Curved expandable cage

An expandable intervertebral implant includes a first endplate and a second endplate, a first wedge member and a second wedge member spaced from the first wedge member that couple the first and second endplates together. The first and second wedge members are configured to translate along an actuation member housed between the first and second endplates to cause the implant to expand from a first collapsed configuration into a second expanded configuration. The actuation member has a first threaded section spaced apart from a second threaded section where the first and second threaded sections are at an angle with each other. The actuation member is configured to move the first and second wedge members from the first collapsed configuration into the second expanded configuration so that the first and second endplates separate from each other to contact and engage the endplates of the adjacent vertebral bodies.

TECHNICAL FIELD

The present invention relates to an expandable intervertebral implant, system, kit and method.

BACKGROUND

The human spine is comprised of a series of vertebral bodies separated by intervertebral discs. The natural intervertebral disc contains a jelly-like nucleus pulposus surrounded by a fibrous annulus fibrosus. Under an axial load, the nucleus pulposus compresses and radially transfers that load to the annulus fibrosus. The laminated nature of the annulus fibrosus provides it with a high tensile strength and so allows it to expand radially in response to this transferred load.

In a healthy intervertebral disc, cells within the nucleus pulposus produce an extracellular matrix (ECM) containing a high percentage of proteoglycans. These proteoglycans contain sulfated functional groups that retain water, thereby providing the nucleus pulposus within its cushioning qualities. These nucleus pulposus cells may also secrete small amounts of cytokines such as interleukin-1.beta. and TNF-.alpha. as well as matrix metalloproteinases (“MMPs”). These cytokines and MMPs help regulate the metabolism of the nucleus pulposus cells.

In some instances of disc degeneration disease (DDD), gradual degeneration of the intervetebral disc is caused by mechanical instabilities in other portions of the spine. In these instances, increased loads and pressures on the nucleus pulposus cause the cells within the disc (or invading macrophases) to emit larger than normal amounts of the above-mentioned cytokines. In other instances of DDD, genetic factors or apoptosis can also cause the cells within the nucleus pulposus to emit toxic amounts of these cytokines and MMPs. In some instances, the pumping action of the disc may malfunction (due to, for example, a decrease in the proteoglycan concentration within the nucleus pulposus), thereby retarding the flow of nutrients into the disc as well as the flow of waste products out of the disc. This reduced capacity to eliminate waste may result in the accumulation of high levels of toxins that may cause nerve irritation and pain.

As DDD progresses, toxic levels of the cytokines and MMPs present in the nucleus pulposus begin to degrade the extracellular matrix, in particular, the MMPs (as mediated by the cytokines) begin cleaving the water-retaining portions of the proteoglycans, thereby reducing its water-retaining capabilities. This degradation leads to a less flexible nucleus pulposus, and so changes the loading pattern within the disc, thereby possibly causing delamination of the annulus fibrosus. These changes cause more mechanical instability, thereby causing the cells to emit even more cytokines, thereby upregulating MMPs. As this destructive cascade continues and DDD further progresses, the disc begins to bulge (“a herniated disc”), and then ultimately ruptures, which may cause the nucleus pulposus to contact the spinal cord and produce pain.

One proposed method of managing these problems is to remove the problematic disc and replace it with a device that restores disc height and allows for bone growth between the adjacent vertebrae. These devices are commonly called fusion devices, or “interbody fusion devices”. Current spinal fusion procedures include transforaminal lumbar interbody fusion (TLIF), posterior lumbar interbody fusion (PLIF), and extreme lateral interbody fusion (XLIF) procedures.

SUMMARY

The present invention relates to expandable intervertebral implants. The expandable intervertebral implants are preferably fusion implants used to fuse two adjacent vertebral bodies in the spine.

In a preferred embodiment, the implant is constructed with an actuation member that can be rotated to expand and contract two opposing endplates of the implant. The actuation member has a first threaded section and a second threaded section where each threaded section extends along a straight central longitudinal portion of the actuation member. The first threaded section is angularly offset from the second threaded section, the angle offset preferably between 15° and 55°. Along the actuation member between the first and second threaded section is a section that can flexibly rotate such that rotation of the first threaded section in a first rotational direction causes the second threaded section to also rotate in the first rotational direction. The threading on the first and second threaded sections is preferably opposite. Wedge members are positioned onto the first and second threaded sections and the wedge members translate along the threaded sections to enable the implant to expand from a collapsed configuration to an expanded configuration.

According to one embodiment of the present invention the expandable implant is designed for insertion into an intervertebral space between a superior vertebral body and an adjacent inferior vertebral body. The expandable implant comprises a superior endplate having a superior outer surface for contacting the superior vertebral body and an superior inner surface opposite the superior outer surface along a transverse direction. The implant also comprises an inferior endplate having an inferior outer surface for contacting the inferior vertebral body and an inferior inner surface opposite the inferior outer surface along the transverse direction. The superior endplate is movably coupled to the inferior endplate such that the superior endplate can be translated relative to the inferior endplate along the transverse direction. The implant comprises an insertion end portion and a trailing end portion opposite the insertion end portion and a first side surface and a second side surface opposite the first side surface along a lateral direction perpendicular to the transverse direction. An actuation member is housed at least partially between the inferior endplate and the superior endplate, the actuation member having a first threaded section extending along a first central longitudinal axis of the actuation member and a second threaded section extending along a second central longitudinal axis of the actuation member, wherein the first central longitudinal axis and the second central longitudinal axis form an angle between about 15° and about 75°. A first wedge member is threadedly mated with the first threaded section and a second wedge member is threadedly mated with the second threaded section. When the actuation member is rotated around the first and second central longitudinal axes the first wedge translates along the first threaded section and the second wedge translates along the second threaded section to cause the superior endplate to move apart from the inferior endplate in the transverse direction from a collapsed implant configuration to an expanded implant configuration.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Referring toFIG. 1, a superior vertebral body2and an adjacent inferior vertebral body4defines an intervertebral space9extending between the vertebral bodies2and4. The superior vertebral body2defines superior vertebral surface6, and the adjacent inferior vertebral body4defines an inferior vertebral surface8(the vertebral surfaces are usually the vertebral endplates that are surgically prepared for accepting the implant). The vertebral bodies2and4are commonly anatomically adjacent, but may be the remaining vertebral bodies after an intermediate vertebral body has been removed from a location between the vertebral bodies2and4. The intervertebral space9inFIG. 1is illustrated after a discectomy, whereby the disc material has been removed or at least partially removed to prepare the intervertebral space9to receive an intervertebral implant or implant10, as shown inFIGS. 2A-2B(the implant may also be referred to as a “spacer” or “fusion spacer” in the technical community). The inserted and expanded implant10is designed to achieve an appropriate height restoration for the intervertebral space9. The intervertebral space9can be disposed anywhere along the spine as desired, including at the lumbar, thoracic, and cervical regions of the spine.

Referring toFIGS. 2A-2B, an embodiment of the present invention is depicted as a TLIF implant10. The expandable intervertebral implant or implant10defines an implant body13that defines a distal or insertion end12and a proximal or trailing end14that is spaced from and opposite the insertion end12. The implant10is designed and configured to be inserted into an intervertebral space in a direction from the trailing end14toward the insertion end12, also referred to herein as an insertion direction. The insertion direction for a TLIF implant is generally not a straight line, but rather a curved path that may be oriented along or approximately along an implant axis that is along the center-width line of the implant10. The trailing end14is configured to couple with one or more insertion instruments, which are configured to support and carry the implant10into the intervertebral space9, and/or actuate the implant10from a collapsed configuration C shown inFIG. 2Ainto an expanded configuration E shown inFIG. 2B.

The implant10has a superior endplate or shell18and an inferior endplate or shell20that are held together and that can expand and contract relative to each other in the transverse direction T to change the height of the implant10within the intervertebral space9. The superior endplate or shell18has a superior or outer/upper bone-contacting surface32and the inferior endplate or shell20has an inferior or outer/lower or second bone contacting surface132spaced from the superior bone-contacting surface32along the transverse direction T. The superior and inferior bone contacting surfaces32and132are configured to engage the superior and inferior vertebral bodies2and4, respectively, at the respective vertebral surfaces6,8. Each of the superior and inferior bone contacting surfaces32and132can be convex or partially convex, for instance, one portion of the surface is convex while another portion can be planar; these surfaces can be convex along the length of the implant10and also convex along the width in the lateral direction A. The bone contacting surfaces32and132can also define a texture41, such as spikes, ridges, pyramid-shapes, cones, barbs, indentations, or knurls, which are configured to engage the superior and inferior vertebral surfaces6and8, respectively, when the implant10is inserted into the intervertebral space9. The bone contacting surfaces32and132may be partially textured. For instance, the bone contacting surfaces32and132can include specific patterns of textured and non-textured portions. For a TLIF implant10as depicted, the texture41can be in the form of parallel, curved ridges43that are the peaks of the pyramid-shaped textures depicted inFIG. 2A-B, and that are curved in the insertion path direction.

As used herein, the term “proximal” and derivatives thereof refer to a direction from the distal or insertion end12toward the proximal end14. As used herein, the term “distal” and derivatives thereof refer to a direction from the proximal end14toward the insertion end12. As used herein, the term “superior” and derivatives thereof refer to a direction from the inferior bone contact surface132toward the superior bone-contacting surface32. As used herein, the term “inferior” and derivatives thereof refer to a direction from the superior bone-contacting surface32toward the inferior bone contacting surface132.

Continuing withFIGS. 2-3, the implant10includes a pair of wedge members coupled to an actuation member26. The pair of wedge members includes a first wedge member22and a second wedge member24that in the preferred design function to couple the superior endplate18to the inferior endplate20. The first and second wedge members22and24can translate along the actuation member26so as to move the superior endplate18relative to the inferior endplate20along the transverse direction T to alter the height of the implant10; that is, as explained below, the actuation member can be rotated to move the wedge members22,24along the actuation member26to raise and to lower the height of the implant10(the transverse distance between the superior and inferior bone contacting surfaces32,132). In this embodiment, the actuation member26has a relatively narrow flange28extending from the actuation member26along the transverse direction T toward the superior endplate18and the inferior endplate20. In a preferred design, the superior endplate18has a superior inner surface33and the inferior endplate20has an inferior inner surface133that in conjunction define a channel135. The implant10is configured such that when the implant10is in the collapsed configuration C shown inFIG. 2A, a substantial majority of the actuation member26, at least a portion of first wedge member22and at least a portion of the second wedge member24are disposed within the channel135; that is, preferably, only the proximal end portion26pof the actuation member26is outside the channel135and the back portions of the wedge members22,24are outside the channel135in the collapsed configuration C. The implant endplates and/or wedge members can be formed of polyether ether ketone (PEEK) or any other suitable biocompatible polymeric material, or a metal alloy. The actuation member26can formed from a biocompatible polymeric material or metallic alloy, such as titanium or steel. It should be appreciated that the any suitable material can be used to form the implant components as described herein. For instance, an entirety of the implant can be made from a titanium alloy. For instance, an entirety of the implant can be made from a titanium-aluminium-niobium (TAN) alloy.

Referring toFIGS. 3-4D, the inferior endplate20is configured for coupling with the first wedge member22, the second wedge member24, and at least a portion of the flange28. The inferior endplate20can define a cavity42configured to partially house the first and second wedge members22and24, and the actuation member26. The inferior endplate20has an inferior inner surface133that includes a preferably planar surface35athat forms the top surface of the two lateral side walls36iand40ithat can be preferably designed to match up to similarly angled opposing surfaces on the superior endplate18, and a multi-contoured surface35bthat forms part of the channel135. The inferior endplate20also defines first and second ramp surfaces44and46. The inferior endplate20further defines a first side surface33aand a second side surface33bopposite the first side surface33a.The first and second side surfaces33aand33bextend between the bone-contacting surface132and the top planar surface35aalong the transverse direction T. The inferior endplate20thus defines a first sidewall36iand a second sidewall40ispaced from the first sidewall36ialong the lateral direction A. As illustrated, the channel135extends along the length of the inferior endplate20and along the lateral direction A between the opposed first and second sidewalls36iand40i.In the embodiment shown, the first and second sidewalls36iand40iconverge with the inferior bone contacting surface132to form a tapered insertion end16(FIG. 2A).

Continuing withFIGS. 3-4D, the first and second sidewalls36iand40iare configured to receive the flange28. The first sidewall36ican define at least one slot, for instance a first slot52for receiving a portion of the flange28located on the actuation member26. The first slot52is disposed in sidewall40iat a location between the insertion end12and the trailing end14of the inferior endplate20. The sidewall36ican define at least one or second slot54for receiving another portion of the flange28. The second slot54is disposed in the sidewall36iat a location between the insertion end12and the trailing end14. The second slot54is aligned, for instance laterally aligned, with and opposing the first slot52such that each slot52and54is positioned to receive a portion of the flange28. The slots52and54are also configured to mate with the structure of the flange28. For instance, the slots52,54have an inner profile that is curvilinear and corresponds to the curvilinear profile of the flange28. In other alternate embodiments, the slots52and54may have a rectilinear shape. It should be appreciated that the slots52and54may have any desired shape that can slidingly receive a portion of the flange28. For example, if the flange28has a square profile, the slots52and54can be configured to mate with the square shaped flange. In alternate embodiments, the walls36iand40ican include a plurality of spaced slots spaced apart along the length of the implant10and disposed on the sidewalls36iand40ito receive a corresponding number of flanges or flanges portions extending from the actuation member26.

The inner surface133of the inferior endplate20is also designed with a feature to couple the wedge members22,24with the endplate. In one embodiment, along inner walls39i,45iof the sidewall36iand40i,respectively, there is a groove37icut into the inner walls39i,45iin the lateral direction A. The grooves37iare configured to engage a corresponding tab portion of the first and second wedge members22and24as further detailed below. The inferior endplate20has four grooves37ithat are in two sets of pairs. The grooves37iextend in a parallel fashion to the ramp surfaces44,46along the length of the implant10. The pair of grooves37ion the first side3of the inferior endplate20extend from a point adjacent the trailing end14toward the middle section7of the implant10and parallel ramp surface46in a direction toward the inferior surface132in the transverse direction T. In a similar fashion, on the opposite second side5of the implant, the pair of grooves37iextend from a point adjacent the insertion end12toward the middle section7of the implant10and parallel ramp surface44in a direction toward the inferior surface132in the transverse direction T. The grooves37iextend toward the middle section7and terminate at a point either at the longitudinal center, or near the longitudinal center of the implant10or if a flange28is present, preferably before the slots52,54. While each side3,5is illustrated has having a pair of grooves37i,each side3,5can have a single groove, or more than two grooves or other form of recess to capture the wedge members22,24.

Continuing withFIGS. 3-4D, the inferior endplate20defines ramp surfaces44and46, for instance a first ramp surface44and a second ramp surface46that are configured to mate with and slide along portions of the first and second wedge members22and24. The first ramp surface44extends from a point proximate the insertion end12toward the middle section7on an angle toward the inferior bone contacting surface132. The ramp surface44is declined to abut and slidingly receive a portion of the second wedge member24. The second ramp surface46extends from a point proximate the trailing end14toward the middle section7on an angle toward the inferior bone contacting surface132, and is declined to abut and slidingly receive a portion of the first wedge member22. The ramps surfaces44and46also extend laterally along the lateral direction A between the opposing first and second walls36iand40i.Each ramp surface44and46can define a ramp angle β (not shown) defined with respect to planar surface35a.It should be appreciated that the angle β can vary as needed, and preferably is between about 10° and about 65°. The inferior endplate20can also define a curvilinear portion48disposed at the trailing end14that is cut into the second ramp surface46. The curvilinear portion48is configured to align with a corresponding curvilinear portion on the superior endplate18. When the endplates18and20are in the collapsed configuration as shown inFIG. 2A, the curvilinear portions define an access opening50that provides access to the actuation member26, as further detailed below.

As shown inFIGS. 4E-4H, the superior endplate18is configured similarly to the inferior endplate20. The superior endplate18thus includes similar structural features that correspond to the structural features described above with respect to the inferior endplate20. The two endplates are designed to close against each other and house the actuation member26with the wedge members22,24connected thereto. The superior endplate18is configured for coupling with the first wedge member22, the second wedge member24, and at least a portion of the flange28. The superior endplate18can define a cavity42configured to partially house the first and second wedge members22and24, and the actuation member26. The superior endplate18has a superior inner surface33that includes a preferably planar surface35athat forms the top surface of the two lateral side walls36sand40sthat can be preferably designed to match up to similarly angled opposing surfaces on the inferior endplate20, and a multi-contoured surface35bthat forms part of the channel135. The superior endplate18also defines first and second ramp surfaces44and46. The superior endplate18further defines a first side surface33aand a second side surface33bopposite the first side surface33a.The first and second side surfaces33aand33bextend between the bone-contacting surface32and the top planar surface35aalong the transverse direction T. The superior endplate18thus defines a first sidewall36sand a second sidewall40sspaced from the first sidewall36salong the lateral direction A. As illustrated, the channel135extends along the length of the superior endplate18and along the lateral direction A between the opposed first and second sidewalls36sand40s.In the embodiment shown, the first and second sidewalls36sand40sconverge with the superior bone contacting surface32to form a tapered insertion end16(FIG. 2A).

Continuing withFIGS. 4E-H, the first and second sidewalls36sand40sare configured to receive the flange28. The first sidewall36scan define at least one slot, for instance a first slot52for receiving a portion of the flange28located on the actuation member26. The first slot52is disposed in sidewall40sat a location between the insertion end12and the trailing end14of the superior endplate18. The sidewall36scan define at least one or second slot54for receiving another portion of the flange28. The second slot54is disposed in the sidewall36sat a location between the insertion end12and the trailing end14. The slot54is aligned, for instance laterally aligned, with and opposing the slot52such that each slot52and54is positioned to receive a portion of the flange28. The slots52and54are also configured to mate with the structure of the flange28. For instance, the slots52,54have an inner profile that is curvilinear and corresponds to the curvilinear profile of the flange28. In other alternate embodiments, the slots52and54may have a rectilinear shape. It should be appreciated that the slots52and54may have any desired shape that can slidingly receive a portion of the flange28. For example, if the flange28has a square profile, the slots52and54can be configured to mate with the square shaped flange. In alternate embodiments, the walls36sand40scan include a plurality of spaced slots spaced apart along the length of the implant10and disposed on the sidewalls36sand40sto receive a corresponding number of flanges or flanges portions extending from the actuation member26.

The inner surface33of the superior endplate18is also designed with a feature to couple the wedge members22,24with the endplate. In one embodiment, along inner walls39s,45sof the sidewall36sand40s,respectively, there is a groove37scut into the inner walls39s,45sin the lateral direction A. The grooves37sare configured to engage a corresponding tab portion of the first and second wedge members22and24as further detailed below. The superior endplate18has four grooves37sthat are in two sets of pairs. The grooves37sextend in a parallel fashion to the ramp surfaces44,46along the length of the implant10. The pair of grooves37son the first side3of the superior endplate18extend from a point adjacent the trailing end14toward the middle section7of the implant10and parallel ramp surface46in a direction toward the superior surface32in the transverse direction T. In a similar fashion, on the opposite second side5of the implant, the pair of grooves37sextend from a point adjacent the insertion end12toward the middle section7of the implant10and parallel ramp surface44in a direction toward the superior surface32in the transverse direction T. The grooves37sextend toward the middle section7and terminate at a point near the longitudinal center of the implant10, and if the flange28is present in the design then preferably before the slots52,54. While each side3,5is illustrated has having a pair of grooves37s,each side3,5can have a single groove, or more than two grooves or other form of recess to capture the wedge members22,24.

Continuing withFIGS. 4E-H, the superior endplate18defines ramp surfaces44and46, for instance a first ramp surface44and a second ramp surface46that are configured to mate with and slide along portions of the first and second wedge members22and24. The first ramp surface44extends from a point proximate the insertion end12toward the middle section7on an angle toward the superior bone contacting surface32. The first ramp surface44is inclined to abut and slidingly receive a portion of the second wedge member24. The second ramp surface46extends from a point proximate the trailing end14toward the middle section7on an angle toward the superior bone contacting surface32, and is inclined to abut and slidingly receive a portion of the first wedge member22. The ramp surfaces44and46also extend laterally along the lateral direction A between the opposing first and second walls36sand40s.Each ramp surface44and46can define a ramp angle β (not shown) defined with respect to planar surface35a.It should be appreciated that the angle β can vary as needed, and preferably is between about 10° and about 65°. The superior endplate18can also define a curvilinear portion48disposed at the trailing end14that is cut into the second ramp surface46. The curvilinear portion48is configured align with a corresponding curvilinear portion on the inferior endplate20. When the endplates18and20are in the collapsed configuration as shown inFIG. 2A, the curvilinear portions define an access opening50that provides access to the actuation member26, as further detailed below.

The superior and inferior endplates18,20are designed to be mated together. In a preferred embodiment, the two endplates are mated together by the wedge members22,24that track within the grooves37. The planar surfaces35aof the superior and inferior endplates18,20are designed to contact, or come close to contact, with each other when the implant is in its collapsed position (FIG. 2A). The superior endplate18and inferior endplate20can define opposing indentations98at the trailing end14of the implant10. The indentations98are configured to receive a portion of an insertion tool (not shown).

The superior endplate18and inferior endplate20can also define respective openings or through-holes30. Each opening or through-hole30has been configured to receive at least a portion of the first and second wedge members22and24to maximize the compact design and the expansion characteristics of the implant10. The openings30partially receive portions of the first and second wedge members22and24when the implant10is in the collapsed configuration C (FIG. 2A), which allows for the dimensions of the first and second wedge members22and24to be increased over wedge members used in implants without an opening30configured to permit a portion of the wedge member to extend therethrough. Thus, the implant10has a collapsed configuration that is compact and less invasive, and an expanded configuration that is dimensionally stable. The openings30have the additional benefit of promoting bone growth when implanted in the intervertebral space9. The opening30extends through the superior endplate18and similarly through the inferior endplate.

Referring toFIGS. 3 and 5A-5D, the first wedge member22and the second wedge member24are configured for slidable coupling to the superior and inferior endplates18and20. The first and second wedge members22and24are configured similarly, and for illustrative purposes, only the first wedge member22will be described below. The first wedge member22defines a wedge body74extending along a central wedge axis CL between a narrow, outer end75and a wider, inner end76spaced from the outer end75along the central wedge axis CL. The wedge axis CL is preferably aligned with the central axis of the actuation member26and extends along the length of the wedge (in the embodiment shown, the implant10is designed to expand evenly in the superior and inferior directions because the wedges are designed in a symmetric fashion; the wedge could be designed with different angles for the wedge faces (and even one side could be designed with a flat face) so that expansion can be uneven in the superior and inferior directions). As show inFIGS. 3 and 7B, the first wedge narrow end75is positioned facing toward the outer or trailing end14of the implant10, while the inner wide end76is positioned to face the middle portion7(and opening30) of the implant10. Further, the second wedge member24has a wedge body wherein the narrow outer end75is positioned facing toward the distal or insertion end12of the implant10and the inner wide end76is positioned facing toward the middle portion7(and opening30) of the implant.

The wedge body74rides along and on the actuation member26to provide a mechanical means to separate the superior and inferior endplates18,20to expand the implant10. The wedge body74has a superior surface77and an opposing inferior surface78. The superior surface77is angled from the narrow end75to the wide end76, and the inferior surface78is similarly angled in the opposite direction. That angle is preferably between about 10° and about 65° with respect to the central axis CL for the superior surface77(and oppositely angled for the opposing surface78). The angle preferably matches the angle for ramp surfaces44,46and also the angle for the grooves37. The wedge body74has protrusions, tabs, or tongues82extending along the sides79,80; the protrusions82are designed to fit and track within the grooves37such that as the wedge body74tracks along the actuation member26and the wedge members22,24translate along the actuation member26away from the middle portion7the wedge members22,24force the superior and inferior endplates18,20away from each other relatively to cause the implant10to move from its collapsed position to its expanded position. The wedge body74has a superior edge76sand an inferior edge76ithat define a height H1for the wedge. The wedge body74has a central bore81that is preferably internally threaded to mate with the external threading on the actuation member26.

Referring now toFIGS. 6A-6F, an embodiment for the actuation member26is depicted for description purposes. The actuation member26is configured to couple the first and second wedge members22and24together while also providing stability to the superior endplate18and inferior endplate20during implant expansion. The actuation member26is angled or curved at its middle section90that separates a second threaded section91and a first threaded section92, the threaded sections91,92having threads99. The second threaded section91preferably is constructed such that there is a length of threaded straight rod having a center longitudinal axis CL1, and similarly the first threaded section92preferably is constructed such that there is a length of threaded straight rod having a center longitudinal axis CL2(seeFIG. 6E). The two center longitudinal axis lines CL1and CL2form an angle, α, between them where the angle α is preferably between about 15° and about 75°; more preferably between about 15° and about 55°; more preferably between about 20° and about 50°; more preferably between about 25° and about 45°; more preferably between 30° and 40°, and in some embodiments between 33° and 37°. It is preferred that the first and second threaded sections91,92each extend along a respective straight longitudinal section of the actuation member; however, the first and second threaded sections91,92could be non-straight. In this latter configuration, a line can be drawn between a point in the center of the actuation member26at the beginning and at the end of the threads99on each of the first and second threaded sections91,92. The angle between these two lines would then form angle α. The first and second threaded sections91,92are preferably formed from steel, a titanium alloy, cobalt chrome, nitinol, polymers, or combinations of the foregoing materials.

In the embodiment depicted, the middle section90of the actuation member26can be constructed to include a flexible rod, which in this instance is in the form of a cable93that is made up of several wire segments94. The middle section90is thus flexible and can enable the actuation member26to be rotated at one end by an actuation tool and that rotation will be maintained evenly for both the first and section threaded sections91,92. The pitch for the threads99on the first threaded section92is preferably the same as the pitch on the threads99on the second threaded section91, except that the pitch is opposite hand between the first and second threaded section91,92. In this regard, the internal threads within the bores81for the first and second wedge members22,24are designed to mate with the respective threads of the respective first and second threaded sections91,92, and are thus also opposite handed such that when the actuation member26rotates, the first and second wedge members22and24translate along the actuation member26toward each other or away from each depending on the rotation direction of the actuation member26. The thread pattern on each threaded section91,92may have the same pitch such that the first and second wedge members22and24can translate along the actuation member26at the same rate. The thread pitch can be different if needed when different distraction profiles are desired in the expanded configuration (e.g. kyphotic or lordotic). The proximal end26pof the actuation member26can define a socket26econfigured to receive or support a portion of an insertion instrument, as further detailed below. The socket26ecan have any configuration as need to receive an instrument, such as hex, Phillips, flat, star, square, etc.

Thus, the shaft95of the actuation member26is curved along its length and defines a second threaded section91disposed distally relative to the flange28(or in the second side5proximate the insertion end12), and a first threaded section92disposed proximally from the flange28(or in the first side3proximate the trailing end14). The shaft95can have a length L1extending from a distal end96along a central axis CA extending along the center of the shaft (seeFIG. 6A) to a proximal end97, where the length L1can extend between about 24 to about 32 mm. The length of each of the first and second threaded sections91,92is preferably equal, but can be different, and is preferably between about 6 mm to about 12 mm, more preferably between about 8 mm to about 9 mm. The length of middle section90, which extends between the first and second threaded sections91,92is preferably between about 8 mm to about 13 mm, more preferably between about 9 mm to about 11 mm. As shown inFIGS. 6A-E, the middle section90is constructed with a first cable section93aextending between the second threaded section91and the flange28and a second cable section93bextending between the first threaded section92and the flange28. The length of each of the first and second cable sections93a,93bis preferably about equal, but can be different, and preferably is each from about 4 mm to about 7 mm long, and more preferably from about 4.5 mm to about 5.5 mm long along the central axis CA (seeFIG. 6A). The flange28is preferably about 2 mm to about 5 mm long along the central axis CA between faces28a,28b,and preferably about 2 mm to about 3 mm in height between faces28c,28d(seeFIG. 6E).

As seen inFIGS. 2A-2B and 7A-7D, the implant10can have initial dimensions and expanded dimensions. For instance, the implant can have first implant height D1defined between the opposing first and second bone contacting surfaces32and132when the implant is in its collapsed position C, and second implant height D2defined between the opposing first and second bone contacting surfaces32and132when the implant is in its expanded position E. The distance is measured from the surfaces32,132, and not from the tops of any textures41(teeth, etc.) that are commonly used with such surfaces. In an embodiment, the first implant height D1can range between about 7 mm and 15 mm, preferably between about 7 mm and 10 mm, and the second expanded implant height D2can range between about 10 mm and 20 mm, preferably between about 10 mm and 13 mm. In the expanded position E, the opposed superior and inferior inner planar surfaces35a,which in the collapsed position C preferably abut one another, can be spaced apart any distance as desired within the stated range, such as between about 3 mm and 5 mm. For instance, in one embodiment, the first height D1can be 7 mm while the expanded, second height D2can be 10 mm. In another embodiment, the first height D1can be 9 mm and the expanded, second height D2can be 13 mm. Other dimensions are possible as well. For example first heights can be up to 7 mm, 9 mm, or greater. The implant10also has a width, and in one embodiment, the first and second bone contacting surfaces32and132can define a dimension in the lateral direction A as desired, such as between 8 mm and 12 mm.

The overall system includes one or more insertions tools. An insertion tool can include a handle and a shaft extending from the handle toward an implant supporting end. The implant supporting end can be configured to support, for instance carry or engage with a portion of the implant10. The implant supporting end can include spaced apart tabs configured and sized to be received in the implant indentations98. When the implant tabs engage the indentations98, the tool can position and/or insert the implant10into the intervertebral space9. An additional tool can be used to expand the implant10from the collapsed configuration C to the expanded configuration E. This tool can include a handle and a shaft extending from the handle toward a working end configured to engage the proximal end26pof the actuation member26, such that rotation of the tool can cause rotation of the actuation member26.

Referring toFIGS. 7A-7D, implant10is configured to expand from the collapsed configuration C (FIG. 7B) to the expanded configuration E (FIG. 7D). When in the first or collapsed configuration C, the first and second wedge members22and24are disposed in the implant such that the inner ends76face and are spaced apart from each other to define a gap therebetween extending over the middle section90. The first and second wedge members22,24are threaded onto the actuation member26such that the first threaded section92is disposed within the bore81of the first wedge member22and the second threaded portion91is disposed within the bore81of the second wedge member24. In the collapsed position C, the wedge members22,24are preferably located near or at the inner ends61of the threaded sections91,92, and are spaced apart from the sides28a,28bof the flange. The inclined surfaces77and78of the wedge members22,24are adjacent to opposing ramp surfaces44and46of the respective inferior and superior endplates20,18. In one embodiment, the inner end superior edge and inferior edges76sand76iextend into the opening30and can be located within or above/below a plane containing the bone contacting surfaces32,132. Portions of the first and second wedge members22and24, for instance edges76s,76i,disposed in the opening30allows for a wedge profile that aids the endplates18and20separation with relatively little advancement of the first and second wedge members22and24along the actuation member26.

When the actuation member26is rotated via a tool engaged at the proximal end26p,the first threaded portion92of the actuation member26causes the first wedge member22to translate toward the trailing end14of the implant10. The inclined surfaces77and78bear against the ramp surfaces44and46to separate the superior endplate18from the inferior endplate20along the transverse direction to move the implant10from the collapsed position C to the expanded position E. The protrusions or tabs82of the first wedge member22slide along the grooves37i,37sin a controlled manner. In conjunction, because the middle portion90of the actuation member26is a flexible cable, at the same time while the first wedge member22is translating toward the implant trailing end14, the second threaded portion91of the actuation member26engages the bore81of the second wedge member24and causes the second wedge member24to translate toward the insertion end12of the implant10. Again, the inclined surfaces77and78of the second wedge member24slide along the ramp surfaces44and46so as to separate the superior endplate18from the inferior endplate20along the transverse direction T. Again, the protrusions or tabs82of the second wedge member24slide along respective grooves37s,37i.The flange28remains disposed in the slots52,54during actuation of the implant10and provides additional stability against sheer when the implant10is expanded. The embodiment shown inFIGS. 7A-7Dillustrates the superior endplate18separating from the inferior endplate20along a transverse direction T while remaining generally parallel to each other. In other alternate embodiments, the implant can be configured to such that a lordotic or kyphotic distraction is achieved. For example, the threaded portions of the actuation member can be configured to cause one wedge member to translate at a faster rate compared to the other wedge member. In such an embodiment, when the implant10is expanded, the superior endplate18will be angularly offset from the inferior endplate20.

The implant10can be used in TLIF surgical procedures. In general terms, the intervertebral disc space9is prepared by removing the appropriate amount of natural disc material to the surgeon's preference and preparing the endplate vertebral surfaces6,8for receiving the implant10. The implant10is inserted into the intervertebral space9defined between a superior vertebral body2and an inferior vertebral body4. Preferably, the intervertebral implant10is inserted into the intervertebral space9in the fully collapsed configuration, although the implant10could be slightly expanded. The method further includes the step of expanding the intervertebral implant10from a collapsed configuration to a final expanded configuration. When the implant10is in the collapsed configuration, the first and second bone contacting surfaces32and132are spaced from each other a first distance in the transverse direction T.

As described above, the actuation member26is rotatable about its central axis CA to cause the implant10to expand from a collapsed configuration to an expanded configuration. As described above, a tool is used to rotate the actuation member26to cause the first and second wedge members22and24translate along the actuation member26and to move away from each other to expand the implant10. The actuation member26can be rotated until the first wedge member22abuts a stop member63, which prevents further rotation of the actuation member26in the expansion direction. The stop member63can be a ring that has a threaded internal bore and that is placed onto the first threaded section92after the first wedge member22is assembled onto the implant10. The actuation member26is rotatable in a contraction direction opposite the expansion direction so as to cause the wedge members22and24to move toward each other, thereby moving the endplates18and20toward each other in a direction from an expanded position toward a collapsed configuration. The implant10thus can be expanded in the cranial-caudal or superior-inferior direction, the transverse direction T, to engage the adjacent vertebral bodies2,4.

There are other mechanical components that can be used in the present invention to provide for the simultaneous rotation of the first and second threaded sections91and92of the actuation member26to cause the first and second wedge members22,24to simultaneously expand the implant10by imparting a rotational force upon the actuation member26at its proximal end26p.For example, inFIGS. 8A-8E, a dual universal joint embodiment is shown for the actuation member26. The dual universal joint102is located in the middle section90of the actuation member26. The dual universal joint102is constructed with a first universal joint assembly107and a second universal joint assembly108. The first universal joint assembly107has a fork103acoupled to the first threaded section92, preferably integrally formed with the first threaded section92. The fork103ais coupled to a center block (or ball)104aby way of pins106athat extend through opposed openings109ain the fork103a.The center block104ais also coupled to center fork105aby way of pins106athat extend through openings109a.The second universal joint assembly108has a fork103bcoupled to the second threaded section91, preferably integrally formed with the second threaded section91. The fork103bis coupled to a center block104bby way of pins106bthat extend through opposed openings109bin the fork103b.The center block104bis also coupled to center fork105bby way of pins106bthat extend through openings109b.In this embodiment, the dual universal joint102along with the first and second threaded sections92,91form the actuation member26for the implant10. Apart from the mechanical mechanism for permitting the simultaneous rotation of the two threaded sections91,92being different between this dual universal joint102embodiment and the flexible cable93embodiment inFIGS. 2-7, the remaining parts and function of the implant are the same. In that regard, when the actuation member26having the dual universal joint102is used in the implant the angle between the first threaded section91and the second threaded section92is the same as described above with the flexible cable93embodiment.

Another embodiment for the actuation member26is shown inFIGS. 9A-9E, a turn buckle embodiment. The turn buckle112is located in the middle section90of the actuation member26. The turn buckle112is constructed with a first inner end113acoupled to the first threaded section92, preferably integrally formed with the first threaded section92. The first inner end113ais partially threaded with threads99but is cut along its two sides116ato form a reduced profile loop section and the sides116ahave a hole119a.An inner shaft114aalso has a loop section with a hole115a.The hole119aof the inner end113areceives the loop section of the inner shaft114aand the hole115aof the inner shaft114areceives the loop section of the inner end113ato form part of the turn buckle112on the first threaded section92side of the actuation member26. The turn buckle112is further constructed with a second inner end113bcoupled to the second threaded section91, preferably integrally formed with the second threaded section91. The second inner end113bis partially threaded with threads99but is cut along its two sides116bto form a reduced profile loop section and the sides116bhave a hole119b.An inner shaft114balso has a loop section with a hole115b.The hole119bof the inner end113breceives the loop section of the inner shaft114band the hole115bof the inner shaft114breceives the loop section of the inner end113bto form part of the turn buckle112on the second threaded section91side of the actuation member26. In this embodiment, the turn buckle112along with the first and second threaded sections92,91form the actuation member26for the implant10. Apart from the mechanical mechanism for permitting the simultaneous rotation of the two threaded sections91,92being different between this turn buckle112embodiment and the flexible cable93embodiment inFIGS. 2-7, the remaining parts and function of the implant are the same. In that regard, when the actuation member26having the turn buckle112is used in the implant the angle between the first threaded section91and the second threaded section92is the same as described above with the flexible cable93embodiment.

Still another embodiment for the actuation member26is shown inFIGS. 10A-10E, a universal joint embodiment. The universal joint122is located in the middle section90of the actuation member26. The universal joint122is constructed with a fork123acoupled to the first threaded section92, preferably integrally formed with the first threaded section92. The fork123ais coupled to a center block (or ball)124by way of pins126that extend through opposed openings129ain the fork123a.The center block124is also coupled to opposing fork123bby way of pins126that extend through openings129b.The fork123bcoupled to the second threaded section91, preferably integrally formed with the second threaded section91. In this embodiment, the universal joint122along with the first and second threaded sections92,91form the actuation member26for the implant10. Apart from the mechanical mechanism for permitting the simultaneous rotation of the two threaded sections91,92being different between this universal joint122embodiment and the flexible cable93embodiment inFIGS. 2-7, the remaining parts and function of the implant are the same, except that the flange28is not present in the embodiment as shown. In that regard, when the actuation member26having the universal joint122is used in the implant the angle between the first threaded section91and the second threaded section92is the same as described above with the flexible cable93embodiment.

Yet another drive mechanism that can form the basis for another embodiment for the actuation member26is shown inFIGS. 11A-11D, a dual wired cylinder embodiment. The dual wired cylinder142is also a flexible rod like the cable93embodiment and is located in the middle section90of the actuation member26. The dual wired cylinder142is constructed with a first wired cylinder143acoupled to the first threaded section92, preferably integrally formed with the first threaded section92. The first wired cylinder143ais preferably formed from surgical grade metal alloy such as a titanium alloy as a wire turned to form a cylinder shape. At its opposite end, the first wired cylinder143ais connected to a second wired cylinder143bthat is connected at its opposite end to the second threaded section91. The flange28can optionally be formed between the first and second wired cylinders143a,b as shown. In this embodiment, the dual wired cylinder142along with the first and second threaded sections92,91form the actuation member26for the implant10. Apart from the mechanical mechanism for permitting the simultaneous rotation of the two threaded sections91,92being different between this dual wired cylinder142embodiment and the flexible cable93embodiment inFIGS. 2-7, the remaining parts and function of the implant are the same. In that regard, when the actuation member26having the dual wired cylinder142is used in the implant the angle between the first threaded section91and the second threaded section92is the same as described above with the flexible cable93embodiment.

Each of the superior endplate18and inferior endplate20can include one or more radiographic markers. The implant10can define one or more bores (not shown) sized and dimensioned to receive a radiographic marker therein. For example, a radiographic marker can be disposed near the nose16in either the superior endplate18or the inferior endplate20, or both. The markers can thus identify the location of the nose16of the implant and also the extent of expansion of the implant10when the markers are located in each endplate. For example, when the implant10is inserted into the intervertebral space9, and the implant10is expanded from the first configuration C to the expanded configuration E, the markers can separate along the transverse direction T. With image analysis, the extent of plate separation can be determined or indicated by observing the extent of separation between the markers disposed in the superior endplate18compared to the marker disposed in the inferior endplate20.