(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2003/0139813 A1
`
`Messerli et al.
`(43) Pub. Date:
`Jul. 24, 2003
`
`US 20030139813A1
`
`(54)
`
`(76)
`
`INTERVERTEBRAL IMPLANT FOR
`TRANSFORAMINAL POSTERIOR LUMBAR
`INTERBODY FUSION PROCEDURE
`
`Inventors: Dominique Messerli, West Chester, PA
`(US); David Gerber, Exton, PA (US);
`David Paul, Phoenixville, PA (US);
`Kenneth Isamu Kobayashi, Exton, PA
`(US)
`
`Correspondence Address:
`PENNIE AND EDMONDS
`1155 AVENUE OF THE AMERICAS
`NEW YORK, NY 100362711
`
`(21) Appl. No.:
`
`10/293,997
`
`(22)
`
`Filed:
`
`Nov. 13, 2002
`
`Related US. Application Data
`
`(63) Continuation-in-part of application No. 09/848,178,
`filed on May 3, 2001.
`
`Publication Classification
`
`(51)
`
`Int. Cl.7 ........................................................ A61F 2/44
`
`(52) us. Cl.
`
`.......................................................... 623/1711
`
`(57)
`
`ABSTRACT
`
`An intervertebral implant for fusing vertebrae is disclosed.
`The implant has a body with curved, substantially parallel
`posterior and anterior faces separated by two narrow implant
`ends, superior and inferior faces having a plurality of
`undulating surfaces for contacting upper and lower vertebral
`endplates, and at least one depression in the anterior or
`posterior face for engagement by an insertion tool, at least
`two vertical through-channels extending through the implant
`from the superior face to the inferior face, a chamfer on the
`superior and inferior surfaces at one of the narrow implant
`ends, and a beveled edge along a perimeter of the superior
`and inferior faces. The arcuate implant configuration and the
`chamfers on the superior and inferior faces at the narrow end
`facilitate insertion of the implant from a transforaminal
`approach into a symmetric position about the midline of the
`spine so that a single implant provides balanced support to
`the spinal column. The implant may include radiopaque
`markers extending through the thickness of the implant to
`indicate the location and size of the implant. The implant
`may be formed of a plurality of interconnecting bodies
`assembled to form a single unit. An implantation kit and
`method are also disclosed.
`
`
`
`MSD 1007
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`Patent Application Publication
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`US 2003/0139813 A1
`
`Jul. 24, 2003
`
`INTERVERTEBRAL IMPLANT FOR
`TRANSFORAMINAL POSTERIOR LUMBAR
`INTERBODY FUSION PROCEDURE
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`[0001] This application is a continuation-in-part of US.
`patent application Ser. No. 09/848,178, filed May 3, 2001.
`
`FIELD OF THE INVENTION
`
`[0002] The present invention is directed to an interverte-
`bral implant, its accompanying instrumentation and their
`method of use. More particularly, the present invention is
`directed to an intervertebral implant and instrumentation for
`use in a transforaminal posterior lumbar interbody fusion
`procedure.
`
`BACKGROUND OF THE INVENTION
`
`[0003] A number of medical conditions such as compres-
`sion of spinal cord nerve roots, degenerative disc disease,
`herniated nucleus pulposus, spinal stenosis and spondylolis-
`thesis can cause severe low back pain. Intervertebral fusion
`is a surgical method of alleviating low back pain. In poste-
`rior lumbar interbody fusion (“PLIF”), two adjacent verte-
`bral bodies are fused together by removing the affected disc
`and inserting posteriorly one or more implants that would
`allow for bone to grow between the two vertebral bodies to
`bridge the gap left by the removed disc.
`
`[0004] One variation of the traditional PLIF technique is
`the
`transforaminal posterior
`lumbar
`interbody fusion
`(T—PLIF) technique. Pursuant to this procedure, an implant
`is inserted into the affected disc space via a unilateral (or
`sometimes bilateral), posterior approach, offset from the
`midline of the spine, by removing portions of the facet joint
`of the vertebrae. The T—PLIF approach avoids damage to
`nerve structures such as the dura, cauda equina and the nerve
`root, but the resulting transforaminal window available to
`remove the affected disc, prepare the vertebral endplates,
`and insert the implant is limited laterally by soft tissue and
`medially by the cauda equina.
`
`[0005] A number of different implants typically used for
`the traditional PLIF procedure have been used for the
`T—PLIF procedure with varying success. These include
`threaded titanium or polymer cages, allograft wedges, rings,
`etc. However, as these devices were not designed specifi-
`cally for the T—PLIF procedure, they are not shaped to be
`easily insertable into the affected disc space through the
`narrow transforaminal window, and may require additional
`retraction of the cauda equina and nerve roots. Such retrac-
`tion can cause temporary or permanent nerve damage. In
`addition, some of these implants, such as the threaded
`titanium or polymer cage, suffer from the disadvantage of
`requiring drilling and tapping of the vertebral endplates for
`insertion. Further, the incidence of subsidence in long term
`use is not known for such cages. Finally, restoration of
`lordosis, i.e., the natural curvature of the lumbar spine is
`very difficult when a cylindrical or square titanium or
`polymer cage is used.
`
`[0006] As the discussion above illustrates, there is a need
`for an improved implant and instrumentation for fusing
`vertebrae via the transforaminal lumbar interbody fusion
`procedure.
`
`SUMMARY OF THE INVENTION
`
`[0007] The present invention relates to an intervertebral
`implant (“T-PLIF implant”) and its use during a transfo-
`raminal lumbar interbody fusion procedure. In a preferred
`embodiment, the T—PLIF implant has an arcuate body with
`curved, preferably substantially parallel, posterior and ante-
`rior faces separated by two narrow implant ends, and supe-
`rior and inferior faces having textured surfaces for contact-
`ing upper and lower vertebral endplates. Preferably,
`the
`textured surfaces comprise undulating structures which may
`include projections, such as teeth, of a saw-tooth or pyra-
`midal configuration, or ridges which preferably penetrate the
`vertebral endplates and prevent slippage. The narrow
`implant ends may be rounded or substantially flat. The
`arcuate implant configuration facilitates insertion of the
`implant via a transforaminal window. The implant, which
`may be formed of allogenic bone, metal, or plastic, may also
`have at least one depression, such as a channel or groove, in
`the posterior or anterior face for engagement by an insertion
`tool, such as an implant holder. In a preferred aspect, the
`superior and inferior faces are convex, and the thickness of
`the implant tapers with its greatest thickness in the middle
`region between the narrow ends of the implant, i.e., at a
`section parallel to a sagittal plane, and decreasing toward
`each of the narrow ends.
`
`In another embodiment, the T—PLIF implant pref-
`[0008]
`erably has curved, substantially parallel posterior and ante-
`rior faces extending along a longitudinal axis of the implant,
`a pair of convex narrow ends separating the posterior and
`anterior faces, a chamfer on the superior and inferior faces
`at one of the convex narrow ends, a beveled edge along a
`perimeter of the superior and inferior faces, and at least one
`depression in the anterior or posterior face for engagement
`by an insertion tool, where the superior and inferior faces
`contact upper and lower vertebral endplates and define a
`thickness of the implant. The T—PLIF implant preferably has
`at least two vertical through-channels extending through the
`implant from the superior face to the inferior face, each
`vertical through-channel having a width and walls on pos-
`terior and anterior sides of the width. The arcuate implant
`configuration and the chamfer on the inferior and superior
`faces at the narrow insertion end of the implant facilitate
`insertion of the implant via the transforaminal window. In a
`preferred aspect, the implant also has at least two anterior-
`posterior horizontal through-channels extending through the
`implant from the posterior face to the anterior face. The
`implant may also feature at
`least one lateral horizontal
`through-channel extending from a narrow end of the implant
`inward toward an adjacent anterior-posterior horizontal
`through-channel. Each of the channels may be packed with
`bone-graft and/or bone growth inducing material to aid in
`spinal fusion. In one exemplary embodiment, the walls on
`the posterior and anterior sides of the width of the vertical
`through-channels have a thickness greater than the width of
`the vertical through channels. The implant may be formed of
`a radiolucent polymer material selected from the polyaryl
`ether ketone family (PAEK), such as polyether ether ketone
`(PEEK) or polyether ketone ketone (PEKK), or other suit-
`able biocompatible material of sufficient strength, such as
`titanium. The implant may include one or more radiopaque
`marker, such as pins or screws, extending substantially
`through the thickness of the implant to indicate implant
`location and size in postoperative spinal scans.
`
`22
`
`22
`
`

`

`US 2003/0139813 A1
`
`Jul. 24, 2003
`
`In another preferred embodiment, the implant is
`[0009]
`formed of a plurality of interconnecting bodies assembled to
`form a single unit. In this configuration, the plurality of
`interconnecting bodies forming the T—PLIF implant may be
`press-fit together and may include one or more pin(s) or
`screw(s) extending through an opening in the plurality of
`bodies to hold the bodies together as a single unit. Adjacent
`surfaces of the plurality of bodies may also have mating
`interlocking surfaces that aid in holding the bodies together
`as a single unit.
`
`In still another preferred embodiment, the present
`[0010]
`invention relates to a kit for implanting an intervertebral
`implant
`into an affected disc space of a patient via a
`transforaminal window. The kit includes an implant having
`an arcuate body with curved, preferably substantially par-
`allel, posterior and anterior faces separated by two narrower
`implant ends, superior and inferior faces preferably having
`a textured surface, such as projections or teeth, for contact-
`ing and preferably penetrating upper and lower vertebral
`endplates. The superior and inferior faces may define a
`thickness. Preferably the implant has at least one depression
`in its posterior or anterior face near one of its ends for
`engagement by an insertion tool. The implant may also have
`two or more vertical through-channels extending through the
`implant from the superior face to the inferior face, each
`vertical through-channel having a width and walls on pos-
`terior and anterior sides of the width, a chamfer on the
`superior and inferior surfaces at an insertion end and a
`beveled edge along a perimeter of the superior and inferior
`faces. The kit may further include one or more trial-fit
`spacer(s) for determining the appropriate size of the implant
`needed to fill the affected disc space, an insertion tool having
`an angled or curved neck for holding and properly position-
`ing the implant during insertion through the transforaminal
`window, and an impactor having an angled or curved neck
`for properly positioning the implant within the affected disc
`space. The face of the impactor may be concavely shaped to
`mate with the narrow end of the T—PLIF implant during
`impaction. The kit may further include a lamina spreader for
`distracting vertebrae adjacent to the affected disc space, an
`osteotome for removing facets of the vertebrae adjacent to
`the affected disc space to create a transforaminal window,
`one or more curettes, angled and/or straight, for removing
`disc material from the affected disc space, a bone rasp for
`preparing endplates of the vertebrae adjacent the affected
`disc space, and a graft implant tool for implanting bone graft
`material into the affected disc space. The kit may still further
`include a curved guide tool to guide the implant into the
`affected disc space. In another preferred embodiment, the
`implant of the kit includes two or more anterior-posterior
`horizontal through-channels extending through the implant
`from the posterior face to the anterior face, wherein a portion
`of the walls on the posterior and anterior sides of the width
`of the vertical through-channels of the implant may have a
`thickness greater than the width of the vertical
`through
`channels. The implant of the kit may also include one or
`more lateral horizontal through-channel(s) extending from a
`narrow end of the implant
`inward toward an adjacent
`anterior-posterior horizontal through-channel. Each of the
`channels may be packed with bone-graft and/or bone growth
`inducing material prior to and/or after insertion to aid in
`spinal fusion. The implant may also include one or more
`radiopaque markers, such as pins, that extend substantially
`through the thickness of the implant.
`
`In yet another aspect, a method for implanting an
`[0011]
`intervertebral implant into an affected disc space of a patient
`via a transforaminal window is described. The transforami-
`
`nal window is created, the disc space is prepared and bone
`graft material may be inserted into the affected disc space.
`Using an insertion tool, an implant
`is inserted into the
`affected disc space via the transforaminal window and
`seated in a portion of the disc space closer to the anterior
`edge of the disc space than the posterior edge of the disc
`space. As discussed above, the implant preferably has an
`arcuate body with curved, substantially parallel posterior
`and anterior faces separated by two narrow implant ends,
`superior and inferior faces having a plurality of undulating
`surfaces for contacting upper and lower vertebral endplates,
`and preferably at least one depression at a first end for
`engagement by the insertion tool. In the present method, the
`arcuate implant configuration facilitates insertion of the
`implant via the transforaminal window. The implant may be
`inserted along an arcuate path. The method may further
`comprise impacting the implant with an impactor tool to
`properly position the implant within the affected disc space.
`Either or both the insertion tool and the impactor tool may
`be angled to facilitate insertion, alignment, placement and/or
`proper seating of the implant. The implant may also feature
`two or more vertical through-channel(s) extending through
`the implant from the superior face to the inferior face, each
`vertical through-channel having a width and walls on pos-
`terior and anterior sides of the width, a chamfer on the
`superior and inferior faces at the insertion end, and a beveled
`edge along a perimeter of the superior and inferior faces. The
`implant may also have two or more anterior-posterior hori-
`zontal
`through-channel(s) extending through the implant
`from the posterior face to the anterior face and/or at least one
`lateral horizontal through-channel extending from a narrow
`end of the implant
`inward toward an adjacent anterior-
`posterior horizontal through-channel. Each of the channels
`may be packed with bone-graft and/or bone growth inducing
`material before implantation and/or after implantation to aid
`in spinal fusion.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0012] FIG. 1 is a top view of a typical human vertebrae
`showing the transforaminal window through which an
`implant according to the present invention is inserted;
`
`[0013] FIG. 2A is a cross-section view of an embodiment
`of an implant according to the present invention;
`
`[0014] FIG. 2B is a side view along the longer axis of the
`implant of FIG. 2A;
`
`[0015] FIG. 2C is a cross-section view taken along line
`2C-2C of FIG. 2B;
`
`[0016] FIG. 2D is a perspective view of the implant of
`FIG. 2A;
`
`[0017] FIG. 3A is a partial cross-section view of another
`embodiment of an implant according to the present inven-
`tion;
`
`[0018] FIG. 3B is a partial cross-section view along the
`longer axis of the implant of FIG. 3A;
`
`[0019] FIG. 3C is a cross-section view taken along line
`3C-3C of FIG. 3B;
`
`23
`
`23
`
`

`

`US 2003/0139813 A1
`
`Jul. 24, 2003
`
`3
`
`[0020] FIG. 3D is a perspective view of the implant of
`FIG. 3A;
`
`[0043] FIG. 16C is a partial cross-section top view of the
`implant of FIG. 16A;
`
`[0021] FIG. 4 is a perspective view of still another
`embodiment of the implant of the present invention;
`
`[0044] FIG. 16D is a perspective view of the implant in
`FIG. 16A;
`
`[0022] FIG. 5 is an aXial view of a typical human verte-
`brae showing the implant of FIG. 4 in an asymmetric final
`position.
`
`[0023] FIG. 6 is a posterior view of a section of human
`spine prior to preparation of the transforaminal window;
`
`[0045] FIG. 16E is a partial side view of the implant taken
`along line 16E-16E in FIG. 16C;
`
`[0046] FIG. 17A is a partial cross-section side view along
`the longer aXis of still another embodiment of an implant
`according to the present invention;
`
`[0024] FIG. 7 is a posterior view of a section of human
`spine with the transforaminal window prepared;
`
`[0047] FIG. 17B is a partial cross-section side view along
`the shorter aXis of the implant of FIG. 17A;
`
`[0025] FIG. 8A depicts an angled bone curette for use
`during the T—PLIF procedure;
`
`[0026] FIG. 8B depicts another angled bone curette for
`use during the T—PLIF procedure;
`
`[0027] FIG. 8C depicts an angled bone curette removing
`disc material from an affected disc space;
`
`[0028] FIG. 9A depicts an angled bone rasp for use during
`a T—PLIF procedure;
`
`[0029] FIG. 9B depicts an angled bone rasp removing
`material from an affected disc space;
`
`[0030] FIG. 10A depicts a trial-fit spacer for use during a
`T—PLIF procedure;
`
`[0031] FIG. 10B depicts a trial-fit spacer being inserted
`into an affected disc space via a transforaminal window;
`
`[0032] FIG. 11A depicts an implant holder for use during
`a T—PLIF procedure;
`
`[0033] FIG. 11B depicts the tips of the implant holder
`shown in FIG. 11A;
`
`[0034] FIG. 11C depicts an posterior view of the human
`spine showing a T—PLIF implant being inserted with an
`implant holder;
`
`[0035] FIG. 11D depicts a top view of a human vertebrae
`showing a T—PLIF implant being inserted with in an implant
`holder;
`
`[0036] FIG. 12 depicts an implant guide tool for use with
`the T—PLIF implant;
`
`[0037] FIG. 13A depicts an angled impactor tool for use
`with the T—PLIF implant;
`
`[0038] FIG. 13B is a close-up view of the tip of the
`impactor tool shown in FIG. 13A;
`
`[0039] FIG. 14 is a top view of a typical human vertebrae
`showing an implant according to the present invention being
`properly positioned into an affected disc space using the
`impactor tool shown in FIG. 13A;
`
`[0040] FIG. 15 is a top view of the vertebrae of FIG. 1
`showing the T—PLIF implant in a final position; and
`
`[0041] FIG. 16A is a partial cross-section side view along
`the longer aXis of still another embodiment of an implant
`according to the present invention;
`
`[0042] FIG. 16B is a partial cross-section side view along
`the shorter aXis of the implant of FIG. 16A;
`
`[0048] FIG. 17C is a partial cross-section top view of the
`implant of FIG. 17A; and
`
`[0049] FIG. 17D is a perspective view of the implant in
`FIG. 17A;
`
`[0050] FIG. 17E is a partial side view of the implant taken
`along line 17E-17E in FIG. 17C;
`
`[0051] FIG. 18 is a side view of another preferred embodi-
`ment of the implant of the present invention.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`[0052] While various descriptions of the present invention
`are provided below,
`it should be understood that
`these
`descriptions are intended to illustrate the principals of the
`present invention and its various features, which can be used
`singly or in any combination thereof. Therefore, this inven-
`tion is not to be limited to only the specifically preferred
`embodiments described and depicted herein.
`
`interbody
`lumbar
`[0053] The transforaminal posterior
`fusion implant (“T-PLIF implant”) is designed for use as an
`intervertebral spacer in spinal fusion surgery where an
`affected disk is removed from between two adjacent verte-
`brae and replaced with an implant that provides segmental
`stability and allows for bone to grow between the two
`vertebrae to bridge the gap created by disk removal. Spe-
`cifically, the T—PLIF implant is designed for the transforami-
`nal lumbar interbody fusion (T—PLIF) technique, which, as
`shown in FIG. 1, involves a posterior approach 12, offset
`from the midline 14 of the spine, to the affected interverte-
`bral disk space 16. The window 18 available for implant
`insertion using the T—PLIF technique is limited medially by
`the dura or cauda equina 20 and the superior eXiting nerve
`root (not shown).
`
`[0054] As shown in FIGS. 2A through 2D, in a preferred
`embodiment, the T—PLIF implant has an arcuate, “rocker-
`like” body 22 with curved anterior and posterior faces 24, 26
`to facilitate the offset insertion of the implant through the
`narrow approach window 18 into the disk space. Preferably,
`the anterior and posterior faces 24 and 26 are substantially
`parallel, separated by a pair of narrow ends 25. Narrow ends
`25 may be rounded or blunt. The superior and inferior
`surfaces 28, 30 preferably have projections, such as teeth 32,
`for engaging the adjacent vertebrae. Teeth 32 on superior
`and inferior surfaces 28, 30 preferably provide a mechanical
`interlock between implant 22 and the end plates by pen-
`etrating the end plates. The initial mechanical stability
`afforded by teeth 32 minimizes the risk of post-operative
`expulsion/slippage of implant 22. Teeth 32 may have a
`
`24
`
`24
`
`

`

`US 2003/0139813 A1
`
`Jul. 24, 2003
`
`saw-tooth shape, where one side of the tooth is perpendicu-
`lar to the superior or inferior surface, or a pyramid shape,
`where each tooth has four sides and forms an acute angle
`with the superior or inferior face. Preferably, implant body
`22 has at least one channel or slot 34 on one end of implant
`22 for engagement by a surgical instrument, such as an
`implant holder 66 (shown in FIG. 11A). It should be noted
`that implant 22 may also be configured with a channel 34 on
`only one side or without channels altogether. Other known
`methods for engaging the implant with surgical instruments,
`such as a threaded bore for receiving the threaded end of a
`surgical tool or a non-threaded bore for receiving an expand-
`able head of an insertion tool, may also be used.
`[0055] As shown in FIG. 2B, thickness 31 of implant 22
`is greatest at
`the mid-section between the two narrow
`implant ends 25 and tapers gradually along the longitudinal
`axis 36 of implant 22 so that it is thinnest at the narrow ends
`25 of implant 22. The taper is preferably arcuate and
`provides a convex configuration and a proper anatomical fit,
`while also facilitating insertion of implant 22 into the
`affected disc space. It should be noted that in a preferred
`embodiment, thickness 31 does not taper or change along the
`shorter axis 37 of implant 22. Thus for any given cross
`section taken perpendicular to the longitudinal axis 36 of the
`implant,
`the distance between the superior and inferior
`surfaces 28 and 30 remains substantially constant. In alter-
`nate embodiments, however, thickness 31 may change or
`taper along shorter axis 37 of implant 22. The dimensions of
`implant 22 can be varied to accommodate a patient’s
`anatomy, and the thickness of the implant is chosen based on
`the size of the disk space to be filled. Preferably, implant 22
`has a maximum thickness 31 at its mid-section of about 7.0
`
`to about 17.0 mm, and may be formed of metal, allograft, a
`metal-allograft composite, a carbon-fiber polymer, pure
`polymer or plastic or combinations of these materials. The
`implant may also be formed of a resorbable polymer. The
`thickness at the narrow ends 25 of implant 22 may range
`from about 1.5 to about 2.0 mm less than the maximum
`
`thickness at the mid-section. The implant may range from
`about 26 to about 32 mm in length, and have a width from
`about 9 to 11 mm. Implant 22, which as shown most clearly
`in FIG. 2A is symmetric about at least one axis of rotation
`37, is intended for symmetric placement about the midline
`14 of the spine (see FIG. 19). The arcuate configuration of
`implant 22 facilitates insertion of the implant from the
`transforaminal approach into a symmetric position about the
`midline of the spine so that a single implant provides
`balanced support to the spinal column.
`[0056] As shown in FIGS. 3A-3D, in an alternate embodi-
`ment implant 22 may be formed of two or more pieces 38
`preferably having interlocking grooves 39 and pallets 40 that
`may be press-fit and fastened together with pins or screws
`42. The number and orientation of pins or screws 42 can be
`varied.
`In addition or alternatively,
`the pieces may be
`fastened using glue, cement or a welding or bonding pro-
`cess. This multi-component configuration may be particu-
`larly useful for implants formed of allograft bone, since it
`may be difficult and/or impractical to obtain a single, suf-
`ficiently large piece of allograft for some applications. In the
`case of implants formed completely of artificial (i.e., non-
`allograft) materials, such as steel, plastic or metallic or
`non-metallic polymer, a one-piece implant may be more
`practical. As shown in FIG. 3C, in a preferred embodiment
`for any given cross-section taken perpendicular to the lon-
`
`the distance between the
`gitudinal axis of the implant,
`superior and inferior surfaces 28 and 30 remains substan-
`tially constant.
`
`[0057] As in the previous embodiment, the anterior and
`posterior faces 24, 26 are preferably substantially parallel,
`and, as shown, may be defined by radii of curvature R1 and
`R2, where R1, for example, may be in the range of 25-35
`mm and preferably about 28 mm and R2, for example, may
`be in the range of 15 to 25 mm and preferably about 19 mm.
`The superior and inferior surfaces 28, 30 are arcuate shaped
`and the implant has a thickness 31, which is preferably
`greatest at a center portion between narrow ends 25 and
`gradually tapers becoming thinnest at narrow ends 25.
`Tapering thickness 31 may be defined by a radius of curva-
`ture R3, where R3 for example, may be in the range of 85
`to 115 mm and preferably about 100 mm. As shown, the
`component pieces 46, 48 of implant 22 have holes 44 to
`accommodate pins or screws 42. Holes 44 are preferably
`drilled after component pieces 38 have been stacked one on
`top of the other. The multiple pieces 38 are then assembled
`with screws or pins 42 so that practitioners receive the
`implant 22 as a single, pre-fabricated unit. The upper com-
`ponent piece 46 has an arcuate superior surface preferably
`with teeth 32, while its bottom surface is preferably config-
`ured with grooves and pallets preferably to interlock with
`the upper surface of lower component piece 48. The arcuate
`inferior surface 30 of lower component piece 48 also pref-
`erably has teeth 32 for engaging the lower vertebral endplate
`of the affected disc space. Either or both superior and
`inferior surfaces 28, 30 may have ridges, texturing or some
`other form of engaging projection in place of teeth 32.
`
`[0058] Reference is now made to FIGS. 16A-16E, which
`display still another preferred embodiment of the implant of
`the present invention. Similar in profile to the embodiments
`shown in FIGS. 2A and 3A, the anterior and posterior faces
`24, 26 are substantially parallel, and, as shown, may be
`defined by radii of curvature R1 and R2, where R1, for
`example, may be in the range of 25 to 35 mm and preferably
`about 29 mm and R2, for example, may be in the range of
`15 to 25 mm and preferably about 19 mm. The superior and
`inferior surfaces 28, 30 are arcuate shaped and the implant
`has a thickness 31, which is preferably greatest at a center
`portion between narrow ends 25 and gradually tapers
`becoming thinnest at narrow ends 25. Tapering thickness 31
`may be defined by a radius of curvature R3, where R3 for
`example, may be in the range of 85 to 115 mm and
`preferably about 100 mm. Superior and inferior surfaces 28,
`30 preferably have a textured surface which may include a
`plurality of undulating surfaces, such as, for example, teeth
`32, for engaging the upper and lower vertebral endplates of
`the affected disc space. (Note: For sake of clarity, teeth 32
`are not pictured in FIGS. 16C-16E, 17C-17E or on the
`inferior face of the implant shown in FIGS. 16B & 17B.)
`
`[0059] As shown, the implant has depressions or slots 34
`on both its anterior and posterior face that mate with an
`insertion tool 66 (shown in FIGS. 11A & 11B). As shown in
`FIGS. 11B, 16C and 17C, projections 69 on the tips 67 of
`insertion tool 66 mate with scalloped depressions 81, within
`slots 34 to securely hold the implant during insertion. The
`implant has a pair of vertical through-channels 74 extending
`through the implant from the superior surface 28 to the
`inferior surface 30, which may be packed with bone graft
`and other bone growth inducing material prior to and/or after
`
`25
`
`25
`
`

`

`US 2003/0139813 A1
`
`Jul. 24, 2003
`
`implantation to aid in spinal fusion. Preferably, the implant
`also has a chamfer 75 on both its superior and inferior
`surfaces 28, 30 at insertion end 79. As shown best in FIGS.
`16D and 16E, chamfers 75 form a wedge-like shape at
`insertion end 79 to facilitate implant insertion through the
`transforaminal window. Chamfers 75 begin at a section of
`the implant at an angle [3 from the midline of the implant,
`where [3 may be in the range of 15° to 30° and preferably
`about 23°, and taper to the end of narrow insertion end 79.
`As shown in FIG. 16E, chamfers 75 form an angle y with the
`vertical wall of narrow insertion end 79, where y may be in
`the range of 50° to 80° and preferably about 60°.
`
`[0060] Preferably, implant 22 also includes a beveled edge
`76 along the perimeter of its superior and inferior surfaces
`28, 30 As shown in FIG. 16B, beveled edge 76 may be
`beveled at an angle (X to the vertical axis, which may be in
`the range of 25° to 45° and preferably about 37°. Beveled
`edge 76 is free from teeth 32 and both facilitates implant
`insertion and handling of the implant by physicians. Since
`edges 76 are free from teeth 32, the perimeter edges of the
`implant are unlikely to become snagged by tissue during
`implant insertion and a surgeon is less likely to tear protec-
`tive gloves while handling the implant prior to and during
`insertion.
`
`[0061] As shown in FIG. 16C, in a preferred embodiment,
`the thickness of the walls T1 on the anterior and posterior
`sides of vertical through-channels 74 is greater than the
`width W1 of vertical through-channel 74. For example, for
`an implant with walls of equal thickness, T1 may be in the
`range of 3.4 to 4.0 mm and preferably about 3.5 mm and W1
`may be on the order of 3.2 to 2.0 mm. The total implant
`width may be in the range of 9 to 11 mm, and preferably
`about 10 mm. It should be emphasized that the implant
`shown in FIGS. 16A-16C has walls 82 of equal t