Cage and plate system

Abstract

A system, such as for spinal fixation, may include a delivery instrument, a cage implant, and a plate. The cage implant and the plate may be integrated onto the delivery instrument to maintain an alignment between the cage and the plate. The delivery instrument may include first and second attachments to releasably secure the cage and plate, respectively, to the delivery instrument. A first actuator may control a releasable engagement of the delivery instrument to the cage, and a second actuator may releasably lock the plate to a shaft of the delivery' instmment. The delivery' instrument may include a geometry' interfacing yvith the plate to align the plate with the cage implant, such as to limit the plate from rotating when sliding up and down the shaft.

Description

CAGE AND PLATE SYSTEMCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 651,097, filed May 23, 2024, which is incorporated by reference herein in its entirety and for all purposes.TECHNICAL FIELD

[0002] This disclosure is directed to medical devices, systems and methods. More specifically, this disclosure is directed to devices, systems and methods related to spinal fixation procedures.BACKGROUND

[0003] Anterior cervical plates are used as a form of fixation for anterior cervical discectomy and fusion (ACDF) procedures. Often, after a cervical cage is implanted in the cervical disc space, an anterior plate is added spanning the disc space and is anchored to the adjacent anterior aspect of the cervical vertebral bodies with screws. Some techniques have the plate directly mounted to the back of the cage implant, which can restrict how deep, posteriorly, the cage implant can be placed due to the plate abutting against the cervical vertebral body. Other techniques do not integrate the plate with the cage, which may result in poor plate positioning. For example, it can be challenging to properly align the plate to the cage. In addition, it can be challenging to properly orient the plate so that it is not rotationally skewed to one direction relative to the vertebral construct.

[0004] Accordingly, a need exists for new cervical anterior cage and plate systems and methods.SUMMARY

[0005] In accordance with embodiments of the present disclosure, a system includes a delivery instrument, a cage implant, and a plate. The cage implant and the plate may be integrated onto the delivery instrument to maintain an alignment between the cage implant and the plate.

[0006] In examples, the delivery instrument may include a first attachment and a second attachment. The cage implant may be configured to engage the first attachment to releasably secure the cage implant to the delivery instrument. The plate may be configuredto engage the second attachment to releasably secure the plate to the delivery instrument. The delivery’ instrument may be configured to releasably engage the cage implant. The delivery instrument may include a geometry interfacing with the plate to align the plate with the cage implant. The system may include a first actuator to releasably couple the cage implant to the delivery' instrument, and a second actuator to releasably couple the plate to the delivery instrument. The first actuator may include a knob to control a threading of the delivery instrument to the cage implant. The second actuator may include a spring loaded piston biasing the plate against a stop defined on the delivery instrument. The system may include at least two screws for anchoring the plate to adjacent vertebral bodies. The plate may include at least one cam rotatable to position the at least one cam over the at least two screws to limit the at least two screws from backing out. The at least two screws may include a first screw, a second screw, and a third screw. The at least one cam may include a first cam and a second cam, the first cam rotatable to position the first cam over the first screw and the second screw, the second cam rotatable to position the second cam over the second screw and the third screw.

[0007] In accordance with embodiments of the present disclosure, a system includes a delivery instrument including a first attachment and a second attachment, a cage implant configured to engage the first attachment to releasably secure the cage implant to the delivery instrument, and a plate configured to engage the second attachment to releasably secure the plate to the delivery instrument.

[0008] In examples, the first attachment may include a threaded end of the delivery instrument for threaded engagement with the cage implant. The system may include a knob coupled to the threaded end to control a threading of the threaded end to the cage implant for an attachment or detachment of the cage implant to the delivery instrument. The second attachment may include a flat for mating engagement with a key of the plate. The system may include a spring loaded piston biasing the key against a stop defined on the delivery instrument. The delivery' instrument may include a handle and a shaft, the first attachment defined at or proximate an end of the shaft, the second attachment defined adjacent the handle. The cage implant may be a cervical cage implant, and the plate may be an anterior plate for anchoring to anterior aspects of adjacent cervical vertebral bodies.

[0009] In accordance with embodiments of the present disclosure, a system for spinal fixation includes a cage implant for positioning within a disc space, a plate for anchoring to anterior aspects of adjacent vertebral bodies, and a delivery instrument configured toreleasably engage the cage implant and the plate, the delivery instrument including a geometry interfacing with the plate to align the plate with the cage implant.

[0010] In examples, the delivery instrument may include a shaft, and wherein the geometry may include a key way defined on the shaft to interface with a key of the plate to provide a directional positioning of the plate relative to the shaft. The geometry may limit the plate from rotating when sliding up and down the shaft to align the plate with the cage implant. The shaft may include a cam lock, the plate rotatable along the cam lock between an unlocked position on the shaft and a locked position on the shaft. The cam lock may be a quarter turn cam lock.

[0011] In addition to the exemplar}' aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 illustrates a system including a cage implant and a plate in accordance with embodiments of the present disclosure.

[0013] FIG. 2 illustrates an exploded view of the system of FIG. 1 in accordance with embodiments of the present disclosure.

[0014] FIGS. 3A-3C illustrate an attachment of a plate to a delivery instrument in accordance with embodiments of the present disclosure.

[0015] FIG. 4 illustrates a use of a delivery system to position a cage implant within a disc space in accordance with embodiments of the present disclosure.

[0016] FIGS. 5A-5B illustrate a use of a delivery system to position a plate relative to a cage implant in accordance with embodiments of the present disclosure.

[0017] FIGS. 6A-6B illustrate a use of a delivery system to anchor a plate to adjacent anterior aspects of vertebral bodies in accordance with embodiments of the present disclosure.

[0018] FIG. 7 illustrates an anchor screw back out prevention feature in accordance with embodiments of the present disclosure.

[0019] FIG. 8 illustrates adjacent cage and plate systems implanted at adjacent levels in accordance with embodiments of the present disclosure.DETAILED DESCRIPTION

[0020] The following description of certain embodiments is merely exemplary in nature and is in no way intended to limit the invention or its applications or uses. In the following detailed description of embodiments of the present systems and methods, reference is made to the accompanying drawings which form a part hereof, and which are shown by way of illustration specific embodiments in which the described systems and methods may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice presently disclosed systems and methods, and it is to be understood that other embodiments may be utilized and that structural and logical changes may be made without departing from the spirit and scope of the present system. Moreover, for the purpose of clarity, detailed descriptions of certain features will not be discussed when they would be apparent to those with skill in the art so as not to obscure the description of the present system. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the present system is defined only by the appended claims.

[0021] As used herein, “vertebrae” may refer to cervical vertebrae unless otherwise indicated. Embodiments are not limited to cervical vertebrae, however, and may encompass other vertebrae or groups of vertebrae along the spine of a subject.

[0022] As used herein, “subject” may refer to a human (e.g., patient) afflicted with a spinal condition, e.g., spinal stenosis, injury or disease, which may be degenerative. The condition may impact the integrity and / or positioning of one or more vertebrae, which may cause chronic pain and instability.

[0023] As used herein, “device” may refer to a spinal fixation device, rod fixation device, or component(s) thereof. At least a portion of the device, e.g., the distal end, may be inserted into a cervical facet joint. Accordingly, the disclosed devices, components and / or portions thereof may, in some examples, be considered or referred to as intrafacet implants. At least another portion of the device, e.g., the tulip member, may be configured to couple and secure a connecting rod.

[0024] The terms “distal” and “proximal” are used to refer to a position or direction relative to the treating clinician, such as a surgeon. “Distal” and “distally” refer to a position that is distant from, or in a direction away from, the treating clinician. “Proximal” and “proximally” refer to a position that is near, or in a direction toward, the treating clinician.

[0025] For the following defined terms, certain definitions shall be applied unless a different definition is given elsewhere in this disclosure. The terms “a,” “an.” and “the” are used to include one or more than one, independent of any other instances or usages of"at least one” or “one or more.” The term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B.” All numeric values are assumed to be modified by the term “about,” whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (e g., having the same function or result). In many instances, the term “about” can include numbers that are rounded to the nearest significant figure. The recitation of numerical ranges by endpoints includes all numbers and subranges within and bounding that range (e.g., 1 to 4 includes 1, 1.5, 1.75, 2, 2.3, 2.6, 2.9, etc. and 1 to 1.5, 1 to 2, 1 to 3, 2 to 3.5, 2 to 4, 3 to 4, etc.).

[0026] Embodiments disclosed herein provide means to place a cage implant into a disc space and attach a plate that maintains the centering and vertical alignment of the plate relative to the cage and disc space. For example, the cage and plate may be integrated onto a single delivery' instrument that maintains the alignment between the cage and the plate. The integration between the cage and the plate through a single delivery' instrument may streamline an ACDF procedure, such as reducing the number of steps needed to implant the cage and plate.

[0027] In examples, the geometry of the plate may allow the plate to be “stackable,” such as positioned adjacent similar plates. In such examples, the cage and plate system can be implanted at adjacent levels without plate interference, such as due to the plate’s unique size and shape.

[0028] FIG. 1 illustrates a system 100 for spinal fixation in accordance with embodiments of the present disclosure. The system 100 may include a delivery' instrument 102, a cage implant 104, and plate 106. The delivery' instrument 102 may include a handle 112 and a shaft 114. such as to deliver the cage implant 104 and plate 106 to a target site (e.g., to position, place, or otherwise deliver the cage implant 104 and plate 106 into or near a disc space, such as a cervical disc space). The handle 112 may' be defined on a proximal end of the delivery instrument 102, such as defining the proximal end. The shaft 114 may extend from the handle 112, such as towards a distal end of the delivery instrument 102. The shaft 114 may define a longitudinal axis of the delivery instrument 102, and the handle 112 and shaft 114 may be coaxially aligned along the longitudinal axis. Depending on the application, the shaft 114 may have a circular or non-circular crosssection, such as for purposes described below.

[0029] The cage implant 104 may be configured to be placed or implanted in a disc space between adjacent vertebrae. For example, the cage implant 104 may be a cervicalcage implant 104 for placement within a cervical disc space, such as for ACDF. The cage implant 104 may have a textured exterior surface 118 (e.g.. distinct teeth, raised ridges, serrations, or other protruding features) configured to engage a disc space. In examples, the cage implant 104 may include distally tapered, beveled or chamfered surfaces, such as to facilitate insertion of the cage implant 104 within the disc space. Although described with reference to cervical disc space and ACDF, the cage implant 104 may be implanted within other disc spaces along the spine.

[0030] In examples, the cage implant 104 may be integrated onto the delivery instrument 102. For example, the cage implant 104 may be coupled to the distal end of the delivery instrument 102 to facilitate placement of the cage implant 104 within the disc space via the delivery instrument 102. In examples, the cage implant 104 may be coupled to the delivery instrument 102 so as to allow easy removal of the delivery instrument 102 from the surgical site after implanting the cage. For example, the delivery instrument 102 may be coupled to the back end or rear face of the cage implant 104, such as to allow the delivery instrument 102 to be pulled away from the cage implant 104 with minimal interference to the surgical site.

[0031] The plate 106 may cooperate with the cage implant 104 to fuse adj acent vertebral bodies together. For example, the plate 106 may be positioned for anchoring to anterior aspects of adjacent vertebral bodies (e.g., adjacent cervical vertebrae, such that the plate 106 may be considered an anterior cervical plate). The plate 106 may include multiple apertures 124, such as to receive anchoring screws, as described below. In examples, the plate 106 may be integrated onto the delivery' instrument 102. For instance, the plate 106 may be coupled to the shaft 114, such as in aligned engagement to maintain an alignment between the cage and the plate 106.

[0032] FIG. 2 illustrates an exploded view of the system 100 in accordance with embodiments of the present disclosure. The delivery instrument 102 may be configured to releasably engage the cage implant 104. For example, the delivery instrument 102 may include a first attachment 202, and the cage implant 104 may be configured to engage the first attachment 202 to releasably secure the cage implant 104 to the delivery instrument 102. In the example of FIG. 2, the first attachment 202 includes a threaded end 206 of the delivery' instrument 102 for threaded engagement with the cage implant 104. The first attachment 202 (e.g., threaded end 206) may be defined at or proximate an end of the shaft 114.

[0033] In examples, the system 100 may include a first actuator 210 to releasably couple the cage implant 104 to the delivery instrument 102. The first actuator 210 may include a knob 214 to control a threading of the delivery instrument 102 to the cage implant 104. For example, the threaded end 206 may be controlled by the knob 214, such as the threaded end 206 rotated by the knob 214 to provide an attachment or detachment of the cage implant 104 to the delivery instrument 102. In the example shown, the knob 214 is rotatably coupled to the end of the handle 112, such as defining the proximal end of the delivery instrument 102.

[0034] The plate 106 may include a center bore 218. The center bore 218 may be shaped to match or closely match the shaft 114. For example, the delivery instrument 102 (e.g., shaft 114) may include a geometry interfacing with the center bore 218 to align the plate 106 thereto, such as to align the plate 106 with the cage implant 104. In examples, the geometry may include a keyway 222 defined on the shaft 114 (e.g., along the length of the shaft 114 from the distal end to the handle 112), and the plate 106 may include a key 224 (e.g., in the center bore 218). The keyway 222 may interface with the key 224 to provide a directional positioning of the plate 106 relative to the shaft 114. For example, the keyway 222 and key 224 may allow the plate 106 to slide onto the delivery instrument 102 (e.g., along the shaft 114). The geometry may limit the plate 106 from rotating when sliding up and down the shaft 114, such as to align the plate 106 with the cage implant 104 when the plate 106 is positioned near the cage implant 104.

[0035] FIGS. 3A-3C illustrate an attachment of the plate 106 to the delivery instrument 102 in accordance with embodiments of the present disclosure. In examples, the plate 106 may be releasably secured to the delivery instrument 102. For instance, the delivery instrument 102 may include a second attachment 304. and the plate 106 may be configured to engage the second attachment 304 to releasably secure the plate 106 to the delivery instrument 102. In the examples of FIGS. 3A-3C, the second attachment 304 is defined adjacent the handle 112. The second attachment 304 may include a flat 308 (e.g., defined in the shaft 114) for mating engagement with the key 224. In examples, the shaft 114 may include a cam lock 312. The plate 106 may be rotatable along the cam lock 312 between an unlocked position on the shaft 114 and a locked position on the shaft 114.

[0036] In examples, the system 100 may include a second actuator 316 to releasably couple the plate 106 to the delivery instrument 102. The second actuator 316 may include a spring loaded piston 318. The piston 318 may be integrated with the handle 112, such as the piston 318 arranged to slide or otherwise move into and out of the handle 112 at thejunction between the shaft 114 and the handle 112. In such examples, the spring or other biasing element may be positioned within the handle 112. The piston 318 may bias the key 224 against a stop 322 defined on the delivery instrument 102. The stop 322 may be formed as a result of defining the flat 308 in the shaft 114. For example, cutting the flat 308 in the shaft 114 may define the shaft 114. Although described as spring loaded, the piston 318 may be biased by or through other means or mechanisms, such as different biasing elements.

[0037] FIGS. 3A-3C illustrate an example attachment of the plate 106 to the delivery instrument 102. Referring to FIG. 3A, the plate 106 may be slid along the shaft 114 towards the handle 112. For example, the key 224 may be aligned with the key way 222 to provide directional control of the plate 106 along the shaft 114. The center bore 218 (e.g.. key 224) and the mating geometry of the shaft 114 may limit the plate 106 from rotating when sliding up and down the shaft 114, such as to provide vertical alignment of the plate 106 with the cage implant 104. The plate 106 may be slid to contact the piston 318, such as an end of the piston 318 protruding from the handle 112.

[0038] Referring to FIG. 3B, the plate 106 may be pushed against the piston 318 (e.g., against the bias provided by the piston 318), moving or pressing the piston 318 into the handle 112. Pushing the plate 106 against the piston 318 may reveal the cam lock 312 on the shaft 114.

[0039] Referring to FIG. 3C. after the cam lock 312 is revealed, the plate 106 may be rotated around the shaft 1 14. For example, the plate 106 may be rotated to align the key 224 with the flat 308 on the shaft 114. When the key 224 is aligned with the flat 308, the piston 318 may bias the plate 106 (e.g., key 224) against the stop 322 to lock the plate 106 in place on the shaft 114. In examples, the cam lock 312 may be a quarter turn cam lock, such that the plate 106 is rotated a quarter turn between the unlocked position and the locked position.

[0040] FIG. 4 illustrates a use of the system 100 to position the cage implant 104 within a disc space 400 (e.g., a cervical disc space) in accordance with embodiments of the present disclosure. The disc space 400 may be prepared to receive the cage implant 104, such as per standard ACDF procedure. The plate 106 may be loaded onto the delivery instrument 102 (e.g., as described above with reference to FIGS. 3A-3C), and the cage implant 104 may be coupled to the shaft 114 (e.g., as described above with reference to FIG. 2). The delivery instrument 102 may be positioned near the disc space 400 to implant the cage implant 104. For example, after the cage implant 104 is aligned with the disc space 400,the surgeon or other operator may mallet the cage implant 104 into the targeted disc space 400 (e.g., mallet the end of handle 112).

[0041] FIGS. 5A-5B illustrate a use of the system 100 to position the plate 106 relative to the cage implant 104 in accordance with embodiments of the present disclosure. After the cage implant 104 is positioned within the disc space 400, the plate 106 may be unlocked from the cam lock 312. For example, the plate 106 may be pulled back, proximally, against the bias of the piston 318 and rotated (e.g.. a quarter turn) to the unlocked position, such as to align the key 224 with the keyway 222 on the shaft 114. Once unlocked, the plate 106 may be slid down the shaft 114 toward the cage implant 104. The plate 106 may slid down the shaft 114 until the plate 106 abuts anterior aspects of adjacent vertebral bodies 502.

[0042] FIGS. 6A-6B illustrate a use of the system 100 to anchor the plate 106 to the adjacent vertebral bodies 502 in accordance with embodiments of the present disclosure. After the plate 106 abuts the anterior aspects of the adjacent vertebral bodies 502, the plate 106 may be anchored to the vertebral bodies 502 using at least two screws 600. For example, the system 100 may include a first screw 600A, a second screw 600B, and a third screw 600C for anchoring the plate 106 to the vertebral bodies 502.

[0043] Referring to FIG. 6 A, tw o screw s 600 (e.g., the first screw 600A and the second screw 600B) may be inserted at the bottom of the plate 106 while the delivery instrument 102 is still attached to the cage implant 104. In this manner, the alignment of the plate 106 with the cage implant 104 may be maintained.

[0044] Referring to FIG. 6B, the delivery instrument 102 may be released from the cage implant 104. For example, the knob 214 may be rotated to unthread the delivery instrument 102 (e.g., threaded end 206) from the cage implant 104. After the delivery instrument 102 is removed, one or more additional screws 600 (e.g., the third screw 600C) may be inserted at the top of the plate 106.

[0045] FIG. 7 illustrates an anchor screw back out prevention feature in accordance with embodiments of the present disclosure. In examples, the plate 106 may include at least one cam 702 (e.g.. one cam 702. multiple cams 702. a first cam 702A and a second cam 702B. etc.) rotatable to position the cam(s) 702 over the screws 600 to limit the screw s 600 from backing out post-procedure. Each cam 702 may include multiple prongs 706. The prongs 706 may extend radially from a center portion 708. The center portion 708 may be rotatably coupled to the plate 106.

[0046] The cam(s) 702 may be rotated over the heads of the screws 600 to limit the screws 600 from backing out, such as the cam(s) 702 rotated so that their prongs 706 overlap the screw heads. The first cam 702 A may be rotated to position the first cam 702 A (e.g., the prongs 706 of the first cam 702 A) over one or multiple screws 600, such as over the first screw 600A and the third screw 600C. The second cam 702B may be rotated to position the second cam 702B (e.g., the prongs 706 of the second cam 702B) over one or multiple screws 600, such as over the second screw 600B and the third screw 600C.

[0047] FIG. 8 illustrates adjacent cage and plate systems implanted at adjacent levels in accordance with embodiments of the present disclosure. In examples, the cage implant 104 and plate 106 can be implanted at adjacent levels (e g., adjacent cervical levels) without plate interference. For instance, the plate 106 may be sized and shaped to allow stacking of adjacent plates 106 along adjacent levels of the spine. For example, each plate 106 may be sized and shaped to nest with an adjacent plate 106. In examples, the plate 106 may be small enough to provide a gap 804 between the plates 106 at adjacent levels.

[0048] Of course, it is to be appreciated that any one of the examples, embodiments or processes described herein may be combined with one or more other examples, embodiments and / or processes or be separated and / or performed amongst separate devices or device portions in accordance with the present systems, devices and methods.

[0049] Finally, the above-discussion is intended to be merely illustrative of the present system and should not be construed as limiting the appended claims to any particular embodiment or group of embodiments. Thus, while the present system has been described in particular detail with reference to exemplary embodiments, it should also be appreciated that numerous modifications and alternative embodiments may be devised by those having ordinary skill in the art without departing from the broader and intended spirit and scope of the present system as set forth in the claims that follow. Accordingly, the specification and drawings are to be regarded in an illustrative manner and are not intended to limit the scope of the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A system comprising: a delivery7instrument; a cage implant; and a plate, wherein the cage implant and the plate are integrated onto the delivery instrument to maintain an alignment between the cage implant and the plate.

2. The system of claim 1, wherein: the delivery instrument comprises a first attachment and a second attachment; the cage implant is configured to engage the first attachment to releasably secure the cage implant to the delivery instrument; and the plate is configured to engage the second attachment to releasably secure the plate to the delivery instrument.

3. The system of claim 1, wherein the delivery' instrument is configured to releasably engage the cage implant, and wherein the delivery instrument comprises a geometry interfacing with the plate to align the plate with the cage implant.

4. The system of claim 1, further comprising: a first actuator to releasably couple the cage implant to the delivery' instrument; and a second actuator to releasably couple the plate to the delivery instrument.

5. The system of claim 5, wherein: the first actuator comprises a knob to control a threading of the delivery instrument to the cage implant; and the second actuator comprises a spring loaded piston biasing the plate against a stop defined on the delivery' instrument.

6. The system of claim 1, further comprising at least two screws for anchoring the plate to adjacent vertebral bodies.

7. The system of claim 6, wherein the plate comprises at least one cam rotatable to position the at least one cam over the at least two screws to limit the at least two screws from backing out.

8. The system of claim 7, wherein: the at least two screws comprises a first screw, a second screw, and a third screw; the at least one cam comprises a first cam and a second cam, the first cam rotatable to position the first cam over the first screw and the second screw, the second cam rotatable to position the second cam over the second screw and the third screw.

9. A system comprising: a delivery instrument comprising a first attachment and a second attachment; a cage implant configured to engage the first attachment to releasably secure the cage implant to the delivery instrument; and a plate configured to engage the second attachment to releasably secure the plate to the delivery instrument.

10. The system of claim 9, wherein the first attachment comprises a threaded end of the delivery instrument for threaded engagement with the cage implant.

11. The system of claim 10, further comprising knob coupled to the threaded end to control a threading of the threaded end to the cage implant for an attachment or detachment of the cage implant to the delivery’ instrument.

12. The system of claim 9, wherein the second attachment comprises a flat for mating engagement with a key of the plate.

13. The system of claim 12. further comprising a spring loaded piston biasing the key against a stop defined on the delivery instrument.

14. The system of claim 9, wherein the delivery' instrument comprises a handle and a shaft, the first attachment defined at or proximate an end of the shaft, the second attachment defined adjacent the handle.

15. The system of claim 9, wherein the cage implant is a cervical cage implant, and wherein the plate is an anterior plate for anchoring to anterior aspects of adjacent cervical vertebral bodies.

16. A system for spinal fixation, the system comprising: a cage implant for positioning within a disc space; a plate for anchoring to anterior aspects of adjacent vertebral bodies; and a delivery instrument configured to releasably engage the cage implant and the plate, the delivery instrument comprising a geometry interfacing with the plate to align the plate with the cage implant.

17. The system of claim 16, wherein the delivery instrument comprises a shaft, and wherein the geometry comprises a key way defined on the shaft to interface with a key of the plate to provide a directional positioning of the plate relative to the shaft.

18. The system of claim 17, wherein the geometry limits the plate from rotating when sliding up and down the shaft to align the plate with the cage implant.

19. The system of claim 17, wherein the shaft comprises a cam lock, the plate rotatable along the cam lock between an unlocked position on the shaft and a locked position on the shaft.

20. The system of claim 19, wherein the cam lock is a quarter turn cam lock.

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