shank 20. Further extending axially and outwardly from the neck 42 is the shank head 22 that provides a connective or capture apparatus disposed at a distance from the shank body 40, and thus at a distance from the vertebra when the shank body 40 is implanted in such vertebra.

[0071] The shank head 22 is configured for a pivotable connection between the shank

20 (with the attached retainer 70) and the receiver 100 prior to fixing of the shank 20 in a desired position with respect to the receiver 100. In particular, the shank head 22 has the circumferential horizontal capture recess 32 that allows for the shank head 22 to connect with either a multi-planar or a uni-planar receiver assembly 14, and in particular with either a multi-planar or a uni-planar retainer 70 which is engageable with a complementary multi-planar or uni-planar receiver 100, respectively. This feature of the pivotal bone anchor assembly or system can advantageously provide for selectable multi-planar or uni-planar motion of a receiver 100 with respect to the shank head 22, as determined by a surgeon or medical professional in an operating environment after implantation of the shank body 40 into a vertebra, but prior to the coupling or capture of the shank head 22 with a receiver assembly 14. As defined herein, the capability of connecting with either a multi-planar or a uni-planar receiver assembly 14 in an operating environment, without further configuration or modification, is useful for designating the shank head 22 as a universal shank head.

[0072] Furthermore, it will be appreciated that the horizontal capture recess 32 extends circumferentially entirely around the shank head 22, without any planar surfaces or flats being formed into the sides of the shank head 22. This results in a substantially continuous 360 degree contact between the shank head 22, the retainer 70, and a receiver seating surface 132 (FIGS. 10-11 ) that avoids high-stress discontinuities while providing for a smooth continuous engagement between the internal components that resists pull-out at all angulation angles. In a multi-planar embodiment the partial spherical outer surface 74 of the resilient open retainer 70 and the partial spherical seating surface 132 of the receiver cavity 126 are continuous and unbroken, providing for polyaxial or multi-planar pivotal motion between the shank 20 and the multi-planar receiver 100. In a uni-planar embodiment, such as that shown in FIGS. 1 and 10-11 , the partial spherical outer surface 74 of the resilient open retainer 70 and the partial spherical seating surface 132 of the receiver cavity 126 are modified to include outwardly-projecting pegs 79 and inwardly-extending pockets 133, respectively, that restrict the pivotal motion between the shank and the receiver to a single plane. Nevertheless, the substantially continuous 360 degree contact between the shank head, the retainer, and the receiver seating surfaces can be maintained in the uni-planar embodiment to provide a secure pull-out resistant connection between the components at all angulation angles.

[0073] As shown in FIGS. 2-3, in one aspect the inner recess surface 34 of the horizontal capture recess 32 can have a curved profile that gradually curves downwardly and outwardly as moving from the upper ledge surface 33 to the lower ledge surface 35, and which can be complementary with a curvate inner surface 76 of the resilient open retainer 70. Nevertheless, it is understood that the inner recess surface 34 can have a variety of profiles, including but not limited to a cylindrical profile, a frusto-conical profile, a reversed curved profile that gradually curves downwardly and inwardly as moving from the upper ledge surface 33 to the lower ledge surface 35, and the like.

[0074] Extending upwardly from the upper ledge surface 33 is an upper cylindrical surface 30 having a radius that is substantially equal to the radius of the lower cylindrical surface 36. Extending further upwardly from the upper cylindrical surface 30 is an upper partial spherical or domed surface 28. The upper partial spherical surface 28 has an outer radius configured for sliding cooperation and ultimate frictional mating with a substantially spherical concave bottom surface 166 of the pressure insert 150 (FIGS. 10-11 ) that has the same or substantially similar radius as the partial spherical surface 28. In addition, the radius of the upper partial spherical surface 28 can substantially equal to both the radius of the lower partial spherical surface 38 and a partial spherical outer surface 74 of the multi-planar retainer 70, so that the three partial spherical surfaces 28, 74, 38 align, when the resilient open retainer 70 is captured or secured within the capture recess 32, to form a united shank head 22 / retainer 70 structure that is substantially spherical.

[0075] Also shown in FIG. 3, located near or adjacent to the upper partial spherical surface 28 is an annular planar top surface 26 that surrounds an internal drive feature 24 or drive socket. The illustrated internal drive feature 24 is an aperture formed in the top surface 26 and has a hex shape designed to receive a hex tool (not shown) of an Allen wrench type, into the aperture for rotating and driving the shank body 40. The seat or base surface 25 of the drive feature 24 is disposed perpendicular to the shank axis 21 , with the drive feature 24 otherwise being coaxial with the axis 21. In operation, a driving tool is received in the internal drive feature 24, being seated at the base surface 25 and engaging the six faces of the drive feature 24 for both driving and rotating the shank body 40 into the vertebra, either before or after the shank 20 is attached to the receiver assembly 14, with the shank body 40 being driven into the vertebra with the driving tool extending into the multi-planar receiver 100.

[0076] In one aspect the shank 20 can be cannulated, with a bore 46 extending through the entire length thereof, and centered about the central longitudinal axis 21 of the shank 20. The bore 46 is defined by an inner cylindrical wall of the shank 20 and has a circular opening at the shank tip 48 and an upper opening communicating with the internal drive 24 at the surface 25. The bore 46 is coaxial with the threaded shank body 40 and the shank head 22. The bore 46 provides a passage through the shank 20 interior for a length of wire (not shown) inserted into the vertebra prior to the insertion of the shank body 40, the wire providing a guide for insertion of the shank body 40 into the vertebra.

[0077] Also shown in FIG. 2, in one aspect of the disclosure the bone anchor or shank

20 can further include a removable resilient capture recess protection sleeve 50 installed over the horizontal capture recess 32 that is formed into the shank head 22 or capture portion of the bone anchor, so as to prevent soft tissue and bone chips from entering and clogging the capture recess 32 prior to introduction of the shank head 22 into a receiver assembly, as described in more detail below.

[0078] With reference now to FIG. 4, in some cases an error can occur during the placement of the bone anchor during surgery, in which the implanted bone anchor 20 is so far embedded into the bone 16 that the neck region 42 and/or the shank head 22 are below the natural surface 17 of the bone 16. Leaving the bone anchor 20 in this state could prevent complete attachment of a receiver assembly 14 and/or prevent full articulation of the receiver 100 relative to the shank head 22 after coupling the receiver assembly 14 to the shank head 22. To resolve this situation without backing the bone anchor 20 out from the bone 16, the reamer tool 200 shown in FIGS. 5-8 can be used to prepare the shank head for receiving a receiver assembly 14 by creating sufficient lateral clearance for complete attachment and full articulation of the receiver assembly 14 relative to the shank head.

[0079] With reference to FIGS. 5-6, the reamer 200 generally includes body or shaft 202 with a cutting head 204 at a lower end or front face 206 having cutting flutes 208 with leading edge front face cutters 210. The reamer 200 further includes a closed central bore 212 with a front face opening 214 having a diameter sized at least for the neck 42 of the bone anchor 20 and a length sized to accommodate at least the shank head 22 and the upper portion of shank neck region. The closed central bore 212 has a closed end with a spherical surface 216 that is complementary with the shank head upper partial spherical surface 28 to allow rotation of reamer tool on the shank head 22. In one aspect the cutting flutes 208 of the illustrated embodiment may be separated by slots 222 to allow the cutting head 204 to first expand around the shank head 22, and to then close around the lower partial spherical surface 38 to clear the material adjacent the neck 42 of the bone screw 20. However, in other embodiments the cutting flutes may be not be slotted and the cutting head may not be expandable, so that the front face cutter cuts a straight cylindrical column in the bone underneath the shank head.

[0080] In one aspect the cutting flutes 208 can also be spiral-wound to better remove bone chips and soft tissue from the front face during use. In addition, the body or shaft 202 of the reamer 200 may be cannulated with a narrow bore 218 extending through the entire length thereof along a longitudinal axis, and with a driver attachment structure 220 at an upper end opposite the cutting end that allows for attachment of a variety of driving tools.

[0081] During use, the reamer tool cutting head 204 is dropped, generally while rotating, toward bone anchor 20 (FIG. 6) until the shank head 22 enters the front face opening 214 and the leading edge front face cutters 210 engage with patient bone 16. The reamer tool is rotated or continue to rotate while moving downward to cut an annular trench 18 into the bone material 16 surrounding the shank head 22, until the upper partial spherical surface 28 of the bone anchor contacts the closed end spherical surface 216 of the central bore 212, as shown in FIG. 7. In the embodiment with slotted cutting flutes 208, the front face 206 of the cutting head first expands and then contracts around the shank head 22 as the shank head moves further into the closed central bore 212. After the shank head contacts the closed spherical end surface 216, the reamer tool 200 is removed (FIG. 8) to expose the embedded shank head 22 now having sufficient lateral clearance for complete attachment and full articulation of a receiver assembly 14 relative to the shank head 22 (FIG. 9).

[0082] With reference now to FIGS. 10-11 , the internal components of the pivotal bone anchor assembly 10 shown in FIG. 1 , namely the two-piece positioner 170 and positioner pins 190, the retainer 70, and the pressure insert 150, can be pre- assembled into the receiver 100 to form a receiver assembly 14 that is suitable for storage, shipping, and eventually use in a surgical setting. In the pre-assembled or shipping configuration shown in the drawings, the retainer 70 is securely supported and maintained within the positioner chamber portion 128 of the receiver cavity 126 by the two-piece positioner 170, with the retainer 70 being centralized in space above both the receiver bottom opening 136 and the partial spherical seating surface 132. The pressure insert 150 is also held in its vertical position within the receiver central bore 114 by the insert ridges 158 being fully enclosed within receiver upper grooves 120 to prevent any upward movement of the pressure insert 150 relative to the multi- planar receiver 100, and to allow for downward movement or deployment of the pressure insert 150 only with considerable direct force to the upper curvate seating surface 156 of the pressure insert 150 that may be provided by the appropriate tooling, as disclosed in more detail below. In the shipping configuration the pressure insert 150 is also held or‘clocked’ in angular position by upper flanges 182 that project inwardly from the positioner wing portions 180 to surround the opposing skirts 164 that project outwardly from the insert base 162.

[0083] In preparation for assembly with the bone anchor 20, the pre-assembled receiver assembly 14 is configured for positioning above the shank head 22 with tooling, such a deployment tool, with the receiver bottom opening 136 generally aligned with the upper partial spherical surface 28 of the shank head 22. As described in detail below, the receiver assembly 14 is then moved downward and engaged, coupled, or assembled to the shank head 22 with the deployment tool to form the pivotal bone anchor assembly 10 shown in FIGS. 45-46.

[0084] FIG. 12 illustrates a deployment tool 300 for removably engaging the receiver assembly 14 of the pivotal bone anchor assembly 10 for subsequent assembly and deployment to the head of a bone anchor, such as the shank head 22 of bone anchor 20 described above. The deployment tool 300 generally comprises a three level “Shaft-Within-Tube-Within-Tube” design that, when fully assembled, includes a central “bayonet” type tool, such as central bayonet drive shaft 370, that is slidably supported within an inner locking tube 330 that, in turn, is slidably supported within an outer support tube 310.

[0085] The inner locking tube 330 has a spring-loaded connection with the outer support tube 310 provided by a spring mechanism that is positioned within a lower shaft handle 350 located at the proximal ends of the outer support tube 310 and inner locking tube. The outer support tube 310, inner locking tube 330, and lower shaft handle 350 together define an engagement assembly 304 that engages the receiver assembly.

[0086] The central bayonet drive shaft 370 has a translating threaded connection with an upper shaft handle 390 that, in turn, can be connected to the lower shaft handle 350 with a locking twist-on connection. Other connection mechanisms are also possible. The central bayonet drive shaft 370 and upper shaft handle 390 together define a bayonet assembly 308.

[0087] With reference to FIGS. 13-14, the outer support tube 310 includes two elongated apertures or slots 312 that extend proximally from the distal end 319 of the outer support tube 310, to separate the outer support tube into two flexible legs 314 that are configured to expand away from each other. As shown in FIGS. 14 and 18, a pair of end effectors 320 can be securely mounted within the distal ends 316 of the flexible legs 314. [0088] With reference to FIGS. 15-17, the inner surface 322 of each of the end effectors 320 is sized and shaped to securely engage and mate with the outer surface 108 of the receiver 100 of the receiver assembly 14. For instance, each of the end effectors can include at least one protrusion structure or tab 323 that becomes engaged within a tool engagement recess 140 formed into the outer surface 108 of the receiver 100. Other tool engagement configurations for securing the receiver assembly 14 with the end effectors 320 are also possible. The upper or proximal ends of the end effectors include tapered upper projections 326 that are configured to slidably receive and engage with the distal end 339 of the inner locking tube 330 to prevent expansion of the flexible legs 314 during the pressure insert deployment process, as described in more detail below.

[0089] The outer surface 324 of each of the end effectors 320 can also sized and shaped to securely engage and mate with the distal ends 316 of the flexible legs 314, as noted above. For example, mounting tabs 325 can project outwardly from the outer surface 324 to be received within corresponding mounting apertures 318 formed in the distal ends 316 of the flexible legs 314.

[0090] With reference to FIGS. 18-20, the inner locking tube 330 is slidably received within the outer support tube 310 having attached end effectors 320 at the distal ends 316 of the flexible legs 314. The inner locking tube 330 can also include two elongated apertures or slots 332 that extend proximally from the distal end 339 of the inner locking tube 330, but which slots 332 are much shorter than the longer slots 312 in the outer locking tube 310 to ensure that the distal end 339 of the inner locking tube 330 remains a more rigid structure.

[0091] In FIG. 19 the inner locking tube 330 is shown in the upper retracted position within the outer support tube 310, with the distal ends 336 of the inner locking tube 330 spaced from the tapered upper projections 326 of the end effectors 320, and an inner pin aperture 338 at the upper or proximal end of the inner locking tube 330 being in an upper location that is covered by the outer support tube 310.

[0092] In FIG. 20 the inner locking tube 330 is shown in the lower locked position within the outer support tube 310, with the distal ends 336 of the inner locking tube 330 sliding between the tapered upper projections 326 of the end effectors 320 and the inner surface of the outer support tube 310, thereby preventing the legs 314 of the outer support tube 310 from flexing outward. In addition, the inner pin aperture 338 at the upper or proximal end of the inner locking tube 330 has moved downward to a lower location that is now aligned with an outer pin aperture 328 formed into the upper or proximal end of the outer support tube 310.

[0093] FIG. 21 illustrates the engagement assembly 304 portion of the deployment tool, in which the inner locking tube 330 is slidably positioned within the outer support tube 310, and with proximal or uppers ends of the both tubes 310, 330 being coupled together via the lower shaft handle 350. In FIG. 21 the inner locking tube 330 is in the upper retracted position relative to the outer support tube 310.

[0094] FIGS. 22-23 are cross-sectional side views of the lower shaft handle portion of the engagement assembly, with the inner locking tube in the upper retracted position in FIG. 22 and in the downward locking position in FIG. 23. In one aspect of the present disclosure a spring-loaded release pin 356 can be mounted to the side of the outer support tube 350 over the outer pin aperture 328 in the outer support tube 310, with the tip of the pin bearing against the outer surface of the inner locking tube in the upper retracted position in FIG. 22. The inner pin aperture 338 in the inner locking tube 330 slides down to become aligned with the outer pin aperture 328 and the spring-loaded release pin 356 in the downward locking position, as shown in FIG. 23, allowing the pin to engage the inner pin aperture 338 to hold the inner locking tube in the locking position.

[0095] FIG. 24a shows the bayonet assembly 308 comprising the central bayonet drive

370 shaft which is rotatably secured to the upper shaft handle 390. The distal end of the central bayonet drive shaft (FIG. 24b) includes a shaped deployment tip 376 with a rounded lower surface 378 that sized and shaped to engage the upper curvate seating surface 156 of the pressure insert 150 located within the receiver assembly 14 (FIGS. 10-11 ).

[0096] With reference to FIGS. 25-26, inserting the central bayonet drive shaft 370 into the engagement assembly 304 and engaging the upper shaft handle 390 with the lower shaft handle 350 using the twist-on connection 394 can be used to activate or move the inner locking tube from the upper retracted position (FIG. 25) to downward locking position (FIG. 26), with the spring-loaded release pin 356 pressing inward in the downward locking position to engage the inner pin aperture 338. Other mechanisms or configurations for activating the inner locking tube are possible.

[0097] FIGS. 27-28 illustrate the movement of the central bayonet drive shaft 370 through the completely assembled deployment tool 300 when the central bayonet drive shaft 370 is rotated relative to the upper shaft handle 390 that, in turn, is connected with the lower shaft handle 370. Specifically, rotating the central bayonet drive shaft 370 with the driver attachment structure 382 located at the proximal end of the drive shaft 370 causes the shaped deployment tip 376 to move downward through the inner locking tube toward the end effectors 320 mounted at the distal ends 316 of the legs 314 of the outer support tube 310.

[0098] One exemplary embodiment for engaging the end effectors 320 located at the distal end 316 of the deployment tool with a receiver assembly 14 is shown in FIGS. 29-33. With reference first to FIG. 29, the engagement assembly 304 of the deployment tool, without the bayonet assembly, is positioned over the pre-assembled receiver assembly 14 so that the slots 312 in the outer support tube 310 align with the receiver channel 106. The inner locking tube 330 will be in the upper retracted position.

[0099] With reference to FIG. 30, the distal end 316 of the outer support tube 310 is pushed onto the upper end of the receiver assembly 14, with the inner surfaces 322 of the end effectors 320 slidably engage with the outer surfaces 108 of the receiver 100.

[00100] With reference to FIGS. 31-32, the engagement assembly 304 continues to move downward until the flexible legs 314 of the outer support tube 310 expand away from each other to allow the end effectors 320 to slide down the outer surfaces 108 of the receiver 100 (FIG. 31 ), until the end effector protrusions 323 become engaged within the tool engagement recesses 140 and the inner surfaces 322 of the end effectors fit tightly around the exterior of the receiver 100 (FIG. 32). [00101] With reference to FIG. 33, the bayonet assembly 308 is inserted into the engagement assembly 304 and secured together using the locking twist-on connection 394 (see FIGS. 25-26) to move the inner locking tube 330 downward within the outer support tube 310 to become engaged between the tapered upper projections 326 of the end effectors 320 and the inner sidewall of the outer support tube 330 (see FIGS. 19-20), thereby locking the receiver assembly 14 to the distal end 316 of the deployment tool (FIG. 33). At the same time the spring-loaded release pin 356 mounted to the side of the outer support tube 310 can engage the inner pin aperture 338 in the inner locking tube 330 to hold the inner locking tube in the activated downward locking position (see FIGS. 25-26).

[00102] Another exemplary embodiment for mounting and deploying the receiver assembly 14 to the shank head 22 of a bone anchor 20 is shown in FIGS. 34-44. With reference first to FIGS. 34-35, the receiver assembly is positioned over the shank head using the deployment tool 300 (FIG. 34) and moved downward until the shank head 22 enters the receiver bottom opening 326. The deployment tool is then pushed downward until the shank head upper partial spherical surface 28 first contacts the retainer 70, causing the expansion of both the retainer and its supporting positioner around the shank head. The pushing continues until the shank head reaches max push-through, in which the shank head upper partial spherical surface abuts the concave bottom surface of the pressure insert and the retainer curvate inner surface bears against the shank lower partial spherical surface (FIG. 35).

[00103] With reference to FIG. 36, the receiver assembly 14 is pulled back upward using the deployment tool 300 until the retainer 70 first snaps into and is captured by the horizontal shank capture recess 32, with the retainer curvate inner surface bearing against the outwardly-facing shank head groove curvate surface. The pulling of the receiver assembly 14 back upward continues while the retainer disengages from the positioner and becomes seated on the receiver partial spherical seating surface.

[00104] With reference to FIGS. 37-38, the central bayonet drive shaft is now rotated relative to the upper shaft handle to move the shaped deployment tip 376 downward to engage the upper curvate seating surface 156 of the pressure insert 150. After the initial engagement with the insert upper seating surface 150, the deployment tip 356 continues to be driven downward so as to apply considerable force to the top of the pressure insert 150, thereby pushing the insert ridges 158 downward out of the upper receiver grooves 120 and onto the discontinuous cylindrical surface 118 of the receiver central bore, where the pressure insert 150 encounters an interference fit that resists the downward motion. The force required to overcome this interference fit can be about 200 pounds-force or greater. It is contemplated that variety of torque- generating mechanisms or apparatus can be connected to the drive attachment structure 382 of the central bayonet drive shaft 370 (see FIGS. 27a and 28a) to continue rotating the central bayonet drive shaft to overcome the interference fit and continue driving the pressure insert downward.

[00105] With shown in FIG. 38, the driving of the insert ridges 158 downward out of the upper receiver grooves 120 and onto the discontinuous cylindrical surface 118 of the receiver central bore during deployment can temporarily cause the upwardly- projecting arms 152 of the pressure insert 150 to deflect inward, narrowing the gap at the top of the insert channel 154. With the pressure insert in this position, the rod would not fit within the insert channel. Moreover, the shaped deployment tip 376 can include curvate recesses 380 above the rounded rod-shaped lower surface 378 that are configured to provide clearance for the inwardly-deflected arms 152 of the pressure insert 150.

[00106] With reference to FIGS. 39-40, continued rotation of the central bayonet drive shaft 370 relative to the upper shaft handle continues to drive the pressure insert 150 downward with the deployment tool 300 until the insert ridges 158 snap into the lower receiver grooves 122, the insert concave spherical bottom surface 166 fully engages the shank head upper partial spherical surface 28, and the retainer outer partial spherical surface 74 fully engages the receiver partial spherical seating surface 132 to establish a friction fit.

[00107] The friction fit is provided from above by sliding frictional engagement between the insert concave spherical bottom surface 166 and the shank head upper partial spherical surface 28 and/or the retainer outer partial spherical surface 74, and from below by sliding frictional engagement between the receiver partial spherical seating surface 132 and the retainer outer partial spherical surface 74 and/or the shank head lower partial spherical surface 38. It will be appreciated that manufacturing tolerances that might compromise an effective friction fit are accommodated by adjusting the vertical position of the pressure insert during deployment with the deployment tool. The deployment tool forces the pressure insert, shank, and retainer, and receiver into tight contact for an effective friction fit that accommodates small variations in part dimensions.

[00108] With reference to FIG. 41 , the central bayonet drive shaft can now be rotated in the opposite direction relative to the upper shaft handle to retract the shaped deployment tip 376 from the receiver assembly and put the bayonet assembly back into position for use with in another deployment. The bayonet assembly can be disengaged and withdrawn from the engagement assembly 304 by reversing the twist- on connection and withdrawing the central bayonet drive shaft from within the inner locking tube. The inner locking tube 330 will remain in its downward activated locking position and engaged with the end effectors 320 until the release pin is pulled.

[00109] With reference to FIG. 42, the release pin can be pulled to release the inner locking tube 330 from the end effectors 320 and allow the spring-loaded connection between outer support tube 310 and the inner locking tube 30 to push the inner locking tube back upward to its non-activated position.

[00110] With reference to FIGS. 43-44, the engagement assembly is now pulled upward until the flexible legs 314 of the outer support tube 310 expand away from each other to allow the end effectors 320 to slide of the outer surfaces 108 of the receiver 100 (FIG. 43). The engagement assembly 304 can now be removed from the pivotal bone anchor assembly 10 (FIG. 44).

[00111] FIGS. 45-46 show the assembled pivotal bone anchor assembly 10, in which the receiver assembly 14 is secured the shank head 22 of the bone anchor with a friction fit the firmly holds the position of the receiver relative to the shank head without a holding force, while still allowing for movement/adjustment of the receiver position with an applied force. The friction fit allows for rotation of the receiver around the shank head, with an applied twisting force, so as to align the receiver channel with the receiver channels of an adjacent bone anchor assembly. The friction fit allows for angulation of the receiver relative the shank head, with a moment force, so as to align the receiver channel with the receiver channels of an adjacent bone anchor assembly, through sliding frictional engagement of the retainer lower partial spherical surface relative to the receiver partial spherical seating surface.

[00112] An alternative embodiment of the deployment tool 400 that is further useful for the reduction and final assembly of the pivotal bone anchor 10 to a locked position is shown in FIGS. 47-48. In this variation the inner locking tube 430 is provided with an extended slot 432 that corresponds with at least a portion of the slot 412 of the outer support tube 410, allowing for an elongated rod 90 to be positioned within the aligned slots of the engagement assembly 404 and reduced into the channel of the bone anchor receiver using the bayonet assembly (FIG. 47) or similar central“bayonet” type tool. In addition, the position of the elongate rod 90 can be maintained by an additional sliding tube (not shown) that can be either external or internal to the engagement assembly 404.

[00113] It is foreseen that additional embodiments of the engagement assembly and/or the bayonet assembly can be configured to allow for the threaded placement of the closure 80 down into the receiver central bore, so as to complete the final assembly of the pivotal bone anchor assembly (FIG. 48). In particular, it is further contemplated that additional embodiments of the central bayonet drive shaft or versions of similar central“bayonet” type tools for performing the same or different functions from those described above are also possible and considered to fall within the scope of the present disclosure. For example, a central“bayonet” type tool or assembly different from the bayonet assembly disclosed in FIG. 47 above could be used to reduce the elongated rod into the receiver channel of the pivotal bone anchor assembly, as shown in FIG. 48. Alternatively, the proximal or upper ends of the multiple adjacent deployments tools could be tied or linked together to allow for simultaneous manipulation of multiple screws. [00114] Yet another embodiment of the deployment tool 500 of the present disclosure is shown in FIG. 49, in which the inner locking tube 530 of the engagement assembly 504 includes a raised projection or bump feature 534 that interacts with a ramp feature 513 formed into the outer support tube 510, such as a rounded restriction formed into one or more of the slots 512 in the outer support tube 510. In this alternative embodiment the spring-loaded release pin 556 is also engaged with a reduced diameter slot 540 in the inner locking tube 530 that is slightly spaced below the pin aperture 538, and which engagement positions the inner locking tube 530 in a slightly spring-loaded but unlocked state relative to the outer support tube 510, as shown in FIG. 50.

[00115] With reference to FIG. 51 , the unlocked engagement assembly 504 can be manipulated so that end effectors slide over the receiver assembly 14, forcing the distal ends 516 of the outer support tube 510 to spread. During engagement with the receiver assembly the bump feature 534 remains disengaged from ramp feature 513.

[00116] With reference to FIG. 52, the bayonet assembly (not shown) is now inserted into the unlocked engagement assembly and secured together using the locking twist-on connection, so as to move the inner locking tube 530 downward within the outer support tube 510 to engage with the end effectors 520 and thereby lock the receiver assembly 14 to the distal end 516 of the deployment tool. At the same time the spring- loaded release pin 536 engages the inner pin aperture 538 in the inner locking tube 330 to hold the inner locking tube in the activated downward locking position.

[00117] With reference to FIGS. 53 and 54, after coupling and deployment of the receiver assembly 14 to a shank head of a bone anchor, and subsequent removal of the bayonet assembly (not shown), the inner locking tube is released by pulling on the spring loaded pin 536. In the initial travel the inner locking tube 530 disengages from the end effectors 520 (FIG. 53), after which the bump feature 534 on the inner locking tube 530 rides upward along the ramp feature 513 on the outer support tube 510, thereby forcing the split distal ends 516 of the outer support tube 510 to expand and release the receiver assembly 14 from the deployment tool 500 (FIG. 54). [00118] As indicated above, the invention has been described herein in terms of preferred embodiments and methodologies considered by the inventor to represent the best mode of carrying out the invention. It will be understood by the skilled artisan, however, that a wide range of additions, deletions, and modifications, both subtle and gross, may be made to the illustrated and exemplary embodiments of the composite substrate without departing from the spirit and scope of the invention. These and other revisions might be made by those of skill in the art without departing from the spirit and scope of the invention that is constrained only by the following claims.

Claims

CLAIMS What is claimed is:

1. A deployment tool for securing a receiver assembly to a head of a bone anchor, the deployment tool comprising:

an outer support tube having end effectors at a distal end for coupling to the exterior of the receiver assembly having an actuatable contact surface for operably engaging the bone anchor head with a friction fit upon deployment with a force greater than or about 200 pounds force;

an inner locking tube slidably movable within the outer support tube and engageable with the end effectors in a downwardly locked position so as to the lock the distal end of the outer support tube around the receiver assembly; and

a central bayonet drive shaft insertable through the inner locking tube,

wherein the central bayonet drive shaft is downwardly movable within the inner locking tube when the inner locking tube is in the locked position to engage the actuatable deployment surface within the receiver assembly with a force greater than or about 200 pounds force to secure the receiver assembly to the bone anchor head with a friction fit.