.
`
`United States Patent [19]
`Brantigan
`
`USOO5425772A
`
`[11] Patent Number:
`[45] Date of Patent:
`
`5,425,772
`Jun. 20, 1995
`
`Sep- 20, 1993
`
`Attorney, Agent, or Firm—Hill, Steadman & Simpson
`[57]
`ABSTRACI.
`Block or plug implants provide weight-bearing support
`for adjacent vertebrae in a vertebral column while al
`lowing suf?cient area between and beside the plugs for
`packing of autologous bone graft to allow bony healing
`and fusion. The plugs have a laterally directed slot to
`allow ingrowth of blood supply from the side and to
`allow locking the permanent device in place with living
`bone. The plugs have a Patterned surface to grip the
`vertebrae. Plugs used for fusion in the L4-5 and LS-Sl
`levels are wedged-shaped to reproduce the normal
`shape of these discs, which are higher anteriorly than
`posteriorly. The height of the plugs is greater than the
`width The implants are made of a biocompatible cap
`bon ?ber reinforced polymer or alternately made of
`traditional orthopaedic implant materials such as
`chrome cobalt, stainless steel or titanium. In the surgical
`procedure, undamaged annulus ?brous disc tissue con
`necting the adjacent vertebrae is preserved and a pair of
`side-by-side implant plugs are forced into side-by-side
`transverse channels in the adjoining vertebrae to stretch
`the remaining annulus and support body weight applied
`through the vertebrae. The plugs are bottomed in the
`channels on cortex bone and bone ingrowth and fusion
`is facilitated by packing a patient’s own graft into the
`center of the plug and beside and between the two
`adjacent plugs.
`
`[54] PROSTHETIC IMPLANT FOR
`INTERVERTEBRAL SPINAL FUSION
`[76] Inventor:
`J91"! W‘ Brantigan’ 13405 Parker
`Cm’ Omaha’ Nebr' 68154
`[21] APPL No; 123,191
`_
`[22] Flledi
`__ A61F 2/44
`_
`[51] Int Cl 6
`........................................ “6.25/17. 606/61
`[52] U
`. .................................... ..
`,
`.
`_.
`[ 8] Fleld of Search
`623/17’ 606/61
`[56]
`References Cited
`- U_S_ PATENT DOCUMENTS
`
`5
`
`........................... ..
`
`'
`
`’
`
`’
`
`?ungz .................................. .. 623/17
`38 Y '
`
`"""""""""""""""" "
`623/17
`4’878’915 11/1989 Brantigan
`"""""""""
`606/61
`4:961:740 10/1990 Ray ____________ __
`606/61 '
`5,015,247 5/1991 Michelson ,
`623/ 16
`5,147,402 9/1992 Bohler et a1. .
`623/17
`5,192,327 3/ 1993 Brantigan ........ ..
`5,320,644 6/1994 Baumgartner ...................... .. 623/17
`
`FOREIGN PATENT DOCUMENTS
`1007661 3/1983 U.S.S.R. .............................. .. 606/61
`1175464 8/1985 U.S.S.R.
`1424826 9/1988 U.S.S.R. .............................. .. 606/61
`1650114 5/1991 U.S.S.R. .............................. .. 606/61
`
`Primary Examiner—David H. Willse
`
`11 Claims, 3 Drawing Sheets
`
`10a
`
`

`

`US. Patent
`
`June 20, 1995
`
`Sheet 1 of 3
`
`5,425,772
`
`PIC-3.1
`
`H62
`
`

`

`US. Patent
`
`June 20, 1995
`
`Sheet 2 of 3
`
`FIG. 6
`
`19
`
`19d
`
`|
`190: 1%
`
`110k.
`
`

`

`US. Patent
`
`June 20, 1995
`
`Sheet 3 0f 3
`
`5,425,772
`
`FIG. 10 ('9‘‘
`
`~
`
`31
`
`

`

`1
`
`PROSTHETIC IMPLANT FOR INTERVERTEBRAL
`SPINAL FUSION
`
`25
`
`5,425,772
`2
`brae and to provide a permanent weight supporting
`strut maintaining the disc space.
`My prior aforesaid U.S. Pat. No. 4,878,915 disclosed
`a further improved surgical procedure by providing the
`rigid implants or blocks with tool receiving end spaces
`facilitating their insertion onto the prepared sites and
`having geometric patterns of roughened surfaces on the
`peripheries of the implants enhancing the bone growth.
`My prior aforesaid U.S. Pat. No. 4,834,757 discloses a
`further improved prosthetic implant having recesses in
`the form of through slots be packed with bone graft
`material.
`My prior aforesaid U.S. Pat. No. ‘5,192,327 describes
`stackable oval implants for anterior lumbar interbody
`fusion or vertebral reconstruction of fracture or tumor.
`The Bagby U.S. Pat. No. 4,501,269 discloses a cylin
`drical basket seated in a cylindrical hole bored trans
`versely across the bones of a spinal joint of a bone
`vwhich permits free rocking rotation between bone and
`basket and only communicates bone fragments packed
`in the basket through perforations in the basket. Noth
`ing was provided to lock the basket against rotation and
`blood supply was limited by the perforations.
`The Ray U.S. Pat. No. 4,961,740 discloses a cylindri
`cal dowel-plug implant with a screw-thread surface to
`be threaded into a cylindrical drilled hole in the verte
`brae, Wh?e this hollow implant permitted packing of
`bone graft material therein, it had very small perfora
`tions limitating ingrowth of blood supply and inhibiting
`bony healing. The device, being cylindrical and seated
`in a cylindrical hole, allowed relative rotation or rock
`ing which inhibited or destroyed bone fusion.
`The Michelson U.S. Pat. No. 5,015,247 also disclosed
`cylindrical dowel shaped plug implants in cylindrical
`drilled holes in vertebrae permitting rotation and a rela
`tive movement between the plug and vertebrae during
`healing. Bone graft material packed within the plug
`could only communicate with the vertebrae through
`small holes limiting blood supply and bone ingrowth.
`The present invention now further improves this art
`by providing inert narrow rectangular or parallelepiped
`plugs or blocks implanted in mating grooves or chan
`nels of adjacent vertebrae in spaced side-by-side rela
`tion with imperforate continuous top and bottom faces
`providing a greater area of weight bearing support and
`an interior adapted to be fully packed with bone growth
`material fully exposed to the vertebrae without inter
`vening obstructions. The narrow width dimension of
`the plug minimizes the widths of the plug receiving
`grooves, provides more spacing from adjacent nerves
`and increases the graft bone areas. The weight bearing
`top and bottom surfaces or faces are roughened prefera
`bly serrated, to provide teeth for biting into the verte
`brae. The plugs also have smooth side faces to prevent
`damage to adjacent bone faces and to facilitate inser
`tion. The invention includes wedge shaped plugs or
`blocks for restoring normal spinal alignment especially
`in the lower lumbar levels.
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention relates to the art of prosthetic devices
`implanted between adjacent vertebrae to treat or pre
`vent back or neck pain in patients with ruptured or
`degenerated intervertebral discs. More speci?cally, the
`invention deals with improvements in prosthetic strut
`forming plugs or blocks facilitating bone ingrowth from
`adjoining vertebrae which are rectangular or, speci?
`cally, parallelepiped shaped, with height greater than
`width providing substantial wide roughened top and
`bottom surface areas for supporting adjacent vertebrae
`while having narrower smooth sides to minimize dam
`aging surgical exposure and nerve root retraction re
`quired during their surgical implantation. The plugs
`have a horizontal or lateral slot providing a receptacle
`for packing bone graft material, have tapered leading
`ends, a tool receiving trailing end and are composed of
`radiolucent rigid inert material for visualization of post
`operative bone healing.
`2. Description of the Prior Art
`As pointed out in my U.S. Pat. Nos. 4,743,256,
`4,834,757, 4,878,915, and 5,192,327, the leading cause of
`low back pain arises from rupture or degeneration of
`lumbar intervertebral discs. Pain in the lower extremi
`30
`ties (sciatica) is caused by the compression of spinal
`nerve roots by damaged discs between the vertebrae
`and low back pain is caused by collapse of the disc and
`the adverse effects of bearing the majority of the body
`weight through a damaged unstable vertebral joint.
`Disc excision with posterior lumbar interbody fusion
`(PLIF) reconstructs the normal anatomic relationships
`between the bony and the neural structures and has
`many advantages. Weight-bearing through a solid bony
`fusion mass between vertebral bodies relieves the me
`40
`chanical pain of the traditional unstable degenerative
`disc and generally prevents long-term disc collapse or
`further degenerative changes. The complete disc exci
`sion prevents recurrent herniation of the same degener
`ated disc.
`However, this PLIF procedure has several serious
`disadvantages in that it is technically very dif?cult, and,
`therefore not as successful or widely used as it might be.
`It requires interbody bone grafting to achieve both a
`strut-like support that bears the entire body’s weight
`through the vertebral bodies, and it requires bony heal
`ing of the grafted bone to achieve permanent fusion.
`It is well understood in orthopaedic surgery that
`grafted bone heals by a process known as “creeping
`substitution” in which blood capillaries ?rst grow into
`the grafted bone, the grafted bone is reabsorbed, and
`then new bone cells are laid down along the bony ma
`trix of the graft. During the time that the bone graft is
`being reabsorbed, the weight-bearing strength is re
`duced at least 50%, causing crushing of the graft and
`failure of the surgery.
`My prior aforesaid U.S. Pat. No. 4,743,256 discloses
`an improved surgical method for eliminating spinal
`back pain caused by ruptured or degenerated vertebral
`discs by spanning the disc space between adjacent ver
`tebrae with rigid inert implants having surfaces facilitat
`ing bone ingrowth and bottomed on prepared sites of
`the vertebrae to integrate the implant with the verte
`
`60
`
`45
`
`50
`
`55
`
`SUMMARY OF THE INVENTION
`The present invention now provides rigid inert, nar
`row vertebral prosthetic implant plugs or blocks which
`are higher than wide, have imperforate top and bottom
`weight bearing surfaces with serrations or projecting
`peaks that bite into adjoining vertebrae surfaces,
`smooth side faces which will not damage adjacent ver
`tebrae surfaces and an unimpeded open side lateral win
`dow or slot for bone graft material in full communica
`
`65
`
`

`

`10
`
`20
`
`25
`
`35
`
`5,425,772
`3
`tion with the space between adjacent vertebrae which
`can also be packed with bone graft material. The top
`and bottom weight bearing spaces are preferably trans
`versely serrated providing teeth to bite into the verte
`brae and adjoining valleys to accommodate bone in
`growth.
`The narrow plugs need only be about 7 to 9 mm wide
`and because their weight bearing top and bottom faces
`are not slotted they will provide increased weight bear
`ing areas even though they are narrower than vertically
`slotted plugs.
`Typical plugs or blocks will have heights of 8.5 to
`12.5 mm and preferably supplied three sizes of 8.5; 10.5;
`or 12.5 mm.
`Typical teeth or serrations projecting from the
`weight bearing surfaces will have heights of 0.75 to 1.5
`mm with spaces between the peaks of 2 to 2.5 mm.
`Typical plug lengths will be 21 to 25 mm and prefera
`bly supplied in three sizes of 21, 23, or 25 mm.
`A typical horizontal or laterally directed slot or win
`dow through the plug will extend substantially the full
`length of the plug and be wide or high enough to pro
`vide top and bottom struts of about 2.5 to 3.5 mm. The
`ends of the slot are spaced inwardly from the leading
`and trailing ends of the plug to provide strong rigid
`strut support with widths from 3 to 6 mm.
`The plugs have a peripherally tapered leading end or
`nose sloping about 30 degrees from the sides and top
`and bottom faces of the plug.
`Wedge-shaped plugs for the lumbar L4-5 and LS-Sl
`levels of the human spinal column are also provided by
`this invention. These plugs are higher anteriorly than
`posteriorly to allow restoration of normal disc contour
`and sagittal plane alignment. This is very important for
`the lower two lumbar discs, L4-5 and L5-Sl.
`Typical posterior heights for the wedge shaped plugs
`are 8.5 to 12.5 mm, preferably supplied in three sizes of
`8.5, 10.5, or 12.5 mm. Typical heights for the anterior
`ends ofthe plug are 11 to 15 mm in three sizes of 11, 13
`or 15 mm. This provides a typical 2.0 mm wedge effect.
`The bone graft is packed between and beside two
`adjacent implants in full communication with their hori
`zontal or lateral side slots which are also packed with
`bone graft material. The slots allow blood supply to
`grow from the sides to the bone between the two im
`plants.
`The implants are preferably made of a radiolucent
`material such as carbon ?ber reinforced polymer such
`as PEEK (polyetherether ketone) or Ultrapek (poly
`ether ketone ether ketone ketone). Alternately polycar
`bonate, polypropylene, polyethylene, or polysulfone
`types ?led with glass or carbon ?bers can be used.
`These materials are supplied by ICI Industries of Wil
`mington, Del., Fiber-Rite Corporation of Winona,
`Minn, or BASF. Other orthopaedic implant materials
`such as stainless steel, titanium, and chrome cobalt are
`useful.
`
`4
`bottomed in the grooves and smooth faced side areas
`with a horizontal window or slot ?lled with bone graft
`and supporting the vertebrae in place of the human disc
`therebetween which has been partially excised to re
`move damaged and herniated tissue and to supply
`grafted bone to be reabsorbed by the vertebrae for ac
`celerated fusion of the adjoining vertebrae.
`FIG. 2 is a posterior elevational view of a portion of
`FIG. 1 taken along the line II—-II of FIG. 1.
`FIG. 3 is a transverse sectional view, with parts in
`elevation and broken away in section, along the line
`III-III of FIG. 2.
`FIG. 4 is a perspective view of a preferred form of
`permanent implant plug of this invention.
`FIG. 5 is a side elevational view of the implant plug
`of FIG. 4.
`FIG. 6 is a fragmentary enlarged detailed view of the
`support area serrations or teeth of the implant plug of
`FIG. 5.
`FIG. 7 is a top plan view of the implant plug of FIGS.
`4 and 5.
`FIG. 8 is an end view along the line VIII—VIII of
`FIG. 5.
`FIG. 9 is an end view along the line IX-—IX of FIG.
`
`5.
`FIG. 10 is a perspective view of an alternative wedge
`block con?guration for the implant plug of this inven
`tion.
`FIG. 11 is a side view of the wedge block of FIG. 10.
`FIG. 12 is a left hand end-view of FIG. 11.
`FIG. 13 is a right hand end-view of FIG. 11.
`
`DESCRIPTION .OF THE PREFERRED
`EMBODIMENTS
`In FIGS. 1-3, the reference numeral 10 illustrates
`generally the lower portion of a human vertebrae col
`umn with adjacent vertebrae supported on prosthetic
`implant blocks or plugs 11 of this invention.
`In FIG. 1, the vertebral column 10 shows the ?ve
`lower vertebrae Nos. 1-5. Adjacent vertebrae Nos. 2
`and 3 and adjacent vertebrae Nos. 3 and 4 are separated
`by and supported on the prosthetic implant blocks or
`plugs 11 of this invention. Vertebrae Nos. 1 and 2 and
`vertebrae Nos. 4 and 5 are illustrated as supported on
`and separated by healthy or undamaged human discs 12
`maintaining a disc space 13 between the adjoining verte
`brae.
`Damaged portions of the natural human discs 12 have
`been excised from the vertebrae Nos. 2 and 3 and Nos.
`3 and 4 with the discs spaces 14 being maintained by the
`implant blocks or plugs 11. It is preferred to retain as
`much as possible of the healthy annulus tissue of the
`discs 12 between the vertebrae so that the remaining
`disc tissue 12a will at least partially surround the im
`plants and will be held under tension by these implants.
`However some of the remaining disc tissue may have to
`be excised to open up spaces for the implant plugs.
`The opposed faces of adjoining vertebrae with dam
`aged discs therebetween have aligned ?at sided rectan
`gular channels or grooves 15 cut therein transversely of
`the axis of column 10. These traverse channels 15 are
`sufficiently deep and wide to span the central soft can
`cellous bone and include the hard cortex bone of the
`adjacent vertebrae. The undamaged human disc 12a
`remaining between the vertebrae is also cut or trimmed
`to received the implants 11 so that as much healthy
`annulus ?brous tissue as is available will surround the
`implants.
`
`45
`
`50
`
`55
`
`PREFERRED EMBODIMENTS
`Preferred embodiments of the invention are illus
`trated in annexed drawings in which:
`FIG. 1 is a side-elevational view of the lower portion
`of a human vertebral column with parts broken away
`and shown in section to illustrate narrow ?at-sided
`rectangular or parallelepiped prosthetic implant plugs
`or blocks of this invention inserted in rectangular
`grooves or channels in the opposed faces of adjoining
`vertebrae with maximum top and bottom support areas
`
`65
`
`

`

`20
`
`25
`
`5,425,772
`6
`5
`The preferred ?at sided rectangular channels have
`tool 20 can thus gently guide the plug into its position in
`blind ends 16 to be abutted by the implants 11.
`the grooves and because the plugs are narrow the
`As shown in FIGS. 2 and 3, the implants 11 are in the
`grooves or channels receiving them can be of reduced
`form of pair of side by side rectangular (speci?cally
`width providing more space between adjoining nerves
`of the vertebrae thereby greatly facilitating the surgical
`parallelepiped) plugs inserted endwise into the trans
`technique.
`verse channels 15. These channels have ?at bottoms and
`side walls to snugly embrace the top and bottom ends or
`After the plugs are seated in their grooves or chan
`faces and the side faces of the rectangular plugs. The
`nels the tension load induced by stretching the verte
`soft cancellous bone of the vertebrae is illustrated at 17
`brae can be released permitting the stretched disc mate
`in FIG. 3 and is surrounded by the hard cortex bone 18.
`rial to pull the vertebrae faces toward each other caus
`The channels 15 include portions of this hard cortex
`ing them to engage the sharp teeth or serration to ?rmly
`anchor the plug in position and bottom it ?rmly on the
`bone so that the implants span the soft cancellous bone
`bottoms of the channels or grooves. The teeth will be
`and rest on the hard cancellous bone 18.
`?rmly anchored to prevent any relative movement be
`The channels 15 can be formed by a mortise cutting
`tween the vertebrae and the plugs during healing. The
`chisel tool and in the event disc tissue 120 blocks the
`beveled leading end of the plug facilitates insertion of
`paths for the plugs 11, tissue can be trimmed or spread
`the plug in proper position into the receiving channels
`apart to open up the paths.
`The implant plugs or blocks as pointed out above, are
`or grooves of the vertebrae. The insertion tool is re
`rigid, inert, solid, rectangular (parallelepiped), narrow,
`moved from the threaded hole 11g of the plug when the
`higher than wide and longer than high as explained
`plug is properly seated in the vertebrae channels or
`above. These blocks 11 have ?at, continuous unslotted
`grooves.
`In the modi?ed embodiment 10a shown in FIGS.
`tops and bottoms 11a, ?at smooth sides 11b, a ?at front
`10-13 the same reference numerals applied to the FIGS.
`end wall 11c, and a ?at back end wall 11d. The front
`1-9 embodiment are used to identify the same portions
`wall 11c is beveled to a reduced rectangular nose sur
`of the plug. However in the embodiment 100 the plug
`rounded by ?at sided tapered walls Me with corners
`11f The back end wall 11d has an internally threaded
`30 is formed into a wedge shape with an anterior end 31
`higher than the posterior end 32 providing a wedge
`blind axial hole 11g at the center of the wall.
`effect which will permit the posterior ends of the chan
`The tops and bottoms 11a of the plug are continuous
`nels or grooves cut into the adjoining vertebrae to be
`and unslotted with traverse teeth or serrations 19 there
`pulled closer together than the anterior sides of the
`across. These teeth have sharp peaks 19a with slopping
`side walls 19b diverging to the surfaces 11 and provid
`vertebrae. The channels, however, are cut to the same
`ing valleys 190 between the peaks. The peaks 19a will
`depth as described above for the plugs 10 so that when
`bite into the adjoining vertebrae faces when the plugs
`the tension load on the spaced apart adjoing vertebrae is
`released the opposed vertebrae faces can be pulled to~
`are installed while the valleys 190 can receive bone
`gether into full seated engagement with the plug, allow
`implant material or remain open for bone ingrowth.
`ing restoration of the normal disc contour and sagittal
`In the surgical procedure the adjoining vertebrae are
`plane alignment. This feature is important for the lower
`tensioned to stretch the ?brous disc tissue between the
`two lumbar disc, L4-5 and in the LS-Sl. In the surgical
`channel cut vertebrae. Slots are cut in the tissue to
`register with the channels 15. It is preferred to remove
`procedure a noose like suture may be used to pull the
`the nucleus pulposus from the damaged disc 12 leaving
`opposed faces of the vertebrae toward each other into
`40
`full biting engagement with the entire length of the
`an annulus of ?brous tissue connecting the adjoining
`plug.
`vertebrae and surrounding the inserted blocks 11. An
`insertion tool 20 is threaded into the threaded tapped
`Although the invention has been described with re
`end hole 11g of the back end wall 11d of the block 11.
`spect to preferred embodiments, it is not to be so limited
`The plug 11 has a single horizontal slot 21 through
`as changes and modi?cations can be made which are
`the longitudinal axis thereof with unimpeded open ends
`within the full intended scope of the invention as de
`?ned by the appended claims.
`in the smooth side faces 11b of the plug. The horizontal
`slot is generally rectangular in shape and may have
`I claim as my invention:
`1. A surgical prosthetic device adapted to maintain
`rounded ends 21a. The slot preferably has a height
`normal disc space between adjoining vertebrae in, a
`about one-third the height of the block and a length
`spinal column having transverse posterior to anterior
`extending close to the front and rear ends 11c and 11d of
`open ended ?at sided channels with bottoms of uniform
`the block. The thickness of these ends at the slot are
`sufficient to provide rigid connecting legs which will
`depth along their lengths cut in the end faces of the
`adjoining vertebrae adapted to provide an unimpeded
`maintain the height of the plug under full loads of the
`supply of bone graft material facilitating fusing the
`vertebrae under even the most adverse conditions.
`vertebrae together which comprises, a rigid rectangular
`The slot 21 is packed with bone graft material 22.
`wedge shape block de?ned by top, bottom, side and end
`This bone graft material is also packed between and
`walls, said block being higher than wide and longer
`beside the plugs and around the plugs in the disc space
`than high, said top and bottom walls being imperforate
`between the vertebrae.
`and oriented to converge from the anterior to the poste
`The teeth 19 preferably extend across the full widths
`of the tops and bottoms 11a of the plug to provide saw
`rior ends of the channels and permit the vertebrae re
`ceiving the block in the channels to be pulled together
`like serrations ?rmly biting into the opposed ?at bot
`to restore normal disc contour and sagittal plane align
`toms of the channels 15. During the surgical procedure
`ment, said side walls of the block being smooth to pre
`the disc space between the adjoining vertebrae is in
`creased preferably beyond the height of the plug when
`vent irritation of the sides of the channels, said side
`65
`walls having a slot providing a chamber to receive bone
`bottomed in the channels or grooves and the smooth
`growth material packed around the block, one of said
`sides 11b of the plug will slide into the channels without
`end walls of the block having a tool receiving recess
`damaging the side faces of the grooves. The insertion
`
`30
`
`35
`
`45
`
`55
`
`

`

`5,425,772
`7
`facilitating insertion of the block into the channels, and
`said top and bottom walls of the block having teeth for
`biting into the bottoms of the channels.
`2. The device of claim 1 wherein the wedge shaped
`block has an anterior end about 2 mm higher than the
`posterior end.
`3. The device of claim 1 wherein the block has a
`posterior height of about 8.5 to 12.5 mm and an anterior
`height of about 11 to 15 mm.
`4. A surgical prosthetic device adapted for fusing
`together spaced adjoining vertebrae on opposite sides of
`the disc in a spinal column prepared with a pair of later
`ally spaced posterior to anterior rectangular channels of
`uniform depth along their lengths providing side and
`bottom walls which comprises, an inert narrow rigid
`wedge shaped plug higher than wide and longer than
`high, said plug de?ned by top, bottom, side, and end
`walls, said top and bottom walls of the plug being im
`perforate and having means for locking with the bottom
`walls of adjoining vertebrae, said top and bottom walls
`20
`of the plug also being inclined for converging toward
`the posterior ends of the channels, said side walls of the
`plug having a slot therethrough for receiving bone
`growth material facilitating fusion of the plug to the
`adjoining vertebrae, and said plug having a tool receiv
`ing portion facilitating insertion of the plug between the
`adjoining vertebrae with the top and bottom walls of
`the plug bottomed on the bottom walls of the channels
`of said adjoining vertebrae and with the incline of said
`top and bottom walls of the plug permitting the verte
`brae to be pulled together to restore normal disc con
`tour and to maintain sagittal alignment of the vertebrae.
`
`8
`5. The device of claim 4 wherein the means for lock
`ing are teeth adapted to bite into the adjoining verte
`brae.
`6. The device of claim 4 wherein the slot extends
`longitudinally of the plug.
`7. The device of claim 4 wherein the side walls of the
`plug are smooth.
`8. The device of claim 4 wherein the tool receiving
`portion is a recess in an end wall of the plug.
`9. A pair of wedge shaped prosthetic devices adapted
`for fusing together spaced adjoining vertebrae in a spi
`nal column prepared with a pair of laterally spaced
`posterior to anterior rectangular channels in their ad
`joining faces with each said pair of devices having an
`imperforate support function separate from a fusion
`function which comprises, a pair of wedge shaped inert
`rigid plugs de?ned by top, bottom, side and end walls,
`each of said plugs being substantially narrower than
`high and longer than high, said top and bottom walls
`having surfaces for engaging the bottoms of the chan
`nels and being oriented to converge along their length
`toward the posterior end of the channels receiving the
`plug, said side walls having smooth ?at faces with bone
`growth receiving windows con?gured to face the sides
`of the channels, and one of said end walls of each plug
`having a tool receiving recess facilitating insertion of
`the plug in its channels.
`10. The device of claim 9 wherein the window of
`each plug is a slot through the plug.
`11. The device of claim 9 wherein the windows are
`provided by a horizontal slot through the plug.
`* *
`* * *
`
`15
`
`25
`
`35
`
`45
`
`55
`
`65
`
`