_
`
`Unlted States Patent [19]
`Kozak et al.
`'
`
`USOO5397364A
`
`5,397,364
`[11] Patent Number:
`[45] Date of Patent: Mar. 14, 1995
`
`RB Y
`54 ANTERIOR
`[
`]
`M 01) FUSION DEVICE
`
`'
`FOREIGN PATENT DOCUMENTS
`
`[75] Inventors: ‘Jeffrey Kozak, Houston, Tex.; Larry
`Boyd, Memphis, Tenn.
`
`WO90/00037 l/1990 WIPO .
`WO92/l4423 9/1992 WIPO .
`
`.
`
`.
`
`.
`
`7
`:
`[ 3] Asslgnee 22:3‘ Medlcal’ Inc" Memphis’
`'
`[21] Appl. No.: 134,049
`[22] Filed_
`Oct 12 1993
`'
`'
`’
`
`v
`
`.6 _ _ ' ‘ . _
`
`51
`
`In _
`
`E53 Ufs Cé]
`[58] Fielh of'
`
`[56]
`
`. _ _ _ . ' . i _ _ . . _ . _ . _ . _ _ _ _ “
`
`623
`' ' ' ' " 623A; 11 16
`' ' ' ' ' '
`""""""""""""""" "
`’
`’
`References Cited
`
`Us PATENT DOCUMENTS
`4,759,766 7/1988 Buettner-Janx Ct a1. ........... .. 623/17
`4,772,287 9/1988 Ray et a1. ............ ..
`623/17
`4,863,476 9/1989 Shepperd ..
`623/17
`4,878,915 11/ 1989 Brantigan --
`- 623/ 17
`4,892,545 I/ 1990 Day et a1 ---- -_
`- 623/17
`FDOVe eta‘lil
`i’ggfil’ggl
`-
`17
`' 623;};
`4’932’975 M1990 M13; ‘3; a1‘ '
`623/17
`_____ H
`4:936’848 6/1990 Bagby
`. 623/17
`5,002,576 3/1991 Fuhrmann et al
`.. 623/17
`5,147,404 9/ 1992 Downey ........... 1.
`5,192,327 3/1993 Brantigan ............................ .. 623/17
`
`Primary Examiner—David Isabella
`
`Attorney, Agent, or Firm-Woodard, Emhardt,
`Naughton, Moriarty & McNett
`[57]
`.ABSTRACT
`An interbody fusion device includes a pair of lateral
`spacers and a pair of central spacers, each sized for
`
`percutaneous introduction through a disc resection
`
`portal in the disc annulus. Each of the lateral spacers
`includes opposing side faces de?ning a channel therein,
`while each of the central spacers includes arms at their
`opposite ends con?gured to be received within a chan
`nel of a corresponding lateral spacer. The arms and
`channels are interlocking to prevent separation of the
`Components Once assembled Within the intmdiscal
`space. The assembly of the central and lateral spacers
`de?nes a cavity therebetween for insertion of bone graft
`material. The central and lateral spacers are con?gured
`so that the bone graft cavity is oriented over the weak
`est, but most vascular and biologically active, bone of
`the vertebral body, while the lateral spacers are situated
`adjacent the disc annulus and over the strongest verte
`bral bm‘e
`
`18 Claims, 9 Drawing Sheets
`
`20
`
`ANTERIOR
`
` 1
`
`NUVASIVE 1034
`NuVasive, Inc. v. Warsaw Orthopedic, Inc.
`IPR2013-00206
`IPR2013-00208
`
`

`

`US. Patent
`U.S. Patent
`
`Mar. 14, 1995
`Mar. 14, 1995
`
`Sheet 1 of 9
`Sheet 1 of 9
`
`5,397,364
`5,397,364
`
`
`
` 2
`
`
`
`

`

`US. Patent
`
`» Mar. 14, 1995
`
`Sheet 2 of 9
`
`5,397,364
`
`+ POSTER'OR
`
`STRONGEST
`(RING APOPHYSIS)
`
`+ POSTERIOR
`
`24
`
`+
`ANTERIOR
`
`23
`
`7g. 3
`
` 3
`
`
`
`

`

`US. Patent
`US. Patent
`
`Mar. 14, 1995
`Mar. 14, 1995
`
`Sheet 3 of 9
`Sheet 3 of 9
`
`5,397,364
`5,397,364
`
` by
`
`D‘
`
`//s g
`
`//a.s
`
` 4
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`

`

`US. Patent
`
`Mar. 14, 1995
`
`Sheet 4 0f 9
`
`5,397,364
`
`
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`
` 5
`
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`

`

`US. Patent
`US. Patent
`
`-Mar.-14, 1995
`-Mar. 14, 1995
`
`Sheet 5 of 9
`Sheet 5 of 9
`
`5,397,364
`5,397,364
`
`fig.18
`
`
` 6
`
`
`
`

`

`US. Patent
`US. Patent
`
`Mar. 14, 1995
`Mar. 14, 1995
`
`Sheet 6 of 9
`Sheet 6 of 9
`
`5,397,364
`5,397,364
`
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`US. Patent
`US. Patent
`
`Mar. 14, 1995
`Mar. 14, 1995
`
`Sheet 7 of 9
`Sheet 7 of 9
`
`5,397,364
`5,397,364
`
`
`fig. 24
`
` 8
`
`
`
`

`

`U.S. Patent
`US. Patent
`
`Mar. 14, 1995
`Mar. 14, 1995
`
`Sheet 8 of 9
`Sheet 8 of 9
`
`5,397,364
`5,397,364
`
`130
`
`130
`
`126
`12
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`US. Patent
`
`Mar. 14, 1995
`
`Sheet 9 of 9
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`5,397,364
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`

`1
`
`ANTERIOR INTERBODY FUSION DEVICE
`
`5,397,364
`2
`the adjacent vertebrae, while also preventing disc inter
`space collapse due to end plate cavitation, for instance.
`There is also a need for a fusion device that is safe and
`effective and still consistent with traditional surgical
`arthrodesis practice.
`In connection with the development of the interbody,
`fusion device of the present invention, Applicants have
`ascertained certain design principals that should be met
`for a safe and effective device. One important principal
`is that the load transmitted between adjacent vertebrae
`should be on the strongest part of the vertebral body.
`One problem with some prior art fusion devices, and
`even some prosthetic disc devices, is that a large portion
`of the load is reacted against the weakest part of the
`vertebral body which can lead to cavitation of the de
`vice into the surrounding vertebral endplates with sub
`sequent collapse of the intradiscal space and even dam
`age to the vertebra itself.
`Further, a preferred interbody fusion device should
`?t the patient’s intradiscal anatomy and restore, as close
`as possible, the proper anatomic relationship of the disc,
`pedicle, nerve root and facet joint in order to avoid
`future physiological problems. Restoration of the nor
`mal disc height will also return the disc annulus to ten
`sion, reducing annular bulge or prolapse and promoting
`interspace stability. At the same time, the device should
`not shield the lumbar spine from all of the stresses nor
`mally borne by the spine, since it has been found that
`reduction of normal stress on the vertebrae can result in
`loss of bone mass and strength.
`Finally, the interbody fusion device should provide
`enough interspace rigidity to eliminate the need for
`external ?xation or rigid ?xation plates. With these
`goals in mind, Applicants have developed the anterior
`interbody fusion device and method of the present in
`vention.
`
`SUMMARY OF THE INVENTION
`The present invention contemplates an interbody
`fusion device configured for insertion into the intradis
`cal space following resection of the disc material
`through a portal in the disc annulus. The device in
`cludes a pair of lateral spacers formed in a generally
`semicircular con?guration and occupying less than half
`of the area of the intradiscal space. Each of the lateral
`spacers de?nes a channel in opposing and interiorly
`facing side faces. The device further includes a pair of
`central spacers, each con?gured at their respective ends
`for engaging the channels in the lateral spacers. The
`channels and ends of the central spacers are con?gured
`for interlocking engagement, such as a dovetail, so that
`the central spacers can be slidably inserted and removed
`only along the length of the charmel. In other words,
`the interlocking feature between the lateral and central
`spacers maintains a predetermined and ?xed lateral
`separation between the lateral spacers so that the lateral
`spacers are disposed adjacent the disc annulus and,
`more signi?cantly, over the region of the vertebral
`body having the highest strength and load bearing capa
`bility.
`Each component of the interbody fusion device, the
`lateral and central spacers, is sized for insertion through
`a single portal in the disc annulus. However, when
`assembled within the intradiscal space, the fusion device
`occupies the entire space, leaving only a central cavity
`between the spacers for the insertion of the bone graft
`material. This central cavity is situated over the weak
`
`BACKGROUND OF THE INVENTION
`This invention relates to spinal implants for use as
`anterior ?xation devices, and to an implant which is to
`be placed into the intervertebral space left after the
`removal of a damaged spinal disc to assist in promoting
`interbody fusion.
`A major cause of persistent, often disabling, back pain
`can arise by disruption of the disc annulus, chronic
`in?ammation of the disc, or relative instability of the
`vertebral bodies surrounding a given disc, such as might
`occur due to a degenerative disease. In the more severe,
`disabling cases, some form of mechanical limitation to
`the movement of vertebrae on either side of the subject
`disc is necessary. In the more severe cases, the disc
`tissue is irreparably damaged, thereby necessitating
`removal of the entire disc. However, when the disc
`nucleus is removed without subsequent stabilization, the
`same disabling back pain often recurs due to persistent
`in?ammation and/or instability.
`Various approaches have been developed to stabilize
`the adjacent vertebral bodies following excision of the
`disc material. In one approach, two adjacent vertebra
`are fused posterio-laterally, according to a standard
`technique, by rigid plates engaged at their ends to re
`spective vertebrae by way of screws. However, it has
`been found that posterior fusion with rigid plates can be
`associated with pseudoarthrosis and implant loosening
`and/ or failure.
`Another approach involves the use of posterio-lateral
`fusion and rigid posterior instrumentation, as described
`above, with the addition of an interbody graft or im
`plant placed from the posterior approach. Although a
`signi?cant improvement in fusion rate can be achieved
`with this approach, scarring of the spinal nerves can
`occur which may lead to pain or neurologic de?cit.
`In yet another approach, anterior grafts are imple
`mented. Three general types of anterior devices are
`40
`presently known. In one type, the entire vertebral body
`is replaced by an implant that spans the vertebral and
`two surrounding intradiscal spaces. This approach is
`frequently used where the vertebral body is also dam
`aged by way of a tumor, a fracture and the like. In
`another approach, only the disc is replaced by a pros
`thetic disc. In this approach, the object is not fusion
`between the vertebrae at the instrumented level, but
`rather replacement of the disc mechanical features by
`an implant.
`A third approach, to which the present invention is
`more particularly directed, concerns a device adapted
`to promote fusion or arthrodesis across the intradiscal
`space. In the upper lumbar spine, bone grafts can be
`placed within the disc and the surrounding vertebrae
`can be stabilized with a plate placed on the lateral verte
`bral body using screws projecting into the bodies. This
`approach is not possible in the lower lumbar disc spaces
`due to the regional vascular anatomy. Unfortunately,
`more than 90% of the lumbar fusions are performed in
`the lower lumbar region. Therefore, there exists a need
`for a device to stabilize adjacent vertebrae, such as in
`the lower lumbar region, which device is primarily
`con?ned within the given disc space.
`While a few devices of this type are known (such as
`the device of Dove shown in US. Pat. No. 4,904,261),
`there remains a need for an anterior lumbar interbody
`fusion device that will improve the fusion rate between
`
`50
`
`45
`
`60
`
`
`11
`
`
`
`

`

`15
`
`5,397,364
`3
`4
`est, but most vascular and biologically active, bone of
`FIG. 5 is a top perspective cross-sectional view of the
`inter body fusion device shown in FIG. 1 taken along
`the vertebral body. Clamping means, such as screws,
`line 5—5 as viewed in the direction of the arrows.
`are used to maintain the spacers in their assembled con
`?guration within the intradiscal space.
`FIG. 6 is a top perspective view of a lateral spacer
`component of the fusion device shown in FIG. 1.
`The lateral spacers are provided with threaded bores
`FIG. 7 is an end view of the lateral spacer component
`in their anterior faces to receive the clamping screws. In
`shown in FIG. 6.
`addition, the bores accept an insertion rod that is used to
`FIG. 8 is a bottom perspective view of the posterior
`guide the lateral spacers into the intradiscal space, and
`spacer component of the fusion device shown in FIG. 1.
`that is eventually used to spread the lateral spacers apart
`FIG. 9 is an end view of the posterior spacer compo
`within the space. Once separated, the central spacers
`nent shown in FIG. 8.
`are inserted using a guide rod engaging a guide bore in
`FIG. 10 is a top view of the posterior spacer compo
`each spacer. In this manner, the lateral and central spac
`nent shown in FIG. 8.
`ers are assembled and interlocked like the pieces of a
`FIG. 11 is a bottom perspective view of the anterior
`three-dimensional puzzle. Bone graft material is prefera
`spacer component of the fusion device shown in FIG. 1.
`bly inserted after the posterior central spacer has been
`FIG. 12 is an end view of the anterior spacer compo
`positioned and before insertion of the anterior central
`nent shown in FIG. 8.
`spacer.
`FIG. 13 is a top view of the anterior spacer compo
`Alternative embodiments of the invention contem
`nent shown in FIG. 8.
`plate a fusion device having only one central spacer,
`FIG. 14 is a top perspective view showing the place
`and a device that accepts a number of bone screws to
`ment of the lateral spacer components of the interbody
`anchor the device to an adjacent vertebra. The inven
`fusion device shown in FIG. 1, as representative of a
`tion further contemplates instruments for the insertion
`step in the method of implanting the device.
`and assembly of the device components. In one particu
`FIG. 15 is a top partial cross-sectional view showing
`lar aspect, rack and pinion driven spreader bars are used
`a lateral spacer component of the interbody fusion de
`to spread the lateral spacers within the intradiscal space.
`vice depicted in FIG. 14 with a spreader rod positioned
`One important object of the present invention is to
`in the device.
`provide a fusion device that can restore or maintain the
`FIGS. 16-18 are top perspective views showing fur
`normal geometry of the intradiscal space, such as disc
`ther steps of the insertion and assembly of the interbody
`height and sagittal angle. Another object resides in the
`fusion device.
`multiple component aspect of the device that permits
`FIG. 19 is a top elevational partial cross-sectional
`the introduction of components that by themselves can
`view of the ?xation screw used to couple the compo
`be inserted through a typical disc resection portal, but
`nents of the device, along with the driving too] used to
`when assembled within the intradiscal space occupy
`insert the screw.
`substantially the entire space.
`FIG. 20 is a side elevational view of the interbody
`fusion device shown in FIG. 6, illustrating the uniform
`A further object is to provide a device that is self
`stabilizing within the disc space by providing convex
`thickness of the device.
`FIG. 21 is a side elevational view of an alternative
`surfaces to engage the concave vertebral body end
`plates.
`con?guration of an interbody fusion device similar to
`that shown in FIG. 20 with sagittal face angulation.
`40
`Yet another object of the fusion device of the present
`FIG. 22 is a bottom perspective view of an anterior
`invention is realized in that the multiple component
`spacer component modi?ed from the component de
`aspect of the device permits the creation of a bone graft
`picted in FIG. 11.
`cavity at the most biologically and vascularly active
`FIG. 23 is an end view of the anterior spacer compo
`area of the vertebral body, thereby encouraging strong
`nent shown in FIG. 22.
`and rapid fusion. Furthermore, the load bearing compo
`FIG. 24 is a view in the sagittal plane of an interbody
`nents of the device are situated over the strongest bone
`fusion device arranged between two vertebrae in which
`of the vertebrae.
`the device includes the modi?ed anterior spacer compo
`Other objects, as well as certain bene?ts, achieved by
`nent depicted in FIGS. 22 and 23.
`the present invention will be readily discerned on con
`FIG. 25 is a bottom perspective view of an anterior
`sideration of the following written description and ac
`interbody fusion device similar to the device depicted in
`companying ?gures directed to the invention.
`FIG. 24, except using two anchoring screws.
`FIG. 26 is a front perspective view of an alternative
`embodiment of an anterior interbody fusion device ac
`cording to the present invention utilizing a single cen
`tral spacer.
`FIG. 27 is a top perspective view of a further embodi
`ment of the invention in which a bone graft material
`insert is shaped for disposition between two lateral spac
`ers of the device.
`FIG. 28 is a top perspective view of instrumentation
`for insertion of the interbody fusion device of the pres
`ent invention.
`
`35
`
`DESCRIPTION OF THE FIGURES
`FIG. 1 is a top perspective view of a preferred em
`bodiment of the anterior interbody fusion device of the
`present invention.
`FIG. 2 is a top view of a lumbar vertebra with the
`interbody fusion device of FIG. 1 in position on the
`vertebral body.
`FIG. 2A is a representation of the vertebral body
`showing the regions of varying bone strength in the
`body.
`FIG. 3 is an A-P view of the interbody fusion device
`shown in FIG. 1 as disposed between two lumbar verte
`brae.
`FIG. 4 is a view in the sagittal plane of the interbody
`fusion device oriented between adjacent vertebrae.
`
`65
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`For the purpose of promoting an understanding of
`the principles of the invention, reference will now be
`
`
`12
`
`
`
`

`

`5
`
`5,397,364
`5
`6
`made to the embodiments illustrated in the drawings
`fusion techniques. In the early history of anterior fusion,
`and speci?c language will be used to describe the same.
`a 15 inch incision was made through the abdomen and
`It will nevertheless be understood that no limitation of
`the relatively large single piece fusion components were
`the scope or the invention is thereby intended, such
`implanted through that incision. Now, anterior fusion in
`alterations and further modi?cations in the illustrated
`preferably accomplished through a much smaller 1.5-2
`device, and such further applications of the principles of
`inch incision without splitting any of the abdominal
`the invention as illustrated therein being contemplated
`muscles. In a typical procedure, the surgeon will make
`as would normally occur to one skilled in the art to
`an incision of this size to permit visualization of approxi
`which the invention relates.
`mately 45° of the disc annulus. Newer disc resection
`In accordance with one embodiment of the invention,
`techniques are readily adapted to incisions of this lim
`an interbody fusion device 20 is depicted in FIG. 1.
`ited size. However, until Applicants’ invention, no in
`Generally, the fusion device 20 is a four component
`terbody fusion device was known by Applicants which
`device. The device 20 includes a pair of lateral spacers
`provided load-sharing over such a signi?cant portion of
`21, a posterior central spacer 22 and an anterior central
`the vertebral body, yet which is still capable of being
`spacer 23, the central spacers of which are engaged to
`inserted through the small discectomy incisions.
`the lateral spacers to hold them apart. A pair of ?xation
`Thus, the interlocking components of the fusion de
`screws 24 are provided for locking the entire assembly
`vice 20 have been con?gured for ease of insertion and
`together to form the completed fusion device 20. The
`ease of assembly. As can be seen in FIGS. 1 and 5-6,
`fully assembled device 20 de?nes a cavity 25 between
`each lateral spacer 21 is fanned by a body 29 having
`the lateral and central spacers, which cavity is adapted
`opposite end plate faces 30. These end place faces 30 are
`to receive bone graft material therein.
`con?gured to contact the end plates of the adjacent
`For example, the device 20 is shown situated between
`vertebral bodies. Preferably, the area of each of the end
`adjacent lumbar vertebrae L4 and L5 in FIGS. 2-4.
`plate surfaces 30 is approximately % of the total area
`More speci?cally, in FIG. 2, the device 20 is shown
`occupied by the complete fusion device 20.
`oriented against the vertebral body B. The cavity 25
`In a speci?c embodiment, the end plate faces 30 can
`de?ned by the components of the device 20 is ?lled with
`include a porous biocompatible coating. In one speci?c
`a bone graft material G. The graft material G could be
`embodiment, the lateral spacers 21, as well as the other
`cancellous bone or bone chips as is known in the art, or
`components of the device, may be composed of tita
`a suitable bone graft substitute material. As shown in
`nium coated with a hydroxapatite coating. This coating
`FIGS. 3 and 4, the interbody fusion device 20 maintains
`can promote fusion between each of the lateral spacers
`the adjacent vertebrae L at the appropriate intradiscal
`21 and the corresponding vertebral bodies B. Each of
`distance. The bone graft material G ?lls the entire cav
`the end plate faces 30 includes a beveled edge 31 around
`ity 25 between the adjacent vertebrae, and over time
`the perimeter of the lateral spacer 21. The beveled edge
`fuses the two vertebrae together.
`31 facilitates insertion between adjacent vertebrae and
`A comparison between FIGS. 2 and 2A can illustrate
`serves the obvious function of reducing trauma to sur
`one important feature of the present invention. In FIG.
`rounding tissue that might follow a device having sharp
`edges.
`2A, the vertebral body B is represented by its regions of
`bone strength. It has been discovered that the central
`The body 29 of the lateral spacer 21 includes an inter
`kidney-shaped portion B1 of the vertebral body B com
`lock channel 24 de?ned in one side face 33 of the body,
`prises mostly the weak cancellous bone. An annular
`as shown most clearly in FIG. 6. The interlocking chan
`kidney-shaped region B; around the central portion
`nel 34 has an end face 35 that is angled from the poste
`contains stronger bone, while the ring apophysis B3 has
`rior to the anterior end of the device 20. The interlock
`the strongest bone of the vertebral body. With this in
`channel 34 further includes opposite beveled walls 36
`mind, the present invention strives to load those regions
`which are angled toward each other from the closed
`of the vertebral body B that have the strongest load
`end to the open end of the channel, as readily seen in
`bearing capability. For example, the entire fusion de
`FIG. 7. These walls 36 are oriented to include an angle
`vice 20 assumes a generally annular kidney-shape, cor
`A, which in one speci?c embodiment is 45°.
`responding to the annular kidney-shape of the stronger
`The body 29 of each lateral spacer 21 further includes
`bone B2 and B3 in the vertebral body B. This overall
`a screw bore 37 de?ned in the anterior face of the body
`shape of the device 20 is achieved by the lateral spacers
`29. This screw bore 37 terminates at its base in a
`having each a partial lens shape, while the posterior
`threaded bore 38 which is adapted to engage one of the
`spacer 22 and anterior spacer 23 have an exterior con
`?xation screws 24 shown in FIG. 1. The screw bore 37
`tour generally corresponding to the central portions of
`also includes a head recess 39 which permits the head of
`the stronger vertebral body bone. The bone graft mate
`the ?xation screw to reside enshrouded within the body
`rial G in the cavity 25 is generally positioned over the
`20. The anterior face of each of the lateral spacers 29
`weakest portion B1 of the vertebral body B. However,
`also includes a spacer notch 40 de?ned in the body at
`this portion B1 is also known to be highly vascular and
`the end of the interlock channel 34 and immediately
`biologically active, so that it is an excellent location for
`adjacent the screw bore 37, as shown most clearly in
`bone graft incorporation and fusion.
`FIG. 6.
`Further details of the interbody fusion device 20 are
`The particular features of each lateral spacer 21 are
`shown in the cross-sectional view of the FIG. 5. In
`adapted for interlocking engagement with each of the
`accordance with the present invention, the components
`central spacers 22 and 23. First, describing the posterior
`are interlocking to increase the strength and rigidity of
`central spacer 22, it can be seen in FIGS. 5 and 8-10,
`the assembled device 20, while implementing a con
`that the posterior spacer 22 includes a spacer body 45
`struction that is easy to assemble to the close con?nes of
`having a pair of dovetail arms 47 projecting from the
`65
`a spinal surgical procedure. One problem with prior art
`sides of the body. The dovetail arms 47 include opposite
`devices that consist of but a single piece is that these
`angled faces 48 which are con?gured to be engaged
`devices are not readily adapted for modern anterior
`within the interlock channel 34 of each of the lateral
`
`60
`
`30
`
`55
`
`
`13
`
`
`
`

`

`20
`
`5,397,364
`7
`8
`spacers 21. Thus, each of the angled faces 48 de?nes an
`intradiscal space or annular region. For example, the
`included angle approximately equal to the angle A at
`area of the endplate face 30 of each of the lateral spacers
`which the beveled walls 36 of the channel 34 are ori
`21 is less than half of the annular area. The end faces 46
`ented.
`of the posterior central spacer 22 and the end faces 56 of
`Each of the dovetail arms 47 includes a curved end
`the anterior central spacer 23 occupy an area that is
`signi?cantly less than the annular area (see, for example,
`face 49 which is con?gured to mate with the curved end
`wall 35 of the interlock channel 34 in each lateral spacer
`FIG. 2). This minimal surface area and size of each of
`the components making up the interbody fusion device
`21. It can be seen from FIGS. 5 and 10 that the end face
`49 of the dovetail arms 47 are also angled complimen
`20 means that the device can be used in minimally inva
`sive procedures.
`tary with the angle of the end wall 35 in the lateral
`spacers 21. Each of the dovetail arms 47 further in
`Thus, in one method of implanting the device, a stan
`dard anterior discectomy and distraction is performed.
`cludes an interior extension 50 to ?ll nearly half of the
`length of the interlock channel 34 in the lateral spacers
`After the disc nucleus has been removed, the vertebral
`bodies 29. Finally, the posterior spacer body 45 de?ned
`end plates can be prepared in a known fashion. Once the
`a central guide bore 51 therein which is used during
`end plates of the adjacent vertebrae have been pre
`assembly of the device, as will be described in more
`pared, a pair of lateral spacers 21 can be inserted into
`the surgical site, with the adjacent vertebrae being sepa
`detail herein.
`rately distracted to permit proper location of each of
`It can be seen, particularly from FIG. 5, that the
`posterior central spacer 22 is positioned with each of the
`the lateral spacers 21.
`dovetail arms 47 oriented into a respective interlock
`In one embodiment, introduction of each lateral
`channel 34 in each of the lateral spacers 21. The poste
`spacer 21 is accomplished by way of a spreader rod 80,
`rior spacer 22 is moved along each of the channels until
`shown in FIG. 14. The details of the spreader rod 80
`the end face 49 of each of the dovetail arms 47 contacts
`can be discerned from FIG. 15. In particular, it is seen
`the end wall 35 of each of the interlock channels 34. The
`that the spreader rod 80 includes a locator pin 81, which
`complimentary angular portions of the interlock chan
`extends into the screw bore 37 of the lateral spacer body
`25
`nels 34 and the dovetails arms 47 prevent lateral separa
`29. The spreader rod 80 can also include a pusher stop
`tion between the components. That is, the posterior
`82 which has a diameter larger than the threaded bore
`spacer body 22 maintains the lateral distance between
`but which is adapted to ?t within the head recess 39 of
`each of the lateral spacers 21 when the interbody fusion
`the lateral spacer 21. The spreader rod 80 can then be
`device 20 is oriented between adjacent vertebrae.
`used to manipulate and push the lateral spacers 21 into
`A further component of the fusion device 20 is the
`a proper position between the adjacent vertebrae. Pref
`anterior central spacer 23, which is shown in detail in
`erably, the two lateral spacers 21 are initially inserted
`FIGS. 4 and 11—l3. In particular, the anterior central
`immediately side by side and even with their respective
`spacer 23 includes a spacer body 55 having a pair of
`side faces 33 in direct contact. Once the spacers are
`generally arranged overlapping the vertebral body, the
`posteriorly directed arms 57 extending therefrom. Each
`35
`of the arms 57 includes opposite angled faced 58 which,
`spacers 21 are separated by moving the spreader rods 80
`apart using a separate spreader bar (not shown). The
`like the dovetail arms 47 of the posterior spacer, are
`con?gured to engage within the interlock channels 34 in
`spreader bar can be con?gured to graft the ends of each
`the lateral spacers 21. Each of the posterior arms 57
`of the spreader rods 80 external to the patient to push
`includes an end face 59 which directly abuts the end of
`the bars apart, and thereby separate the lateral spacers
`40
`each of the anterior extensions 50 of the dovetail arms
`21 by an appropriate dimension.
`47 for the posterior central spacer 22. Thus, when both
`Once the lateral spacers 21 are properly oriented, the
`anterior and posterior spacers are engaged within the
`posterior central spacer 22 is introduced into the pa
`tient. A guide rod 85 is provided for advancing the
`lateral spacer interlock channels 34, the two central
`spacers are ?rmly pressed into contact with each other.
`posterior central spacer 22 into proper position. In One
`The anterior spacer body 55 also includes an inner
`speci?c embodiment, the guide rod 85 can be threaded
`posteriorly directed face 60 adjacent each of the arms
`to engage similar threads in the guide bore 51 of the
`57. This face 60 contacts a portion of the spacer notches
`posterior spacer 22. The spacer body is supported at the
`40 in each of the lateral spacers 21, in order to maintain
`end of the guide rod 85, which is then used to advance
`the anterior spacer in position. The anterior spacer body
`and manipulate the posterior central spacer into posi
`55 further includes a pair of notches 62 de?ned in the
`tion with its dovetail arms 47 oriented within the inter
`sides of the body and oriented along the anterior por
`locking channels 34 of each of the lateral spacers 21.
`tion of the posterior directed arms 57. In the assembled
`Some manipulation of the posterior central spacer 22 is
`con?guration, these notches 62 align with the corre
`generally required to position the dovetail arms 47
`sponding head recesses 39 in the lateral spacer bodies
`properly within each of the interlock channels 34. Thus,
`29. The notches 62 in the anterior central spacer 23
`it is of some bene?t to utilize a guide rod 85 that has
`combine with the head recesses 39 to form a generally
`some capability for gripping or engaging the central
`circular recess to receive the head of a ?xation screw 24
`spacer.
`therein. Finally, the anterior spacer body 55 includes a
`Once the posterior spacer 22 is in position, the guide
`central bore 64, which is aligned with the bore 51 in the
`rod 85 can be unscrewed from the guide bore 51 of the
`posterior central spacer 22 when the device is being
`posterior body 45 and removed from the patient. The
`assembled.
`guide rod 85 can then be threaded into the similarly
`As previously indicated, the interbody fusion device
`threaded bore 64 in the anterior spacer 23, to facilitate
`20 of the present invention includes several compo
`introduction of the anterior central spacer 23. In one
`nents, each of which is small enough to be implanted
`alternative, the guide rod 85 can be maintained in posi
`65
`through a typical anterior disc resection portal. More
`tion in connection with the guide bore 51 of the poste
`particularly, the area of each of the end faces of the
`rior spacer body 45 and the anterior central spacer 22
`components is substantially less than the area of the
`advanced separately along the guide rod 85 into its
`
`50
`
`55
`
`IS
`
`30
`
`45
`
`
`14
`
`
`
`

`

`20
`
`25
`
`5,397,364
`10
`proper position. A separate pusher would be required to
`mm) thick to correlate to the thickness of the patient
`gradually push the anterior spacer body 55 along the
`intradiscal space. The lateral separation of each of the
`rod until it is oriented in its proper interlocking position.
`lateral spacers 21 is maintained by the posterior and
`In this instance, the bore 64 in the anterior central
`anterior central spacers 22 and 23. Each of these spacers
`spacer 23 would be unthreaded and be larger than the
`has a width between its interlocking arms of about 0.787
`rod 85.
`inches (20 mm) in the speci?c embodiment. As with the
`Prior to locating the anterior central spacer 23, the
`lateral spacers 21, each of the central spacers 22 and 23
`bone graft or bone graft substitute can be introduced
`can be provided in a number of sized