WO2009064787A2

WO2009064787A2 - Adjustable height intervertebral implant

Info

Publication number: WO2009064787A2
Application number: PCT/US2008/083240
Authority: WO
Inventors: Joshua Mcmanus; Dominique Messerli; David S. Rathbun
Original assignee: Synthes (U.S.A.); Synthes Gmbh
Priority date: 2007-11-12
Filing date: 2008-11-12
Publication date: 2009-05-22
Also published as: WO2009064787A3

Abstract

An adjustable height intervertebral implant (10) for total, partial, or nucleus replacement of an intervertebral disc space includes an upper endplate (20) for contacting a first vertebra, a lower endplate (30) for contacting a second vertebra and a mechanism (50) for moving the upper endplate with respect to the lower endplate so that once the implant is inserted into an intervertebral disc space, the implant can be expandable from a first insertion configuration to a second expanded configuration. The mechanism for moving the upper endplate with respect to the lower endplate preferably includes a plurality of telescopic gear sets (52a, 52b). The telescopic gear sets are directly connected to one another.

Description

TITLE OF THE INVENTION ADJUSTABLE HEIGHT INTERVERTEBRAL IMPLANT

CROSS-REFERNCE TO RELATED APPLICATIONS

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

60/987,314, filed on November 12, 2007, entitled "EXPANDABLE INTERBODY SPACER," the contents of which is incorporated in its entirety by reference herein.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to an intervertebral implant, and, more particularly, to an adjustable height intervertebral implant.

[0003] Degenerative disc disease or degeneration of a vertebral body often results in a loss of disc height, which in turn can cause facet and nerve impingement, among other things. One standard of care is to replace the damaged intervertebral disc with an intervertebral implant or a damaged portion or an entire vertebral body with an intervertebral implant. That is, an intervertebral implant may be inserted into the intervertebral disc space of two neighboring vertebral bodies or into the space created by removal of portions of or the entire vertebral body after removal of damaged portions of the spine. Preferably, the intervertebral implant restores the spine, as much as possible to a natural state, i.e. to restore the original height of the intervertebral disc and thus the original distance between the two neighboring or adjacent vertebral bodies or vertebral bodies in various levels of the spine. It would be desirable to construct an intervertebral implant that is relatively simple to insert into a patient's spine at a relatively small size and is able to expand to restore the original height of the removed spinal material or to a height desired by a surgeon. BRIEF SUMMARY OF THE INVENTION

[0004] Briefly stated, a preferred embodiment of the present invention is directed to an adjustable height intervertebral implant for total, partial, or nucleus replacement of an intervertebral disc space or replacement of an intervertebral disc. The adjustable height intervertebral implant may be sized and configured as a posterior lumbar interbody fusion (PLIF) implant, a transforaminal posterior lumber interbody fusion (T-PLIF) implant, etc. and may be configured for implantation via an anterior approach, a lateral approach, a posterior approach, etc.

[0005] The adjustable height intervertebral implant preferably includes an upper endplate for contacting a first vertebra, a lower endplate for contacting a second vertebra and a mechanism for moving the upper endplate with respect to the lower endplate so that once the implant is inserted into an intervertebral disc space or generally into a space created by removal of damaged portions of the spine, the implant can be expandable from a first insertion configuration to a second expanded configuration. In this manner, the adjustable height intervertebral implant can be inserted into the intervertebral disc space in the first insertion configuration through, for example, a minimally invasive procedure or small incision. Thereafter, the adjustable height intervertebral implant can be expanded to the second expanded configuration. Expanding the implant from the first insertion configuration to the second expanded configuration increases the overall height of the implant from a smaller, insertion height Hi to a larger, expanded height H₂ and provides parallel and/or lordotic intervertebral distraction.

[0006] In one preferred embodiment of the present invention, the mechanism for moving the upper and lower endplates with respect to one another includes a plurality of interconnected telescopic gear sets. More preferably, the plurality of telescopic gear sets is directly coupled to one another so that no intermediate gear or member is required. Each telescopic gear set preferably includes an outer gear, a first intermediate gear, a second intermediate gear and an inner gear. The outer gear includes an external thread for engaging an external thread formed on an outer gear of an adjacent telescopic gear set. The outer gear also includes an internal thread for engaging an external thread formed on the first intermediate gear. A second intermediate gear is press-fit into the outer gear and includes an internal gear that meshes with an external gear on an inner gear.

[0007] In another preferred embodiment of the present invention, the plurality of telescopic gear sets may be interconnected via a pinion gear. Each telescopic gear set preferably includes an outer gear, an intermediate gear and an inner gear so that rotation of the outer gear causes the intermediate and inner gears to move relative thereto. The outer gear includes an external thread for threadably engaging the pinion gear and an internal thread for engaging an external thread formed on the intermediate gear, which includes an internal thread for engaging an external thread formed on the inner gear. [0008] In yet another preferred embodiment, the upper and lower endplates may be hingeably connected via one or more links so that movement of the upper endplate with respect to the lower end plate increases a height of the implant. The upper endplate and the lower endplate each include a plurality of ridges extending therefrom so that in a second expanded configuration the plurality of ridges extending from the upper endplate engage the plurality of ridges extending from the lower endplate to securely maintain the height of the implant in the second expanded configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The foregoing summary, as well as the following detailed description of the preferred embodiments of the application, will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the adjustable height intervertebral implant of the present application, there are shown in the drawings preferred embodiments. It should be understood, however, that the application is not limited to the precise arrangements and instrumentalities shown. In the drawings:

[0010] Fig. IA illustrates an exploded, perspective view of an adjustable height intervertebral implant according to a first preferred embodiment of the present application;

[0011] Fig. IB illustrates a side elevational, cross-sectional view of the adjustable height intervertebral implant shown in Fig. IA taken along line IB-IB of Fig. IA, wherein the implant is in a first insertion configuration;

[0012] Fig. 1C illustrates a side elevational, cross-sectional view of the adjustable height intervertebral implant shown in Fig. IA taken along line 1C-1C of Fig. IA, wherein the implant is in a second expanded configuration;

[0013] Fig. 2A illustrates a side elevational view of an adjustable height intervertebral implant according to a second preferred embodiment of the present application;

[0014] Fig. 2B illustrates a side elevational, cross-sectional view of the adjustable height intervertebral implant shown in Fig. 2A taken along line 2B-2B of Fig. 2A; [0015] Fig. 3 A illustrates a side perspective view of an adjustable height intervertebral implant according to a third preferred embodiment of the present application and in a first insertion configuration;

[0016] Fig. 3B illustrates a side perspective view of the adjustable height intervertebral implant shown in Fig. 3A and in a second expanded configuration;

[0017] Fig. 4A illustrates a side perspective view of an adjustable height intervertebral implant according to a fourth preferred embodiment of the present application and in a first insertion configuration;

[0018] Fig. 4B illustrates a side perspective view of the adjustable height intervertebral implant shown in Fig. 4A and in a second expanded configuration;

[0019] Fig. 5 A illustrates a side perspective view of an adjustable height intervertebral implant according to a fifth preferred embodiment of the present application and in a first insertion configuration;

[0020] Fig. 5B illustrates a side perspective view of the adjustable height intervertebral implant shown in Fig. 5A and in a second expanded configuration;

[0021] Fig. 6A illustrates a side elevational, cross-sectional view of an adjustable height intervertebral implant according to a sixth preferred embodiment of the present application and in a first insertion configuration;

[0022] Fig. 6B illustrates a side elevational, cross-sectional view of the adjustable height intervertebral implant shown in Fig. 6A and in a second expanded configuration;

[0023] Fig. 7A illustrates a side elevational, cross-sectional view of an adjustable height intervertebral implant according to a seventh preferred embodiment of the present invention; [0024] Fig. 7B illustrates a side elevational, cross-sectional view of the adjustable height intervertebral implant shown in Fig. 7A and in a second expanded configuration;

[0025] Fig. 8A illustrates an exploded, perspective view of an adjustable height intervertebral implant according to an eighth preferred embodiment of the present invention;

[0026] Fig. 8B illustrates a cross-sectional view of the adjustable height intervertebral implant shown in Fig. 8 A, take along line 8B-8B of Fig. 8 A, and in a second expanded configuration;

[0027] Fig. 9A illustrates a top perspective view of an adjustable height intervertebral implant according to a ninth preferred embodiment of the present application and in a first insertion configuration;

[0028] Fig. 9B illustrates a top perspective view of the adjustable height intervertebral implant shown in Fig. 9A and in a second expanded configuration;

[0029] Fig. 9C illustrates a side elevational, cross-sectional view of the adjustable height intervertebral implant shown in Fig. 9A, taken along line 9C-9C of Fig. 9 A;

[0030] Fig. 1OA illustrates a side elevational, cross-sectional view of an adjustable height intervertebral implant according to a tenth preferred embodiment of the present application and in a first insertion configuration;

[0031] Fig. 1OB illustrates a side elevational, cross-sectional view of the adjustable height intervertebral implant shown in Fig. 1OA and in a second expanded configuration; [0032] Fig. 1OC illustrates a side elevational, cross-sectional view of an alternate embodiment of the adjustable height intervertebral implant shown in Fig. 1OA and in the first insertion configuration;

[0033] Fig. 1OD illustrates a side elevational, cross-sectional view of the alternate embodiment of the adjustable height intervertebral implant shown in Fig. 1OC and in the second expanded configuration;

[0034] Fig. 1 IA illustrates a side elevational, cross-sectional view of an adjustable height intervertebral implant according to an eleventh preferred embodiment of the present application and in a first insertion configuration;

[0035] Fig. 1 IB illustrates a side elevational, cross-sectional view of the adjustable height intervertebral implant shown in Fig. 1 IA and in a second expanded configuration;

[0036] Fig. 12 illustrates a side elevational, cross-sectional view of an adjustable height intervertebral implant according to a twelfth preferred embodiment of the present application;

[0037] Fig. 13A illustrates a side elevational, cross-sectional view of an adjustable height intervertebral implant according to a thirteen preferred embodiment of the present application and in a first insertion configuration; and

[0038] Fig. 13B illustrates a side elevational, cross-sectional view of the adjustable height intervertebral implant shown in Fig. 13A and in a second expanded configuration. DETAILED DESCRIPTION OF THE INVENTION

[0039] Certain terminology is used in the following description for convenience only and is not limiting. The words "right", "left", "top" and "bottom" designate directions in the drawings to which reference is made. The words "inwardly" and "outwardly" refer to directions toward and away from, respectively, the geometric center of the device and designated parts thereof. The words, "anterior", "posterior", "superior", "inferior" and related words and/or phrases designate preferred positions and orientations in the human body to which reference is made and are not meant to be limiting. The terminology includes the above-listed words, derivatives thereof and words of similar import.

[0040] Certain exemplary embodiments of the invention will now be described with reference to the drawings. In general, such embodiments relate to an adjustable height intervertebral implant 10, 10', 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200 ("10-1200"). More specifically, the present application is directed to an adjustable height intervertebral implant 10-1200 for total or partial disc or vertebral body V replacement or for nucleus replacement of a spinal disc. The adjustable height intervertebral implant 10-1200 of preferred embodiments of the present application will be described in connection with spinal disc replacement herein, but one of ordinary skill in the art will understand that the system as well as the components thereof may be used for replacement of tissue in other parts of the body including, for example, knee, hip, shoulder, finger or other joint replacement or for bone augmentation. [0041] As will be described in greater detail below, the adjustable height intervertebral implant 10-1200 of the preferred embodiments is preferably used for intervertebral support of the spine for patients that require interbody fusion at one or more levels. The adjustable height intervertebral implant 10-1200 may be implanted by a surgeon into the patient's body in a compressed, non-expanded or first insertion configuration, thereby allowing a smaller incision than would be necessary for implantation of a non-expandable intervertebral implant. Implantation of the adjustable height intervertebral implant 10-1200 in the first insertion configuration may also make it easier to insert the implant 10-1200 past a buildup of posterior osteophites or other structures that may inhibit a surgeon's access to the spine. The adjustable height intervertebral implant 10-1200 allows surgeons to implant a larger intervertebral implant in the disc space, without having to do an excessive amount of boney resection and soft tissue retraction. Once the implant 10-1200 is inserted into the disc space, the implant 10-1200 may be expanded to a second expanded configuration to provide parallel and/or lordotic intervertebral distraction. That is, the adjustable height intervertebral implant 10-1200 may be implanted by a surgeon into the patient's body in a compressed, non- expanded or first insertion configuration wherein the implant 10-1200 has a height H₁. Thereafter, once inserted into the disc space, the implant 10-1200 may be expanded to a second expanded configuration wherein the implant 10-1200 has a height H₂, H₂ being larger than H₁.

[0042] As will be described in greater detail below, the adjustable height intervertebral implant 10-1200 preferably includes an upper endplate 20, 20', 220, 320, 420, 520, 620, 720, 820, 920, 1020, 1120, 1220 ("20-1220") for contacting a first or superior vertebra V, a lower endplate 30, 30', 230, 330, 430, 530, 630, 730, 830, 930, 1030, 1130, 1230 ("30-1230") for contacting a second or inferior vertebra V and a mechanism 50, 50', 250, 350, 450, 550, 650, 750, 850, 950, 1050, 1150, 1250 ("50- 1250") for coupling and moving the upper and lower endplates 20-1220, 30-1230 with respect to one another. The mechanism 50-1250 enables the upper and lower endplates 20-1220, 30-1230 to expand in the cranial/caudal direction or generally away from each other toward the second expanded configuration when the implant 10-1200 is inserted into the disc space.

[0043] The adjustable height intervertebral implant 10-1200 may, for example, fill the entire intervertebral disc space to replace the entire intervertebral disc. Alternatively, a plurality of adjustable height intervertebral implants 10-1200 may be used to fill the intervertebral disc space. For example, two or more smaller adjustable height intervertebral implant 10-1200 may be used to fill the intervertebral disc space. Alternatively, the adjustable height intervertebral implant 10-1200 may be sized and configured to only partially replace an intervertebral disc space, such as for example, to replace a nucleus.

[0044] Referring to Figs. IA- 1C, the adjustable height intervertebral implant 10 of a first preferred embodiment preferably includes an upper endplate 20 for contacting a first, superior vertebra V, a lower endplate 30 for contacting a second, inferior vertebra V and a mechanism 50 for moving the upper and lower endplates 20, 30 with respect to one another. The implant 10 may also include an optional locking plate 40 for securing the mechanism 50 to one of the endplates 20, 30 (shown as the lower endplate 30). Preferably, the locking plate 40 is sized and configured to hold the mechanism 50 for moving the upper and lower endplates 20, 30 in a fixed position relative to one of the endplates 20, 30, preferably the lower endplate 30, while permitting the mechanism 50 to rotate relative thereto. Once activated, the mechanism 50 will preferably move the endplates 20, 30 apart or pull them towards one another, depending upon how the surgeon manipulates the mechanism 50.

[0045] In the first preferred embodiment, the mechanism 50 is comprised of a plurality of interconnected, telescopic gear sets 52. The adjustable height intervertebral implant 10 of the first preferred embodiment includes two parallel telescopic gear sets 52a, 52b that move the upper and lower endplates 20, 30 relative to each other. Alternatively, as will be appreciated by one of ordinary skill in the art, the adjustable height intervertebral implant 10 of the first preferred embodiment may include any number of telescopic gear sets 52 such as, for example, 1, 3, or more. [0046] Each of the telescopic gear sets 52a, 52b includes a plurality of individual gears 54a, 54b, 54c so that rotation of the telescopic gear sets 52a, 52b causes the plurality of individual gears 54a, 54b, 54c to move relative to each another. As shown, each of the telescopic gear sets 52a, 52b preferably includes three individual gears 54a, 54b, 54c. Alternatively, as will be appreciated by one of ordinary skill in the art, the telescopic gear sets 52a, 52b may be comprised of any number of individual gears such as, for example, 2, 4, or more. That is, each of the telescopic gear sets 52a, 52b preferably includes three individual gears 54a, 54b, 54c sized and configured to be housed one inside the other. Each of the individual gears 54a, 54b, 54c are preferably interconnected via a threaded engagement. For example, an outer gear 54a preferably includes an internal thread for engaging an external thread formed on an intermediate gear 54b, which includes an internal thread for engaging an external thread formed on an inner gear 54c so that rotation of the outer individual gear 54a causes the intermediate gear 54b and the inner gear 54c to telescope, which in turn causes the upper and lower endplates 20, 30 to move with respect to one another. Alternatively, the mechanism 50 may be any other type of gears that drive movement of the upper and lower endplates 20, 30 relative to each other.

[0047] Each one of the individual gears 54a, 54b, 54c preferably includes a torque stopper 56 so that the individual gears 54a, 54b, 54c are prevented from separating from one another in order to prevent accidental disassembly.

[0048] The telescopic gear sets 52a, 52b may be directly or indirectly linked to one another by any means including but not limited to via an interconnecting gear such as, for example, a pinion gear 60 so that, in use, when more than one of the telescopic gear set 52a, 52b is used, rotation of one of the telescopic gear sets 52a, 52b rotates the interconnecting or pinion gear 60 which, in turn, rotates the other one of the telescopic gear sets 52a, 52b. Alternatively, the telescopic gear sets 52a, 52b may be linked by any other means including but not limited to, for example, a chain or belt or the telescopic gear sets 52a, 52b may be configured to rotate independently of one another. [0049] As best shown in Fig. IA, at least one of the telescopic gear sets 52a, 52b is preferably sized and configured to contact and engage an instrument 75 for rotating the telescopic gear sets 52a, 52b. The instrument 75 preferably includes an external thread 76 for engaging the external thread formed on the outer gear 54a of one of the telescopic gear sets 52a, 52b. The upper and lower endplates 20, 30 are preferably sized and configured to allow the instrument 75 to access and activate the mechanism 50 for moving the upper and lower endplates 20, 30 with respect to one another. Alternatively, the instrument 75 may be, for example, a motor that is located within the implant 10 and activated via a remote control.

[0050] The mechanism 50 of the first preferred embodiment may be fixed or otherwise secured to either of the endplates 20, 30 by the locking plate 40. The locking plate 40 is sized and configured to hold the telescopic gear sets 52a, 52b in place while permitting the gear sets 52a, 52b to rotate. Alternatively, any attaching method that does not restrict the functionality of the gear sets 52a, 52b may be used. [0051] In use, after the adjustable height intervertebral implant 10 is inserted into the desired intervertebral disc space in the first insertion configuration, the instrument 75 may be inserted into the interior space between the upper and lower endplates 20, 30 for engaging and rotating one of the telescopic gear sets 52a, 52b. Rotation of the instrument 75 causes the outer individual gear 54a of the telescopic gear set 52 to rotate, which in turn causes the intermediate and inner gears 54b, 54c to telescope with respect to the outer gear 54a and with respect to each other, which in turn causes the upper endplate 20 to move away from the lower endplate 30. In this manner, the adjustable height intervertebral implant 10 can be inserted into the intervertebral disc space in the first insertion configuration (shown in Fig. IB) through, for example, a minimally invasive procedure or small incision. Thereafter, the adjustable height intervertebral implant 10 can be activated, causing the implant 10 to expand to the second expanded configuration (Fig. 1C). Expanding the implant 10 from the first insertion configuration to the second expanded configuration increases the overall height of the implant 10 from a smaller, insertion height Hi to a larger, expanded height H₂ and distracts the adjacent vertebral bodies. [0052] Referring to Figs. 2A and 2B, an adjustable height intervertebral implant

10' in accordance with a second preferred embodiment includes the upper endplate 20' for contacting a first vertebra V and the lower endplate 30' for contacting a second vertebra V. In this second preferred embodiment, the mechanism 150 for moving the upper and lower endplates 20', 30' includes a pair of interconnected telescopic gear sets 152 wherein the telescopic gear sets 152 are directly coupled to one another. The interconnected telescopic gear sets 152 preferably do not incorporate the interconnecting pinion gear 60 or other similar structure, as is included in the first preferred embodiment. In the second preferred embodiment, each of first and second telescopic gear sets 152 preferably includes four individual gears 154a, 154b, 154c, 154d. Alternatively, as will be appreciated by one of ordinary skill in the art, the individual gears 154a, 154b, 154c, 154d may be comprised of any number of individual gears such as, for example, 2, 3, or more. The individual gears 154a, 154b, 154c, 154d are preferably arranged so that an outer gear 154a is externally threaded so that rotation of the externally threaded outer gear 154a rotates an opposite handed, externally threaded outer gear 154a of an adjacent one of the telescopic gear sets 152. In addition, the outer gear 154a preferably also includes an internal thread for engaging an external thread formed on a first intermediate gear 154b. The first intermediate gear 154b is preferably fixed to the lower endplate 30' such that the outer gear 154a rotates relative to the first intermediate gear 154b and lower endplate 30 during expansion and/or contraction. A second intermediate gear 154c is preferably press-fit into an internal bore of the outer gear 154a and includes an internal thread that meshes with an external thread on an inner gear 154d. The outer gear 154a and second intermediate gear 154c preferably define a generally cylindrically-shaped groove 151 therebetween that receives the first intermediate gear 154b therein in the first insertion configuration and assists in guiding the rotation and translation of the outer and second intermediate gears 154a, 154c relative to the first intermediate gear 154b. The internal thread on the second intermediate gear 154c preferably engages the external thread formed on an inner gear 154d to drive the translation of the inner gear 154d as the outer and second intermediate gears 154a, 154c rotate. Thus, in use, rotation of the outer gear 154a causes the second intermediate gear 154c to rotate therewith due to the press-fit of the second intermediate gear 154c into the outer gear 154a. Rotation of the outer gear 154a in a first direction causes the internal thread on the outer gear 154a and the external thread on the first intermediate gear 154b to drive the external gear 154a and the second intermediate gear 154b away from the lower endplate 30'. This rotation further causes the internal thread and external thread on the second intermediate gear 154c and the inner gear 154d to urge the inner gear 154d away from the lower endplate 30' and the outer and second intermediate gears 154a, 154c. The inner gear 154d is preferably fixed to the upper endplate 20'. Accordingly, the upper and lower endplates 20', 30' preferably separate away from the outer and second intermediate gears 154a, 154c as the outer gear 154a is driven in the first direction. In contrast, if the outer gear 154a is driven in an opposite, second direction, the second intermediate and outer gears 154c, 154a draw the inner gear 154d and the first intermediate gear 154b toward each other and the upper and lower endplates 20', 30' toward the first insertion configuration (Fig. 2A). [0053] In use, after the adjustable height intervertebral implant 10' of the second preferred embodiment is inserted into the desired intervertebral disc space in the first insertion configuration, the instrument 75 may be inserted into an interior space between the endplates 20', 30' to engage and rotate one of the telescopic gear sets 152 by engaging the external threads on the outer gear 154a. Rotation of the instrument 75 to drive the outer gear 154a in the first direction causes the outer individual gear 154a of both of the telescopic gear sets 152 to rotate, which in turn causes the first intermediate gear 154b and the inner gear 154d to telescope with respect to the outer gear 154a and the second intermediate gear 154c, which in turn causes the upper endplate 20' to move with respect to the lower endplate 30'. In this manner, the adjustable height intervertebral implant 10' can be inserted into the intervertebral disc space in the first insertion configuration (Fig. 2A) through, for example, a minimally invasive procedure or small incision. Thereafter, the adjustable height intervertebral implant 10' can be activated, causing the implant 10' to expand to the second expanded configuration (shown in Fig. 2B). Expanding the implant 10' from the first insertion configuration to the second expanded configuration preferably increases the overall height of the implant 10' from a smaller, insertion height Hi to a larger, expanded height H₂ and distracts the adjacent vertebral bodies V. The intervertebral implant 10' of the second preferred embodiment preferably expands the upper and lower endplates 20', 30' symmetrically in height relative to the outer and second intermediate gears 154a, 154c such that the implant 10' may be utilized to distract the adjacent vertebra V following insertion. [0054] The outer gear 154a and the second intermediate gear 154c may be integrally formed as opposed to the second intermediate gear 154c being press-fit into the outer gear 154. For example, the outer and second intermediate gears 154a, 154c may be constructed of an injection molded polymeric material to form a one-piece gear. [0055] Referring to Figs. 3A and 3B, an adjustable height intervertebral implant

200 of a third preferred embodiment includes an upper endplate 220 for contacting a first vertebra V, a lower endplate 230 for contacting a second vertebra V and a mechanism 250 for moving the upper and lower endplates 220, 230 with respect to one another. In this embodiment, the mechanism 250 for moving the upper and lower endplates 220, 230 preferably includes a pin 252 rototably coupled to the upper and lower endplates 220, 230 proximate one end of the upper and lower endplates 220, 230. The pin 252 is preferably located at the posterior end of the implant 200, although, it is envisioned that the pin 252 may be located at the anterior end of the endplates 220, 230. In use, movement of the upper endplate 220 with respect to the lower endplate 230 causes the upper endplate 220 to rotate with respect to the lower endplate 230 about the pin 252 from a first insertion configuration (Fig. 3A) to a second expanded configuration (Fig. 3B), thereby increasing or creating an angle between the upper and lower endplates 220, 230 of the implant 200 and increasing the overall height of the implant 200 proximate at least one end from a smaller, insertion height Hi to a larger, expanded height H₂.

[0056] The upper and lower endplates 220, 230 preferably include a plurality of interconnecting ridges 254a, 254b that allow the upper and lower endplates 220, 230 to securely lock in the second expanded configuration. That is, the plurality of ridges 254a, 254b formed on the upper and lower endplates 220, 230 preferably include a plurality of interlocking teeth 255 a, 255b so that rotation of the upper endplate 220 with respect to the lower endplate 230 causes the upper endplate 220 to engage the lower endplate 230 at the next highest teeth 225a, 225b to secure the upper and lower endplates 220, 230 in the second expanded configuration via a ratcheting type mechanism. In use, the implant 200 is preferably inserted into the intervertebral disc space in the first insertion configuration through a relatively small incision such that the end of the implant 200 proximate the pin 252 is initially inserted through the incision. Once the implant 200 is positioned between the vertebrae V, the implant 200 may be expanded by mechanically separating the upper and lower endplates 220, 230 proximate the rear end such that the endplates 220, 230 pivot about the pin 252 toward the second expanded configuration. When the surgeon is satisfied with the position of the upper endplate 220 with respect to the lower endplate 230, the mechanical expansion force may be released and the teeth 255a, 255b maintain the implant 200 in the second expanded configuration. The teeth 255 a, 255b may be released to move the implant 200 back toward or to the first insertion configuration to remove the implant 200 from between the vertebrae V or to a more preferably second expanded configuration.

[0057] Referring to Figs. 4A and 4B, an adjustable height intervertebral implant

300 in accordance with a fourth preferred embodiment includes an upper endplate 320 for contacting a first vertebra V, a lower endplate 330 for contacting a second vertebra V and a mechanism 350 for moving the upper and lower endplates 320, 330 with respect to one another. In this fourth preferred embodiment, the mechanism 350 is comprised of a pair of links 352a, 352b hingeably coupled to the upper and lower endplates 320, 330. The links 352a, 352b preferably include a posterior link 352a at one end of the endplates 320, 330 and an anterior link 352b at an opposite end of the endplates 320, 330. That is, the upper and lower endplates 320, 330 are preferably interconnected to one another via the anterior and posterior links 352a, 352b so that movement of the upper and lower endplates 320, 330 with respect to one another causes the links 352a, 352b to rotate from a first insertion configuration (Fig. 4A) wherein the links 352a, 352b are oriented generally parallel to a longitudinal axis 301 of the implant 300 to a second expanded configuration (Fig. 4B) wherein the links 352a, 352b are oriented generally perpendicular to the longitudinal axis 301 of the implant 300, thereby increasing the effective cranial/caudal height of the links 352a, 352b and thus the overall height of the implant 300 from a smaller, insertion height Hi to a larger, expanded height H₂. Although it is envisioned that the implant 300 may include only one link 352 at either the anterior or posterior end of the endplates 320, 330.

[0058] Once the implant 300 has been moved from the first insertion configuration to the second expanded configuration, the upper and lower endplates 320, 330 preferably include a plurality of interconnecting ridges 354a, 354b that secure the upper and lower endplates 320, 330 in the second expanded configuration. That is, once the implant 300 has been moved from the first insertion configuration to the second expanded configuration, upper ridges 354a formed on the upper endplate 320 align with and engage lower ridges 354b formed on the lower endplate 330 to secure the upper and lower endplates 320, 330 in the second expanded configuration.

[0059] Referring to Figs. 5A and 5B, an adjustable height intervertebral implant

400 in accordance with a fifth preferred embodiment includes two interconnected endplates 420, 430, each including a number of guide rails 452a, 452b formed thereon. In use, after the implant 400 has been implanted into the intervertebral disc space in an insertion configuration (Fig. 5A), the surgeon moves the upper endplate 420 with respect to the lower endplate 430 to expand the implant 400 to a second expanded configuration. Movement of the upper endplate 420 with respect to the lower endplate 430 causes upper guide rails 452a formed on the upper endplate 420 to move along lower guide rails 452b formed on the lower endplate 430, which, as a result of the size and configuration of the guide rails 452a, 452b (as will be described in greater detail below), causes the upper and lower endplates 420, 430 to move apart with respect to one another. [0060] The upper and lower guide rails 452a, 452b preferably have a wedge- shape so that the implant 400 may be expanded from the first insertion configuration to the second expanded configuration by slidably moving the upper endplate 420 with respect to the lower endplate 430. That is, slidably moving the upper endplate 430 with respect to the lower endplates 430 causes the upper guide rails 452a to ride along the lower guide rails 452b, this, as a result of their wedge-shape, results in an increase in the overall height of the implant 400 from a smaller, insertion height Hi to a larger, expanded height H₂. Alternatively, the upper and lower guide rails 452a, 452b may be any other shape including but not limited to triangles, bumps, or any shape where relative movement, preferably sliding or translational movement, of the endplates 420, 430 relative to each other results in an increased height of the implant 400. [0061] The implant 400 of the fourth preferred embodiment also includes a locking mechanism 454 for securely maintaining the endplates 420, 430 and the implant 400 in the second expanded configuration. The locking mechanism 454 may be any mechanism capable of maintaining the endplates 420, 430 in the second expanded configuration, for example, a multi-step ratchet tooth locking mechanism. [0062] Referring to Figs. 6A and 6B, an adjustable height intervertebral implant

500 in accordance with a sixth preferred embodiment includes an upper endplate 520 for contacting a first vertebra V, a lower endplate 530 for contacting a second vertebra V and a mechanism 550 for moving the upper and lower endplates 520, 530 with respect to one another. The upper and lower endplates 520, 530 each preferably include one or more guide rails 522, 532 on an inner side. The mechanism 550 is preferably comprised of the guide rails 522, 532 and a pair of wedges 552 that interact with the guide rails 522, 532. The wedges 552 are preferably in sliding contact with the guide rails 522, 532. The mechanism 550 also preferably includes a threaded spindle 554 for threadably engaging the pair of wedges 552 so that, in use, rotation of the spindle 554 causes the wedges 552 to move relative to each other and to slide along the upper and lower endplates 520, 530, which, as a result of the size and configuration of the guide rails 522, 532 (as will be described in greater detail below), causes the upper and lower endplates 520, 530 to move with respect to one another. That is, the wedges 552 preferably include a threaded aperture 560 for receiving the threaded spindle 554 so that rotation of the spindle 554 in one direction causes the wedges 552 to move towards one another, which in turn, causes the wedges 552 to slide along the guide rails 522, 532, pushing the endplates 520, 530 apart and thus increasing the overall height of the implant 500 from a smaller, insertion height Hi to a larger, expanded height H₂. Rotation of the spindle 554 in the opposite direction causes the wedges 552 to move away from one another, which in turn, causes the wedges 552 to slide along the guide rails 522, 532, urging the endplates 520, 530 closer together.

[0063] The upper and lower endplates 520, 530 preferably each include at least one guide rail 522, 532 extending substantially from the inner side of the endplates 520, 530. Each guide rail 522, 532 preferably has a height, as measured from the bone contacting surface of the endplates 520, 530 so that the guide rail 522, 532 is higher in the middle 523, 533 than at the ends 524, 534. For example, the shape of the guide rails 522, 532 may be triangular, or any other shape such as an arcuate shape so long as movement of the wedges 552 along the guide rails 522, 532 moves the upper and lower endplates 520, 530 closer together or further apart. The guide rails 522, 532 may contain a notch (not shown) formed therein so that as the wedges 552 are moved in one direction they may be secured against movement in the opposite direction. Each of the wedges 552 may also include a guide groove (not shown) formed therein, wherein the guide grooves receive the guide rails 522, 532 therein. The guide grooves preferably correspond, in depth and size, to the guide rail 522, 532 on which they slide. [0064] The spindle 554 preferably includes a tool engagement portion 562, formed on an end thereof. The tool engagement portion 562 preferably engages an instrument, such as, for example, a screwdriver. Alternatively, any other mechanism or tool for moving the wedges 552 may be used, for example a hydraulic mechanism, an electric motor, etc.

[0065] Referring to Figs. 7A and 7B, an adjustable height intervertebral implant

600 in accordance with a seventh preferred embodiment includes an upper endplate 620 for contacting a first vertebra V, a lower endplate 630 for contacting a second vertebra V and a mechanism 650 for moving the upper and lower endplates 620, 630 with respect to one another. The adjustable height intervertebral implant 600 also preferably includes an intermediate member 640 coupled to the upper and lower endplates 620, 630. The mechanism 650 is preferably comprised of a plurality of plates 660 such that, in use, the upper and lower endplates 620, 630 are moved with respect to one another, by insertion of the plurality of plates 660 between the upper and lower endplates 620, 630 and/or into the intermediate member 640. The plurality of plates 660 may have uniform or variable heights to permit various degrees of expansion between the upper and lower endplates 620, 630. For example, in use, the upper endplate 620 may be moved with respect to the lower endplate 630 by the incremental insertion of one millimeter (1 mm) individual plates of the plurality of plates 660 into the intermediate member 640. In use, incremental insertion of the plates 660 increases the overall height of the implant 600 from a smaller, insertion height Hi to a larger, expanded height H₂. [0066] The plurality of plates 660 preferably includes a tip 661 on the leading edge thereof to facilitate insertion. In use, the plurality of plates 660 may also be provided in various widths so that thinner width plates 660a having a width substantially equivalent to the width of the upper endplate 620 may be initially inserted in order to move the upper endplate 620 with respect to the lower endplate 630. Thereafter, wider plates 660b may be used to move the intermediate member 640, and hence the upper endplate 620, with respect to the lower endplate 630.

[0067] The intermediate member 640 preferably includes one or more projections

642 for engaging one or more stops 644 formed in the upper and lower endplates 620, 630. Alternatively, the upper and lower endplates 620, 630 may include the projections and the intermediate member 640 may include the stops. The intermediate member 640 may contain any number of sections and may be coupled to the upper and lower endplates 620, 630 by any means.

[0068] Referring to Figs. 8B and 8A, an adjustable height intervertebral implant

700 in accordance with an eighth preferred embodiment includes an upper endplate 720 for contacting a first vertebra V, a lower endplate 730 for contacting a second vertebra V and a mechanism 750 for moving the upper and lower endplates 720, 730 with respect to one another. The upper endplate 720 preferably includes a plurality of depending arms 722, wherein each arm 722 includes a projection 724. The lower endplate 730 preferably includes a complementary depression 732 that receives the plurality of arms 722 and projections 724 therein. The depression 732 includes a plurality of notches 734 formed on one or more inner walls 733 thereof. The notches 734 are preferably in the form of teeth formed along the inner wall 733 of the depression 732. Alternatively, as will be appreciated by one of ordinary skill in the art, the upper endplate 720 may include the depression and the lower endplate 730 may include the arms and projections. [0069] In use, the projections 724 and notches 734 operate as interlocking teeth so that the implant 700 may be expanded from a smaller, insertion height Hi to a larger, expanded height H₂ by moving the upper and lower endplates 720, 730 apart with respect to one another. That is, in use, as the implant 700 is expanded, the plurality of arms 722 deflect, allowing the projections 724 to move from one of the notches 734 to the next. In this manner, the mechanism 750 operates in the general manner of a ratcheting mechanism. The interlocking projections 724 and notches 734 secure the implant 700 in the expanded configuration so that the endplates 720, 730 are generally prevented from collapsing toward an insertion configuration (not shown) following initial expansion. The plurality of arms 722 may be manually manipulated to collapsed the upper endplate 720 relative to the lower endplate 730 to move the implant 700 from the second expanded configuration to the first insertion configuration.

[0070] The interlocking projections 724 and notches 734 are preferably configured to generally prevent the implant 700 from collapsing from the expanded configuration toward the insertion configuration without the use of some instrument to inwardly deflect the arms 722 so that the interlocking projections 724 and notches 734 may be temporarily disengaged. Any number of projections 724 and notches 734 of any size may be used and the depression 732 may have nearly any size and shape that allows the implant 700 to retain its functionality and withstand the normal operating conditions of the implant 700. In addition, multiple depressions and projections may be used. [0071] Referring to Figs. 9A-9C, an adjustable height intervertebral implant 800 in accordance with a ninth preferred embodiment includes an upper endplate 820 for contacting a first vertebra V, a lower endplate 830 for contacting a second vertebra V and a mechanism 850 for moving the upper and lower endplates 820, 830 with respect to one another. The upper endplate 820 preferably includes a projection 822 while the lower endplate 830 preferably includes a depression 832 that receives the projection 822 therein. Alternatively, as will be appreciated by one of ordinary skill in the art, the upper endplate 820 may include the depression and the lower endplate 830 may include the projection.

[0072] The implant 800 of the ninth preferred embodiment includes a locking ring 840 that fits substantially within the depression 832 formed in the lower endplate 830. The locking ring 840 preferably receives the projection 822 extending from the upper endplate 820 in an assembled configuration. The projection 822 and locking ring 840 including a plurality of interlocking teeth 852 formed thereon so that the implant 800 may be expanded from a smaller, insertion height Hi to a larger, expanded height H₂ by moving the upper and lower endplates 820, 830 apart from each other with the interaction of the teeth 852 formed on the projection 822 and the locking ring 840 limiting that ability of the endplates 820, 830 to collapse back together from an expanded configuration (Fig. 9B) to an insertion configuration (Fig. 9A). In use, the locking ring 840 expands as the upper and lower endplates 820, 830 are moved in the cranial/caudal direction or away from each other, thereby allowing the teeth 852 formed on the projection 822 to move from one tooth to the next tooth formed on the locking ring 840. In this manner, the mechanism 850 generally acts as a ratcheting mechanism. [0073] After the teeth 852 move past the locking ring 840, the locking ring 840 decreases in diameter limiting the ability of the implant 800 to collapse. The implant 800 preferably includes an access hole 860 in the lower endplate 830 for receiving a tool to act upon the locking ring 840 so that the locking ring 840 can be manually expanded to temporarily disengage the interlocking teeth 852 so that the implant 800 may be collapsed to the insertion configuration.

[0074] Referring to Figs. 1OA and 1OB, an adjustable height intervertebral implant 900 of a tenth preferred embodiment includes an upper endplate 920 for contacting a first vertebra V, a lower endplate 930 for contacting a second vertebra V and a mechanism 950 for moving the upper and lower endplates 920, 930 with respect to one another. The implant 900 preferably also includes one or more membranes 952 for interconnecting the upper and lower endplates 920, 930, the one or more membranes 952 defining an interior cavity 952a. In use, the mechanism 950 includes a fluid 954 injected into the interior cavity 952a. Injection of the fluid 954 into the interior cavity 952a causes the upper and lower endplates 920, 930 to move apart. Alternatively, the interior cavity 952a can be filled with a gas, gel or a solid, thereby increasing the pressure inside the interior cavity 952a and expanding the implant 900 from a smaller, insertion height Hi to a larger, expanded height H₂. An increase in pressure in the interior cavity 952a may result from the mechanical introduction of the material or a chemical reaction within the material that causes the material's expansion. The interior cavity 952a may be filled with cement that hardens and fixes the height of the implant 900 when the cement cures and hardens. Alternatively, as generally shown in Figs. 1OC and 1OD, the interior membrane 950 may be in the form of a series of telescoping cylinders 954. [0075] Referring to Figs. 1 IA and 1 IB, an adjustable height intervertebral implant 1000 in accordance with an eleventh preferred embodiment includes an upper endplate 1020 for contacting a first vertebra V , a lower endplate 1030 for contacting a second vertebra V and a mechanism 1050 for moving the upper and lower endplates 1020, 1030 with respect to one another. The mechanism 1050 preferably includes two sets of links 1052, 1054 with a turnbuckle 1056 threaded through a connection point 1058, 1060 of each pair of links 1052, 1054 so that, in use, rotation of the turnbuckle 1056 causes the connection points 1058, 1060 on the links 1052, 1054 to move towards or away from one another, thereby increasing, or decreasing, the overall height of the implant 1000 from a smaller, insertion height Hi to a larger, expanded height H₂. [0076] Referring to Fig. 12, an adjustable height intervertebral implant 1100 in accordance with a twelfth preferred embodiment includes an upper endplate 1120 for contacting a first vertebra V, a lower endplate 1130 for contacting a second vertebra V and a mechanism 1150 for moving the upper and lower endplates 1120, 1130 with respect to one another. The lower endplate 1130 includes a plurality of depressions 1132 for rotatably receiving one or more links 1152. Each of the links 1152 preferably includes a slot 1154. The upper endplate 1120 is operatively connected to the one or more links 1152. The links 1152 are preferably interconnected via a rod 1160 coupled to the slot 1154 formed in the links 1152 such that lateral movement of the rod 1160 causes the links 1152 to rotate and move out of the depressions 1132 formed in the lower endplate 1130, which in turn causes the effective cranial/caudal height of the links 1152 to increase and the upper endplate 1120 to move with respect to the lower endplate 1130, thereby increasing the overall height of the implant 1100 from a smaller, insertion height Hi to a larger, expanded height H₂. The rod 1160 preferably includes a plurality of teeth 1162 formed thereon to facilitate movement in one direction but limit or inhibit movement in the other direction, thereby locking the implant 1100 in the second expanded configuration.

[0077] Referring to Figs. 13A and 13B, an adjustable height intervertebral implant 1200 in accordance with a thirteenth preferred embodiment includes an upper endplate 1220 for contacting a first vertebra V, a lower endplate 1230 for contacting a second vertebra V and a mechanism 1250 for moving the upper and lower endplates 1220, 1230 with respect to one another. In this thirteenth preferred embodiment, the mechanism 1250 includes a deformable lattice or membrane 1252 that interconnects the upper and lower endplates 1220, 1230. In use, the upper and lower endplates 1220, 1230 may be manually expanded from a smaller, insertion height Hi to a larger, expanded height H₂ by an instrument, which causes the lattice or membrane 1252 to plastically deform, thereby urging the implant 1200 toward and into the second expanded configuration.

[0078] In use, the preferred adjustable height intervertebral implants 10-1200 may, for example, have a height of approximately seven millimeters (7.0 mm) in the first insertion configuration and be incrementally expanded to a maximum height of approximately fifteen millimeters (15.0 mm). Alternatively, the preferred implants 10- 1200 may be constructed to be smaller or larger and expand more or less, depending on the purpose for which it is expected to be used and the amount of material removed from a patient's spine, which will be replaced by the implants 10-1200. [0079] The adjustable height intervertebral implants 10-1200 and its related components may be constructed from any biocompatible material including, but not limited to, titanium, titanium alloy such as TAN, TAV, etc., stainless steel, CoCr, a resorbable polymer, PEEK, bone, etc.

[0080] The upper and lower endplates 20-1220, 30-1230 may be textured to facilitate engagement with the first and second vertebral bodies V. For example, the upper and lower endplates 20-1220, 30-1230 may include teeth, spikes, one or more keels, etc. to facilitate purchase between the endplates 20-1220, 30-1230 and the vertebrae V. Additionally, each endplate 20-1220, 30-1230 may be constructed in a variety of shapes and sizes, so long as its function is not compromised. The upper and lower endplates 20-1220, 30-1230 may also include one or more voids for facilitating bone-in-growth and/or for receiving bone chips.

[0081 ] Features described herein may be used singularly or in combination with other features. In addition, features disclosed in connection with one embodiment may be interchangeable with a feature or features disclosed in another embodiment. Therefore the presently disclosed embodiments are to be considered as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and not limited to the foregoing description. [0082] It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. An adjustable height intervertebral implant for insertion between first and second vertebral bodies, the implant comprising:

an upper endplate for contacting the first vertebra;

a lower endplate for contacting the second vertebra; and

a mechanism for moving the upper and lower endplates with respect to one another, the mechanism including first and second telescopic gear sets directly coupled to one another and mounted between the upper endplate and the lower endplate, the telescopic gear sets including at least an outer gear and an inner gear.

2. The implant of claim 1 , wherein the first and second telescopic gear sets each include at least three individual gears.

3. The implant of claim 2, wherein each one of the telescopic gear sets includes the outer gear, a first intermediate gear, a second intermediate gear and the inner gear, the outer gear including an external thread for engaging an external thread formed on an outer gear of an adjacent telescopic gear set, the outer gear including an internal thread for engaging an external thread formed on the first intermediate gear, the second intermediate gear press-fit into the outer gear, the second intermediate gear including an internal thread for engaging an external thread formed on the inner gear.

4. An adjustable height intervertebral implant for insertion between first and second vertebral bodies, the implant comprising:

an upper endplate for contacting the first vertebra;

a lower endplate for contacting the second vertebra; and

a first telescopic gear set directly coupled to a second telescopic gear set and mounted between the upper and lower endplates, wherein the first and second telescopic gear sets each include an outer gear, a first intermediate gear, a second intermediate gear and an inner gear, the outer gear of the first telescopic gear set including an external thread for engaging an external thread formed on the outer gear of the second telescopic gear set, the outer gear also including an internal thread for engaging an external thread formed on the first intermediate gear, the second intermediate gear press-fit into the outer gear and including an internal thread for engaging an external thread formed on the inner gear.

5. The implant of claim 4 wherein the inner gear is fixed to the upper endplate.

6. The implant of claim 4 wherein the first intermediate gear is fixed to the lower endplate.

7. The implant of claim 4 wherein the outer gear and the second intermediate gear define a groove therebetween, the first intermediate gear received in the groove in a first insertion configuration.

8. The implant of claim 4 wherein rotation of the outer gear of the first telescopic gear set in a first direction drives the upper and lower endplates away from the outer and second intermediate gears.

9. The implant of claim 4 wherein the inner gear is fixed to the upper endplate and the first intermediate gear is fixed to the lower endplate, rotation of the outer gear and the second intermediate gear in a first direction urging the upper and lower endplates away from the outer and second intermediate gears.

10. The implant of claim 4 wherein the outer gear and the second intermediate gear and integrally formed.

11. The implant of claim 10 wherein the outer and second intermediate gears are constructed of a polymeric material.

12. An adjustable height intervertebral implant for insertion between first and second vertebral bodies, the implant comprising:

an upper endplate for contacting the first vertebra;

a lower endplate for contacting the second vertebra; and

at least one link hingeably connecting the upper endplate to the lower endplate, the at least one link oriented generally parallel to a longitudinal axis of the implant in a first insertion configuration and oriented generally perpendicular to the longitudinal axis in a second expanded configuration.

13. The implant of claim 12, wherein the upper endplate and the lower endplate include a plurality of upper and lower ridges extending therefrom toward the opposing one of the upper and lower endplates, respectively, the plurality of upper and lower ridges positioned in facing engagement in the second expanded configuration to securely maintain a height of the implant.