WO2007038611A2

WO2007038611A2 - Modular intervertebral implant and instrumentation

Info

Publication number: WO2007038611A2
Application number: PCT/US2006/037695
Authority: WO
Inventors: Lytton A. Williams; Daniel F. Justin; T. Wade Fallin; Nathan Pierce; Darin R Ewer; Ray Gardocki
Original assignee: Infinity Orthopedics Company, Ltd.
Priority date: 2005-09-26
Filing date: 2006-09-26
Publication date: 2007-04-05
Also published as: US8435295B2; US20070093900A1; WO2007038611A3; JP2009509662A; US20100057205A1; AU2006294725A1; US7618459B2; US20070072475A1; US20130231748A1; EP1928364A4; US20070073311A1; EP1928364A2

Abstract

A revisable intervertebral implant may include two end plates designed to detachably receive a variety of intermediate components including articulating bearing inserts, elastic inserts, and fusion blocks. Each intermediate component may be secured to a snap insert that snaps into engagement with the corresponding end plate in response to pressure urging the intermediate component toward the end plate along a cephalad-caudal direction. The end plates may first be secured to the corresponding vertebral bodies, and then the intermediate component(s) may be snapped into locking engagement with the implanted end plates to complete in-situ assembly of the intervertebral implant. The implant may easily be revised. Alternative configurations include intermediate components that slide laterally or anteriorly into engagement with the end plates. Corresponding instrumentation facilitates preparation, adjustment, implantation, and revision of such implants.

Description

MODULAR INTERVERTEBRAL IMPLANT AND INSTRUMENTS

BACKGROUND OF THE INVENTION

1. The Field of the Invention

[0001] The present invention relates generally to spinal orthopedics, and more precisely, to intervertebral implants.

2. The Relevant Technology

[0002] Severe back pain can be caused by a number of different ailments, including spinal stenosis, degenerative disc disease, spondylolisthesis, and the like. Many such ailments can be corrected by controlling or limiting relative motion between the affected vertebrae. Accordingly, a variety of devices including artificial discs and fusion devices have been proposed.

[0003] Such devices are limited in that they typically provide only one mode of correction. Many such devices cannot be replaced or corrected. This is particularly true with intervertebral implants, in which bone-growth is often stimulated to integrate the implants with the surrounding bone tissue. Thus, if the device fails to solve the problem, there may be no other recourse for the patient.

[0004] Further, many known devices are expensive or difficult to manufacture, or are difficult to implant. Some known intervertebral devices require the adjacent vertebrae to be distracted excessively, thereby endangering the surrounding ligaments and other connective tissues. Known instrumentation for the preparation and implantation of spinal implants possesses corresponding limitations. Accordingly, there is a need in the art for implants and instrumentation that remedy these problems. Such implants and instruments would considerably enhance outcomes for patients with spinal disorders.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Various embodiments of the present invention will now be discussed with reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. [0006] Figure 1 is a perspective view of the total disc implant in a portion of the spine, according to one embodiment of the invention.

[0007] Figure 2 is a perspective view of the total disc implant shown in Figure 1 in a disassembled state. [0008] Figure 3 is a perspective view of the bone-facing side of the inferior end plate shown in Figure 2.

[0009] Figure 4 is a perspective lateral side view of the inferior end plate shown in Figure

2.

[0010] Figure 5 is a cephalad view of the bearing-facing side of the inferior end plate shown in Figure 2.

[0011] Figure 6 is a perspective view of the superior end plate shown in Figure 2.

[0012] Figure 7 is a perspective view of the caudal side of the inferior bearing shown in

Figure 2.

[0013] Figure 8 is a perspective view of the cephalad side of the inferior bearing shown in Figure 2.

[0014] Figure 9 is a perspective view of the cephalad side of the superior bearing shown in Figure 2.

[0015] Figure 10 is a perspective view of the caudal side of the superior bearing shown in

Figure 2.

[0016] Figure 11 is a perspective view of the bearing-facing side of the snap shown in

Figure 2.

[0017] Figure 12 is a perspective view of the end plate-facing side of the snap shown in

Figure 2.

[0018] Figure 13 is a lateral view of the snap shown in Figure 2.

[0019] Figure 14 is a perspective view of an alternative embodiment of a total disc implant, in a disassembled state.

[0020] Figure 15 is a perspective view of an interbody disc fusion implant, in a disassembled state.

[0021] Figure 16 is a perspective view of the fusion cage shown in Figure 15.

[0022] Figure 17 is a perspective view of another alternative embodiment of a total disc implant, in a disassembled state.

[0023] Figure 18 is a perspective view of a bone-facing side of the inferior endplate shown in Figure 17.

[0024] Figure 19 is a perspective view of a bearing-facing side of the inferior endplate shown in Figure 17.

[0025] Figure 20 is a perspective view of a caudal side of the inferior bearing shown in

Figure 17. [0026] Figure 21 is a perspective view of a cephalad side of the inferior bearing shown in

Figure 17.

[0027] Figure 22 is a perspective view of a cephalad side of the superior bearing shown in Figure 17.

[0028] Figure 23 is a perspective view of a caudal side of the superior bearing shown in

Figure 17.

[0029] Figure 24 is a perspective view of a bone-facing side of the snap fastener shown in

Figure 17.

[0030] Figure 25 is an enlarged perspective side view of the snap fastener shown in

Figure 17.

[0031] Figure 26 is a perspective view of a bearing-facing side of the snap fastener shown in Figure 17.

[0032] Figure 27 is a perspective view illustrating a portion of a spine.

[0033] Figure 28 is a perspective lateral view of one embodiment of a total disc implant implanted in the spine, comprising inferior and superior end plates, inferior and superior bearings, and a plurality of clips.

[0034] Figure 29 is a perspective anterior view of the total disc implant of Figure 28 in an disassembled state.

[0035] Figure 30 is a bottom elevation view of the clip shown in Figure 29.

[0036] Figure 3 lis a top elevation view of the clip shown in Figure 29.

[0037] Figure 32 is a perspective side view of the clip shown in Figure 29.

[0038] Figure 33 is a perspective posterior view of the bone engaging side of the inferior end plate shown in Figure 29.

[0039] Figure 34 is a lateral end view of the inferior end plate shown in Figure 29.

[0040] Figure 35 is a perspective anterior view of the bearing engaging side of the inferior end plate shown in Figure 29, and one clip.

[0041] Figure 36 is a perspective posterior view of the bearing engaging side of the superior end plate shown in Figure 29, and one clip.

[0042] Figure 37 is a perspective posterior view of the caudal side of the inferior bearing and one clip shown in Figure 29.

[0043] Figure 38 is an anterior side view of the inferior bearing shown in Figure 29.

[0044] Figure 39 is a perspective anterior view of the cephalad side of the inferior bearing shown in Figure 29. [0045] Figure 40 is a perspective anterior view of the cephalad side of the superior bearing and one clip shown in Figure 29.

[0046] Figure 41 is an anterior side view of the superior bearing shown in Figure 29.

[0047] Figure 42 is a perspective posterior view of the caudal side of the superior bearing shown in Figure 29.

[0048] Figure 43 is an anterior side view of the total disc implant of Figure 29, in a partially assembled state.

[0049] Figure 44 is a perspective lateral view of one embodiment of a fusion block implant, shown in a portion of the spine.

[0050] Figure 45 is a perspective anterior view of the cephalad side of the fusion block shown in Figure 42.

[0051] Figure 46 is an anterior side view of the fusion block shown in Figure 42.

[0052] Figure 47 is a perspective anterior-cephalad view of the fusion block shown in

Figure 42, and two clips.

[0053] Figure 48 is a perspective lateral side view of the fusion block implant of Figure

44, in a partially assembled state.

[0054] Figure 49 is a perspective view of an intervertebral disc motion preservation implant in an assembled state.

[0055] Figure 50 is a perspective view of an adjustable support assembly, a pivot assembly, and an end plate instrument assembly.

[0056] Figure 51 is a perspective view of a bearing instrument assembly and the pivot assembly shown in Figure 50, and the implant shown in Figure 49.

[0057] Figure 52 is a top elevation view of the pivot assembly shown in Figure 50.

[0058] Figure 53 is a perspective view of the end plate instrument assembly and the pivot assembly shown in Figure 50, and two end plates.

[0059] Figure 54 is a perspective view of the pivot assembly shown in Figure 50 and two end plate holders.

[0060] Figure 55 is a side elevation view of the pivot assembly and end plate holders shown in Figure 54, with hidden parts shown in phantom.

[0061] Figure 56 is a side elevation view of the distal end of an end plate holder shown in

Figure 6 and an end plate, with hidden parts shown in phantom.

[0062] Figure57 is a side elevation view of the distal end of a spike guard.

[0063] Figure 58 is a side elevation view of the distal end of the spike guard shown in

Figure 57 mounted on an end plate. [0064] Figure 59 is a perspective view of the distal end a primary spacer.

[0065] Figure 60 is a side elevation view of the end plate instrument assembly shown in

Figure 53, and two end plates.

[0066] Figure 61 is a perspective view of an intervertebral disc motion preservation implant in a disassembled state.

[0067] Figure 62 is a perspective view of the distal end of a secondary spacer.

[0068] Figure 63 is a side elevation view of the distal end of two end plate holders and end plates shown in Figure 56, and two primary spacers shown in Figure 12, and two secondary spacers shown in Figure 62.

[0069] Figure 64 is a perspective view of the distal end of an angle compressor and an end plate.

[0070] Figure 65 is a perspective view of the distal end of a bearing holder.

[0071] Figure 66 is a perspective view of the distal end of the bearing holder shown in

Figure 65, attached to the superior bearing and the inferior bearing shown in Figure 61.

[0072] Figure 67 is a perspective view of the distal end of a height compressor.

[0073] Figure 68 is a perspective view of the distal end of the bearing holder and bearings shown in Figure 66, attached to the height compressor shown in Figure 67.

[0074] Figure 69 is a side elevation view of the distal end of the bearing instrument assembly and implant shown in Figure 51.

[0075] Figure 70 is a perspective view of an alternative bearing guidance assembly, the support assembly, the pivot assembly and the end plate assembly.

[0076] Figure 71 is an enlarged exploded view an alternative disc motion preservation implant.

[0077] Figure 72 is a perspective view of a bearing holder, holding the bearing components of the implant of Figure 71.

[0078] Figure 73 is an enlarged view of an inferior side of a distal end of the bearing holder of Figure 72.

[0079] Figure 74 is an enlarged view of a superior side of the distal end of the bearing holder of Figure 72.

[0080] Figure 75 is an enlarged view of a superior and an inferior bearing mounted on the distal end of the bearing holder.

[0081] Figure 76 is an enlarged view of the bearing holder with mounted bearings inserted in the end plate assembly.

[0082] Figure 77 is a perspective view of a compressor. [0083] Figure 78 is an enlarged view of the distal end of the compressor of Figure 77.

[0084] Figure 79 is a perspective view of a superior feeler gauge.

[0085] Figure 80 is a perspective view of an inferior feeler gauge.

[0086] Figure 81 is a perspective view of a fusion block attached to the distal end of the bearing holder of Figure 72.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0087] The present invention relates to human spinal disc replacement systems. Those of skill in the art will recognize that the systems and methods described herein may be readily adapted for other modular implant systems for anatomic replication of orthopedic joints by man made implant systems.

[0088] Referring to Figure 1, a perspective view illustrates one embodiment of an implant 50, which may be referred to as a total disc implant, implanted in a portion of the spine. In this embodiment of the invention, the total disc implant includes two end plates 100, 200, two bearings 300, 400, and two snap fasteners 500 (not visible in Figure 1) which releasably hold the bearings to the end plates. The implant 50 is designed for placement between spinal vertebrae to replace degenerated intervertebral disk material. More specifically, the implant 50 of Figure 1 is designed to be inserted between the vertebral bodies 22, 42 of the first and second vertebrae 20, 40, respectively, after removal of the intervertebral disc (not shown). The vertebral bodies 22, 42 are rasped and flat surfaces on them are prepared to fit the end plates 100, 200.

[0089] The procedure to implant the total disc implant may be conducted from any of three approaches: anterior, right lateral, or left lateral. In addition, should there be any subsequent procedure for adjustment of the implant 50 or replacement of any component thereof, such procedure may be carried out from any one of the three approaches. [0090] Figure 2 illustrates the implant 50 in a disassembled state, so that all components are visible. During the implantation procedure, the end plates 100, 200 are pressed into place onto the vertebral bodies, with the inferior end plate 100 in a caudal position on vertebral body 22, and superior end plate 200 in a cephalic position on vertebral body 42. The end plates 100, 200 may be implanted in either order (inferior first or superior first). Once implanted, the two end plates 100, 200 appear as mirror images of one another with their bearing facing sides facing one another. Next, the inferior 300 and superior bearings 400 are attached to the end plates, using the snap fasteners 500 as releasable connectors. A set force delivered by the implantation instrumentation (not shown) presses each snap fastener 500 into place. The inferior bearing 300 is attached to the inferior end plate 100 with one snap fastener 500 between them, and the superior bearing 400 is attached to the superior end plate 200 with another snap fastener 500 between them. Like the end plates, the bearings 300, 400 may also be attached in either order.

[0091] Figure 3 illustrates a bone-facing side of one end plate. In the illustration, the end plate depicted is the inferior end plate 100, and so the bone-facing side 102 is in the caudal direction. In this embodiment of the invention the superior end plate 200 is identical to the inferior end plate 100 in every way except in orientation once implanted in the body. Thus, when the superior end plate 200 is implanted, its bone-facing side will be in the cephalic direction. With this exception due to orientation noted, Figures 3 and 4 and the description of the end plate below also apply to the superior end plate 200. However, it is appreciated that in alternative embodiments of the invention, the end plates may or may not be identical in size, shape, or configuration.

[0092] As viewed in Figures 3 and 4, the inferior end plate 100 is quadrilateral in form, with rounded corners, and is bilaterally symmetrical. It has a bone-facing side 102, a bearing- facing side 104, an anterior end 106, a posterior end 108, a right end 110 and a left end 112. The end plate is slightly wedge-shaped, with the height of the anterior end 106 slightly greater than the posterior end 108. This is to match the natural lordotic angle of the lumbar vertebrae as closely as possible. In alternative embodiments, it is appreciated that the end plates 100, 200 need not have a quadrilateral configuration but can be square, circular, or have any other polygonal or irregular configuration. Furthermore, it is appreciated that the end plates 100, 200 can be configured at any desired wedge angle or can have substantially parallel top and bottom surfaces.

[0093] The inferior end plate 100 has a bone engaging face 114 and a bearing engaging face 116 which are connected by a support member 118. Projecting from the bone engaging face 114 is a plurality of anchoring members in the form of bone engaging spikes 120. Each bone engaging spike 120 is columnar in form and projects perpendicularly in the caudal direction from the bone engaging face 114. The caudal end of each bone engaging spike 120 tapers and terminates in an acute angle. This angled tapering creates a point which facilitates seating the inferior end plate 100 in the adjacent vertebral body 22 during the implantation process; the point will more easily penetrate the vertebral body 22 than would a blunt end. [0094] A hollow grafting channel 122 runs through the center of each bone engaging spike 120. Each grafting channel 122 originates on the bearing engaging face 114, runs through the support member 118, and ends at the pointed termination of the bone engaging spike 120. This hollowed point configuration may be compared to the point of a hypodermic needle, and further facilitates the penetration of the vertebral body 22 by the bone engaging spikes 120. The grafting channels 122 also allow for the growth of bony columns from the vertebral body 22 through the channels, thereby fusing the inferior end plate 100 to the vertebral body 22.

[0095] Figure 5 illustrates the bearing-facing side 104 of the inferior end plate 100. Near the corner formed by the posterior end 108 and the left end 112 is a peg port 124. The peg port 124 is a circular opening originating on the bearing-engaging face 116 and recessed into the support member 118. Partway through the support member 118, the width of the peg port 124 constricts and the port continues as a grafting channel 122, exiting through a bone engaging spike 120 on the bone-facing side 102. A similar peg port 124 is located near the right posterior corner.

[0096] Centered on the anterior end 106 of the bearing-facing side 104 is a pocket 126. Similar pockets are centered on the right end 110 and the left end 112. Each pocket 126 is a rectangular segment cut from the edge of the bearing-engaging face 116 and extending caudally into the support member 118. Once the cutaway area is below the bearing-engaging face 116, the slot widens on either lateral side, and deepens perpendicularly into the support member 118, toward the center of the end plate. The pockets 126 are places where implantation instruments (not shown) may grip or otherwise connect with the end plates during the implantation procedure. The number, size, configuration and placement of pockets may vary in other embodiments of the invention.

[0097] As seen in Figures 3, 4 and 5, a snap port 130 is located on the end plate 100, laterally centered but slightly displaced toward posterior end 108. The snap port 130 is an opening from the bearing-facing side 104 to the bone-facing side 102, circumscribed by a tapered wall 132. The tapered wall 132 angles outward toward the bone-facing side 102, such that the cross-sectional area of the snap port 130 on the bearing-facing side 104 is smaller than the cross-sectional area of the same snap port 130 on the bone-facing side 102. [0098] Figure 6 is a perspective view of the superior end plate 200. Note that as discussed earlier, the superior end plate 200 is identical to the inferior end plate 100 in every way except in orientation once implanted. However, as illustrated, this does mean that the right end 210 and left end 212 of the superior end plate 200 are reversed from the right end 110 and left end 112 of the inferior end plate 100.

[0099] Once the end plates 100, 200 are implanted, the bearings 300, 400 are inserted and attached to the end plates. Figure 7 illustrates the caudal side of the inferior bearing 300. The inferior bearing 300 is of the same approximate quadrilateral shape and dimension as the inferior end plate 100. It has a caudal side 302, a cephalad side 304, an anterior end 306, a posterior end 308, a right end 310 and a left end 312. On the caudal side 302 is an end plate- engaging face 314. Centered along the anterior end 306 is an instrument port 316, which is an opening originating on the end plate engaging face 314, passing through a support member 318, and terminating on an inferior articulation surface 330. Additional instrument ports 316 are centered on the right end 310 and the left end 312. Protruding from the end plate- engaging face 314 near the posterior right and left corners are two pegs 320. The pegs 320 fit into the peg ports 124 shown in Figure 5, when the inferior bearing 300 is attached to the inferior end plate 100. The fitting of the pegs 320 into the peg ports 124 assist in reducing shear stress on the implant.

[00100] Occupying the central area of the inferior bearing 300 is a cap 322, surrounded by a trough 324. The cap is a quadrilateral protrusion from the end plate engaging face 314, and the surface of the cap 322, while parallel to the end plate engaging face 314, is slightly elevated from it. The trough 324 which surrounds the cap is recessed from the end plate engaging face 314 into the support member 318. The outer boundary of the trough is a tapered wall 326. The tapered wall 326 angles inward from the bottom of the trough 324 to the top, such that the cross sectional area of the trough 324 at its deepest point is larger than its cross sectional area where it meets the surface of the end plate engaging face 314. [00101] Figure 8 displays the cephalad side 304 of the inferior bearing 300. The cephalad side has an inferior articulation surface 330 from which arises a rounded dome 332. The dome 332 is centered laterally on the cephalad side 304 of the inferior bearing 300, but is slightly displaced toward the posterior end 308.

[00102] Figure 9 illustrates the cephalad side 402 of the superior bearing 400. It has a cephalad side 402, a caudal side 404, an anterior end 406, a posterior end 408, a right end 410 and a left end 412. On the cephalad side 404 is an end plate-engaging face 414. Centered along the anterior end 406 is an instrument port 416, which is an opening originating on the end plate engaging face 414, passing through a support member 418, and terminating on a superior articulation surface 430. Additional instrument ports 416 are centered on the right end 410 and the left end 412. Protruding from the end plate-engaging face 414 near the posterior right and left corners are two pegs 420. The pegs 420 fit into the peg ports 224 shown in Figure 6, when the inferior bearing 400 is attached to the superior end plate 200. The fitting of the pegs 420 into the peg ports 224 assist in reducing shear stress on the implant.

-Page 9- , [00103] Occupying the central area of the superior bearing 400 is a cap 422, surrounded by a trough 424. The cap 422 is a flat-topped protrusion from the end plate engaging face 414, and the surface of the cap 422, while parallel to the end plate engaging face 414, is slightly elevated from it. The trough 424 which surrounds the cap is recessed from the end plate engaging face 414 into the support member 418. The outer boundary of the trough is a tapered wall 426. The tapered wall 426 angles inward from the bottom of the trough 424 to the top, such that the cross sectional area of the trough 424 at its deepest point is larger than its cross sectional area where it meets the surface of the end plate engaging face 414. [00104] The caudal side 404 of the superior bearing 400 is illustrated in Figure 10. A rounded cup 432 is recessed into the support member 418 of the caudal side 404. The cup 432 is centered laterally on the caudal side 404, but is slightly displaced toward the posterior end 408. A ridge 434 encircles the cup 432. The ridge is raised substantially from the support member 418. A smooth superior articulation surface 430 overlays the ridge 434 and the cup 432 such that where they meet, there is no discernable transition between the two features. [00105] As seen in Figure 2, the snap 500 serves as the connector between the inferior end plate 100 and the inferior bearing 300, and between the superior end plate 200 and the superior bearing 400. Figures 11, 12 and 13 illustrate the snap 500 alone. In this embodiment of the invention, the snap 500 is quadrilateral and generally dish-like in form, with a bone- facing side 502 which is a substantially flat plane, and a bearing facing side 504 which is a flat plane circumscribed by a raised rim 506. It is appreciated that in alternative embodiments of the invention, the snap feature may be quadrilateral, circular or any other shape or configuration. The outer edge of the rim 506 is formed by a dual-tapered wall 508. As seen best in Figure 13, the dual-tapered wall 508 is equally wide at the bone-facing side 502 and at the bearing-facing side 504, but constricts at the midpoint between the two sides 502, 504. [00106] Figure 2 best illustrates how all the components of the implant 50 fit together. During or after manufacture, but before the implantation procedure, one snap 500 is fitted over the cap 322 of the inferior bearing 300, and a second snap 500 is fitted over the cap 422 of the superior bearing 400. As the rim 506 of the snap 500 is pressed into the trough 324 of the inferior bearing 300, the dual-tapered wall 508 compresses to pass into the trough 324, then expands out into place such that the dual-tapered wall 508 fits against the tapered wall 326 of the trough. Because the widest part of the dual-tapered wall 508 is wider than the opening of the trough 324, the snap 500 is locked into place, and can only be removed from the inferior bearing 300 with significant force. The second snap 500 is attached to the superior bearing 400 in the same manner. [00107] The inferior end plate 100 is implanted in the vertebral body 22, and the superior end plate 200 is implanted in the vertebral body 42. The inferior bearing 300 is pressed into place in the inferior end plate 100. The bone-facing side 502 of the snap 500, now protruding from the caudal side 302 of the inferior bearing 300, is pressed into the snap port 130 of the inferior end plate 100. As the bone-facing side 502 of the snap 500 is pressed into the snap port 130, the dual-tapered wall 526 compresses to pass into the snap port 130, then expands out into place such that the dual-tapered wall 526 fits against the tapered wall 132 of the inferior end plate 132. Because the widest part of the dual-tapered wall 526 is wider than the opening of the snap port 130, the snap 500 is locked into place, and can only be removed from the inferior end plate 100 with significant force.

[00108] The superior bearing 400 and its snap 500 are attached to the superior end plate 200, in the same manner as described above for the inferior end plate 100 and bearing 300. Then the inferior articulation surface 330 is allowed to contact the superior articulation surface 430. Although in this description, the inferior bearing and its snap were attached first, followed by the superior bearing and its snap, it is appreciated that the bearings may be attached in either order. It is also appreciated that should there be any subsequent procedure for replacement or adjustment of any of the end plates, bearings or snaps, such procedure may be carried out from any one of the three approaches; anterior, left lateral or right lateral. [00109] Other embodiments of the invention can provide the same function while employing alternate snap connections. Figure 14 depicts a disassembled total disc implant 60, which employs an alternate snap feature to lock the bearings to the end plates. In this embodiment, the inferior bearing 300 is connected to the inferior end plate 100 via a ring- shaped snap 500. Similarly, the superior bearing 400 is connected to the superior end plate 200 by the same ring-shaped snap 500. The mechanism by which the snap locks the bearings to the end plates is equivalent to the snap feature described in the first embodiment; in both embodiments the snap feature compresses to pass through a constrictive feature, and then expands out to lock the components in place.

[00110] If fusion of the vertebrae is required, an embodiment of the invention including a fusion block may be implemented. Figure 15 depicts an interbody disc fusion implant 70, in a disassembled state. In this embodiment, the implant consists of an inferior end plate 100, a superior end plate 200, two ring-shaped snaps 500 and a fusion cage 600. The interbody disc fusion implant 70 may be implanted from an anterior approach, a right lateral approach, or a left lateral approach. It may be implanted as part of the initial implantation procedure, or it may replace inferior and superior bearings, upon their removal. [ϋϋlll] Figure 16 illustrates the fusion cage 600. In this embodiment of the invention, the fusion cage 600 is quadrilateral and box-like in shape. It has a caudal side 602, a cephalad side 604, an anterior end 606, a posterior end 608, a right end 610 and a left end 612. It is symmetrical such that the right and left ends 610, 612 are mirror images of one another and the caudal and cephalad sides 602, 604 are also mirror images. A plurality of notches 630, designed for gripping by implantation instruments (not shown) are at the edges of the caudal and cephalad sides 602, 604.

[00112] A plurality of grafting holes 614 perforates each end of the fusion cage. Before, during or after positioning of the end plates between the vertebral bodies, the fusion cage 600 is at least partially packed with an osteogenic substance. In this application, "osteogenic substance" is broadly intended to include natural bone, such as autogenous bone graft or bone allograft, synthetic bone, growth factors and cytokines (including bone morphogenic proteins), and/or combinations thereof. After implantation, growth of bone material through the grafting holes will assist in the fusion of the fusion cage and end plates to the vertebrae. [00113] A larger grafting port 616 is centered on the fusion block, with its openings on the caudal and cephalad sides. Recessed into the surface of the fusion block 600 and circumscribing the grafting port 616, is a trough 618. Around each opening of the grafting port, but to the inside of the trough 618, is a raised rim 620. The raised rim 620 protrudes from surface of the fusion block 600. The inner wall 622 of the raised rim 620 is smooth and is a continuous part of the grafting port 616. The outer wall 624 of the raised rim 620 constricts between the top of the rim and where it joins the trough 618. This constriction is designed to hold the snap ring 500, seen in Figure 15.

[00114] Referring to Figure 17, an alternative embodiment of a total disk implant is shown. The implant 1050 comprises an inferior end plate 1100, a superior end plate 1200, an inferior bearing 1300, a superior bearing 1400, and two snap fasteners 1500. As with the implant 50, the implant 1050 is designed for placement between spinal vertebrae to replace degenerated intervertebral disk material. Methods for placement, assembly and implantation of the implant 1050 are the same as those described for the implant 50. [00115] Referring to Figure 18, an enlarged view of a bone-facing side of the end plate 1100 is shown. The end plates 1100, 1200 are identical to one another, differing only in their orientation as they are placed between the vertebral bodies. End plate 1100 will be described in detail, but it is appreciated that the same description applies to the end plate 1200. The end plate 1100 has a bone-facing side 1102, and a bearing-facing side 1104. An irregularly shaped snap port 1130 occupies the center of the end plate 1100, creating an opening from the bone-facing side 1102 to the bearing-facing side 1104. A plurality of bone-engaging spikes 1120 are located on the bone-facing side 1102, each adjacent to a grafting channel 1122. Each bone-engaging spike 1120 is of a crescent shape, protruding from the bone- facing side 1102 and terminating with an acute edge. Several small diameter bone-engaging spikes 1121, with small grafting channels 1123 are interspersed with the bone-engaging spikes 1120 and grafting channels 1122.

[00116] The large size of the grafting channels 1122 creates favorable conditions for bone ingrowth once the implant 1150 is in place. Also, the crescent shapes of the bone-engaging spikes 1120 allow for good engagement with the vertebral body, but without requiring an excessive amount of feree to press into place. The spikes 1122, 1121 also provide shear resistance once the end plate 1100 is implanted in the vertebral body.

[00117] The snap port 1130 occupies much of the surface area of the end plate 1100. The large opening size of the snap port 1130 maximizes space available for bone ingrowth. The irregular shape of the snap port 1130 allows more contact area for the snap connection, and offers more torsional resistance than a regularly shaped, round port. The snap port 1130 is encircled by a wall 1132. At several points on the wall 1132, a recess 1134 is indented into the wall 1134.

[00118] Referring to Figure 19, an enlarged view of the bearing-facing side 1104 of the end plate 1100 is shown. The end plate 1100 has an anterior end 1106 and a posterior end 1108. The grafting channels 1122, 1123 open out on the bearing facing side 1104, as does the snap port 1130. Three pockets 1126 are indented into sides of the end plate 1100, on the anterior end 1106 and the two lateral sides. The pockets 1126 are shaped to engage with the instruments used to insert the end plate 1100.

[00119] Referring to Figure 20, a caudal side of the inferior bearing 1300 is shown. The inferior bearing 1300 has a caudal side 1302, a cephalad side 1304, an anterior end 1306 and a posterior end 1308. Three instrument ports 1316 perforate the inferior bearing 1300, one on the anterior end 1306 and one on each lateral side. A rounded cap 1322 protrudes from the center of the caudal side 1302, and is surrounded by a trough 1324. The trough 1324 is surrounded by a wall 1326. Indented into each lateral side of the wall 1326 is a long recess 1328.

[00120] Referring to Figure 21, the cephalad side 1304 of the inferior bearing 1300 is shown. The three instrument ports 1316 open out on the cephalad side 1304. A round dome 1332 rises from the surface of the cephalad side 1304. [00121] Referring to Figure 22, a cephalad side of the superior bearing 1400 is shown. The superior bearing 1400 has a cephalad side 1402, a caudal side 1404, an anterior end 1406, and a posterior end 1408. Three instrument ports 1416 perforate the inferior bearing 1400, one on the anterior end 1406 and one on each lateral side. A rounded cap 1422 protrudes from the center of the caudal side 1402, and is surrounded by a trough 1424. The trough 1424 is surrounded by a wall 1426. Indented into each lateral side of the wall 1426 is a long recess 1428.

[00122] Referring to Figure 23, the caudal side 1404 of the superior bearing 1400 is shown. The three instrument ports 1416 open out on the caudal side 1404. A circular ridge 1434 rises from the caudal side 1404 of the superior bearing 1400. In the center of the circle formed by the ridge 1434, a cup 1432 is depressed into the superior bearing 1400. The cup 1432 on the superior bearing 1400 and the dome 1432 on the inferior bearing 1300 form the bearing surfaces when the implant 1050 is implanted.

[00123] Referring to Figure 24, a bone-facing side 1502 of one snap fastener 1500 is shown. The bone-facing side 1502 is flat and has a generally square shape, with a central body 1506 and an irregular outer edge 1508. The snap fastener has an anterior end 1510, a posterior end 1512, and two lateral sides 1514. Two connection slots 1516 perforate the snap fastener, each generally parallel to a lateral side 1512 of the body 1506. Four connection ports 1518 are located just inside the outer edge 1508, one each on the anterior and posterior ends 1510, 1512, and one on each lateral side 1514. There is a gap 1520 in the outer edge 1508 adjacent to each connection port 1518, such that the outer edge 1508 is not continuous but each connection port 1518 has an opening to the outside of the fastener 1500. Formed onto the outer edge 1508 immediately adjacent to each gap 1520 is a tab 1522, each tab 1522 being a protrusion from the outer edge 1508, extending in the same plane as the body 1506. [00124] Referring to Figure 25, an enlarged side view of a snap fastener 1500 is shown, in order to depict the tabs 1522 in greater detail. Each tab 1522 has a sloped bone-facing side 1532 and a sloped bearing-facing side 1534. The slope of the bearing-facing side 1534 is steeper than the slope of the bone-facing side 1532. This is so that when the tabs 1522 are snapped into the recesses 1134 in the walls 1132 of the end plate 1100, more force is required to remove the snap fastener 1500 from the end plate 1100 than it takes to snap the snap fastener 1500 to the end plate 1100 or 1200.

[00125] Referring to Figure 26, a bearing-facing side 1504 of the snap fastener 1500 is shown. In the center of the body 1506, a raised rim 1536 surrounds a rectangular dish 1538. Protruding on each lateral side of the rim 1536 is a long tab 1540. The long tabs 1540 are configured to fit into the long recesses 1328, 1428 on the bearings 1300, 1400 when the snap fastener 1500 is snapped to the bearing. Returning to Figure 25, each long tab 1540 has a bone-facing side 1542 and a bearing-facing side 1544. The slope of the bone-facing side 1542 is 90 degrees, and the slope of the bearing-facing side 1544 is less steep, approximating 45 degrees. This is so that when the snap fastener 1500 is snapped on to the inferior or superior bearing 1300, 1400, it will require considerably less force to snap the fastener 1500 on the bearing than to remove it.

[00126] When the snap fastener 1500 is snapped on to the end plate 1100, the bone-facing side 1532 of the tab 1522 pushes against the bearing-facing side 1104 of the end plate 1100, and the outer edge 1508 flexes slightly until the tab 1522 is forced into the recess 1134. Since the slope on the bearing-facing side 1534 of the tab 1522 is steeper, it would take much more force to remove the tab 1522 from the recess 1 134.

[00127] The cephalad-caudal engagement of the preceding drawings is only one of many embodiments of the invention. In some alternative embodiments, inteπnediate components can slide into engagement with end plates from along lateral, anterior, or posterior approaches, or any combination thereof. Examples of such embodiments will be presented in connection with Figures 27 through 48, as follows.

[00128] Referring to Figure 27, a perspective view illustrates a portion of a spine 2010. Figure 27 illustrates only the bony structures; accordingly, ligaments, cartilage, and other soft tissues are omitted for clarity. The spine 2010 has a cephalad direction 12, a caudal direction 14, ah anterior direction 16, a posterior direction 18, and a medial/lateral axis 20, all of which are oriented as shown by the arrows bearing the same reference numerals. In this application, "left" and "right" are used with reference to a posterior view, i.e., a view from behind the spine 2010. "Medial" refers to a position or orientation toward a sagittal plane (i.e., plane of symmetry that separates left and right sides from each other) of the spine 2010, and "lateral" refers to a position or orientation relatively further from the sagittal plane. [00129] As shown, the portion of the spine 2010 illustrated in Figure 27 includes a first vertebra 2024, which may be the L5 (Fifth Lumbar) vertebra of a patient, and a second vertebra 2026, which may be the L4 (Fourth Lumbar) vertebra of the patient. The systems and methods may be applicable to any vertebra or vertebrae of the spine 2010 and/or the sacrum (not shown). In this application, the term "vertebra" may be broadly interpreted to include the sacrum.

[00130] As shown, the first vertebra 2024 has a body 2028 with a generally disc-like shape and two pedicles 2030 that extend posteriorly from the body 2028. A posterior arch, or lamina 2032, extends between the posterior ends of the pedicles 2030 to couple the pedicles 2030 together. The first vertebra 2024 also has a pair of transverse processes 2034 that extend laterally from the pedicles 2030 generally along the medial/lateral axis 2020, and a spinous process 2036 that extends from the lamina 2032 along the posterior direction 18. [00131] Similarly, the second vertebra 2026 has a body 2048 from which two pedicles 2050 extend posteriorly. A posterior arch, or lamina 2052, extends between the posterior ends of the pedicles 2050 to couple the pedicles 2050 together. The second vertebra 2026 also has a pair of transverse processes 2054, each of which extends from the corresponding pedicle 2050 generally along the medial/lateral axis 20, and a spinous process 2056 that extends from the lamina 2052 along the posterior direction 18. The vertebrae 2024, 2026 are separated from each other by an intervertebral disc 2066.

[00132] Referring to Figure 28, a perspective view illustrates one embodiment of an implant 2070, which may be referred to as a total disk implant. The implant 2070 is designed for placement between spinal vertebrae to replace degenerated intervertebral disc material. More specifically, the implant 2070 is designed to be inserted between the vertebral bodies 2028, 2048 of the first and second vertebrae 2024, 2026, respectively, after removal of the intervertebral disc 2066. The implant 2070 has end plates which secure the implant to the vertebral bodies, and an intermediate component which engages with the end plates, to control or prevent relative motion between the vertebral bodies. The intermediate component may be a first bearing surface configured to articulate with a second bearing surface, to provide relative motion between the vertebral bodies. The intermediate component may also be a deformable elastic insert which provides motion between the vertebral bodies, or a rigid insert to promote fusion, thus preventing relative motion between the vertebral bodies. Retention members, which in this embodiment of the invention take the form of clips, secure the intermediate component to the end plates.

[00133] In the embodiment depicted in Figure 28, the assembled implant 2070 is of a generally rectangular box-like shape with rounded edges, with top and bottom surfaces which form a slight wedge. In alternative embodiments, it is appreciated that implant 2070 need not have a rectangular box shaped configuration but can be square, circular, or have any other polygonal or irregular configuration. Furthermore, it is appreciated that the implant 2070 can be configured at any desired wedge angle or can have substantially parallel top and bottom surfaces. The implant 2070 comprises an inferior end plate 2100, an inferior bearing 2300, a superior bearing 2400, and a superior end plate 2200. When fully assembled, the inferior bearing 2300 is releasably attached to the inferior end plate 2100 by a plurality of clips 2500. The superior bearing 2400 is releasably attached to the superior end plate 2200 by a plurality of clips 2500.

[00134] Figure 29 depicts the implant 2070 in a disassembled state, to illustrate the individual components of the implant. The inferior bearing 2300 has a rounded dome, surrounded by a trough, which fits into a cup, surrounded by a ridge, on the superior bearing 2400. The inclusion of the ridge and trough in the bearing design allows the patient less impeded flexion/extension and lateral bending.

[00135] During the implantation procedure, initially the inferior 2100 and superior 2200 end plates are placed in the intervertebral space, adjacent to the vertebral bodies 2028, 2048. In the embodiment depicted the end plates 2100, 2200 are identical, but are inserted in an opposite orientation from one another. Thus, as depicted in Figures 28 and 29, the inferior end plate 2100 is inserted adjacent to vertebral body 2028 with a bone engaging side 2102 in a caudal direction 14 and a bearing engaging side 2104 in a cephalad direction 12. Conversely, the superior end plate 2200 is inserted adjacent to vertebral body 2048 with a bone engaging side 2202 in a cephalad direction 12 and a bearing engaging side 2204 in a caudal direction 14. Because the features of the end plates 2100, 2200 in this embodiment are identical except in orientation, only the inferior end plate 2100 will be described in detail below. All description of the structure of the inferior end plate 2100 also applies to the superior end plate 2200. However, it is appreciated that in alternative embodiments of the invention, end plates of varying configurations may be used in combination. [00136] Figure 30 depicts a bottom side view of the clip 2500. In this embodiment of the invention the clip 2500 is roughly quadrilateral in shape, with substantially parallel top and bottom sides, and is bilaterally symmetrical. However, it is appreciated that in alternative embodiments, the clip 2500 may vary in configuration and/or use. It has a top side 2510, a bottom side 2512, an interior edge 2514 and an exterior edge 2516. The interior edge 2514 is chamfered on the bottom side 2512. The exterior edge 2516 has a tab 2502 which extends perpendicularly from the edge. The tab 2502 is configured to fit a gap in each end plate 2100 or 2200, and moving the tab into the gap snaps the clip 2500 to the end plate 2100 or 2200. A body 2506 extends from the tab 2502 and the exterior edge 2516 toward the interior edge 2514. One arm 2504 extends perpendicularly from each lateral side of the body 2506, on either side of the tab 2502. A T-shape is formed by the arms 2504 and the body 2506. At the interior end of the body 5206, two prongs 2508 extend initially perpendicularly from the body 2506, then, turning right angles, extend back toward the arms 2504. [00137] Referring to Figure 31, a top side view of the clip 2500 is shown. The outside edges of the prongs 2508 are chamfered on the top side 2510, forming chamfered edges 2518. The chamfered edges 2518 of the prongs 2508 are slightly angled in their lengthwise orientation; that is, the width of the clip 2500 at the interior edge 2514 is slightly narrower than its width at the arms 2508 and exterior edge 2516. A protrusion 2520 projects from the body 2506 on the top side 2510. The protrusion 2520 appears as a square projecting upward from the top side 2510, and is centered between the arms 2508. The protrusion 2520 is wedge-shaped in profile, the higher end adjacent to the tab 2502, and the opposite end slanting down until it is flush with the body 2506 at the midpoint of the body 2506. [00138] Figure 32 depicts a side profile view of the clip 2500. The clip 2500 has a spring bias 2522, such that when the clip 2500 is not secured to another component, the body 2506, the arms 2504 and the tab 2502 are held at a slight downward angle relative to the prongs 2508; that is, the body 2506, the arms 2504 and the tab 2502 angle in the direction of the bottom side 2512.

[00139] Referring to Figure 33, a bone-engaging side view of the inferior end plate 2100 is shown. In this embodiment the inferior end plate 2100 is of a quadrilateral shape with rounded corners, and is bilaterally symmetrical. It has an anterior end 2120, a posterior end 2122, a right end 2124 and a left end 2126. The inferior end plate 2100 has a bone engaging face 2106 and a bearing engaging face 2108 which are connected by a support member 2110. Projecting from the bone engaging face 2106 is a plurality of bone engaging spikes 2112. Each bone engaging spike 2112 is columnar in form and projects perpendicularly in the caudal direction 14 from the bone engaging face 2106. The protruding end of each bone engaging spike 2112 tapers and terminates in an acute angle. This angled tapering creates a point which facilitates seating the inferior end plate 2100 in the adjacent vertebral body 2028 during the implantation process; the point will more easily penetrate the vertebral body 2028 than would a blunt end.

[00140] A hollow grafting channel 2114 runs through the center of each bone engaging spike 2112. Each grafting channel 2114 originates on the bearing engaging face 2108, runs through the support member 2110, and ends at the pointed termination of the bone engaging spike 2112. This hollowed point configuration may be compared to the hollow point of a hypodermic needle, and further facilitates the penetration of the vertebral body 2028 by the bone engaging spikes 2112. The grafting channels 2114 also allow for the growth of bony columns from the vertebral body 2028 through the channels, thereby fusing the inferior end plate 2100 to the vertebral body 2028. [00141] A plurality of grafting ports 2116 is present in the inferior end plate 2100. Each grafting port is an opening from the bearing engaging face 2108 through the support member 2110 to the bone engaging face 2106. The grafting ports 2116 allow for the growth of bony material from the vertebral body 2028 through the ports, thereby fusing the inferior end plate 2100 to the vertebral body 2028.

[00142] A groove 2118 is present on each outer corner of the inferior end plate 2100. Each groove 2118 is an indentation into the support member 2110. Each groove 2118 is designed to fit closely around the end of an insertion tool such that the insertion tool (not shown) may securely grip the inferior end plate 2100 during insertion or removal of the end plate. [00143] Referring to Figure 34, a lateral end view of the inferior end plate 2100 is shown. It is slightly wedge shaped when viewed from either lateral end. That is, the height of the inferior end plate 2100 at the posterior end 2122 is shorter than its height at the anterior end 2120. This is because this embodiment of the invention is designed for the lumbar portion of the spine, which is curved such that the intervertebral space is wider at the anterior end than at the posterior end. However, it is appreciated that the inferior end plate 2100 can be configured at any desired wedge angle or can have substantially parallel top and bottom surfaces.

[00144] Figure 35 illustrates the bearing engaging side 2104 of the inferior end plate 2100, with one clip 2500 snapped on the left side. The end plate 2100 has symmetrically placed lateral gaps 2128 in the right end 2124 and the left end 2126. The anterior end 2120 has an anterior gap 2130 which is identically shaped as the lateral gaps 2128 but is located perpendicular to them. The lateral 2128 and anterior 2130 gaps are shaped to accommodate the insertion of clips 2500, which releasably hold the inferior bearing 2300 to the inferior end plate 2100. The caudal or lower portions of the gaps 2128, 2130, which are cut out of the bone engaging side 2102 of the inferior end plate 2100, are shaped to fit the tab 2502 of the clip 2500. The cephalad or upper portions of the gaps 2128, 2130 are wider to accommodate passage of arms 2504 of the clip 2500. The walls 2132 of the gaps 2128, 2130 are formed from the support member 2110, and are perpendicular to the bearing engaging side 2104 of the inferior end plate 2100.

[00145] Moving toward the center of the inferior end plate 2100, each lateral 2128 and anterior 2130 gap is adjacent to a pocket 2134, which is recessed into the bearing engaging face 2108. The sides of the pocket 2134 are part of the support member 2110. The pocket 2134 is T-shaped to fit the arms 2504 and the body 2506 of the clip 2500 when it is snapped to the inferior end plate 2100. The floor of the pocket 2134 is sloped such that the pocket arms 2136 are deeper than the pocket body 2138. The floor of the pocket body 2138 slopes upward until it is flush with a slot 2140.

[00146] Continuing toward the center of the inferior end plate 2100, the slot 2140 extends from the pocket 2134 to the central grafting port 2116. The slot 2140 is also recessed into the bearing engaging face 2108 but to a lesser extent than the pocket 2134. Each slot 2140 has two side walls which are chamfered, forming two opposing chamfered edges 2142 into which prongs 2508 of the clip 2500 fit closely. The opposing chamfered edges 2142 of each slot 2140 are slightly angled toward one another as the edges approach the center of the inferior end plate 2100. A chamfered wall 2144 is formed by the continuation of the posterior chamfered edges 2142 of the two lateral slots 2140; the two posterior chamfered edges 2142 continue past their respective slots 2140 and meet, forming the chamfered wall 2144. The gaps 2128, 2130, the pocket 2134 and the slot 2140 are shaped to hold the clip 2500 in place once it has been inserted. Once the clip 2500 has been inserted, the chamfered edges 2142 retain the prongs 2508 of the clip 2500, while the tab 2502 of the clip fits into the lateral 2128 or anterior 2130 gap. The spring bias 2522 of the clip 2500 causes the body 2506, arms2504 and tab 2502 to be held in the pocket 2134 against the bearing engaging side 2104 of the inferior end plate 2100 once the clip 2500 has been inserted and the tab 2502 snapped into the gap 2128 or 2130.

[00147] In the embodiment depicted, the inferior end plate 2100 is intended to be implanted using one of three approaches into the intervertebral area with two clips 2500 snapped to it. Implantation may be from an anterior approach, a right lateral approach, or a left lateral approach. If implantation is from the anterior approach, the anterior gap 2130 is left empty with no clip secured, and with clips 2500 snapped in the right and left lateral gaps 2128. When the inferior bearing 2300 is later inserted, an anterior clip 2500 will inserted with it, and once inserted, the anterior clip 2500 is snapped to the inferior end plate 2100, into the empty anterior gap 2130.

[00148] If implantation is from the right lateral approach, the right lateral gap 2128 is left empty with no clip secured, and clips 2500 are snapped in the anterior gap 2130 and left gap 2128 prior to implantation. When the inferior bearing 2300 is later inserted, a right lateral clip 2500 will be inserted with it, and once inserted, the right lateral clip 2500 is snapped to the inferior end plate 2100, into the empty right lateral gap 2128.

[00149] If implantation is from the left lateral approach, the left lateral gap 2128 is left empty with no clip secured and clips 2500 are snapped in the anterior gap 2130 and right gap 2128 prior to insertion. When the inferior bearing 2300 is later inserted, a left lateral clip 2500 will be inserted with it, and once inserted, the left lateral clip 2500 is snapped to the inferior end plate 2100, into the empty left lateral gap 2128. It is appreciated that in alternative embodiments of the invention, the number and location of gaps and associated clips may vary.

[00150] Referring to Figure 36, a bearing facing side of the superior end plate 2200 is shown, with one clip 2500 snapped on the right side. The superior end plate 2200 has a bone facing side 2206 and a bearing facing side 2208. It has a plurality of grafting channels 2214 and grafting ports 2216. An anterior end 2220 has an anterior gap 2230, shaped to receive a clip 2500. The end plate 2200 has a right lateral end 2224 with a gap 2228, and a left lateral end with a gap2228. Each gap 2228, 2230 leads into a pocket 2234. Each pocket 2234 extends into a slot 2240, with chamfered edges 2242. The posterior chamfered edges 2242 of the two lateral slots 2240 meet, forming a chamfered wall 2244.

[00151] Returning to Figures 28 and 29, following the surgical placement of the inferior end plate 2100 with two clips 2500 snapped to it, the superior end plate 2200 is similarly placed, but in a superior orientation on the superior vertebral body 2048. The superior end plate 2200 will also have two clips 2500 snapped to it, in the same positions of the clips 2500 snapped to the inferior end plate 2100.

[00152] Referring to Figure 37, a caudal side of the inferior bearing 2300 is shown, with one clip 2500. The bearing 2300 is quadrilateral in form with rounded edges, and is bilaterally symmetrical. It has a caudal side 2302, a cephalad side 2304, a posterior end 2306, an anterior end 2308, a right end 2310 and a left end 2312. The caudal side 2302 has an end plate engaging surface 2314. Adjacent to the anterior end 2308 is an anterior pocket 2316, which is recessed into the end plate engaging surface 2314. Similarly, adjacent to the right end 2310 is a right pocket 2318 and adjacent to the left end 2312 is a left pocket 2320. Each pocket 2316, 2318, 2320 is recessed into the end plate engaging surface 2314, and is shaped to fit around the protrusion 2520 of the clip 2500.

[00153] Referring to Figure 38, a side profile view of the inferior bearing 2300 is shown. A square detent 2322 is located on the end plate engaging surface 2314, laterally centered but slightly displaced toward posterior end 206. The detent 2322 is elevated from the end plate engaging surface 2314 and has chamfered edges 2324. The cephalad side 2304 has an inferior articulation surface 2330 from which arises a round dome 2332. [00154] Figure 39 illustrates the cephalad side 2304 of the inferior bearing 2300. The dome 2332 is encircled by a trough 2334, which is a recessed ring surrounding the dome 2332. The dome 2332 and its encircling trough 2334 are centered laterally on the cephalad side 2304 of the inferior bearing 2300, but are slightly displaced toward the posterior end 2306. Recessed into the interior articulation surface 2330 on the anterior end 2308 is a notch 2336. The notch is recessed partway into the interior articulation surface 2330 and extends perpendicularly from the edge of the anterior end 2308 to the trough 2334. Similar notches 2336 are present on the right 2310 and left 2312 ends of the inferior bearing 2300. The notches 2336 are designed to fit closely around the end of an insertion tool such that the insertion tool may securely grip the inferior bearing 2300 during insertion or removal of the bearing. It is appreciated that the design and placement of notches may vary in other embodiments of the invention.

[00155] Referring to Figure 40, the superior bearing 2400 with one clip 2500 in the right lateral position is shown. The superior bearing 2400 is quadrilateral in form with rounded edges. It has a cephalad side 2402, a caudal side 2404, a posterior end 2406, an anterior end 2408, a right end 2410 and a left end 2412. The cephalad side 2402 has an end plate engaging surface 2414. Adjacent to the anterior end is an anterior pocket 2416, which is recessed into the end plate engaging surface 2414. Similarly, adjacent to the right end 2410 is a right pocket 2418 and adjacent to the left end 2412 is a left pocket 2420. Each pocket 2416, 2418, 2420 recessed into the end plate engaging surface 2414, and is configured to fit around the protrusion 2520 on the clip 2500.

[00156] Referring to Figure 41 a side profile view of the superior bearing 2400 is shown. A square detent 2422 is located on the end plate engaging surface 2414, laterally centered but slightly displaced toward posterior end 2406. The detent 2422 is elevated from the end plate engaging surface 2414 and has chamfered edges 2424. The caudal side 2404 has a superior articulation surface 2430 into which is depressed a circular cup 2432. The cup 2432 is encircled by a ridge 2434, which appears as a raised ring or donut surrounding the cup 2432. [00157] Referring to Figure 42, a caudal side view of the superior bearing 2400 is shown. The cup 2432 and its encircling ridge 2434 are centered laterally on the caudal side 2404 of the superior bearing 2400, but are slightly displaced toward the posterior end 2406. Recessed into the superior articulation surface 2430 on the anterior end 2408 is a notch 2436. The notch is recessed partway into the superior articulation surface 2430 and extends perpendicularly from the edge of the anterior end 2408 to the ridge 2434. Similar notches2 436 are present on the right 2410 and left 2412 ends of the superior bearing 2400. The notches 2436 are designed to fit closely around the end of an insertion tool such that the insertion tool may securely grip the superior bearing 2400 during insertion or removal of the bearing. It is appreciated that the design and placement of notches may vary in other embodiments of the invention.

[00158] The inferior bearing 2300 and the superior bearing 2400 are inserted together into the space between the end plates 2100, 2200. Inserting the bearings 2300, 2400 together requires less distraction of the vertebral bodies 2028, 2048 than if they were inserted separately. If inserted separately, additional distraction would be required to allow the dome 2332 on the inferior bearing 2300 to pass by the ridge 2434 on the superior bearing 2400. When inserted together, the dome 2332 is fit into the cup 2432, allowing the two bearings 2300, 2400 to fit into the smallest space possible. The bearings 2300, 2400 can be inserted from an anterior approach, a right lateral approach, or a left lateral approach; they will be inserted using whichever approach was chosen for the placement of the end plates 2100, 2200 during the same surgical procedure. However, it is appreciated that should there be any subsequent procedure for replacement or adjustment of the bearings 2300, 2400 such procedure may be carried out from any one of the three approaches.

[00159] Returning to Figure 37, one clip 2500 is held in place next to the inferior bearing 2300 as it is being inserted. The clip may be placed in an anterior position, a right lateral position, or a left lateral position, depending upon which surgical approach is implemented. If an anterior approach is implemented, the chamfered interior edge 2514 of the clip is placed under the anterior chamfered edge 2324 of the detent 2322 of the inferior bearing 2300. Thus, the top side 2510 of the clip 2500 is held against the caudal side 2302 of the inferior bearing 2300. The protrusion 2520 of the clip 2500 fits into the anterior pocket 2316 of the inferior bearing 2300, when the inferior bearing 2300 and the clip 2500 are held together. [00160] If a right lateral approach is implemented, the chamfered interior edge 2514 of the clip is placed under the right chamfered edge 2324 of the detent 2322 of the inferior bearing 2300. The protrusion 2520 of the clip 2500 fits into right pocket 2318 of the inferior bearing 2300, when the inferior bearing 2300 and the clip 2500 are held together. If a left lateral approach is implemented, the chamfered interior edge 2514 of the clip is placed under the left chamfered edge 2324 of the detent 2322 of the inferior bearing 2300. The protrusion 2520 of the clip 2500 fits into left pocket 2320 of the inferior bearing 2300, when the inferior bearing 2300 and the clip 2500 are held together.

[00161] Returning to Figure 40, one clip 2500 is held in place next to the superior bearing 2400 as it is being inserted. The clip may be placed in an anterior position, a right lateral position, or a left lateral position, depending upon which surgical approach is implemented. If an anterior approach is implemented, the chamfered interior edge 2514 of the clip is placed under the anterior chamfered edge 2424 of the detent 2422 of the superior bearing 2400. Thus, the top side 2510 of the clip 2500 is held against the cephalad side 2402 of the superior bearing 2400. The protrusion 520 of the clip 2500 fits into the anterior pocket 2416 of the superior bearing 2400, when the superior bearing 2400 and the clip 2500 are held together. [00162] If a right lateral approach is implemented, the chamfered interior edge 2514 of the clip is placed under the right chamfered edge 2424 of the detent 2422 of the superior bearing 2400. The protrusion 2520 of the clip 2500 fits into right pocket 2418 of the superior bearing 2400, when the superior bearing 2400 and the clip 2500 are held together. If a left lateral approach is implemented, the chamfered interior edge 2514 of the clip is placed under the left chamfered edge 2424 of the detent 2422 of the superior bearing 2400. The protrusion 2520 of the clip 200 fits into left pocket 2420 of the superior bearing 2400, when the superior bearing 2400 and the clip 2500 are held together.

[00163] Referring to Figure 43, the bearings 2300, 2400 are shown immediately prior to being inserted in between the end plates 2100, 2200 from a left lateral direction. As the inferior bearing 2300 and the superior bearing 2400 and their associated clips 2500 are inserted, they are held together and slid along the medial-lateral axis 20 into the space between the end plates 2100, 2200. The bearings 2300, 2400 and clips 2500 are slid between the end plates 2100, 2200 and into the open left lateral gaps 2128, 2228 until the leading chamfered edge 2324 of the detent 2322 engages under the interior edge 2514 of the opposite lateral clip 2500 already in place. Simultaneously, on the superior bearing 2400, the leading chamfered edge 2424 of the detent 2422 engages under the interior edge 2514 of the opposite lateral clip 2500 already in place. Thus engaged, the bearings cannot slide in any further. As the clips 2500 are slid in with the bearings 2300, 2400 the chamfered edges 2518 on the prongs 2508 also slide under the chamfered edges 2142, 2242 of the pockets. [00164] If an anterior approach is used, the bearings 2300, 2400 and clips 2500 are slid in a posterior direction parallel to the end plates 2100, 2200 so that the detents 2322, 2422 slide into the empty anterior gaps 2130, 2230. They are slid until the leading chamfered edge 2324 of the detent 2322 engages under the chamfered wall 2144 at the end of the slot 2140. Simultaneously, on the superior bearing 2400, the leading chamfered edge 2424 of the detent 222 engages under the chamfered wall 2244 at the end of the slot 2240. [00165] After the bearings 2300, 2400 and clips 2500 are fully slid in with all chamfered edges engaged, the tabs 2502 are pinched downward or caudally following the spring bias 2522 so that the tabs 2502 snap into the anterior gaps 2130 or lateral gap 2128 of the inferior end plate 2100, and the arms 2504 are seated in the pockets 2134. Similarly, the tabs 2502 on the clips 2500 adjacent to the superior end plate 2200 are pinched upward in the cephalic direction, so that the tabs 2502 snap into the anterior gaps 2230 or lateral gaps 2228 of the superior end plate 2200, and the arms 2504 are seated in the pockets 2234. Once the tabs 2502 are thus pinched, the spring bias 2522 holds the clips 2500 against end plates 2100, 2200, and bearings 2300, 2400 are prevented from slipping in a lateral, anterior, posterior, caudal or cephalad direction.

[00166] Should revision of the initial implantation be necessary, it can be accomplished by any of the three approaches: anterior, right lateral, or left lateral. For example, if the bearings 2300, 2400 need to be replaced by those of a different size or configuration (or by an elastic insert or the fusion block that will be described below), the surgery may be approached from a different direction than the initial implantation, thus avoiding disturbance of scar tissue. To remove the bearings 2300, 2400, the tabs 2502 of the two clips 2500 on one approach (anterior, right or left) are pinched together. For example, if the anterior approach is used, the tab 2502 of the anterior clip 2500 on the inferior end plate 2100 is pinched toward the tab 2502 of the anterior clip 2500 on the superior end plate 2200. The pinching action will free the tab arms 2504 from the pockets 2134, 2234 of the inferior 2100 and superior 2200 end plates. Simultaneously, the protrusions 2520 on the clips 2500 will fit into the pockets 2316, 2416 in the inferior 2300 and superior 2400 bearings. The clips are then pulled perpendicularly away from the end plates 2100, 2200, with the bearings 2300, 2400 held between them. The replacement bearings 2300, 2400 can then be inserted with clips 2500 in place, as described in the original insertion procedure.

[00167] Figure 44 illustrates a fusion block 2600, shown assembled with the inferior end plate 2100 and the superior end plate 2200, within a portion of the spine. A plurality of clips 2500 are used to position the fusion block 2600 and attach it to the end plates 2100, 2200. The fusion block 2600 may be inserted in place of the inferior bearing 2300 and the superior bearing 2400, if fusion of the involved vertebrae is desired. Insertion of the fusion block 2600 may occur during the initial procedure, following the placement of the inferior and superior end plates 2100, 2200. Alternatively, it can be used to replace the inferior and superior bearings 2300, 2400 after they have been implanted in the patient for some period of time. As with the end plates 2100, 2200 and the bearings 2300, 2400, the fusion block 2600 may be inserted from the anterior, right lateral, or left lateral approach.

[00168] As viewed in Figure 45, fusion block 2600 is of a quadrilateral shape with rounded corners. It has a cephalad side 2602 and a caudal side 2604, which are substantially parallel. It has an anterior end 2606, a posterior end 2608, a right end 2610 and a left end 2612. The cephalad side has a first end plate engaging surface 2640, and the caudal side has a second end plate engaging surface 2642. In this embodiment of the invention the cephalad and caudal sides 2602, 2604 are identical, and the fusion block 2600 is bilaterally symmetrical, with identical right and left ends 2610, 2612. However, it is appreciated that in alternative embodiments, sides and ends may vary from one another and symmetry may or may not occur.

[00169] A plurality of grafting ports 2614, passing through a support member 2620, is present on the fusion block 2600. In this embodiment of the invention, these grafting ports 2614 are configured to line up with the grafting ports 2116, 2216 on the inferior and superior end plates 2100, 2200. These adjacent openings extend through the entire implant to allow growth of bone material through the fusion block 200 and the end plates 2100, 2200, thus fusing the fusion block 2600, end plates 2100, 2200, and vertebral bodies 2028, 2048 together. Before, during or after positioning of the end plates 2100, 2200 between the vertebral bodies, the fusion block 2600 is at least partially packed with an osteogenic substance. In this application, "osteogenic substance" is broadly intended to include natural bone, such as autogenous bone graft or bone allograft, synthetic bone, growth factors and cytokines (including bone morphogenic proteins), and/or combinations thereof. [00170] Referring to Figure 46, an anterior side view of the fusion block 2600 is shown. A plurality of grafting holes 2616 is present on each side of the block, passing through the support member 2620. As with the grafting ports 614 previously described, the grafting holes 2616 allow growth of bone material throughout the fusion block 2600. Grooves 2618 are recessed into the support member2 620 on each outer corner of the block. Each groove 2618 is designed to fit closely around the end of an insertion tool such that the insertion tool (not shown) may securely grip the fusion block 2600 during insertion of the block. [00171] A square first detent 2622 is located on the cephalad side2 602 while a similar, square second detent 2624 is on the caudal side 2604. The detents 2622, 2624 are laterally centered but slightly displaced toward the posterior end 2608. The detents 2622, 2624 project outward from the end plate engaging surfaces 2640,2 642 of each side 2602, 2604. The first detent 2622 has chamfered edges 2626, and the second detent 624 has chamfered edges 2628. [00172] As depicted in Figure 47, adjacent to the anterior end 2608 is a pocket 2630, which is recessed into the first end plate engaging surface 2640. Similar pockets 2630 are adjacent to the right end 2610 and the left end 2612. Each pocket 2630 is recessed into the first end plate engaging surface 2640, and is configured to fit around the protrusion 2520 on the clip 2500. Three pockets 2630 are similarly located on the second end plate engaging surface 2642.

[00173] Returning to Figure 44, before insertion of the fusion block 2600, the end plates 2100, 2200 are placed against the vertebral bodies 2028, 2048 as previously described, each with two clips 2500 snapped in place. The clips 2500 are used to position the fusion block 2600 during the insertion process, and then hold the fusion block in place once inserted. Prior to insertion of the block, the interior edge 2514 of a clip 2500 is slid under a chamfered edge 2626 of the first detent 2622 on the cephalad side 2602. Once the clip is in place, its protrusion 2520 fits into the facing pocket 2630 on the first end plate engaging surface 2640. Similarly, the interior edge 2514 of a clip 2500 is slid under the matching chamfered edge 2628 of the second detent 2624 on the caudal side 2604, with that clip's protrusion 2520 in the facing pocket 2630 of the second end plate engaging surface 2642. As a result, the fusion block 2600 is sandwiched between two clips 2500, the clips being in matching anterior, right lateral or left lateral positions.

[00174] Referring to Figure 48, the fusion block 2600 is shown as is it being inserted from the anterior approach into the gap between the end plates 2100, 2200. The fusion block 2600 and its associated clips 2500 are held together and slid into the empty anterior gaps 2130, 2230 on the end plates 2100, 2200. The fusion block 2600 and clips 2500 are held parallel to the end plates and slid posteriorly into place such that the lateral chamfered edges 2626 of the first detent 2622 engage under the chamfered edges 2242 of the open pocket 2234 on the superior end plate 2200. Simultaneously, the lateral chamfered edges 1628 of the second detent 2624 engage under the chamfered edges 2142 of the open pocket 2134 on the inferior end plate 2100.

[00175] If an anterior approach is used, the fusion block 2600 and clips 2500 are slid until the leading chamfered edges 2626, 2628 of the detents 2622, 2624 engage under the chamfered walls 2244, 2144 at the end of the slots 2240, 2140. If a lateral approach is used, the fusion block 2600 and clips 2500 are slid until the leading chamfered edges 2626, 2628 of the detents 2622, 2624 engage under the interior edges 2514 of the opposite lateral clips 2500 already in place. Thus engaged, the fusion block cannot slide in any further. As the clips 2500 are slid in with the fusion block 2600, the chamfered edges 2518 on the prongs 2508 also slide under the chamfered edges 2142, 2242 of the pockets 2134, 2234. [00176] After the fusion block 2600 and clips 2500 are fully slid in with all chamfered edges engaged, the tabs 2502 are pinched individually toward the end plates following the spring bias 2522 so that the tabs 2502 snap into the anterior gaps 2130, 2230 or lateral gaps 2128, 2228 of the end plates 2100, 2200 and the arms 2504 are seated in the pockets 2134, 2234. Once the tabs 2502 are thus snapped into place, the spring bias 2522 holds the clips 2500 against the end plates 2100, 2200 and the fusion block 2600 is prevented from slipping in a lateral, anterior, posterior, caudal or cephalad direction.

[00177] As with the bearings, if revision of the initial implantation of the fusion block is necessary, it can be accomplished by any of the three approaches: anterior, right lateral, or left lateral. For example, if the fusion block 2600 needs to be replaced by one of a different size or configuration, the surgery may be approached from a different direction than the initial implantation, thus avoiding disturbance of scar tissue. To remove the fusion block 2600, the tabs 2502 of the two clips 2500 on one approach (anterior, right or left) are pinched together. For example, if the anterior approach is used, the tab 2502 of the anterior clip 2500 on the cephalad side 2602 is pinched toward the tab 2502 of the anterior clip 2500 on the caudal side 2604. The pinching action will free the tab arms 2504 from the pockets 2134, 2234 of the inferior 2100 and superior 2200 end plates. Simultaneously, the protrusions 2520 on the clips 2500 will fit into the pockets 2630 in the first and second end plate engaging surfaces 2640, 2642. The clips are then pulled perpendicularly away from the end plates 2100, 2200, with the fusion block 2600 held between them. A replacement fusion block 2600, elastic insert, or bearings 2300, 2400 can then be inserted with clips 2500 snapped in place, as described in the original insertion procedure.

[00178] The present invention includes not only implants, but also instrumentation that can be used to prepare, implant, or revise such implants. Figures 49 through 81 set forth instrumentation that may be used according to selected embodiments of the invention. [00179] Figure 49 illustrates an intervertebral disc motion preservation implant 3014. The implant 3014 is designed for placement between spinal vertebrae to replace degenerated intervertebral disc material. The implant 3014 comprises two end plates 3300, a superior bearing 3800, and an inferior bearing 3850, and two snap fasteners 3900. The end plates 3300 are implanted in the vertebral bodies, and the snap fasteners 3900 hold the bearings 3800, 3850 in place between the end plates 3300.

[00180] Referring to Figure 50, a perspective view illustrates two end plates 3300 and an end plate instrument assembly 3016 necessary to hold and guide the end plates 3300 during the implantation process. Also shown are a pivot assembly 3018 which holds and adjusts the end plate instrument assembly 3016, and an adjustable support assembly 3012 which holds the pivot assembly 3018. The end plates 3300 and the other implant components may be implanted and removed from any one of three approaches: anterior, left lateral or right lateral. Prior to the implantation procedure, the adjustable support assembly 3012 is attached to the operating table on the right or left side, depending upon which approach is to be used. [00181] After the end plates 3300 are implanted, the inferior 3850 and superior bearing 3800 are inserted between the end plates. Figure 51 illustrates a bearing instrument assembly 3017 required to insert the bearings. The bearing instrument assembly 3017 is supported by the pivot assembly 3018, which in turn is held by the adjustable support assembly 3012. [00182] The instrumentation illustrated herein is for an implant 3014 which has a specific anterior-posterior angle. Implants of differing angulation may be implanted and may require a different configuration of instrumentation. That is, instruments of varying sizes and designs may be necessary to implant an implant of a wider or narrower angle. In addition, the order of the procedure described herein may vary for a different implant.

[00183] Figure 52 depicts the pivot assembly 3018. The pivot assembly 3018 comprises an angle adjustment pivot 3100 and a height adjustment pivot 3140. The pivots 3100, 3140 are generally U-shaped and are secured together by two screws 3102. The height adjustment pivot 3140 has a body 3150 and two arms 3152 which extend perpendicularly away from the body 3150 and parallel to one another, forming a U-shape. The angle adjustment pivot 3100 also has a body 3110 and two arms 3112 which form a U-shape. A support feature in the form of support assembly ball 3114 is located on the outer side of each angle adjustment pivot arm 3112. The adjustable support assembly 3012 depicted in Figure 50 attaches to the pivot assembly 3018 via one of the support assembly balls 3114. Which support assembly ball 3114 is used is determined by the surgical approach (anterior, right lateral, or left lateral) and the preference of the surgical personnel.

[00184] An angle adjustment guide arm 3116 extends through an opening in the body 3110 of the angle adjustment pivot 3100. At the proximal end 3118 of the guide arm 3116 is an angle adjustment screw 3120. This angle adjustment screw 3120 extends through the length of the guide arm 3116 and emerges at the distal end 3122 of the guide arm 3116, and is capped by an adjustment nut 3124. An angle adjustment gauge 3130 appears as a series of numbers on the top side of the body 3110. Also on the top side of the body 3110, an adjustment knob 3126 extends through an opening in the body 3110 to the top of the angle adjustment guide arm 3116. Tightening the adjustment knob 3126 secures the angle adjustment guide arm 3116 in place within the angle adjustment pivot 3100. A row of angle guide arm teeth 3128 line the distal end 3122 of the angle adjustment guide arm 3116. [00185] A height adjustment guide arm 3156 extends through an opening in the body 3150 of the height adjustment pivot 3140. At the proximal end 3158 of the guide arm 3156 is a height adjustment screw 3160. This height adjustment screw 3160 extends through the length of the guide arm 3156 and emerges at the distal end 3162 of the guide arm 3156, and is capped by an adjustment nut 3164. A height adjustment gauge 3170 appears as a series of numbers on the top side of the body 3150. Also on the top side of the body 3150, an adjustment knob 3166 extends through an opening in the body 3150 to the top of the height adjustment guide arm 3156. Tightening the adjustment knob 3166 secures the height adjustment guide arm 3156 in place within the height adjustment pivot 3140. A row of height guide arm teeth 3168 line the distal end 3162 of the height adjustment guide arm 3156. [00186] The instrument assembly 3016 and pivot assembly 3018 are depicted in Figure 53. Individual components of the instrument assembly 3016 are positioned, implemented, and removed throughout the implantation procedure. In the embodiment depicted, the instrument assembly 3016 consists of two end plate holders 3200, two spike guards 3400, and two primary spacers 3500. Attached to the distal end of the end plate holders 3200 are two end plates 3300. (Additional spacers not depicted in Figure 53 are used in the procedure and will be illustrated and described as they are used.)

[00187] Figure 54 depicts a top-down view of the pivot assembly 3018 and its connection to the end plate holders 3200. The two end plate holders 3200 are identical to one another; they differ only in orientation during the implantation procedure. Each end plate holder 3200 has a distal first end 3250 and a proximal second end 3260, connected by a shaft 3201. At the second end 3260 of each end plate holder 3200 is a connector 3240 with an opening 3242 and a plurality of connector teeth 3248. One end plate holder is connected to the height adjustment guide arm 3156 by fitting the opening 3242 over the adjustment nut 3164, and meshing the connector teeth 3248 with the height guide arm teeth 3168. The other end plate holder 3200 is connected to the angle adjustment guide arm 116 in an identical manner; by fitting the opening 3242 over the adjustment nut 3124, and meshing the connector teeth 248 with the angle guide arm teeth 3128. Once the end plate holders 3200 are connected to the adjustable guide arms 3116, 3156, the height of the end plate holders 3200 can be adjusted by turning the height adjustment screw 3160, and the angle of the end plate holders 3200 can be adjusted by turning the angle adjustment screw 3120.

[00188] A transparent side view of the proximal end of the end plate holders 3200 and the guide arms 3116, 3156 is shown in Figure 55. Fitted into a longitudinal channel 3210 in each shaft 3201 is a spreader 3220. The spreaders 3220 lie on the inside planes of the end plate holders 3200 such that the spreaders 3220 face one another once the end plate holders 3200 are secured to the adjustment arms 3116, 3156. Each spreader3 220 has a lever 3222 which lies on the outside of the end plate holder 3200. A rod 3226 and lever pin 3224 assembly connect the spreader 3220 to the lever 3222. When the lever 3222 is in the lowered position as in Figure 53, the spreader 3220 is extended distally down the channel 3210 of the shaft 3201.

[00189] An end plate 3300 and its connection to the first end 3250 of the end plate holder 3200 are illustrated in Figure 56. The end plate 3300 has a right lateral end 3302, a left lateral end 3304, an anterior end 3306 and a posterior end 3308. The end plate 3300 has three pockets 3310, placed on the right lateral end 3302, the left lateral end 3304, and the anterior end 3306. The three pockets 3310 are identical in shape and design, only differing in placement on the end plate 3300. Each pocket 3310 has two angled corners 3312. If the implant 3014 is to be placed using the anterior approach, as depicted in Figure 56, the end plate holder 3200 will be connected to the end plate 3300 via the pocket 3310 located on the anterior end 3306. Similarly, if the implant 3014 is to be placed using a right lateral approach, the end plate holder 3200 will be connected via the pocket 3300 on the right end 3302, and if the implant is to be placed using a left lateral approach, the end plate holder 3200 will be connected via the pocket 3310 in the left end 3304.

[00190] The first end 3250 of the end plate holder 3200 comprises an expandable retention interface having two prongs 3202. The two prongs 3202 terminate in angled prong tips 3204, which have radiuses edges 3206. In the embodiment depicted, the anterior approach is used, so the end plate holder 3200 is connected to the end plate 3300 by placing the two prongs 3202 into the pocket 3310 on the anterior end 3306. Once the prongs 3202 are placed in the pocket 3310, the spreader 3220 is extended lengthwise between the two prongs 3202, by lowering the lever 3222 illustrated in Figure 55. As the spreader 3220 extends, the prong tips 3204 are forced apart, and pushed into the outer pocket corners 3312. When the spreader 3220 is fully extended, the spreader tip 3228 is pushed firmly against the end of the pocket 3310, and the prong tips 3204 are forced slightly back, thus seating their rounded edges 3206 against the pocket corners 3312. This seating creates a firm connection between the end plate 3300 and the end plate holder 3200. The second end plate 3300 is connected to the first end 3250 of the second end plate holder 3200 in an identical manner.

[00191] As seen in Figure56, each end plate 3300 has a plurality of spikes 3314. The spikes 3314 comprise hollow, pointed protrusions extending from an exterior surface 3316 of the end plate 3300. The spikes 3314 are positioned such that they form a ring on the exterior surface 3316, but are set back from the ends 3302-3308 of the end plate 3300, allowing an outer ring of flat surface area between the spikes 3314 and the ends 3302-3308. [00192] After each of the end plates 3300 is attached to the end plate holders 3200, a spike guard 3400 is fitted over the exterior surface 3316. As seen in Figure 57, the distal end of each spike guard 3400 terminates in a flat, spatula-like cover plate 3402 that fits over the exterior surface 3316 of the end plate 3300. The inside of the cover plate 3402 has grooves 3404 into which the centrally located spikes 3314 slide as the spike guards 3400 are put on. The spike guards 3400 are put on to the end plates 3300 by sliding them distally parallel to the end plate holders 3200 and onto the end plates, allowing the spikes 3314 to slide into the grooves 3404, illustrated in Figure 58. The outer surface of the cover plate has two curved notches 3406 which come to rest around the spikes 3314 nearest the right end 3302 and left end 3304 of the end plate 3300. These two spikes 3314 are not covered, but the outer surface of the cover plate 3402 extends higher than the ends of the spikes 3314, so the spikes 3314 do not protrude past the cover plate 3402. The cover plate 3402 prevents the spikes 3314 from snagging or scratching anything prior to implantation, and prevents premature contact between the spikes 3314 and the vertebral bodies. The spike guards 3400 are composed of a radiolucent material, so that the end plates 3300 are visible through radiography during the implantation process. Placement and removal of the spike guards 3400 is via handles (not visible in Figure 57). The spike guard depicted in Figures 57 and 58 is designed for use during an anterior approach implantation. It is appreciated that the shape and placement of the spike guards may differ in alternative embodiments of the invention. [00193] Figure 59 depicts the distal end of a primary spacer 3500. The distal end of the primary spacer 3500 terminates in a flat, rectangular plate 3502. A shaft 3504 connects the plate 3502 to a handle at the proximal end (not visible in Figure 59). Raised edges 3506 extend partway up the shaft 3504 from the plate 3502 toward the proximal end. The raised edges 3506 have a distal end 3508 near the plate 3502 and a proximal end 3510 partway up the shaft 3504.

[00194] Figure 60 illustrates the distal ends of the two end plate holders 3200 with attached end plates 3300, spike guards 3400, and one primary spacer 3500. Two primary spacers 3500 are used in the procedure, but only one is illustrated so that the details of the end plate holder 3200 may be seen. Either before or after the spike guards 3400 are fitted over the end plates 3300, the two primary spacers 3500 are slid in between the end plate holders 3200, as also shown in Figure 53. The first primary spacer 3500 is slid parallel to the inner side of the end plate holder 3200 such that the raised edges 3506 clasp around the lateral edges of the end plate holder 3200 and slide inside a lateral groove 3212. When the distal end 508 of the raised edge 3506 contacts the end plate 3300, the primary spacer 3500 is in place and cannot move distally any more. The plate 3502 is in between the two end plates 3300. The other primary spacer 3500 is slid into place next to the other end plate holder 3200, and its plate 3502 comes to rest between the first plate 3502 and the end plate 3300. The primary spacers are radiolucent, so they do not obscure the visibility of the end plates 3300 and vertebral bodies during implantation. The number and positioning of spacers may vary with alternative embodiments of the invention.

[00195] The pivot assembly 3018 and attached instrument assembly 3016 are now ready to be positioned for the implantation procedure. Referring to Figures 50, and 52, the pivot assembly 3018 is attached to the adjustable support assembly 3012 via one of the two support assembly balls 3114. The support assembly 3012 is adjusted so that the pivot assembly 3018 and the instrument assembly 3016 are supported over the patient in a position appropriate to the approach chosen (anterior, right lateral, or left lateral). The instrument assembly .016 is positioned so that the end plates .300 covered with the protective spikes guards .400 are placed between the vertebral bodies. Radiography is employed to observe the positioning of the end plates. At this point, the surgical personnel select the components of the disc implant 3014. The radiolucent spike guards 3400 allow the surgical personnel to see the end plates 3300 in position relative to the vertebral bodies, and the personnel can determine which size, thickness and angle of bearings 3800, 3850 should be used.

[00196] Figure 61 displays an exploded side view of disc implant 3014. The superior bearing 3800 has a superior bearing surface 3802 in which is an indented cup 3810. The inferior bearing 3850 has an inferior bearing surface 3852, from which protrudes a dome 3860. When the bearings 3800, 3850 are held in place between the two end plates 3300, the cup 3810 fits over the dome 3860, and the superior bearing surface 3802 is in contact with the inferior bearing surface 3852. The snap fasteners 3900 connect the bearings 3800, 3850 to the end plates 3300 by fitting into snap ports 3330 on the end plates 3300, and into troughs 3804, 3854 on the bearings 3800, 3850.

[00197] All pieces - end plates 3300, the inferior bearing 3850, the superior bearing 3800 and the snap fasteners 3900 are made in three sizes, where size refers to the area of the component, which will correspond to the area of the vertebral bodies where the disc implants are implanted. The superior bearings 3800 are made in a variety of thicknesses, to match the height of the intervertebral space. The inferior bearings 3850 are made in a variety of angles, in which the height of the posterior end of the inferior bearing is greater than the height of the anterior end of the inferior bearing, to match the angle of the intervertebral space. If deemed necessary, the end plates 3300 can be removed and alternate, differently sized end plates 3300 substituted for them.

[00198] Referring back to Figure 54, the adjustment screws 3160, 3120 on the guide arms 3156, 3116 allow for height and angle adjustment control at the second ends 3260 of the end plate holders 3200 while the first ends 3250 are inserted in the intervertebral space. The height adjustment screw 3160 at the second end 3260 of the end plate holder 3200 can be turned in either direction, raising or lowering the first end 3250 of the end plate holder 3200, until the end plate 3300 is correctly positioned in the intervertebral space. The height measurement gauge 3170 is read on the height adjustment guide arm 3156 and the superior bearing 3800 matching that height is selected. Similarly, the angle adjustment screw 3120 at the second end 3260 of the other end plate holder 3200 can be turned, changing the anterior- posterior angle of the first end 3250 of the other end plate holder 3200, until the end plate 3300 is correctly positioned. The angle measurement gauge 3130 is read on the angle adjustment guide arm 3116 and the inferior bearing 3850 matching that angle is selected. [00199] An alternate method for determining the correct size of end plates 3300 and bearings is to have a group of samples which duplicate the size, thickness and angles of the end plates and bearings. These sample components are each mounted on a shaft to allow temporary insertion into the intervertebral space, to determine if the size, thickness and angle of the components are correct. A sample has the same dimensions as the two end plates, the inferior and superior bearings, and the snap fittings do when they are fitted together as they would be in the intervertebral space. Instead of temporarily inserting and removing the actual end plates and bearings to check for the proper configuration, the samples can be inserted and removed to determine the proper choice for each component.

[00200] Once the correct disc implant 3014 components are chosen, the final position of the end plates 3300 is adjusted. Radiography is used to see where the end plates 3300 and more specifically the spikes 3314 will fit against the vertebral bodies. The angle adjustment screw 3120 is turned to place the end plate holder 3200 and end plate 3300 at the proper angle. The height adjustment screw 3160 is turned to raise or lower the other end plate holder 3200 and end plate 3300. Once the correct angle and height are determined, the adjustment knob 3126 is tightened to lock the angle adjustment guide arm 3116 in place, and the adjustment knob 3166 is tightened to lock the height adjustment guide arm 3156 in place. [00201] With the end plate holders 3200 now locked in place at the correct height and angle, the spike guards 3400 are removed, allowing the now exposed spikes 3314 to engage against the surface of the vertebral bodies. Secondary spacers 3550 are inserted between the primary spacers 3500. This action pushes the end plates 3300 cephalo-caudally away from one another, and presses the spikes 3314 into the vertebral bodies. Figure 62 illustrates the distal end of an individual secondary spacer 3550. The secondary spacer 3550 terminates in a paddle-like plate 3552 that is thicker than the plate 3502 of the primary spacer 3500. A shaft 3554 connects the plate 3552 to a handle (not visible in Figure 62). Partway up the shaft 3554 in a proximal direction from the plate 3552, a pair of rails 3556 are on either side of the shaft 3554. The rails 3556 have squared edges 3558 which extend out from the shaft 3554. [00202] Figure 63 illustrates the distal end of instrument assembly 3016, including end plate holders 3200, and primary and secondary spacers 3500, 3550. The end plate holders 3200 are holding two end plates 3300. The secondary spacers 3550 are inserted one at a time into the space between the two primary spacers 3500. As the secondary spacer 3550 is moved into place, the edges 3558 of the rails 3556 slide into the lateral grooves 3212 on the end plate holder 3200. The secondary spacer 3550 is slid distally until the rails 3556 contact a proximal end 3510 of the raised edges 3506 of the primary spacer 3500, preventing the secondary spacer 3550 from sliding any further. The plate 3552 is now positioned next to the plate 3502 of the primary spacer 3500, and the primary spacer 3500 is sandwiched between the end plate holder 3200 and the secondary spacer 3500. The other secondary spacer 3550 is inserted in the same fashion onto the opposite primary spacer 3500 and end plate holder 3200. The action of inserting the secondary spacers 3550 pushes the spikes 3314 into the vertebral bodies, thus firmly seating the exterior surfaces 3316 of the end plates 3300 against the surface of the vertebral bodies.

[00203] With the end plates 3300 implanted in the vertebral bodies, the primary spacers 3500 and secondary spacers 3550 are removed. Removal is accomplished by grasping the handles of the spacers 3500, 3550 and pulling them proximally until they are free of the instrument assembly 3016.

[00204] Referring back to Figure 51, the bearing instrument assembly 3017 used to place the bearings 3800, 3850 between the implanted end plates 3200 is depicted. This assembly is supported by the pivot assembly 3018, and comprises the end plate holders 3200, an angle compressor 3650, a height compressor 3600, and a bearing holder 3700. At the distal end of the instrumentation set is the intervertebral disc motion preservation implant 3014, which comprises the two end plates 3300, an inferior bearing 3800, a superior bearing 3850, and two snap fasteners 3900, as illustrated in Figure58. The instruments which comprise instrument assembly 3017 are assembled in the following order: the angle compressor 3650 is inserted between the end plate holders 3200; the bearings 3800, 3850 are attached to the bearing holder 3700; the height compressor 3600 is attached to the bearing holder 3700; and the bearing holder 3700 (with attached height compressor 3600 and bearings 3800, 3850) is inserted between the end plate holders 3200.

[00205] Figure 64 depicts the distal end of one angle compressor 3650 with one end plate holder 3200 and one end plate 3300. The angle compressor 3650 is comprised of a handle at the proximal end (not visible in Figure 62), a shaft 3654, and two prongs 3652. The shaft 3654 has raised edges 3658 which extend perpendicularly from the shaft 3654 and bend to form an L-shape. At the distal end of the shaft 3654 are the prongs 3652 which each terminate in an angled ramp 3662. Partway up the shaft 3654 in a proximal direction are a pair of rails 3656. The L-shaped rails 3656 extend in the opposite direction from the raised edges 3658. The angle compressor 3650 is slid onto the end plate holder 3200 which is attached to the angle guide arm 3116 as seen in Figure 54. The raised edges 3658 slide into the lateral grooves 3212 on either side of the end plate holder 3200. The angle compressor 3650 is slid distally down the length of the end plate holder 3200 until the distal ends 3660 of the raised edges 3658 contact the end plate 3300. The prongs 3652 lie on either side of the snap port 3330 of the end plate 3300.

[00206] The inferior side of the distal end of bearing holder 3700 is illustrated in Figure 65. The bearing holder 300 has two handles 3734 at the proximal end (visible in Figure51), and a shaft 3704 which terminates at its distal end at an intersection with a body 3710. Along each lateral side of the shaft 3704 is a camming channel 730 with undulating edges 3732. The body 3710 extends distally and splits into two prongs 3702. The body 3710 and prongs 3702 are generally flat and fork-like in shape, with a superior side 3716 and an inferior side 3718. Where the body 3710 originates at the base of the shaft 3704 are two shoulders 3706, one on each lateral side of the shaft 3704. Each shoulder 3706 extends perpendicularly from the body 3710 in both directions. On each side of each shoulder is a slot 3708 which lies parallel to the prongs 3702 and is open to the inside of the shoulder 3706 adjacent to the shaft 3704. At the base of each shoulder 3706, and between the slot 3708, and the body 3710, is a slanted edge 3720.

[00207] Where the two prongs 3702 meet at the base of the body 3710 is a locking key 3712 with two teeth 3728. The locking key 3712 is mounted on the end of a pin 3722 that extends from the proximal end of the shaft to the distal end, and is enclosed in a channel 3724. At the proximal end of the bearing holder 3700, the pin 3722 emerges from the channel 3724 and is capped by an adjustment nut 3726 (seen in Figure51). When the adjustment nut 3726 is turned, the pin 3722 and the locking key 3712 turn. [00208] Figure 66 depicts a superior side view of superior bearing 3800 and an inferior bearing 3850 mounted on the bearing holder 3700. In the embodiment depicted, the bearings 3800, 3850 are mounted in the anterior position; however they can also be mounted in either of the lateral positions, depending upon which surgical approach is used. Prior to mounting, the snap fasteners 3900 are snapped onto the bearings 3800, 3850. The superior bearing 3800 is mounted on the superior side 3716 of the bearing holder 3700. The superior bearing 3800 is placed parallel to and adjacent to the body 3710, with the cup 3810 surrounded by the prongs 3702. Anterior faceted edges 3806 of the superior bearing 3800 are flush against the slanted edges 3720 of the shoulders 3706. One tooth 3728 of the locking key 3712 protrudes into the anterior instrument port 3816. Simultaneously, the inferior bearing 3850 is placed on the inferior side 3718 of the bearing holder 3700, parallel to and adjacent to the body 3710 and with the prongs 3702 surrounding the dome 3860. Anterior faceted edges 3856 of the inferior bearing 3850 are flush against the slanted edges 3720 of the shoulders 3706, and the other tooth 3728 of the locking key 3712 is protruding through the anterior instrument port 3866. With both bearings 3800, 3850 held thus, the adjustment nut 3726 is turned. The pin 3722 and locking key 3712 turn, and the teeth 3728 on the locking key 3712 engage and tighten down on the edges of the instrument ports 3816, 3866. The bearings 3800, 3850 are thus locked in place on the bearing holder 3700. The inferior bearing surface 3852 and the superior bearing surface 3802 are adjacent to one another, with the dome 3860 encircled by the cup 3810 (not visible in Figure 66).

[00209] Figure 67 illustrates the distal end of the height compressor 3600. At the proximal end is a handle (not visible in Figure 67). The height compressor 3600 has a shaft 3604 with two prongs 3602 at its distal end 3610. Each prong 3602 terminates in an angled ramp 3612. On either lateral side of the shaft 3604 is a raised edge 3608, which extends perpendicularly from the shaft 3604 and bends to form an L-shape. Slightly above the distal end 3610 of the shaft 3604 is a pair of rails 3606, with one rail 3606 located on each raised edge 3608. A second pair of rails 3606 is located some distance proximally along the shaft 3604, one on each raised edge 3608.

[00210] The bearing holder 3700 with attached bearings 3800, 3850, and a height compressor 3600 are shown in Figure 68. The height compressor 3600 is connected to the bearing holder 3700 by sliding the height compressor 3600 parallel to the bearing holder 3700 in the distal direction, on the superior side 3716, allowing the rails 3606 to clasp the camming channel 3730 on each side of the bearing holder 3700. As the height compressor 3600 slides, the prongs 3602 slide into the slots 3708 on the bearing holder 3700. The height compressor 3600 is slid distally until the rails 3606 contact the shoulders 3706 of the bearing holder 3700. At this point the height compressor 3600 cannot slide distally any farther and the prongs 3602 encircle the snap fastener 3900 on the superior bearing3 800. The raised edges 3608 are facing outward.

[00211] After the height compressor 3600 is connected to the bearing holder 3700, these two instruments and the attached bearings 3800, 3850 are inserted as a set between the end plate holders 3200, as seen in Figure 51. The angle compressor 3650 is already in place, connected to one end plate holder 3200, as seen in Figure 64. The distal ends of the bearing holder 3700 and the height compressor 3600, with the attached bearings 3800, 3850 are inserted between the end plate holders 3200, oriented so that the height compressor 3600 is slid in next to the end plate holder 3200 which is suspended from the height adjustment arm 3156 (seen in Figure 54).The height compressor 3600, bearing holder 3700 and bearings 3800, 3850 are slid in a distal direction parallel to the end plate holders 3200. As the instruments are slid in, the rails 3656 of the angle compressor 3650 slide into the camming channels 3730 on the bearing holder 3700, and the prongs 3652 slide into the slots 3708. Simultaneously, the raised edges 3608 of the height compressor 3600 clasp the lateral grooves 3212 of the end plate holder 3200. The instrument set is slid distally until the shoulders 3706 of the bearing holder 3700 contact the end plates 3300. At this point, the instrument set cannot slide in any farther and the prongs 3652 of the angle compressor 3650 encircle the snap fastener 3900 between the end plate 3300 and the inferior bearing 3850. [00212] All components of the intervertebral disc motion preservation implant 3014 are now in position between the vertebral bodies. Figure 69 illustrates the implant 3014 held in place by the end plate holders 3200 and bearing holder 3700. To attach the bearings 3800, 3850 to the end plates 3200 the height and angle compressors 3600, 3650 are removed, one at a time, in either order. The height compressor 3600 is removed by grasping the handle and pulling it proximally. As the height compressor 3600 slides out, the rails 3606 slide proximally along the camming channels 3730 of the bearing holder 3700. As the height compressor 3600 is removed, the prongs 3602 are slid out from between the end plate 3300 and the superior bearing 3800. Just when the prongs 3602 reach the point where they are no longer between the end plate 3300 and the superior bearing 3800, the rails 3606 slide over a widening in the undulating edges 3732 of the camming channels 3730. This forces the bearing holder 3700 slightly closer to compressor 3600, and therefore closer to the end plate holder 3200. Since the prongs 3602 of the height compressor 3600 are no longer between the end plate 3200 and the superior bearing 3800, the additional force snaps the snap fastener 3900 on the bearing 3800 into place in the snap port 3330 on the end plate 3200. [00213] The angle compressor 3650 is removed in the same way. The angle compressor 3650 is removed by grasping the handle and pulling it proximally. As the angle compressor 3650 slides out, the rails 3656 slide proximally along the camming channels 3730 of the bearing holder 3700. As the angle compressor 3650 is removed, the prongs 3652 are slid out from between the end plate 300 and the inferior bearing 3850. Just when the prongs 3652 reach the point where they are no longer between the end plate 3300 and the inferior bearing 3850, the rails3 656 slide over a widening in the undulating edges 3732 of the camming channels 3730. This forces the bearing holder 3700 slightly closer to compressor 3650, and therefore closer to the end plate holder 3200. Since the prongs 3652 of the angle compressor 3650 are no longer between the end plate 3200 and the inferior bearing 3850, the additional force snaps the snap fastener 3900 on the bearing 3850 into place in the snap port 3330 on the end plate 3200. The adjustment nut 3726 on the bearing holder 3700 is turned, so the teeth 3728 disengage from the instrument ports 3816, 3866. All components of the intervertebral implant 3014 are now in place between the end plates 3200.

[00214] Referring to Figures 51 and 56, the bearing holder 3700 is removed by grasping its handles 3734 and pulling it proximally between the end plate holders 3200 until it is free of the end plate holders 3200 and the pivot assembly 18. Each end plate holder 3200 is disengaged from its end plate 3300 by raising the lever 3222. Raising the lever 3222 retracts the spreader 3220, and the prongs 3202 are loosened within the pocket 3310. The end plate holder 3200 can now be removed by pulling it proximally away from the end plate 3200. Thus all of the instrument assembly 3017 is removed from the patient. [00215] Should removal of the implant 3014 or replacement of any of its constituent components be required, such procedure may be carried out in any of the three approaches; anterior, right lateral, or left lateral, regardless of which approach was used during the initial implantation. To remove any component, first each end plate holder 3200 is connected to the pivot assembly 3018, as seen in Figure 54, with the lever 3222 in the lowered position. The prongs 3202 are guided into the pocket 3310 of the end plate 3300, and the lever 3222 is raised. The spreader 3220 moves distally, and the prongs 3202 are spread into the pocket corners 3312. With the end plate holders 3200 now connected to the end plates 3300, the bearing holder 3700 is inserted between the end plate holders 3200, The bearing holder 3700 is oriented so that the superior side 3716 is facing the end plate holder 3200 which is connected to the height adjustment guide arm 3156, and the inferior side 3718 is facing the end plate holder 3200 which is connected to the angle adjustment guide arm 3116. As the bearing holder 3700 is inserted, the prongs 3702 will slide between the bearings 3800, 3850 such that the prongs 3702 lie on either side of the dome 3860. When the prongs 3702 are in place, the adjustment nut 3726 is turned, so that the teeth 3728 engage in the instrument ports 3816, 3866, and the bearings 3800, 3850 are locked to the bearing holder 3700. [00216] Next, the compressors 3600, 3650 are inserted in either order. The height compressor 3600 is slid distally along the end plate holder 3200 which is connected to the height adjustment guide arm 3156, so that the raised edges 3608 slide into and along the lateral groove 3212. As the compressor is slid distally along the end plate holder, the rails 3606 slide over the undulating edges 3732 and into the camming channel 3730. When the ramps 3612 on the prongs 3602 slide in between the end plate 3300 and the superior bearing 3800, their intrusion will pry the snap fastener 3900 apart from the snap port 3330. The angle compressor 3650 is then slid distally along the end plate holder 3200 which is connected to the angle adjustment guide arm 3116, so that the raised edges 3658 slide into and along the lateral groove 3212, and the rails 3656 slide along the camming channel 3730. When the ramps 3662 on the prongs 3652 slide in between the end plate 3300 and the inferior bearing 3850, their intrusion will pry the snap fastener 3900 apart from the snap port 3330. [00217] The bearings 3800, 3850 are now free from the end plates 3300, and attached to the bearing holder 3700. The bearing holder 3700 with the attached bearings 3800, 3850, and the compressors 3600, 3650 are removed simultaneously, by grasping their handles and pulling them proximally out from between the end plate holders 3200. At this juncture new bearings 3800, 3850 may be inserted in the same manner as described previously. [00218] An alternative embodiment of the invention is illustrated in Figures 70 - 81. This embodiment uses many of the same instruments as described for the previous embodiment, and is configured to implant the implant 3014, a fusion block, or an alternative implant. The alternative embodiment comprises alternative bearing placement guidance instrumentation, and compression instrumentation.

[00219] Referring to Figure 70, the support assembly 3012, pivot assembly 3018 and end plate assembly 3016 are shown with an alternative bearing guidance assembly 31017, an alternative implant 31014, and a compressor 31600. The bearing guidance assembly 31017 comprises a bearing holder 31700 with guidance features. The implant 31014 comprises two end plates 31300, a superior bearing 31800, an inferior bearing 31850, and two snap fasteners 31900. The bearing holder 31700 holds and guides the superior and inferior bearings 31800, 31850 as they are inserted between the end plates 31300. The compressor 31600 provides compressive force to the end plates 31300, pushing them toward the bearings 31800, 31850 causing the snap fasteners 31900 to engage to the end plates 31300, thus connecting the end plates 31300 to the bearings 31800, 31850. The compression instrumentation also includes feeler gauges (not shown in Figure 70) which test the snap fastener connection. Although the alternative implant 31014 is depicted in Figures 70 -76, the alternative bearing guidance assembly 31017 could also be used to place the implant 3014, or a fusion block. [00220] Referring to Figure 71, an enlarged exploded view of the alternative disc motion preservation implant 31014 is depicted. Each end plate 31300 has a snap port 31330. The superior bearing 31800 has a trough 31804 on its superior side, and the inferior bearing 31850 has a trough 31854 on its inferior side. The snap fasteners 31900 connect the end plates to the superior and inferior bearings when all components of the implant are snapped together. Prior to implantation, one snap fastener 31900 is snapped into the trough 31804 on the superior bearing 31800, and similarly the second snap fastener 31900 is snapped into the trough 31854 on the inferior bearing 31850.

[00221] Figure 72 depicts the bearing holder 31700, holding the superior and inferior bearings 31800, 31850. A snap fitting 31900 is attached to each bearing 31800, 31850. The superior bearing 31800 is held on a superior side 31716 of the bearing holder 31700, and the inferior bearing 31850 is held on an inferior side 31718. The bearing holder 31700 has two handles 31734 at the proximal end, and a shaft 31704 which terminates at its distal end at an intersection with a body 31710. Along a portion of each lateral side of the shaft 31704 is guide rail 31730, which extend perpendicularly from the shaft 31704 on the inferior side 31718. Near the distal end of the shaft 31704, a pair of slider arms 31732 extends from the superior side 31716, holding a slider link 31736. An inferior feeler gauge 32050 is slidably engaged on the shaft 31704 of the bearing holder 31700.

[00222] Referring to Figure 73, an enlarged view of the inferior side 31718 of distal end of the bearing holder 31700 is shown. At the end of the shaft 31704, the body 31710 extends distally and splits into two prongs 31702. The body 31710 and prongs 31702 are generally flat and fork-like in shape. Where the body 31710 originates at the base of the shaft 31704 are two stops 31708, one on each lateral side of the shaft 31704, which protrude perpendicularly from the shaft on the inferior side 31718. Distal from the stops 31708, where the two prongs 31702 extend from the body 31710, are two shoulders 31706, one on each lateral side of the body 31710. Each shoulder 31706 extends perpendicularly from the body 31710 in both superior 31716 and inferior 31718 directions. [00223] Where the two prongs 31702 meet at the base of the body 31710 is a locking key 31712 with two teeth 31728. The locking key 31712 is mounted on the end of a pin 31722 that extends from the proximal end of the shaft to the distal end, and is enclosed in a channel 31724. At the proximal end of the bearing holder 31700, the pin 31722 emerges from the channel 31724 and is capped by an adjustment nut 31726 (seen in Figure 71). When the adjustment nut 31726 is turned, the pin 31722 and the locking key 31712 turn. [00224] Referring to Figure74, an enlarged view of the superior side 31716 of the distal end of the bearing holder is shown. Just proximal to the body 31710, a slider arm 31732 is linked to each side of the shaft 31704. Extending between the ends of the arms 31732 is the slider link 31736, which has a guide rail 31740 at each of its lateral ends. The guide rails 31740 are configured to grip the lateral edges of the end plate holders 31200 as the bearings 31800, 31850 are inserted or withdrawn, thus guiding the bearings in between the end plates 31300.

[00225] Referring to Figure 75, an enlarged view shows the bearings 31800, 31850 mounted on the distal end of the bearing holder 31700. The bearings 31800, 31850 are mounted on the bearing holder 31700 in the same manner as described previously for the bearings 3800, 3850 and the bearing holder 3700.

[00226] Referring to Figure 76, the bearing holder 31700 with mounted bearings 31800, 31850 is shown inserted between the end plate holders 3200 and the end plates 31300. The bearing holder 31700 and bearings 31800, 31850 are slid in between the proximal ends of end plate holders 3200 as they are held in the pivot assembly 3018. As the bearing holder 31700 is slid distally, the guide rails 31730 are maneuvered so that they clasp the edges of the inferior end plate holder 3200. Similarly, the guide rails 31740 clasp the edges of the superior end plate holder 3200. With the guide rails 31730, 31740 thus engaged, the bearings 31800, 13850 are able to slide in between the end plates 31200 with a minimum of lateral movement and adjustment. When the bearings 31800, 31850 reach the end plates 31200, the shoulders 31706 of the bearing holder 31700 contact the end plates 31300, preventing any further distal movement, and lining the bearings 31800, 31850 up so that the snap fasteners 31900 will correctly engage with the end plates 31300 when compressed. [00227] Referring to Figure 77, a compressor 31600 is shown. The compressor 31600 has a handle 31602, a compression lever 31604, a shaft 31606 and at the distal end of the shaft 31606, a pair of tongs 31608. When the compressor 31600 is implemented, the tongs 31608 push the end plates 31300 toward the bearings 31800, 31850, providing force so the snap fasteners 31900 snap into the snap ports 31330 on the end plates 31300. [00228] Referring to Figure 78, an enlarged view of the distal end of the compressor 31600 is shown. Extending lengthwise along the shaft 31606 is a pull bar 31610, which is pivotably connected at its proximal end to the compression lever 31604, and is pivotably connected at its distal end to the tongs 31608. The tongs 31608 are pivotably connected to a pair of cross links 31612, which are pivotably connected to the distal end of the shaft 31606. When the compression lever 31604 is pulled toward the handle 31602, the pull bar 31610 moves distally parallel to the shaft 31606, and the tongs 31608 are forced together. [00229] Returning to Figure70, the end plate assembly 3016 and the bearing guidance assembly 31017 are shown, with the compressor 31600 grasping the end plate holders 3200. The compressor 31600 is placed so that each tong 31608 is adjacent to the shaft 3201 of each end plate holder 3200. The compression lever 31604 is raised, thus extending the pull bar 31610 and pulling the tongs 31608 together, which push the end plate holders 3200 with the attached end plates 31300 together. The snap fasteners 31900, which are already engaged in the troughs on the bearings 31800, 31850, are pushed into the snap ports 31330 on the end plates 31300.

[00230] Referring to Figure 79, a superior feeler gauge 32000 is shown. The superior feeler gauge 32000 has a handle 32002 and a wide shaft 32004 with guide rails 32006 on each lateral side of the shaft 32004. The shaft 32004 terminates at a tang 32008 which extends distally from the distal end of the shaft 32004.

[00231] Referring to Figure 80, the inferior feeler gauge 32050 is shown. The inferior feeler gauge 32050 has a handle 32052, a shaft 32054, and a body 32060. Guide rails 32056 line each lateral edge of the body 32060, and they enable the gauge 32050 to be slidably engaged to the bearing holder 31700. At the distal end of the body 32060, a tang 32058 extends distally from the body 32060.

[00232] The feeler gauges 32000, 32050 are used to test if the snap fasteners 31900 have properly snapped to the end plates 31300 following compression. The compressor 31600 is removed from the instrument assembly 31017, and the superior feeler gauge 32000 is inserted between the end plate holders 3200 and the bearing holder 31700. The inferior feeler gauge 32050 is already engaged on the bearing holder 31700, as seen in Figure 72. The superior feeler gauge 32000 is inserted on the superior side 31716 of the bearing holder 31700, so that its guide rails 32006 clasp the edges of the superior bearing holder 3200. The gauge 32000 is slid distally until its tang 32008 slides in between the superior end plate 31300 and the superior bearing 31800. If the snap connection between the end plate 31300 and the bearing 31800 has been successfully made, the tang 32008 will not be able to slide between the snap fastener 31900 and the end plate 31300. If, however, the snap fastener 31900 has failed to engage with the snap port 31330 on the end plate 31300, the tang 32008 will continue to slide distally until it lies between the snap fastener 31900 and the end plate 31300. [00233] Similarly, the inferior feeler gauge 32050 is slid distally until its tang 32058 slides in between the inferior end plate 31300 and the inferior bearing 31850. If the snap connection between the end plate 31300 and the bearing 31850 has been successfully made, the tang 32058 will not be able to slide between the snap fastener 31900 and the end plate 31300. If, however, the snap fastener 31900 has failed to engage with the snap port 31330 on the end plate 31300, the tang 32058 will continue to slide distally until it lies between the snap fastener 31900 and the end plate 31300.

[00234] If either snap fastener 31900 has failed to engage with its corresponding end plate 31300, the feeler gauges 32000, 32050 are slid proximally, and the compressor 31600 is realigned with the end plate holders 3200. Compression is again attempted, and re-tested with the feeler gauges until both snap fasteners 31900 are snapped in place on the end plates 31300.

[00235] Referring to Figure 81, a fusion block 32100 is shown attached to the distal end of the bearing holder 31700. When fusion instead of motion preservation is desired, the fusion block 32100 may be inserted in between two end plates 31300 in the intervertebral space, using the same bearing delivery methods as described previously. The fusion block 32100, with two snap fasteners 31900 snapped onto each of its two snap ports 32130, is locked on the end of the bearing holder 31700 using the locking key 31712 mechanism. The fusion block 32100 and snap fasteners 31900 are inserted between the end plates 31300, and snapped to the end plates 31300 using the compressor 31600.

[00236] It is appreciated that the bearing set 31800, 31850 and the fusion block 32100 are interchangeable, using the same instrumentation and implantation methods. If a motion preservation implant has been implanted, but a change to fusion is desired, the patient may be reopened, and the original implant removed with the instrumentation described above. A fusion block may then be implanted with the same instrumentation. If fusion is to be replaced with a motion preservation implant, the procedure may be reversed. It is also appreciated that all procedures described above may be carried out from an anterior approach, a right lateral approach, or a left lateral approach. Scar tissue buildup may be reduced by carrying out any revisions by a different approach, e.g., original implantation from an anterior approach and revision from a left or right lateral approach, or vice versa. [00237] The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. It is appreciated that various features of the above- described examples can be mixed and matched to form a variety of other alternatives. As such, the described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

1. An intervertebral implant comprising: a first end plate configured to be secured to a first vertebral body adjacent to an intervertebral space; and a first intermediate component configured to be lockable into a locked position relative to the first end plate in response to motion between the first intermediate component and the first end plate, wherein the first intermediate component comprises a concave articular surface.

2. The intervertebral implant of claim 1, wherein the first intermediate component is positionable in a free position relative to the first end plate, wherein in the free position, relative motion between the first intermediate component and the first end plate is unrestricted, wherein the first intermediate component is movable between the locked and free positions along a straight pathway having a length of 6 millimeters or less.

3. The intervertebral implant of claim 2, wherein a first force required to lock the first intermediate component into the locked position relative to the first end plate is less than a second force required to move the first intermediate component from the locked position to the free position relative to the first end plate.

4. The intervertebral implant of claim 1, wherein a force required to lock the first intermediate component into the locked position relative to the first end plate is 20 pounds or less.

5. The intervertebral implant of claim 1, wherein the first intermediate component is further configured to be locked in response to motion of the first intermediate component toward the first end plate along a cephalad-caudal path.

6. The intervertebral implant of claim 1, further comprising: a second end plate configured to be secured to a second vertebral body adjacent to the intervertebral space; and a second intermediate component configured to be lockable into a locked position relative to the second end plate in response to motion between the second intermediate component and the second end plate, wherein the second intermediate component comprises a convex articular surface shaped to articulate with the concave articular surface.

7. The intervertebral implant of claim 6, further comprising a third intermediate component configured to be lockable into a locked position relative to the first and second end plates in response to motion between the third intermediate component and the first and second end plates, wherein the third intermediate component comprises a fusion block configured to substantially prevent relative motion between the first and second end plates.

8. The intervertebral implant of claim 1, further comprising a snap fastener separate from the first end plate and the first intermediate component, wherein the snap fastener is shaped to be secured to the first intermediate component and to snap into engagement with the first end plate.

9. The intervertebral implant of claim 1, wherein the first inteπnediate component is configured to be lockable into the locked position after the first end plate is secured to the first vertebral body, and without detaching the first end plate from the first vertebral body.

10. The intervertebral implant of claim 1, wherein the first end plate comprises at least one anchoring member shaped to penetrate the first vertebral body to secure the first end plate to the first vertebral body.

11. An intervertebral implant comprising: a first end plate configured to be secured to a first vertebral body adjacent to an intervertebral space; and a first inteπnediate component configured to be reversibly lockable into a locked position relative to the first end plate in response to motion of the first intermediate component toward the first end plate along a cephalad-caudal path.

12. The intervertebral implant of claim 11, wherein the first intermediate component further comprises a free position relative to the first end plate, wherein in the free position, relative motion between the first intermediate component and the first end plate is unrestricted, wherein the first intermediate component is movable between the locked and free positions along a straight pathway having a length of 6 millimeters or less.

13. The intervertebral implant of claim 12, wherein a first force required to lock the first intermediate component into the locked position relative to the first end plate is less than a second force required to move the first intermediate component from the locked position to the free position relative to the first end plate.

14. The intervertebral implant of claim 11, wherein a force required to lock the first intermediate component into the locked position relative to the first end plate is 20 pounds or less.

15. The intervertebral implant of claim 11, further comprising: a second end plate configured to be secured to a second vertebral body adjacent to the intervertebral space; and a second intermediate component configured to be lockable into a locked position relative to the second end plate in response to motion between the second intermediate component and the second end plate, wherein the second intermediate component comprises a convex articular surface shaped to articulate with the concave articular surface.

16. The intervertebral implant of claim 15, further comprising- a third intermediate component configured to be lockable into a locked position relative to the first and second end plates in response to motion between the third intermediate component and the first and second end plates, wherein the third intermediate component comprises a fusion block configured to substantially prevent relative motion between the first and second end plates.

17. The intervertebral implant of claim 11, further comprising a snap fastener separate from the first end plate and the first intermediate component, wherein the snap fastener is shaped to be secured to the first intermediate component and to snap into engagement with the first end plate.

18. The intervertebral implant of claim 11, wherein the first intermediate component is configured to be lockable into the locked position after the first end plate is secured to the first vertebral body, and without detaching the first end plate from the first vertebral body.

19. The intervertebral implant of claim 11, wherein the first end plate comprises at least one anchoring member shaped to penetrate the first vertebral body to secure the first end plate to the first vertebral body.

20. The intervertebral implant of claim 19, wherein each anchoring member is shaped to define a channel extending therethrough.

21. A method of implanting an intervertebral implant on a spine comprising a first vertebral body adjacent to an intervertebral space, the method comprising: securing a first end plate to the first vertebral body; moving a first intermediate component to a locked position relative to the first end plate, the first intermediate component comprising a concave articular surface; and locking the first intermediate component in the locked position relative to the first end plate in response to the relative motion.

22. The method of claim 21, wherein moving the first intermediate component to the locked position comprises moving the first intermediate component from a free position along a straight pathway to the locked position, the straight pathway having a length of 6 millimeters or less, wherein, in the free position, relative motion between the first intermediate component and the first end plate is unrestricted.

23. The method of claim 22, wherein moving the first intermediate component to the locked position comprises exerting a first force on the first intermediate component, wherein the first force is less than a second force that would be required to move the first intermediate component from the locked position to the free position.

24. The method of claim 21, wherein moving the first intermediate component to the locked position comprises exerting a first force on the intermediate component, wherein the first force is 20 pounds or less.

25. The method of claim 21, wherein moving the first intermediate component to the locked position comprises moving the first intermediate component toward the first end plate along a cephalad-caudal path.

26. The method of claim 21, further comprising: securing a second end plate to a second vertebral body adjacent to the intervertebral space; and moving a second intermediate component to a locked position relative to the second end plate, the second intermediate component comprising a convex articular surface shaped to articulate with the concave articular surface; and locking the second intermediate component in the locked position relative to the second end plate in response to the relative motion.

27. The method of claim 26, further comprising: detaching the first intermediate component from the first end plate; detaching the second intermediate component from the second end plate; moving a third intermediate component to a locked position relative to the first and second end plates; and locking the third intermediate component into a locked position relative to the first and second end plates in response to the relative motion; wherein the third intermediate component comprises a fusion block configured to substantially prevent relative motion between the first and second end plates.

28. The method of claim 21, further comprising securing a snap fastener to the first intermediate component; wherein locking the first intermediate component in the locked position comprises snapping the snap fastener into engagement with the first end plate.

29. The method of claim 21, wherein locking the first intermediate component in the locked position is carried out after securement of the first end plate to the first vertebral body; wherein locking the first intermediate component in the locked position is carried out without detaching the first end plate from the first vertebral body.

30. The method of claim 21 , wherein securing the first end plate to the first vertebral body comprises penetrating the first vertebral body with at least one anchoring member.

31. A method of implanting an intervertebral implant on a spine comprising a first vertebral body adjacent to an intervertebral space, the method comprising: securing a first end plate to the first vertebral body; moving a first intermediate component along a cephalad-caudal path to a locked position relative to the first end plate; and locking the first intermediate component in the locked position relative to the first end plate in response to the relative motion.

32. The method of claim 31, wherein moving the first intermediate component to the locked position comprises moving the first intermediate component from a free position along a straight pathway to the locked position, the straight pathway having a length of 6 millimeters or less, wherein, in the free position, relative motion between the first intermediate component and the first end plate is unrestricted.

33. The method of claim 32, wherein moving the first intermediate component to the locked position comprises exerting a first force on the first intermediate component, wherein the first force is less than a second force that would be required to move the first intermediate component from the locked position to the free position.

34. The method of claim 31, wherein moving the first intermediate component to the locked position comprises exerting a first force on the intermediate component, wherein the first force is 20 pounds or less.

35. The method of claim 31, further comprising: securing a second end plate to a second vertebral body adjacent to the intervertebral space; and moving a second intermediate component to a locked position relative to the second end plate, the second intermediate component comprising a convex articular surface shaped to articulate with the concave articular surface; and locking the second intermediate component in the locked position relative to the second end plate in response to the relative motion.

36. The method of claim 35, further comprising: detaching the first intermediate component from the first end plate; detaching the second intermediate component from the second end plate; moving a third intermediate component to a locked position relative to the first and second end plates; and locking the third intermediate component into a locked position relative to the first and second end plates in response to the relative motion; wherein the third intermediate component comprises a fusion block configured to substantially prevent relative motion between the first and second end plates.

37. The method of claim 31, further comprising securing a snap fastener to the first intermediate component; wherein locking the first intermediate component in the locked position comprises snapping the snap fastener into engagement with the first end plate.

38. The method of claim 31, wherein locking the first intermediate component in the locked position is carried out after securement of the first end plate to the first vertebral body; wherein locking the first intermediate component in the locked position is carried out without detaching the first end plate from the first vertebral body.

39. The method of claim 31, wherein securing the first end plate to the first vertebral body comprises penetrating the first vertebral body with at least one anchoring member.

40. An intervertebral implant comprising: a first end plate configured to be secured to a first vertebral body; and a first intermediate component that is slidable into engagement with the first end plate along either of at least two selections from the group consisting of a first lateral direction, a second lateral direction different from the first lateral direction, and a posterior direction.

41. The intervertebral implant of claim 40, wherein the first intermediate component is selected from the group consisting of a first bearing surface configured to articulate with a second bearing surface to provide relative motion between the first vertebral body and a second vertebral body, an elastic insert configured to deform to provide motion between the first vertebral body and a second vertebral body, and a rigid insert configured to substantially prevent relative motion between the first vertebral body and a second vertebral body.

42. The intervertebral implant of claim 40, wherein the first intermediate component is detachable from the first end plate to permit replacement of the first intermediate component with a second intermediate component.

43. The intervertebral implant of claim 42, wherein the second intermediate component causes the intervertebral implant to perform a function which is different from a function performed with the first intermediate component.

44. The intervertebral implant of claim 40, further comprising a first retention member configured to be secured to the first end plate independently of the first intermediate component to secure the first intermediate component to the first end plate.

45. The intervertebral implant of claim 44, wherein the first retention member is configured to be inserted into engagement with the first intermediate component.

46. The intervertebral implant of claim 44, wherein the first retention member snaps into securement with the first end plate.

47. The intervertebral implant of claim 44, further comprising a second retention member configured to be secured to the first end plate independently of the first intermediate component and the first retention member to further secure the first intermediate component to the first end plate.

48. The intervertebral implant of claim 47, wherein the first retention member is securable to the first end plate prior to insertion of the first intermediate component along a first direction of the two selections, and the second retention member is securable to the first end plate after the insertion of the first intermediate component, and wherein the second retention member is securable to the first end plate prior to the insertion of the first intermediate component along a second direction of the two selections, and the first retention member is securable to the first end plate after the insertion of the intermediate component.

49. The intervertebral implant of claim 40, further comprising a second end plate configured to be secured to a second vertebral body, wherein the first intermediate component is slidable into engagement with the second end plate along either of at least two selections from the group consisting of the first lateral direction, the second lateral direction, and the posterior direction.

50. An intervertebral implant comprising: a first end plate configured to be secured to a first vertebral body; a first intermediate component configured to engage the first end plate to control or prevent motion of the first vertebral body relative to a second vertebral body; and a first retention member configured to be engageable to the first end plate, wherein the first retention member is slidable into engagement with the first end plate to secure the first intermediate component to the first end plate.

51. The intervertebral implant of claim 50, wherein the first intermediate component is selected from the group consisting of a first bearing surface configured to articulate with a second bearing surface to provide relative motion between the first vertebral body and a second vertebral body, an elastic insert configured to deform to provide motion between the first vertebral body and a second vertebral body, and a rigid insert configured to substantially prevent relative motion between the first vertebral body and a second vertebral body.

52. The intervertebral implant of claim 50, wherein the first intermediate component is detachable from the first end plate to permit replacement of the first intermediate component with a second intermediate component.

53. The intervertebral implant of claim 52, wherein the second intermediate component causes the intervertebral implant to perform a function which is different from a function performed with the first intermediate component.

54. The intervertebral implant of claim 50, further comprising a second retention member configured to be secured to the first end plate independently of the first intermediate component and the first retention member to further secure the first intermediate component to the first end plate.

55. The intervertebral implant of claim 54, wherein the first and second retention members are independently slidable into engagement with the first end plate along either of at least two selections from the group consisting of a first lateral direction, a second lateral direction different from the first lateral direction, and a posterior direction.

56. The intervertebral implant of claim 55, wherein the first retention member is securable to the first end plate prior to insertion of the first intermediate component along a first direction of the two selections, and the second retention member is securable to the first end plate after the insertion of the first intermediate component, and wherein the second retention member is securable to the first end plate prior to the insertion of the first intermediate component along a second direction of the two selections, and the first retention member is securable to the first end plate after the insertion of the intermediate component.

57. The intervertebral implant of claim 50, wherein the first retention member is configured to be inserted into engagement with the first intermediate component.

58. The intervertebral implant of claim 50, wherein the first retention member snaps into securement with the first end plate.

59. The intervertebral implant of claim 50, further comprising a second end plate configured to be secured to a second vertebral body, wherein the first intermediate component is slidable into engagement with the second end plate along either of at least two selections from the group consisting of a first lateral direction, a second lateral direction different from the first lateral direction, and a posterior direction.

60. An intervertebral implant comprising: a first end plate configured to be secured to a first vertebral body; a first intermediate component configured to engage the first end plate to control or prevent motion of the first vertebral body relative to a second vertebral body; and at least two retention members that are activatable independently of each other to secure the first intermediate component to the first end plate.

61. The intervertebral implant of claim 60, wherein the first intermediate component is selected from the group consisting of a first bearing surface configured to articulate with a second bearing surface to provide relative motion between the first vertebral body and a second vertebral body, an elastic insert configured to deform to provide motion between the first vertebral body and a second vertebral body, and a rigid insert configured to substantially prevent relative motion between the first vertebral body and a second vertebral body.

62. The intervertebral implant of claim 60, wherein the first intermediate component is detachable from the first end plate to permit replacement of the first intermediate component with a second intermediate component.

63. The intervertebral implant of claim 60, wherein the second intermediate component causes the intervertebral implant to perform a function which is different from a function performed with the first intermediate component.

64. The intervertebral implant of claim 60, wherein the first intermediate component is slidable into engagement with the first end plate.

65. The intervertebral implant of claim 60, wherein each of the retention members is slidable into engagement with the first end plate along either of at least two selections from the group consisting of a first lateral direction, a second lateral direction different from the first lateral direction, and a posterior direction.

66. The intervertebral implant of claim 60, further comprising a third retention member that is independently activatable to secure the first intermediate component to the first end plate.

67. The intervertebral implant of claim 60, wherein each retention member has an engaged position and a free position relative to the first end plate, and wherein each retention member snaps into engagement in response to motion from the free position to the engaged position.

68. A method for implanting an intervertebral implant, the method comprising: securing a first end plate to a first vertebral body; and sliding a first intermediate component into engagement with the first end plate along either of at least two selections from the group consisting of a first lateral direction, a second lateral direction different from the first lateral direction, and a posterior direction.

69. The method of claim 68, further comprising selecting the first intermediate component from the group consisting of a first bearing surface configured to articulate with a second bearing surface to provide relative motion between the first vertebral body and a second vertebral body, an elastic insert configured to deform to provide motion between the first vertebral body and a second vertebral body, and a rigid insert configured to substantially prevent relative motion between the first vertebral body and a second vertebral body.

70. The method of claim 69, wherein the first intermediate component is replaceable, wherein replacing the first intermediate component comprises detaching the first intermediate component from the first end plate and engaging a second intermediate component with the first end plate.

71. The method of claim 70, wherein engaging the second intermediate component causes the intervertebral implant to perform a function which is different than the function performed with the first intermediate component.

72. The method of claim 68, further comprising securing at least one retention member to the first end plate independently of the first intermediate component, wherein securing the retention member secures the first intermediate component to the first end plate.

73. The method of claim 72, further comprising inserting the first retention member with the first intermediate component.

74. The method of claim 72, further comprising snapping the first retention member to the first end plate to secure the first retention member to the first end plate.

75. The method of claim 72, further comprising securing a second retention member to the first end plate independently of the first intermediate component, wherein securing the second retention member further secures the first intermediate component to the first end plate.

76. The method of claim 75, further comprising selecting from a group including securing the first retention member to the first end plate prior to inserting the first intermediate component along a first direction of the two selections, then securing the second retention member to the first end plate after inserting the first intermediate component, and securing the second retention member to the first end plate prior to inserting the first intermediate component along a second direction of the two selections, then securing the first retention member to the first end plate after the insertion of the first intermediate component.

77. The method of claim 68, further comprising securing a second end plate to a second vertebral body, and sliding the first intermediate component into engagement with the second end plate along either of at least two selections from the group consisting of the first lateral direction, the second lateral direction, and the posterior direction.

78. A method for implanting an intervertebral implant, the method comprising: securing a first end plate to a first vertebral body; engaging a first intermediate component with the first end plate to control or prevent motion of the first vertebral body relative to a second vertebral body; and sliding a first retention member into engagement with the first end plate to secure the first intermediate component to the first end plate.

79. The method of claim 78, further comprising selecting the first intermediate component from the group consisting of a first bearing surface configured to articulate with a second bearing surface to provide relative motion between the first vertebral body and the second vertebral body, an elastic insert configured to deform to provide motion between the first vertebral body and the second vertebral body, and a rigid insert configured to substantially prevent relative motion between the first vertebral body and the second vertebral body.

80. The method of claim 78, wherein the first intermediate component is replaceable, wherein replacing the first intermediate component comprises detaching the first intermediate component from the first end plate and engaging a second intermediate component with the first end plate.

81. The method of claim 80, wherein engaging the second intermediate component causes the intervertebral implant to perform a function which is different than the function performed with the first intermediate component.

82. The method of claim 78, further comprising securing a second retention member to the first end plate independently of the first intermediate component and the first retention member, to further secure the first intermediate component to the first end plate.

83. The method of claim 82, further comprising sliding the first and second retention members independently into engagement with the first end plate along either of at least two selections from the group consisting of a first lateral direction, a second lateral direction different from the first lateral direction, and a posterior direction.

84. The method of claim 83, further comprising selecting from a group including securing the first retention member to the first end plate prior to inserting the first intermediate component along a first direction of the two selections, then securing the second retention member to the first end plate after inserting the first intermediate component, and securing the second retention member to the first end plate prior to inserting the first intermediate component along a second direction of the two selections, then securing the first retention member to the first end plate after the insertion of the first intermediate component.

85. The method of claim 78, further comprising inserting the first retention member with the first intermediate component.

86. The method of claim 78, further comprising snapping the first retention member to the first end plate to secure the first retention member to the first end plate.

87. The method of claim 78, further comprising securing a second end plate to the second vertebral body, and sliding the first intermediate component into engagement with the second end plate along either of at least two selections from the group consisting of a first lateral direction, a second lateral direction different from the first lateral direction, and a posterior direction.

88. A method for implanting a device within an intervertebral space, the method comprising: securing a first end plate to a first vertebral body; engaging a first intermediate component with the first end plate to control or prevent motion of the first vertebral body relative to a second vertebral body; and activating at least two retention members independently of each other to secure the first intermediate component to the first end plate.

89. The method of claim 88, further comprising selecting the first intermediate component from the group consisting of a first bearing surface configured to articulate with a second bearing surface to provide relative motion between the first vertebral body and the second vertebral body, an elastic insert configured to deform to provide motion between the first vertebral body and the second vertebral body, and a rigid insert configured to substantially prevent relative motion between the first vertebral body and the second vertebral body.

90. The method of claim 88, wherein the first intermediate component is replaceable, wherein replacing the first intermediate component comprises detaching the first intermediate component from the first end plate and engaging a second intermediate component with the first end plate.

91. The method of claim 90, wherein engaging the second intermediate component causes the intervertebral implant to perform a function which is different than the function performed with the first intermediate component.

92. The method of claim 88, further comprising sliding the first intermediate component into engagement with the first end plate.

93. The method of claim 88, further comprising sliding each of the retention members into engagement with the first end plate along either of at least two selections from the group consisting of a first lateral direction, a second lateral direction different from the first lateral direction, and a posterior direction.

94. The method of claim 88, further comprising independently activating a third retention member to further secure the first intermediate component to the first end plate.

95. The method of claim 88, further comprising snapping each retention member in response to motion from a free position to an engaged position relative to the first end plate.

96. An intervertebral implant delivery system comprising: a first end plate holder comprising a first end and a second end; a second end plate holder comprising a first end and a second end; and a pivot assembly that couples the first and second end plate holders together; wherein each of the first ends is shaped to retain an end plate of an intervertebral implant to facilitate insertion of the end plate into an intervertebral space; wherein the pivot assembly is configured to permit actuation of the second ends while the first ends are in the intervertebral space to permit adjustment of a thickness and an angulation of a space between the end plates.

97. The intervertebral implant delivery system of claim 96, wherein the angulation comprises an anterior-posterior angulation, wherein the end plate holder is adjustable interoperatively from a lateral approach to determine the angulation.

98. The intervertebral implant delivery system of claim 96, wherein at least one of the first end plate holder, the second end plate holder, and the pivot assembly comprises a support feature attachable to a stationary frame to keep the pivot assembly substantially stationary.

99. The intervertebral implant delivery system of claim 98, further comprising the stationary frame, wherein the support feature comprises a ball extending from the pivot assembly to permit polyaxial positioning of the pivot assembly relative to the stationary frame.

100. The intervertebral implant delivery system of claim 961, further comprising a spike guard shaped to protect a first vertebral body adjacent to the intervertebral space from contact with at least one spike extending from the intervertebral implant.

101. The intervertebral implant delivery system of claim 96, further comprising a first spacer insertable between the first and second end plate holders to urge the end plates toward first and second vertebral bodies, respectively, wherein the first and second vertebral bodies bound the intervertebral space.

102. The intervertebral implant delivery system of claim 101, further comprising a second spacer insertable between the first and second end plate holders to further urge the end plates toward the first and second vertebral bodies.

103. The intervertebral implant delivery system of claim 96, further comprising an intermediate component holder configured to hold a first intermediate component and to facilitate insertion of the first intermediate component into the space between the end plates.

104. The intervertebral implant delivery system of claim 103, wherein the first intermediate component comprises a first articulating bearing, wherein the intermediate component holder is further configured to hold a second articulating bearing and to retain the first and second articulating bearings for simultaneous insertion into the space between the end plates.

105. The intervertebral implant delivery system of claim 96, further comprising a compressor configured to be actuated to urge the end plates together to cause the end plates to snap into engagement with one or more intermediate components positioned between the end plates.

106. An intervertebral implant delivery system comprising: a first end plate holder configured to deliver a first end plate to an intervertebral space from any approach selected from the group consisting of an anterior approach and a lateral approach; and an intermediate component holder configured to deliver a first intermediate component securable to the first end plate to the intervertebral space from any approach selected from the group consisting of an anterior approach and a lateral approach.

107. The intervertebral implant delivery system of claim 106, further comprising a support feature attachable to a stationary frame to keep the pivot assembly substantially stationary.

108. The intervertebral implant delivery system of claim 106, further comprising: a second end plate holder configured to deliver a second end plate to the intervertebral space; and a first spacer insertable between the first and second end plate holders to urge the end plates toward first and second vertebral bodies, respectively, wherein the first and second vertebral bodies bound the intervertebral space.

109. The intervertebral implant delivery system of claim 106, wherein the first intermediate component comprises a first articulating bearing, wherein the intermediate component holder is further configured to hold a second articulating bearing and to retain the first and second articulating bearings for simultaneous insertion into the intervertebral space.

110. The intervertebral implant delivery system of claim 106, wherein the first end plate holder comprises a first end comprising an expandable retention interface configured to engage any of a plurality of slots on a periphery of the first end plate to couple the first end plate to the first end.

111. An intervertebral implant delivery system comprising: a first end plate holder configured to deliver a first end plate to an intervertebral space; a second end plate holder configured to deliver a second end plate to the intervertebral space; and an intermediate component holder configured to deliver first and second articulating bearings to the intervertebral space simultaneously and independently of delivery of the first and second end plates to the intervertebral space.

112. The intervertebral implant delivery system of claim 111, wherein the first end plate holder, second end plate holder, and intermediate component are configured to deliver the first and second articulating bearing surfaces while holding the first and second end plates substantially stationary.

113. The intervertebral implant delivery system of claim 111, further comprising a pivot assembly that couples the first and second end plate holders together, wherein at least one of the first end plate holder, the second end plate holder, and the pivot assembly comprises a support feature attachable to a stationary frame to keep the pivot assembly substantially stationary.

114. The intervertebral implant delivery system of claim 111, further comprising a first spacer insertable between the first and second end plate holders to urge the end plates toward first and second vertebral bodies, respectively, wherein the first and second vertebral bodies bound the intervertebral space.

115. The intervertebral implant delivery system of claim 111, wherein the intermediate component holder is configured to deliver the first and second articulating bearings to the intervertebral space from any approach selected from the group consisting of an anterior approach and a lateral approach.

116. An intervertebral implant delivery system comprising: a compression instrument comprising a first end and a second end; wherein, in response to actuation of the second end, the first end exerts compressive force in a cephalad-caudal direction on first and second end plates of an intervertebral implant within an intervertebral space to secure the end plates to an intermediate component positioned between the end plates.

117. The intervertebral implant delivery system of claim 116, wherein the end plates are configured to be anchored to first and second vertebral bodies bounding the intervertebral space; wherein the first end is configured to exert the compressive force on the end plates without removing the end plates from anchorage to the first and second vertebral bodies.

118. The intervertebral implant delivery system of claim 116, wherein the first end comprises a pair of tongs; wherein the second end comprises a handle and a compression lever that is movable by hand relative to the handle to urge the tongs to move toward each other.

119. The intervertebral implant delivery system of claim 116, further comprising: a first end plate holder configured to deliver the first end plate to an intervertebral space; a second end plate holder configured to deliver the second end plate to the intervertebral space; and a pivot assembly that couples the first and second end plate holders together.

120. The intervertebral implant delivery system of claim 119, further comprising an intermediate component holder configured to deliver a first intermediate component securable to the end plates to the intervertebral space.

121. An intervertebral implant delivery system comprising: a removal instrument comprising a first end and a second end; wherein, in response to actuation of the second end, the first end exerts force in a cephalad-caudal direction on first and second end plates of an intervertebral implant within an intervertebral space to detach an intermediate component from the first and second end plates.

122. The intervertebral implant delivery system of claim 121, wherein the end plates are configured to be anchored to first and second vertebral bodies bounding the intervertebral space; wherein the first end is configured to exert the force on the end plates without removing the end plates from anchorage to the first and second vertebral bodies.

123. The intervertebral implant delivery system of claim 121, wherein the second end comprises a handle and the first end comprises a pair of prongs shaped to slide between the end plates to pry the end plates apart.

124. The intervertebral implant delivery system of claim 121, further comprising: a first end plate holder configured to deliver the first end plate to an intervertebral space; a second end plate holder configured to deliver the second end plate to the intervertebral space; and a pivot assembly that couples the first and second end plate holders together.

125. The intervertebral implant delivery system of claim 124, further comprising an intermediate component holder configured to deliver a first intermediate component securable to the end plates to the intervertebral space.

126. A method for delivering an intervertebral implant, the method comprising: retaining a first end plate of an intervertebral implant with a first end of a first end plate holder; retaining a second end plate of the intervertebral implant with a first end of a second end plate holder coupled to the first end plate holder by a pivot assembly; inserting the first end plate into an intervertebral space; inserting the second end plate into the intervertebral space; and actuating second ends of the first and second end plate holders to adjust at least one of a thickness and an angulation of a space between the end plates.

127. The method of claim 126, wherein the angulation comprises an anterior-posterior angulation, wherein actuating the second ends comprises actuating the second ends from a lateral approach to deteπnine the angulation.

128. The method of claim 126, further comprising attaching at least one of the first end plate holder, the second end plate holder, and the pivot assembly to a stationary frame to keep the pivot assembly substantially stationary.

129. The method of claim 126, further comprising inserting a first spacer between the first and second end plate holders to urge the end plates toward first and second vertebral bodies, respectively, wherein the first and second vertebral bodies bound the intervertebral space.

130. The method of claim 126, further comprising: retaining a first intermediate component with an intermediate component holder; and inserting the first intermediate component into the space between the end plates.

131. The method of claim 130, wherein inserting the intermediate component into the space between the end plates comprises: selecting an approach from the group consisting of a lateral approach and an anterior approach; and inserting the first intermediate component into the space along the selected approach.

132. The method of claim 130, further comprising: detaching a second intermediate component from the first and second end plates; and removing the second intermediate component from the space prior to insertion of the first intermediate component into the space.