GLOBUS MEDICAL, INC.
`EXHIBIT 1009
`IPR2015-to be assigned
`(Globus v. Flexuspine)
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`11 1997 R. p '
`1
`5,
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`lnner .
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`11/1997 M°F‘‘ag“° 8‘ "~ ~
`5588373 11/1997 E“}°° 6‘ 61-
`~
`5,688,274
`11/1997 E6100 6* a1~ ~
`5,688,279
`11/1997 McNu1ty et a1~ ~
`5,688,280
`11/1997 Booth, Jr. et al.
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`5,693,053
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`5,693,100 12/1997 Pisharodi .
`5,697,929
`12/1997 Mellinger ................................ .. 606/61
`5,697,977 12/1997 Pisharodi
`623/17
`5,700,291
`12/1997 Kuslich et al.
`623/17
`5,700,292 12/1997 Margulies
`623/17
`5,702,391
`12/1997 Lin ........ ..
`606/61
`5,702,392 12/1997 Wu et al.
`606/61
`5,702,393
`12/1997 Pfaifer
`606/61
`5,702,394 12/1997 Henry et al.
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`5,702,449
`12/1997 McKay
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`5,702,451
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`623/17
`5,702,452 12/1997 Argenson et al.
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`623/17
`5,702,453
`12/1997 Rabbe et al.
`623/17
`5,702,454 12/1997 Baumgartner
`623/17
`5,702,455
`12/1997 Saggar
`623/17
`5,704,936
`1/1998 Mazel
`606/61
`5,704,937
`1/1998 Martin
`.. 606/61
`5,707,372
`1/1998 Errico et al.
`606/61
`5,707,395
`1/1998 Li
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`5,709,681
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`606/54
`5,709,682
`1/1998 Medoff .
`606/60
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`1/1998 Bagby
`606/61
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`1/1998 Errico et al.
`606/61
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`1/1998 Dombrowski et al.
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`606/69
`5,713,841
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`606/60
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`2/1998 Marnay et al.
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`2/1998 Errico et al.
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`2/1998 Jackson ........ ..
`606/61
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`2/1998 Biedermann et al.
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`2/1998 Rogozinski
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`606/61
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`2/1998 Ochoa et al.
`606/62
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`2/1998 Ojima et al.
`606/76
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`2/1998 Steffee
`623/17
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`2/1998 Lin .......................................... .. 623/17
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`2/1998 Soubeiran ............................... .. 606/61
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`2/1998 Burke ........ ..
`606/74
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`2/1998 Kuslich et al.
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`2/1998 Jackson ................................... .. 606/86
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`3/1998 Wilhelmy ................................ .. 606/84
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`6,045,579
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`U.S. PATENT DOCUMENTS
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`U.S. Patent
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`Apr. 4,2000
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`Sheet 1 of 11
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`6,045,579
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`FIG.
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`FIG. 8
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`FIG. 6B
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`U.S. Patent
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`Apr. 4, 2000
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`Sheet 11 of 11
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`6,045,579
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`1
`ADJUSTABLE HEIGHT FUSION DEVICE
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention generally relates to methods and
`apparatus for promoting an intervertebral fusion, and more
`particularly to an apparatus for
`insertion into a space
`between adjacent vertebrae to facilitate an intervertebral
`fusion while maintaining a substantially natural lordosis of
`the human spine.
`2. Description of the Related Art
`Intervertebral discs that become degenerated due to vari-
`ous factors such as trauma or aging typically have to be
`partially or fully removed. Removal of an intervertebral disc
`can destabilize the spine, making it necessary to replace the
`vertebral disc to maintain the height of the spine and to fuse
`the spine. Spinal implants are often used to prevent collapse
`of the spine. U.S. Ser. No. 08/740,123 filed Oct. 24, 1996
`relates to methods and apparatus for facilitating a spinal
`fusion and is incorporated by reference as if fully set forth
`herein.
`
`After an intervertebral disc is removed, an implant device
`is typically inserted between neighboring vertebrae to main-
`tain normal disc spacing and restore spinal stability, thereby
`facilitating an intervertebral fusion. A conventional implant
`device disposed between neighboring vertebrae is depicted
`in FIGS. 1 and 2. The implant device contains a pair of
`engaging elements 20 that typically contain threading 10 to
`engage the vertebrae. Prior to inserting the engaging
`elements, a vertebral drill is typically inserted within the
`surgical wound to drill into the cortical endplate and remove
`fibrous and nuclear material. A vertebral tap may then be
`used to cut threads into the ends of the neighboring verte-
`brae. The engaging elements tend to be relatively inflexible
`and substantially undeflectable. The engaging elements are
`typically packed with bone graft to facilitate a spinal fusion.
`Conventional implant devices tend to not maintain the
`“lordosis” or natural curvature of the lower lumbar spine. As
`shown in FIG. 1,
`the implant device contains parallel
`engaging sides 12 and 13 to contact vertebra 15.
`It
`is
`typically required that
`the engaging sides be parallel to
`prevent the fusion cage from slipping from the intervertebral
`space. The parallel configuration of the fusion cage tends to
`alter the lordosis of the spine. Such a loss of lordosis may
`result
`in an increased risk to other intervertebral discs
`
`located adjacent to the fusion level that may degenerate due
`to the altered force transmission in the spine.
`FIG. 2 depicts a front view of the engaging elements 20
`of the implant device. The engaging elements are substan-
`tially cylindrical and the region of contact between an
`engaging element and a vertebra is defined by arcuate
`portion 22. The cylindrical geometry of the engaging ele-
`ments tends to provide a relatively small area of contact
`between the fusion cage and the vertebrae. The weight of the
`spine creates pressure on the vertebrae that is concentrated
`proximate the arcuate portions. Subsidence or deformation
`of the cortical layer of the vertebrae tends to result.
`U.S. Pat. No. 5,522,899 to Michelson relates to a spinal
`implant for placement into the spinal disc space to stabilize
`the spine and participate in a vertebra to vertebra bony
`fusion. U.S. Pat. No. 5,489,308 to Kuslich et al. relates to an
`implant for use in spinal stabilization that includes a cylin-
`drical body having external threading and radially disposed
`openings positioned to chip bone into an interior portion of
`the body when the implant
`is installed. The above-
`
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`mentioned patents are incorporated by reference as if fully
`set forth herein.
`
`The above-mentioned prior methods and systems inad-
`equately address, among other things, the need to maintain
`the natural lordosis of the spine. It is therefore desirable that
`an improved spinal implant be derived for facilitating an
`intervertebral body fusion.
`SUMMARY OF THE INVENTION
`
`In accordance with the present invention, a spinal implant
`is provided that largely eliminates or reduces the aforemen-
`tioned disadvantages of conventional implant devices. An
`embodiment of the invention relates to a fusion device for
`
`facilitating an interbody fusion between neighboring verte-
`brae of a human spine. The fusion device preferably includes
`a pair of sides or engaging plates for engaging the vertebrae
`and an alignment device disposed between the engaging
`plates for separating the engaging plates to maintain the
`engaging plates in lordotic alignment. The alignment device
`is preferably adapted to adjust
`the height between the
`engaging plates to customize the fusion device to a particu-
`lar patient. The height of the fusion device preferably varies
`along the length of the device such that the height proximate
`an anterior end of the device differs from the height proxi-
`mate a posterior end of the device.
`The engaging plates are preferably substantially planar so
`as to inhibit subsidence of the vertebrae. The engaging plates
`may contain protrusions extending from their outer faces for
`enhancing an engagement between the vertebra and the
`engaging plate. The protrusions may be adapted to extend
`into the vertebra. The engaging plates preferably include a
`plurality of openings to allow bone growth to occur through
`the engaging plates. The openings in the face of the engaging
`plates preferably have a total area that is between about 60
`percent and about 80 percent of a total surface area of the
`face (including the area of the openings).
`The fusion device may include a retaining plate proximate
`the posterior end that serves as a backing against which bone
`graft may be packed between the engaging plates. The
`fusion device may also include a removable end cap proxi-
`mate the anterior end for maintaining bone graft between the
`engaging plates.
`In an embodiment, the alignment device includes a first
`strut and a second strut
`that each extend between the
`
`therebetween. The
`engaging plates to define the height
`fusion device preferably includes a first side and a second
`side opposite the first side. The first strut preferably runs
`from the anterior end to the posterior end along a location
`proximate the first side, and the second strut preferably runs
`from the anterior end to the posterior end along a location
`proximate the second side. The engaging plates preferably
`include a pair of slots sized to receive ends of the struts. The
`slots may have a substantially dovetail-shaped cross-section
`that is conformed to the shape of the ends. Each slot is
`preferably tapered such that its width narrows in a direction
`from the anterior end to the posterior end whereby the width
`of the slot proximate the posterior end is less than the width
`of the end of the strut. The ends of the struts preferably have
`a lateral width that tapers in substantially the same manner
`as the slots such that a locking taper engagement is formable
`between the slots and the ends of the struts.
`
`The height of each strut preferably varies along the length
`of the strut such that the height between the engaging plates
`differs between the anterior end and the posterior end to
`allow the lordosis of the spine to be maintained. The first and
`second struts may have differing heights to cause the height
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`of the fusion device to vary along the device from the first
`side to the second side to correct for a lateral deviation in the
`spinal column. Each of the struts may include a hinge to
`allow an upper member of the strut to pivot with respect to
`a lower member of the strut.
`
`In an alternate embodiment, the engaging plates include
`slots and the fusion device further includes a pair of pins
`disposed within the slots. Each engaging plate preferably
`includes a rib extending in a substantially perpendicular
`direction from its face. The slot for receiving the pins is
`preferably disposed on the rib. The pins are preferably
`substantially elongated and may extend in a direction from
`the first side to the second side. The fusion device preferably
`further includes a rotatable connector engaging the pins.
`Rotation of the connector preferably causes movement of
`the pins relative to one another to alter the height of the
`fusion device to create a desired lordotic alignment.
`The connector is preferably adapted to move axially
`between the engaging plates and may contain a retaining
`ring for contacting an engaging plate to limit movement of
`the connector through the fusion device. The connector
`preferably moves axially between the engaging plates in a
`direction from the anterior end to the posterior end, thereby
`moving the first pin toward the anterior end and the second
`pin toward the posterior end to increase the height between
`the engaging plates. The connector may be a screw having
`a threaded portion. The first pin may include a threaded
`opening for receiving a threaded portion of the connector.
`The second pin may be connected to an unthreaded portion
`of the connector.
`
`The pins preferably include a receiving section and an
`end. The ends of the pins are preferably sized to fit within the
`slots in the ribs of the engaging plates. The receiving section
`may have a width greater than that of the ends of the pins and
`preferably contains an opening for receiving the connector.
`One engaging plate preferably includes a first slot that
`may terminate in an end that extends in a diverging direction
`from an end of another slot contained on the other engaging
`plate. Movement of one of the pins preferably draws the
`ends of the slots together to alter the amount of separation
`between the engaging plates. The movement of the pins
`relative to one another preferably alters the height proximate
`the anterior end at a faster rate than the height proximate the
`posterior end is altered to achieve a desired lordotic align-
`ment.
`
`In an alternate embodiment, the fusion device contains a
`load-sharing member to promote a spinal fusion. The load-
`sharing member may be axially disposed within the struts.
`The load-sharing member is preferably substantially deflect-
`able to allow movement of one of the engaging plates when
`a compressive force is exerted on the engaging plates. A
`predetermined spacing preferably exists between the upper
`and lower members. Application of a compressive force
`onto the engaging plates preferably deflects the load-sharing
`member and decreases the predetermined spacing between
`the members, thereby decreasing the height of the strut. The
`deflection of the load-sharing member preferably imparts
`stress to bone graft proximate the engaging plates to pro-
`mote the development and growth of bone in accordance
`with Wolff’s law.
`
`The load-sharing member may be a pin having a circular
`cross-section and preferably is disposed in a bore extending
`axially through the strut. The bore preferably has a greater
`width than that of the load-sharing member to provide space
`for deflection of the load-sharing member. The load-sharing
`member may serve as a hinge-pin about which the upper
`member of the strut pivots with respect to the lower member
`of the strut.
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`The fusion device preferably further includes a connector
`for engaging the load-sharing member to impart force to the
`load-sharing member to cause it to deflect. The strut may
`include a threaded opening in its end for receiving the
`connector. The predetermined spacing between the upper
`and lower members may be set
`to a desired length by
`altering the position of the connector in the opening in the
`end of the strut. The load-sharing member may include an
`indention having a substantially planar surface to provide a
`site for engagement with the connector. The connector
`preferably engages the load-sharing member at a fulcrum
`point located at a predetermined horizontal distance from a
`support
`location where the lower member of the strut
`contacts the load-sharing member. The material properties
`of the load-sharing member and the distance between the
`fulcrum point and the support location are preferably con-
`trolled such that the modulus of elasticity across the strut is
`substantially equal to the modulus of elasticity of bone.
`The above embodiments may be used independently or in
`combination.
`
`An advantage of the invention relates to an intervertebral
`body fusion device that substantially maintains the natural
`lordosis of the human spine.
`Another advantage of the invention relates to an interver-
`tebral body fusion device adapted to correct a lateral devia-
`tion in the spinal column.
`Another advantage of the invention relates to an interver-
`tebral body fusion device adapted to deflect to impart stress
`on surrounding bone to promote bone growth.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Further advantages of the present invention will become
`apparent to those skilled in the art with the benefit of the
`following detailed description of the preferred embodiments
`and upon reference to the accompanying drawings in which:
`FIG. 1 depicts a conventional intervertebral body fusion
`implant positioned between neighboring vertebrae.
`FIG. 2 depicts another conventional intervertebral body
`fusion implant that includes a pair of cylindrical members
`positioned between neighboring vertebrae.
`FIG. 3 depicts a top view of a fusion device located on a
`vertebral body.
`FIG. 4a depicts a cross-sectional view of the fusion device
`of FIG. 3 taken along plane I.
`FIG. 4b depicts a cross-sectional view of the fusion of
`FIG. 3 device taken along plane I wherein the fusion device
`contains bone graft and has been adjusted to maintain a
`substantially natural lordosis.
`FIG. 5 depicts a front view of a fusion device.
`FIG. 6a depicts a perspective view of a strut.
`FIG. 6b depicts a side view of a tapered strut.
`FIG. 7 depicts a top view of a fusion device.
`FIG. 8 depicts a front view of a pair of engaging plates.
`FIG. 9 depicts a front view of a fusion device having
`pivotable struts.
`FIG. 10 depicts a top view of a fusion device containing
`a connector.
`
`FIG. 11 depicts an anterior view of a fusion device having
`a connector and cam pins.
`FIG. 12 depicts a cross-sectional view taken along plane
`III of FIG. 11 of the fusion device in a lowered position.
`FIG. 13 depicts a cross-sectional view taken along plane
`III of FIG. 11 of the fusion device in a raised position.
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`FIG. 14 depicts a cross-sectional view taken along plane
`IV of FIG. 11 of the fusion device in a lowered position.
`FIG. 15 depicts a cross-sectional view taken along plane
`IV of FIG. 11 of the fusion device in a raised position.
`FIG. 16 depicts a side View of a fusion device disposed
`between vertebrae.
`
`FIG. 17 depicts a top view of a strut having a tapered end.
`FIG. 18 depicts a cross-sectional view taken along plane
`V of FIG. 17 of the strut in an unloaded position.
`FIG. 19 depicts a cross-sectional view taken along plane
`V of FIG. 17 of the strut in a loaded position.
`FIG. 20 depicts a top view of a fusion device located on
`a vertebral body.
`FIG. 21 depicts a cross-sectional view of the fusion device
`taken along plane VI of FIG. 3.
`FIG. 22 depicts a top view of a conventional fusion cage
`having a pair of cylindrical elements disposed on a vertebra.
`FIG. 23 depicts a side view of one of the cylindrical
`elements in FIG. 22 disposed between neighboring verte-
`brae.
`
`FIG. 24 depicts a front view of the cylindrical element in
`FIG. 23.
`
`While the invention is susceptible to various modifica-
`tions and alternative forms, specific embodiments thereof
`are shown by way of example in the drawings and will
`herein be described in detail.
`It should be understood,
`however, that the drawings and detailed description thereto
`are not intended to limit the invention to the particular form
`disclosed, but on the contrary, the intention is to cover all
`modifications, equivalents and alternatives falling within the
`spirit and scope of the present invention as defined by the
`appended claims.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`A preferred embodiment of an interbody fusion implant
`device 10 for facilitating the formation of a spinal fusion is
`depicted in FIGS. 3-5. A top view of the fusion device is
`depicted in FIG. 3. Fusion device 10 preferably includes a
`pair of sides or engaging plates 12 and 14 for engaging
`vertebral bodies 16 and 18. The engaging plates may contain
`curved edges such that
`the outer face 15 of the plates
`conforms to the shape of the cross-section of the vertebral
`bodies as shown in FIG. 3. The fusion device has a height
`20 defined by the vertical distance between the outer faces
`15 of the engaging plates 12 and 14. The height 20 of the
`fusion device is preferably adjustable and may vary along
`the fusion device between anterior end 22 and posterior end
`24 to maintain the natural lordosis of the spine. Height 20
`may also vary along device 10 from first side 26 to second
`side 28 to correct for a lateral deviation in the spine as may
`occur in scoliosis. Fusion device 10 preferably further
`includes an alignment device for adjusting the height 20 so
`that the natural lordosis of the spine is substantially main-
`tained after the fusion device is implanted. The alignment
`device may be used to adjust the height between the engag-
`ing plates proximate the anterior end and independently
`adjust the height between the engaging plates proximate the
`posterior end.
`A spinal fusion is typically employed to eliminate pain
`caused by the motion of degenerative disk material. Upon
`successful fusion, fusion device 10 becomes permanently
`fixed within the disc space. The fusion device is preferably
`packed with bone graft 40 to promote the growth of bone
`through and around the fusion device. Such bone graft may
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`be packed between engaging plates 12 and 14 prior to,
`subsequent to, or during implantation of the fusion device.
`Bone substitute material that is well known to those skilled
`in the art may be used instead of bone graft. Abone harvester
`kit, commercially available from Spine-Tech, Inc. located in
`Minneapolis, Minn., may be used to inject bone graft
`between the engaging plates. The pamphlet entitled “Bone
`Harvester: Minimally Invasive Bone Harvesting Kit”
`(available from Spine-Tech, Inc.) details the use of the bone
`harvesting kit.
`the faces 15 of
`In an embodiment of the invention,
`engaging plates 12 and 14 contain a plurality of openings 34
`disposed therein to allow bone development and growth
`through the engaging plates 12 and 14 and between fusion
`device 10 and neighboring vertebrae 16 and 18.
`In an
`embodiment, the openings 34 have a combined area that is
`greater than about 50 percent of the area of face 15
`(including the area of the openings 34), more preferably
`between about 60 percent and about 80 percent of the area
`of face 15, and more preferably still about 70 percent or
`more of the area of face 15.
`
`The fusion device may contain a retaining plate 36
`proximate posterior end 24 to provide a backing against
`which bone graft may be packed and to maintain the bone
`graft between the engaging plates. Retaining plate 36 may be
`substantially planar and may contain openings to allow bone
`ingrowth therethrough. A removable endcap 25 may be
`positioned proximate anterior end 22 to contain bone graft
`within the fusion device and to prevent the migration of bone
`graft outside the engaging plates. The endcap 25 may
`contain one or more openings for allowing bone ingrowth
`between a vertebral body and bone graft contained between
`the engaging plates. Endcap 25 is preferably made of a
`plastic material such as polyethylene that tends to be non-
`irritating and non-abrasive to the surrounding tissues.
`A cross section of the fusion device taken through plane
`I of FIG. 3 is depicted in FIG. 4a and FIG. 4b. FIG. 4a shows
`the relative position of engaging plates 12 and 14 before
`height 20 has been adjusted with an alignment device to
`achieve a substantially natural lordosis. FIG. 4b shows the
`relative position of the plates after height 20 has been
`adjusted and bone graft 40 has been packed between the
`engaging plates. FIG. 4b shows that height 20 is greater in
`the vicinity of anterior end 22 as compared to posterior end
`24 to maintain the natural lordosis of the spinal column. The
`faces 15 of the engaging plates 12 and 14 are preferably
`planar to provide a relatively large contact area between the
`engaging plates and the neighboring vertebrae.
`In this
`manner, subsidence of the vertebrae may be prevented
`because the force imparted to the vertebrae from the fusion
`device is not concentrated across a relatively small area of
`the vertebrae as in some conventional implants. Alternately,
`the engaging plates may be non-planar. The engaging plates
`also preferably contain a plurality of spikes or protrusions 38
`extending from the face 15 for enhancing an engagement
`between the vertebra and the engaging plate. The protrusions
`may extend into the vertebra to prevent the fusion device
`from moving out of the disc space. The engaging plates are
`preferably constructed of titanium or a titanium alloy,
`although it is to be understood that other materials (e.g.,
`ceramics, metals, carbon composites) may be used.
`A front view of the fusion implant device is depicted in
`FIG. 5. In an embodiment of the invention, the alignment
`device includes a first strut 30 and a second strut 32 that each
`
`extend between engaging plates 12 and 13 along the length
`of the fusion device from anterior end 22 to posterior end 24.
`As described herein, a “strut” is taken to mean any support
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`member disposed between the engaging plates to separate
`the engaging plates. Strut 30 preferably extends along the
`fusion device proximate first side 26. Strut 32 is preferably
`substantially parallel to strut 30 and may extend along the
`fusion device proximate second side 28. The struts 30 and 32
`serve to create a predetermined spacing between the engag-
`ing plates. The predetermined spacing is preferably such that
`the height 20 is approximately equal to the height of the disc
`material that formerly occupied the disc space between the
`vertebral bodies.
`
`A perspective view of an embodiment of the strut is
`depicted in FIG. 6a. The strut may have an “I-beam” shape
`and preferably includes a pair of ends 50. The ends 50 may
`have a lateral width 51 that is greater than that of the sides
`53. The ends preferably have a “dovetail” shaped cross-
`section as shown in FIG. 6a. The engaging plates preferably
`contain elongated slots 60 (shown in FIGS. 7 and 8) sized to
`receive ends 50 of the first and second struts. The slots 60
`preferably have a complementary dovetail shape as depicted
`in FIG. 8 that conforms to the shape of the end 50. The struts
`may be connected to the engaging plates by sliding ends 50
`into the slots 60 in a direction from anterior end 22 to
`posterior end 24 or vice versa.
`In an embodiment, the slots are tapered such that their
`width narrows in a direction from the anterior end to the
`posterior end as shown in FIG. 7. The ends 50 may be
`tapered (as shown in FIG. 17) such that the lateral width 51
`narrows along the length of the strut. The taper of the lateral
`width of the strut preferably matches that of slot 60. The
`width of the slot proximate the anterior end is preferably
`sized to allow the strut end to be slid into the slot. The width
`
`of the slot proximate the posterior end is preferably less than
`the lateral width 51 of the narrowest portion of end 50. The
`tapering of the slots preferably allows a “locking taper
`engagement” of the strut ends within the slots. A “locking
`taper engagement” is taken to mean a fixable interference fit
`formed between end 50 and slot 60 whereby the strut resists
`dislodgement when force is imparted to the fusion device
`from the adjacent vertebrae. In an alternate embodiment, the
`slots may be tapered such that the width of the slots narrows
`in a direction from the posterior end to the anterior end.
`The first and second struts preferably each have a prede-
`termined height that defines the height of the fusion device.
`The engaging plates 12 and 14 are preferably adapted to
`receive struts of various heights to allow height 20 to be
`varied to fit the needs of the patient. A side view of a tapered
`strut is depicted in FIG. 6b. The tapered strut preferably has
`a height that varies along its length. In this manner,
`the
`tapered strut is positionable between the engaging plates 12
`and 14 to cause height 20 to decrease in a direction from
`anterior end 22 to posterior end 24 whereby the natural
`lordosis of the human spine is maintained by the fusion
`device. The degree of taper of the strut corresponds to a
`desired lordosis and may vary depending upon the size of the
`patient.
`In an embodiment, the first and second struts have dif-
`fering heights to cause height 20 to vary between first end 14
`and second end 16. In this manner, the fusion device may be
`used to correct a lateral deviation in the spinal column as
`may occur in scoliosis. A front view of a fusion device
`containing struts having different heights is depicted in FIG.
`9. Each of the struts preferably contains a hinge pin 70 to
`allow an upper member 72 of the strut to pivot with respect
`to a lower member 74 of the strut. In this manner, the struts
`may be pivoted as shown in FIG. 9 such that the ends of the
`struts are properly aligned with the slots of the engaging
`plates when a height difference exists between the first and
`second struts.
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`To install the fusion device, a discectomy is preferably
`performed from an anterior approach. All cartilage and soft
`tissue are preferably removed from the vertebral endplate as
`would normally be done for placement of a femoral strut
`graft. Such a procedure is well within the knowledge of a
`skilled practitioner of the art. The engaging plates may be
`deployed in the disc space between the adjacent vertebrae.
`A distraction force may be applied to the engaging plates
`using a laminae spreader or similar device to force the
`vertebrae to a selected height and lordotic alignment. The
`use of a laminae spreader is well known to those skilled in
`the art. The proper heights for the first and second struts may
`be determined beforehand using x-ray techniques in which
`the posterior and anterior portions