CA2207336A1 - Adjustable vertebral body replacement - Google Patents

Abstract

An adjustable vertebral boby replacement implant assembly (20) includes a thinwalled cylindrical body (21) configured to span over most of the length between intact vertebrae. The cylindrical body (21) defines a hollow interior (26) with a plurality of bone-ingrowth apertures (28, 29) communicating with the interior. The assembly further includes endplates (22) configured to contact the adjacent vertebra and to engage the cylindrical body therebetween. The cylindrical body and the endplates include mating threads (32, 40, 41) to permit adjustment of the overall height of the implant. In one embodiment is a set screw (24) for locking the cylindrical body to the endplates. In another embodiment, a crimping channel (100) and notch (101) are defined in the endplates to be crimped onto the cylindrical body. A means for connecting the replacement implant to a longitudinal member is provided, which is one embodiment contemplates a clamp and screw assembly (55) and another embodiment includes an arm (94) projecting from the endplates with an opening (95) to receive a longitudinal member (105) therethrough.

Description

WO96117S64 PCT~S95/15654 Al)JUS'l'ABLE v~ L~ RAL BODY REPLAc ~ ;N-L
BACI~GROUND OF T~E INVENTION
'rl1e present inver1tior1 c~ncerns an implant ~or replaceme1lt of one or more vertebral bodies and their adjacent disks.
5 More particularly, t11e vertebral ~ody replacement is particularly well suited for implantation through an anterior approach.
l11e treatment of injuries to the spi1~e has advanced significar1tly since the days of the first recorded surgical l0 procedure for spinal cord injury in the la~e 7~h Century.
l11e techniques, instrumentation and implants ~1ave changed over tlle years and have been better adapted to address many forms of spinal injury and deformities that can occur due to trauma, disease or congenital effects. One type of spi1~al 15 deformity, a kyphosis, involves a prolapse of the vertebral colu~ towards tl-e front of t11e body, o~ten caused by the destruction of the vertebral body itself. This destruction can be in the form of a trauma type injury, such as a fracture or burst injury to the vertebral ~ody, or a 20 non-traumatic deformity caused by a tumor or a degeneratio of the bone in the vertebral body.
Treatment of a kyphosis in the thoracic or lumba-r spine a~pears now to be best achieved through an anterior approach, particularly in order to avoid some of the more severe 25 complications associated wit11 support or replacernent of a damaged vertebral body. In most treatments of a kyphosis, a higll degree of anterior reconstruction of the spine is required, most frequently involving total removal o~ the damage~ vertebral body. In a typical anterior approach, 30 partial or total ablation of the vertebral body and the two W O 96/17564 PCTrUS95tl5654 adjacent vertebral disks is carriecl out. The remainillg space is then distracted to manipulate Lhe spine to its correct orientation.
In many cases, the space is filled with a polymerizable 5 paste or a bone yraft which is frequently modeled to yive it the shape of tlle destroyed vertebral body. Frequently, autologous bone, sucll as tllat extracted from tlle ilium, is used to bridge the space. Tlle polymerizable paste can include a PMMA bone cement. Once the cavity remaining after 10 the removal of the original vertebral body has been filled, an osteosynthesis instrumerlt is positioned between the adjacellt unaffected vertebrae to prevent any relative movemellt therebetween. lhe osteosynthesis device is essential to restabilize the vertebral column, to support the loads to which the tlloracic or lumbar spine is exposed, and to enhance the likelihood and quickness of union of the bone graft material with the adjacent vertebral ~odies. Once Llle bone graft and material is su~ficiently solid, the os~eosynthesis device normally is not subjected to any 20 further mecllanical sLresses.
A known osteosyn~hesis device is depicted in V.S. Patent No. 5,l08,395 to Jean-Marie Laurain, the disclosure of which is incorporated herein by reference. This system is illustrated in FIGS. l and 2 of the present application.
25 Referring first to FIG. l, it can be seen that a damaged vertebra V3 includes a destroyed vertebral body C3. An interior implant l is provided for bridging between t~le two intact vertebrae V2 and V4 to permit removal of the damaged vertebra V3 and iLs adjacent disks D2 and D3.
30 Tlle anterior implant l includes a pair of clamps 2 WlliCh are engaged to the intact vertebral bodies by way of a number of spikes 3. In addition, the clamps 2 are maintained in posiLion by bone screws 5 ex~endinc3 througll screw holes ll, lateral lugs 8 of the c1amps. The implant 1 also includes a plate ~ whicll is configured to span between the intact W O96/17564 PCT~US95115654 vertebrae and is s~ro~ly enougll to support tlle loads yellerated in the spinal column at that location.
~ ach clamp 2 includes a tllreaded post 12 projectin~
therefronl wllicll is configured to pass through a corresponding 5 opening 14 at eacll end of tlle plate 6. A nut 7 is adapted to ellgage the threaded post 12 to fix the plate 6 to eacll of the clamps 2. The surface of the clamps 2 include serra~ions 15 which mate with corresponding serrations 16 at each end of the plate 6, thereby permitting differing angll]ar 10 orientations of tlle ~late rela-ive to each o~ tlle clamps. An openirly 9 is provided through the threaded post 12 of the clamps to receive another bone screw 5 for firm fixation o~
the clamp with the healtlly vertebral bodies V2 and v4.
An important feature of the system described in the '395 15 patent is the provision of notches 18 in each of tlle clamps 2. l'he notches are configured to receive the tips of a ~orceps 19 W~liCh iS used to provide a distraction force betweell the two vertebrae V2 and V4. As sllown in F~G. 2, once the clamps 2 are fixed to the correspondiny intact 20 veltebrae, the forceps 19 are used to distract and peLmit room for placement of a bone graft G. Once the bone graft is in place, the anterior plate 6 can be attached to each of the clamps 2 in the manner previously described. Once the plate is in position, the distraction forceps 19 is removed and the 25 nut 7 tiyhtened to form a rigid construct.
The anterior construct ShOWII in the '395 patent and in E'l~S. 1 and 2 of this application is one system for providing anterior fixation with the use of autologous or allogenic borle gra~t material. Other implants have been devised whicl 30 rely upon an additional element interposed between the adjacent vertebra, in lieu of or in addition to the traditiollal bone graft material. One such device is shown in tlle patent to ~larms et al. no. 4,820,305, which is sold as the "Harms Cage" by the Biedermann-Motech Company. l~llis 35 device contemplates a hollow cylindrical mesh which is W O 96117S64 PCTrUS9S/15654 inserted in the gap between adjacent vertebra, with bone graft material ~eing disposed inside the hollow interior of the mesh.
The patent to Brantigan, No. 5,192,327, SllOWS a device 5 similar to the "Harms Cage" WlliCll is composed of a number of hollow oval-shaped implants within WlliCll bone graft material is disposed. European Patent No. 0 179 695 to Kehr shows a rigid inert body having a num~er of passageways extending L~etween tlle intact vertebrae illtO which bone growth material 10 can be implanted. In addition, the device shown in the Kehr European patent includes a plate spanning between tlle verte~rae having holes for receiving bone screws therethrough.
Another variety of implant devices particularly suited 15 for replacement of verte~ral ~odies include comporlerlts of generally solid construction which completely occupy the empty vertebral space. These devices are represented by the patents to Kapp et al., no. 4,S54,914; Doty, no. 4,599,086i Ogilvie et al., no. 4,636,217; and Downey, no. 5,147,404.
20 Each of these devices is provided with a spike or similar mecllanism for engaging tile end plates of the intact vertebrae to maintain the implant in position. A similar constructioll is followed in the U.S. Patent 5,062,850 to MacMillan et al., although this device includes open space between support 25 columns of the axially fixed vertebral body prosthesis.
In each of the former patents, the implant device requires separate distraction of the intact verte~rae prior to insertion of the device. The following patents show verte~ral prosthesis which include some feature for expansion 30 of the device i7t sitl~ . For example, the Main et al., no.
4,932,975, and Barber no. 5,236,460 show prostheses that telescope througll the admission of a hydraulic fluid. The patents of Rezaian, no. 4,401,112; Wu, no. 4,553,273 and Vaher, no. 4,657,550 show devices that expan~ In situ tlle 35 manipulation of a threaded component. In addition, the W O 96/17564 PCTnUS9S/156S4 Rezaian patent shows a turnbuckle construct of this type wi~h tlle addition of a spiked plate engaged in the opposite intact vertebrae to strengthen the construct.
In recent years, tlle apE~1ication of anterior approaches 5 to instrumenting the spine has become rnore prevalent. As these anterior approaches advance, it becomes of greater necessity to provide a vertebral body replacement that rnee~s all o~ the benefits of anterior surgery without the detriments of the several prior devices. Each of the 1~ above-mentioned verte~ral body replacemellts suffer froln one or more disadvantages. For instance, some of the devices do not provide means for osteosynt~lesis between the intact vertebr~e. These devices lack features that can either permit bone ingrowth or facilitate placement of bone yraft 15 between adjacent healthy vertebrae. It is recognized that a more permanent and stable correction of a kyphotic condition occurs with fusion of a bony mass in place of the replaced vertebra. Thus, any vertebral body replacement should aCCOnlmOdate this aspect. Other vertebral prosthesis offer no 20 means for adjusting the size of the implant to accom[nodate Lhe specific vertebral anatomy. Further, other of the devices do not contemplate some auxiliary fixation to ~lelp provide a stable construct. Each of these needs, and many others, are met by the vertebral body replacement according 25 to the present invention.

W O 96/1756~ PCTrUS95/15654 SUM~1ARY OF INVENTION

The present invention con~emplates a vertebral replacement implant and assembly for fixation o~ the implant in the space left hy a removed vertebra ~etween two intact 5 vertebrae. In one aspect, the implant includes a thin-walled cylindrical body sized to occupy a substantial portion of the space between the intact vertebrae. The cylindrical bo~y is ~lollow with a plurality of apertures througll the wall of the body in comrnunication with tlle interior, to permit bone 10 il]growth ollce the implant is implanted. The opposite ends of Llle cylindrical body carries continuous threads, preferahly Oll the outer surface of the body.
The inventive implant further contemplates a pair of en~p1ates having a sur~ace directed against a corresponding 15 one of the intact vertebrae whell the prosthesis is implanted. The endplates each include a cylindrical portion extending from the end surface, which portion includes threads for matin~ with t~le threaded ends of the cylindrical body. Preferably, the threads of the endplates are internal 20 to tlle cylindrical portion. In one aspect, the end~lates are themselves hollow to provide communication between the hollow interior of the cylindrical body and the adjacent intact vertebrae. Alternatively, the invention contemplates the addition of an end cap to the implant to close the en~
25 surface of the endplates against the adjacent vertebrae-in order to provide additional support for weak vertebrae.
Another feature of the inventioll resides in the provision of means for fixing the cylindrical body to each of the endplates to prevent unthreading of the mating threads of the three components of the implant. In one embodiment, tlle means for fixing includes apertures in the tllreaded portio of the endp1ates wllic}l are threaded to accept a set screw.
Preferably, two set screws are threaded into Lwo sucll apertures in the endp1ates to apply a clarnping pressure WO96117S64 PCT~S95115654 against the cylindrical body engage~ witl1 the endplate.
In another embodime1lt, tl1e means for fixing contemplates a crilnpa~le cylindrical porLio11 of Lhe endplates. In one aspect, t11e cylindrical por~ion includes an annular ring, 5 dissected by a crirn~ing notc}1. l'he application of a crimping ~orce around ~he annular riny reduces the no~ch, and thereby reduces the circu1nference of the cylindrical portion so it is tightly engaged about the cylindrical body threaded t}1erein.
Another inventive aspect resides in the provision of lO means for connecting the implant to a lonyitudinal mernber extending outside the space left by the removed vertebrae.
The longitudinal member may be a plate or a rod that is fixed in a known manner to the adjacent intact verte~rae.
E~referably, the longitudinal member can be used to assist in lS ~1e distraction of t11e intact vertebrae for insertion of tlle verte~ral replacerner1t implant.
ln one embodimer1t, the means for connectin~ inclu~es a clamp configured to clamp ol1to ~he longitudinal member. The clamp supports a screw directed towards the replacemer1t 20 implar1t when it is interpo~ed between the intact verte~rae.
'l'he cylindrical body of the implant includes a nutinber of apertures threaded to receive tl1e connecting screw. Tl1e clamp is preferably slidable along tl1e length of t~1e longitudinal implant to facilitate alignmer1t of the screw Wi~ Lhe number of threaded apertures of Lhe cylindLical body. In addition, the clamp includes a spherical seat, and the screw includes a spherical llead to permit varying angular orientations of tlle screw relative ~o the longitudinal 1ne11lber.
In another embodi1lle11t~ the means for connecting incl~tdes 30 an arm extending from a flange of the endplates. The free end of ~he arm defines an opening ~hrough wl1ic11 the longitudinal member extends. A set screw intersects tl1e openinc3 to provide fixation of the longitudinal member to the arm of the endplates.
One object of the present invetltior1 is to provide a W O 96/17564 PCTrUS9S/15654 vertebral body replacelllerlt implant configured to support the space left by removal of a damayed or diseased vertebra. One objective i5 to provide an implant tllat can be easily adjus~ed to vary the overall length of the implant dependent 5 upon the vertebral level illtO which the implarlt iS
interposed. A further objective of the inventive implant is to permit this length adjustment yet provide means for fixiny tlle components to prevent disengagernent or unthreading.
A furtller object is acllieved by the present inveIltiorl by 10 the provision of means for connecting the vertebral replacement inlplarlt to a longitlldinal member extendiny along tlle length of the spine between the adjacent intact vertebrae. The longitudinal member can be used for distracting the space left by the removed vertebra to 15 facilitate inseltion oE the replacernent implant. Yet anotller object is to provide an implant tllat can house bone growth material to facilitate fusion of the instrumented level.
One benefit of the vertebral body replacement of the present invention is that it provides a strong implant to 20 s~lpport the spinal loads while awaiting fusion oE bone growtl material between tlle intact vertebrae. A further benefit is tllat the implallt can be more easily adjusted to accormnodate spaces at different vertebral levels.
~ther objects and benefits of the invention can be 25 gleaned from the following written description of the inveIltiorl, considered together with t~le accompanyiIIy fiyures and claims.

W O96/17564 PCTrUS95115654 DESCRIPTION OF THE FIGURES

FlG. 1 is an exploded perspective view of a spinal osteosylltllesis implant accordin~ to tlle prior art patent 5,108,395.
FIG. 2 is a view showing a portion of the view of FlG. 1 witll tlle addition of an instrument for permitting positioning of a graft between the vertebrae carrying the clamps associated with the prior device of the '395 patent.
FIG. 3 is an explo~ed perspective view of a vertebral 10 bo~y replacement assembly in accordance with one embodiment of the present invention.
FIG. 4 is an end elevaLional view of an endplate used in corlIlectioll wiLh the vertebral body replacement assembly shown in FIG. 3.
FIG. 5 is a side elevational view of an endplate used witll Lhe vertebral body re~lacement assembly of FIG. 3.
FIG. 6 is a perspective exploded view showing a component of the clamp assernbly used with the vertebral body replacement assembly shown in FIG. 3.
FrG. 7 is a side elevational view of a vertebral body replacement assembly in accordance with anoLher embodiment of ~he invention, particularly for use with an elonyated rod spanniny the vertebral sections.
E'IG. 8 is an erld elevational view of the vertebra1 body 25 replacement assembly shown in FIG. 7, with the assembly shown in position on a intact vertebra.
FIG. 9 is a side elevational view of the assembly shown in FIG. 7 as engaged to an elongated rod.
FIG. 10 is a perspective view of the endplate used with the vertebral body replacement assembly shown in P~1G. 7.
FIG. 11 is an end elevational view of one specific endplate used iIl connection witll the vertebral body replacement assemb1y shown in FIG. 3 in the thoracic spine.
-W O96/17564 PCTrUS95115654 DESCRIPTION OF TI~E PREFERRED EMBODIMENTS

For the purposes of promotirlcJ an understalldiIIy of the pLinciples of tlle inverlLioll, reference will now be made to tlle embodiments illustrated in the drawings and specific 5 language will be used to describe the same. It will neveLtheless be understood tllat no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such ~urtller applications o~ tlle principles of tlle invelltion as 10 illustrated t~lerein being contemplated as would norlnally occur to one skilled in the art to wllich the inventio relates.
Referring llOW to FIG. 3, a vertebral body replacemeIIt assembly 20 is shown in accordance with one embodiment of the 15 present invelltion. l'lle assembly 20 generally inclu~es a tllreaded cylindrical body 21, threaded endplates 22 and erld caps 23. A set ,screw 24 is also provided as one embodiment of a means for fixing each of Lhe end~lates 22 to a corresponding end of the cylindrical body 21. In one 20 specific embodiment, the set screw 24 is a breakable locking screw in wllich the head of the screw shears off when Llle tiglltening tor~ue limit is reached. Such a locking screw is disclosed in co-pendin~ French patent application No. 94 10 377, ~iled on August 29, 1994.
The ~hreaded cylindrical body 21 is formed from a cylindrical wall 25 whicll defines a llollow cavity 26 tllerein. The cavity is configured to receive bone os~eosyllthesis material, whicllrnay be in tlle form of autogenous or allograph material. The cylindrical wall 25 is 30 provided witll a plurality of aperLures 28 in communicatior with the cavity 26. l'hese apertures provide a pa-h for bone or tissue ingrowth to further enhance the stability of the implant. The cylindrical wall 25 includes a second plurality of ~hreaded apertures 29 generally in tlle middle of ~lle W O 96tl7564 PCTnUS95/15654 implant, wllich are configured to engage the support assembly 55 as described in more detail herein.
In one important feature of tlle cylindrical body 21, tlle op~osite ends of the cylindrical wall 25 are formed into 5 external threads 32. In one specific embodiment, the threa~s 3Z extelld from each opposite end over most of the total length of the threaded cylindrical body 21 and are configured ~o engage the threaded endE)lates 22. Each endplate includes a flange 35, whicll prefera~ly assumes a shape to cover a 10 substantial load-bearing area of the end plates of tlle adjacent intact vertebral bodies. A cyIillder 37 is in~eyrally forllled wiLh flanye 35 to extend toward t~le threaded cylindLical body 21 when the endplates 22 are placed within the excised vertebral space. The cylinder 37 of each 15 endplate includes a number of ~hreaded openinys 39 adapted to receive a set screw 24 t}lerein.
l'he cylin~er 37 and ~1ancJe 35 of the endpla~es 22 define a ~ore 40 theretllrough. Tlle inside surface of tlle bore 40 is provided with internal threads 41 whicll are configured to 20 nlate witll the external threads 32 of the cylindrical body 21. In the preferred embodirllerlt, the threads 41 exteIld alony at least the entire length of the cylinder 37 and preferably into the flange 35.
Further details of tlle erld~)lates 22 can be seen in FIGS.
25 4 and 5. As shown in FIG. 5, Lhe cylinder 37 is integrally formed with the flange 35 to define a lordosis angle 43.
This angle is intended to permit use of the vertebral body replacement assembly 20 to replace a damaged vertebra, such as vertebra V3 shown in FIG. 1, and still maintain the 30 normal lordotic curvature of the spine at that level. The end face 36 of t~le flange 35 is provided with vascularization apertures 45 extending throuyh the flange. These apertures 45 are intended to provide an avenue for vascularization of tlle syace between the adjacent vertebrae. l'he end face 36 35 can be provided Witll four spikes, SUCIl a.s spikes 91 shown in WO96/17564 PCT~S95115654 -l2-the embodiment of FIG. 7. AlLernatively, spikes 120 (FIG. 3) can be provided Lhat include a t11readed stem 121 to be engaged in ~hreaded apertures ~6 defi1led in end face 36. In eitl1er case, the s~ikes (9l, 120) are configured to penetrate 5 t11e end plate of t11e adjace11t verte~ra to help mai1ltair1 ~he position of the irnplant in situ.
The end face is further provided with a mounting slot 47 ~assiny across the flange 35 and spanniny along a chord of tl1e internal bore 40. Withi11 each mounting slot is an lO aperture 48 passiny theret11roug11. The cylinder 37 of the endplate 22 is provided wi~h a mounting notch 49 that is aligned with each aperture 48 in the mounting slot 47. This slot 47, aperture 48 and notch 49 are configured to support a1l end cap 23, as herein described. Referriny back to FIG.
15 3, the end cap Z3 includes a yenerally rectangular support bar 50 which is mounted to span across a chord of the flat circular plate 52 of the end cap. At each end of the support bar 50 is an outwardly projectir1y lug 51. Each lug 51 is sized to be received within a corresponding aperture 48, 20 while t11e support bar 50 is itself configured to fit within Lhe mounting slot 47 in the flange 35. Further, each lug 51 slides conveniently into a corresponding mounting notch 49 in the cylinder 37. In this manner, the end cap 23 is held in position, particularly wher1 t11e replacement body asse~nbly is 25 disposed between tlle adjacent intact vertebrae V2 and V4.
~ he end cap 23 provides ad~itional support for the i1nplar1t between the adjacent intact vertebrae. The end cap can be eliminated if bone growth between the adjacent vertebrae and throug11 the replacement body is preferred.
30 Alternatively, the plate 52 of each end cap 23 can be perforated to permit bone inyrowth between the vertebral end pJ.ates and the bone growth material disposed within the tl1readed cylindrical body 21. In the preferred embodi1ne11t, the endplates are show11 solid to provide the maximum load 35 bearing capability for loads along the length of the verLebral colurnn.

W O96/17564 PCTrUS95/15654 In the illus-rated embodimellt, the threads 32 on ~he cylindrical replacement bocly are external threads, while the Lhreads 40 in the endplates are internal. Alternatively, tlle cylinder 37 of the endplates can carry external threads and 5 the cylindrical replacement body carry internal tllreads in tl~e cavity 26. In this latter installce, tlle inner diameter of the cylindrical body would naturally be slightly greater than tlle outer cliameter of tlle cylinder of t~le endplates.
In the preferred embodiment, the cylindrical wall forrning 10 the implant 21 can be rela~ively thin, when compared ac~ainst replacement bodie~ of tlle prior art. In one specific embodiment, the wall i5 one (]) Inm. tllick. Since tlle primar~
load endured by the implant will be axial compression, ratller thall bendin~J, a thin-walled cylinder is appropriate and even 15 desirable.
lt is also preferred that tlle implant 21 include a large number of aper~ures 28, 29 to pro~lote ~issue ingrowLll and vascularization, thereby enllancing the stability of the construct after fusion has occurred. In one specific 20 embodimerlt, tlle total area of Lhe plurality of apertures is at least twenty five percent (25%) of the surface area of the cylindrical body 21.
In use, tlle damaged vertebra, such as vertebra V3 showr in F~G. 1, is removed. In one embodiment, the clamps 2 of 25 the in~erior implant 1 shown in FIGS. 1 and 2 are engaged to tlle intact verte~ral bodies in tl1e manller ShOWll in FIG. 2.
Also sllown in FIG. Z, the forceps 19 can be used to distract the intact vertebrae to permit implantation oE a veLtebral body replacement assernbly 20. In the preferred metllod, the 30 optimum vertebral heigllt is determined and the threaded cylindrical body 21 and threaded endplates 22 are fiLted toc~ether to acllieve that proper heigllt. Specifically, eacll of the end caps can be t~lreaded onto the threaded cylind~ical body 21 until the desj~ed lleight is attained.
lt is important tllat the bottoln edye 44 of tlle ~1ange 3r~

W O 96/17564 PCTnUS95/15654 of eacll of the endplates be yenerally oriented in the same way between tlle two threaded endplates 22. This orientation is importall~ because the replacemellt assem~ly 20 will be disposed between the two intact vertebrae, bearing against 5 tlle end plates of tllose vertebrae. In order to maintain tlle maximum load bearing capability, the ~1anges 35, and particu]arly the end face 36, assurne the shape of the vertebral body against which the endplates bear and are sized to occupy as much area of ~he intact vertebral body end plate 10 as possible.
~ referably, three such shapes are provided to accolmnodate the anatonlic vari~ions of Lhe vertebral bodies at tlle lumbar, thoraco-lumbar and thoracic levels. the configuratioll of the flange 35 sllown in FIC. 4 is applicable 15 to tlle thoraco-lumbar vertebrae. A smaller, more rounded, configuration can be provided for implantatioll at the thoracis level, such as tlle flange 35~ shown in Fl~. 11. I'he flange 35' is also shown as includiny a relief radius 38 to increase the clearance between tlle flange and the dural space 20 llousing the spinal cord. This relief radius 38 is prefera~ly included in all three shapes of the endplate flanges.
In one specific ernbodimellt, the external threads 32 on Llle threaded cylindrical body 21 are cut in opposite directions so that the endplates can be drawn toyether or 25 apart by Lotatillg only the cylinder. Thus, as the cylinder is rotated in one direction, the threads 32 at each of the ends engage the internal threads 41 of each of the end caps 23 in the right direction to draw the end caps togeLher.
Alternatively, the handedness of the threads 32 can be the 30 same at each end so that it is necessary to individually thread each end cap in opposite directions onto the cylindrical body 21. The disadvantage of this arrangelnerlt is that it is more difficult to adjust the heigllt of tlle total assembly 20 while mailltaininy tlle proper orientatioll of each 35 of the lower edges 4~ of tlle end face 36. An advantage is tllat illS~tU the assembly is unable to untllread itself.

- =

WO 96117S64 PCTrUS95/15654 Once the endplates and threade~ cylindrical ~ody have been engaged in ~he E)roper orientation for the correct height, the set screws 24 are ~hreaded into an aypropriate one of the threaded openings 39 in the cylinder 37 of the 5 endplates 22, in order tllat the set screw 24 extend into contact with the threaded cylindrical body 21. Tlle set screws 24 (which can be t~le breaka~le locking screws merl~ioned above) exert a clamping pressure against the body 21 to ~lold it in place. Thus, the set screws 24 provide a 10 means for fixing the components together and prevent rotation of Lhe cylindrical body 21 witll respect to either of the endplates 22. Preferably, two set screws are used at each endplate 23 to firmly fix the associated ends of the threaded cylindrical body 21. To ensure that the set screws 24 15 achieve firrn purchase on the bo~y 21, the apertures 28 in tlle threaded body have a smaller diameter than the set screws 24.
Witll t~le cylinder and endplates thus fixecl at their proper lleight dimension, bone yraft material can thell be inserted into the bore 40 of the endplates and cavity 26 of 20 the cylindrical body 21. After the interior of these components llas been completely filled with bone graft material, the endplates 23 are placed in position with the luys 51 extending through apertures 48, and with support bar 50 passing through mounting slot 97 in each endplate. The 25 replacement assembly 20 can then be disposed between the distracted vertebrae V2 and V4, Once the assembly is properly positiorled with tlle end faces 36 of each of the endplates 22 properly oriented on the vertebral end plates, the distraction forceps 19 are removed so that the assembly 30 20 is clamped in place between tlle two vertebrae.
In order to further ensure that the replacemellt assenlbly 20 will not migrate or slip in its position between the intact ver~ebrae, a support assembly 55 may be provided. In Lhe preferred embodilnent, t~lis support asselnbly 55 is 35 confiyured to mate with the clamps 2 used with the anterior W O 96/17564 PCTrUS95/156S4 imE~larlt system of ~he prior art shown ill FIGS. 1 and 2. The support assembly 55 can also ~e used with other anterior pla~es, such as the Z-PLATE ATL* sold by Danek Medical, lnc., or rod systems such as the CD ~lopf ~ysteln of Sofamor, 5 S.N.C.
ln particular, the support assem~ly includcs a stabilization plate 57, wlliCII can be configured substantially similar to the plate 6 shown in FIG. 1, including the serrations Oll the bottom face of the ends of tlle plate.
10 Mealls for connec~ y the vertebral replacement body assembly 20 to the plate 57 includes a clamp assembly 59 is provided whicll firmly grips the plate 57 to support a lockillg screw 69. 'lihe clamp assernbly 59 includes a pair of clamp halves 60 whicll are preferably in ~he shape of a C to yrip and support 15 the plate 57. Each of the clamp halves 60 include an aperture (not shown) WhiCIl receives a threaded rod 63 of an adjusLIllellt pla~e 62. A nut 64 is threaded Oll the rod 63 to draw Lhe clamp halves 60 together about the stabilization plate 57.
The details of the adjus~me}lt plate 62 are sllowllInoLe clearly in FI~. 6. The adjustment plate includes the t~lreaded rod 63 extending from a face 65 of the plate 62.
The plate 62 also includes an aperture 67 therethrough having a spherical seat surface 68 into whicll a correspondiny Z5 spherical head 70 of the locking screw 69 is received. The locking screw 69 includes a hex recess 71 in its head to accept a driving tool. The locking screw 69 also includes a ~hreaded shank 73 which is adapted to engage one of the threaded apertures 29 in the threaded cylindrical body 21.
30 To help guide the lockiny screw 69 into position, a guide nub 75 is provided having a smaller diameter than the Lhreaded shank 73. The locking screw 69 preferably includes smootll shallk 74 between ~lle head 70 of the screw and the threaded shank 73.
In use, the clalnp halves 60 can be tentatively attached W O96/17564 PCTrUS95/15654 ~ut not clamped to the stabiliza-ion plate 57. The stabilization plate 57 can tllen be engaged to the clamps 2 in each of t~le intact vertebral ~odies and fixed in place by a corresponding nut, such as nut 7 shown in FIG. 1. Witll the 5 sta~ilizatiorl plate 57 tlrus altac~led between the distracted vertebrae, the distraction forceps 19 can be rernoved so that the full load of ~lle spil~al column can be borne by tlle replacement assembly 20. O~lce the distraction forceps have beerl removed, the clamp halves G0 can be adjusted along the 10 lengtll of the plate 57 so tllat the locking screw 69 is aliyned witll an aE~E~ropriate orle oE tlle tllIeaded a~eLtu~es 29 in tlle threaded cylindrical body 21. The syherical contacl:
between the head 70 of tlle locking screw 69 and the spherical seat 68 of the adjustment ~late 62 allows the locking screw 15 to assume wllatever angle is necessary to engage a threaded aperture 29. As so aligned, ~le locking screw 69 call ~hen be easily threaded into one of Lhe apertures 29 unLil it is locked between the adjustment plate 62 and t~le tllreaded cylindrical body 21. At tllis point then, the clamp halves 60 20 can be fully clamped onto t~le plate 57 by tiyhtenillg the nut 64 on the threaded rod 63.
In anotller em~odiment of tlle inverltiorl, a vertebral body re~lacement assembly 80 is collfigured for connection to an elongated distraction or compression rod. ln t~lis 25 embodiment, tlle assembly 80 includes opposite endplates 83 which are configured to threadedly engage a cylindrical body 21. (Tllis cylirldrical body 21 is substantially identical in all respects to tlle cylindrical body 21 descri~ed with respect to FIG. 3). Witll this embodiment, the end~lates 83 include a flange 85 and a cylinder B7 projecting tllerefrom.
Tlle cylinder 87 includes a threaded bore 88 w~licll is threaded to accept the external threads 32 of the cylindrical ~ody 21. Like tlle yrior endpla~es, the endplate 83 includes a plurality of vascularization ~pertures 89 Lorrned througll the flange ~5. The end face 86 of tlle flange 85 includes a WO96/17564 PCT~S95/15654 number of spikes 91 projecting therefrom. lhe spikes are configured to penetrate the end plate of Lhe adjacent vertebral bodies to llelp maintain the position of the inlplant i~situ.
As shown in FIGS. 7 an~ 8 the endplates 83 include an arm 94 projecting from tlle flange 85 Wllicll is a conlponent of a means for connecting the implant to a longitudinal member such as rod 105. A rod bore 95 is defined adjacent tlle free end 94a of the arln 94 witll a set screw bore 96 intersectincJ
10 the rod bore 95 from the free end of the arm 94. A set screw 98 is provided WhiCll is engaged withirl the set screw bore 96 to clamp a rod passin~ therethroucJh.
T~le manner of using the replacement assemb]y 80 in this ernbodiment is shown in FIGS. 8 and 9. In particular tlle 15 endplates 83 are engaged in tlle appropriate vertebrae by way of spikes 91. Again the plates are configured to define an angle 115 to correspond to Lhe proper spinal anatomy at tlle particular vertebral level. A ~istraction plate 107 is moullted into each of tlle intact vertebrae by way of bone 20 screw 108. Tlle plate 107 includes a collar 109 integrally formed thereon through which a distraction rod 105 passes.
T~le distraction rod also extends through each of the rod bores 95 in the arms 94 of the endplates 83. With t~le rod exterlding through each of the bores the set screws 98 fix 25 the endplates in position. Distraction of tlle adjacent vertebrae can be ac~lieved by an appropriately formed instrument that can engage the collars 109 of each of the distraction plates 107 mounted into the respective vertebrae. A set screw (not ShOWIl) can be provided to fix 30 the rod 105 Withill eacll collar 109.
Referriny to FIGS. 7 9 and 10 details of the manrler in whicll the endplates are fixed to the threaded cylindrical body is described. In par~icular the endplates 83 and particularly the cylinder 87 of the endplates is provided 35 Witll a a means for fixing in the forln of a crirnpiny charlnel W O96/17564 PCTrUS9S115654 100 around tlle diameter of the cylinder. At opposite sides of tlle cylinder, a crimpiny notch 101 is provided in the channel 100. In essence, this crimpillg notch is a yap in tlle outer circumference of the channel 100. l'his crimping notch 5 provides a gap which can be closed by an appropriate crimping tool gripping the entire circumference of the crimpiny channel 100. As the crimping tool is tightened, tlle notches 101 close as tlle channel moves together in the direction of the arrows 102. It can be seen that this crimpiny aspect 10 will replace the set screw 24 disclosed with the previous elnbodiment for fixing the endplates to the tllreaded cylindrical ~ody.
While the inventioll has been illustrated and described in ~ detail in the drawings and foregoing description, tlle same is 15 to be considered as illustrative and not restrictive in character, it being ullderstood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.

Claims

What is claimed is:

1. A vertebral replacement implant for interposition in a space left by one or more removed vertebrae between adjacent intact vertebrae, comprising:
a replacement body with opposite ends sized to span a portion of the space between the intact vertebrae, said replacement body having first threads defined thereon at each of said opposite ends, said replacement body further including a cylindrical wall defining a hollow interior, said cylindrical wall defining a plurality of apertures therethrough, said apertures being in communication with said hollow interior of said replacement body to facilitate tissue ingrowth into said replacement body, said replacement body having an outer surface area and said plurality of apertures define an effective area greater than about twenty five percent (25%) of said outer surface area; and a pair of endplates each having an end surface for contacting a respective one of the intact vertebrae when the implant is interposed in the space, each of said endplates having a cylindrical portion integrally extending from said end surface, said cylindrical portion having second threads defined thereon configured to threadedly engage the first threads on said replacement body, each of said endplates further defining a bore therethrough opening at said end surface and at said cylindrical portion.
4. The vertebral replacement implant according to claim 1, wherein the hollow interior of said replacement body is open at said opposite ends.
5. The vertebral replacement implant according to claim 1, wherein said replacement body includes a cylindrical wall defining a hollow interior and is open at said opposite ends.
6. The vertebral replacement implant according to claim 5, wherein each of said endplates defines a bore therethrough opening at said end surface and at said cylindrical portion.

7. The vertebral replacement implant according to claim 6, wherein said first threads on said replacement body are external threads and said second threads on said cylindrical portion of said pair of endplates are internal threads.
8. The vertebral replacement implant according to claim 1, further comprising an end cap for closing said bore of one of said endplates at said end surface thereof, said end cap having means for supporting the end cap on the endplate.
9. The vertebral replacement implant according to claim 1, wherein said first threads on said replacement body are external threads and said second threads on said cylindrical portion of said pair of endplates are internal threads.
10. The vertebral replacement implant according to claim 1, further comprising means for fixing said replacement body to each of said endplates to prevent unthreading of said first and second threads.
11. The vertebral replacement implant according to claim 10, wherein said means for fixing includes:
a number of openings defined in said cylindrical portion of each of said pair of endplates; and a member extendable through one of said number of apertures into contact with said replacement body.
12. The vertebral replacement implant according to claim 11, wherein:
said member is a set screw; and said number of openings is threaded to receive said set screw in threaded engagement.
13. The vertebral replacement implant according to claim 11, wherein said number of openings are defined in said endplates at said second threads.
14. The vertebral replacement implant according to claim 1, wherein each of said endplates includes a flange defining said end surface, said flange extending radially outwardly from said cylindrical portion and defining a shape generally corresponding to the shape of a portion of the intact vertebra against which the endplate is in contact.
15. The vertebral replacement implant according to claim 14, wherein said flange defines a number of vascularization apertures therethrough.
16. A vertebral replacement implant for interposition in a space left by one or more removed vertebrae between adjacent intact vertebrae, comprising:
a replacement body with opposite ends sized to span a portion of the space between the intact vertebrae, said replacement body having first threads defined thereon at each of said opposite ends;
a pair of endplates each having an end surface for contacting a respective one of the intact vertebrae when the implant is interposed in the space, each of said endplates having a cylindrical portion integrally extending from said end surface, said cylindrical portion having second threads defined thereon configured to threadedly engage the first threads on said replacement body, each of said endplates further defining a bore therethrough opening at said end surface and at said cylindrical portion ; and an end cap for closing said bore of one of said endplates at said end surface thereof, said end cap including;
a plate shaped to correspond to said bore opening in said endplate; and a support bar attached to said plate, wherein said endplate further includes a slot defined at said end surface for receiving said support bar so that said plate of said end cap resides flush with said end surface of said endplate.
17. A vertebral replacement implant for interposition in a space left by one or more removed vertebrae between adjacent intact vertebrae, comprising:
a replacement body with opposite ends sized to span a portion of the space between the intact vertebrae, said replacement body having first threads defined thereon at each of said opposite ends; and a pair of endplates each having an end surface for contacting a respective one of the intact vertebrae when the implant is interposed in the space, each of said endplates having a cylindrical portion integrally extending from said end surface, said cylindrical portion having second threads defined thereon configured to threadedly engage the first threads on said replacement body, each of said endplates further defining a bore therethrough opening at said end surface and at said cylindrical portion, said cylindrical portion of each of said endplates further having a length projecting from said end surface and a crimping notch formed along a portion of said length, said cylindrical portion being deformable at said crimping notch to close said notch and thereby reduce the circumference of said cylindrical portion about said replacement body when said body is threadedly engaged to said endplate cylindrical portion.
18. The vertebral replacement implant according to claim 1, wherein each of said pair of endplates includes a number of spikes projecting from said end surface for implantation in a corresponding one of the adjacent intact vertebrae.
19. A vertebral replacement implant for interposition in a space left by one or more removed vertebrae between adjacent intact vertebrae, comprising:
a replacement body with opposite ends sized to span a portion of the space between the intact vertebrae, said replacement body having first threads defined thereon at each of said opposite ends;
a pair of endplates each having an end surface for contacting a respective one of the intact vertebrae when the implant is interposed in the space, each of said endplates having a cylindrical portion integrally extending from said end surface, said cylindrical portion having second threads defined thereon configured to threadedly engage the first threads on said replacement body, each of said endplates further defining a bore therethrough opening at said end surface and at said cylindrical portion, said end surface of each of said pair of endplates defining a number of threaded apertures therein, and a number of spikes projecting from said end surface for implantation in a corresponding one of the adjacent intact vertebrae, each of said spikes including a threaded post configured for engagement with said threaded apertures in said end surface of each of said endplates.
20. A vertebral replacement implant for interposition in a space left by one or more removed vertebrae between adjacent intact vertebrae, comprising:
a replacement body with opposite ends sized to span a portion of the space between the intact vertebrae, said replacement body having first threads defined thereon at each of said opposite ends; and a pair of endplates each having an end surface for contacting a respective one of the intact vertebrae when the implant is interposed in the space, each of said endplates having a cylindrical portion integrally extending from said end surface, said cylindrical portion having second threads defined thereon configured to threadedly engage the first threads on said replacement body, each of said endplates further defining a bore therethrough opening at said end surface and at said cylindrical portion, wherein said cylindrical portion of each of said endplates extends from said end surface at a non-perpendicular angle, said angle corresponding to the curvature of the spine at the space left by the removed vertebra.
21. A vertebral replacement implant for interposition in a space left by one or more removed vertebrae between adjacent intact vertebrae, comprising:
a replacement body with opposite ends sized to span a portion of the space between the intact vertebrae, said replacement body having first threads defined thereon at each of said opposite ends; and a pair of endplates each having an end surface for contacting a respective one of the intact vertebrae when the implant is interposed in the space, each of said endplates having a cylindrical portion integrally extending from said end surface, said cylindrical portion having second threads defined thereon configured to threadedly engage the first threads on said replacement body, each of said endplates further defining a bore therethrough opening at said end surface and at said cylindrical portion, each of said endplates further including a flange defining said end surface and extending outwardly from said cylindrical portion, said flange including an arm projecting away from said cylindrical portion, said arm having a free end configured to extend beyond the adjacent intact vertebrae for engagement to a longitudinal member disposed along the length of the spinal column.
22. The vertebral replacement implant according to claim 21, wherein said arm defines a bore at said free end for receiving the longitudinal member therethrough.
25. An assembly for fixation of adjacent intact vertebrae following removal of an intermediate damaged vertebra, comprising:
a vertebral replacement implant including;
a replacement body with opposite ends sized to span a portion of a space left by the removal of the damaged vertebra, said replacement body having first threads defined thereon and a number of threaded openings around its circumference; and a pair of endplates each having an end surface for contacting a respective one of the intact vertebrae when the implant is interposed in the space, each of said endplates having a cylindrical portion integrally extending from said end surface, said cylindrical portion having second threads defined thereon configured to threadedly engage the threads on said replacement body;
an elongated longitudinal member sized to span between and fixedly engage the adjacent intact vertebrae outside the space left by the removal of the damaged vertebra;
a clamp for connecting said vertebral replacement implant to said longitudinal member, said clamp including a plate, said plate defining an aperture having a spherical seat; and a screw attached to said clamp having threads for engaging one of said threaded openings and a a spherical head configured for engagement within said spherical seat.
26. An assembly for fixation of adjacent intact vertebrae following removal of an intermediate damaged vertebra, comprising:
a vertebral replacement implant including;
a replacement body with opposite ends sized to span a portion of a space left by the removal of the damaged vertebra, said replacement body having first threads defined thereon; and a pair of endplates each having an end surface for contacting a respective one of the intact vertebrae when the implant is interposed in the space, each of said endplates having a cylindrical portion integrally extending from said end surface, said cylindrical portion having second threads defined thereon configured to threadedly engage the threads on said replacement body, each of said endplates including a flange defining said end surface and extending outwardly from said cylindrical portion;
an elongated longitudinal member sized to span between and fixedly engage the adjacent intact vertebrae outside the space left by the removal of the damaged vertebra; and means for connecting said vertebral replacement implant to said longitudinal member including an arm integral with said flange and projecting away from said cylindrical portion, said arm having a free end configured to extend beyond the adjacent intact vertebrae for engagement to the longitudinal member.
27. The assembly for fixation of adjacent intact vertebrae according to claim 26, wherein:
said arm defines a first bore at said free end for receiving the longitudinal member therethrough and a set screw bore at said free end intersecting said first bore; and said means for connecting includes a set screw for threading into said set screw bore, said set screw having a tip for engaging a longitudinal member extending through said first bore.
28. A vertebral replacement implant for interposition in the space left by a removed vertebra between adjacent intact vertebrae, comprising:
a replacement body with opposite ends and having a length sized to span a portion of the space between the intact vertebrae;
a pair of endplates each having an end surface for contacting a respective one of the intact vertebrae when the implant is interposed in the space, each of said endplates having an engagement portion integrally extending from said end surface;
mating threads between said opposite ends of said replacement body and said engagement portion of each of said endplates for engaging said endplates to said replacement body at variable positions along the length of said replacement body; and means for fixing said replacement body to each of said endplates to prevent disengagement of said mating threads.
31. A vertebral replacement implant for interposition in the space left by a removed vertebra between two intact vertebrae, comprising:
a thin-walled cylindrical body defining a hollow interior, the wall of the cylindrical body defining a plurality of apertures having a combined area at least equal to twenty-five percent (25%) of the outer surface area of the body, said body having opposite ends with continuous threads formed at each of said opposite ends; and a pair of endplates, each endplate formed by a flange defining an end surface for contacting a respective one of the intact vertebrae when the implant is interposed in the space, and each endplate further including a cylindrical portion integrally projecting from said flange, said cylindrical portion defining a continuous thread for engagement with the threads at the opposite ends of said thin-walled cylindrical body, each of said endplates defining a bore therethrough to communicate with the hollow interior of said thin-walled cylindrical body when said body is threadedly engaged with the endplate, said cylindrical portion having a length projecting from said end surface and further defining a crimping notch formed along a portion of said length of said cylindrical portion, said cylindrical portion being deformable at said crimping notch to close said notch and thereby reduce the circumference of said cylindrical portion about said cylindrical body when said body is threadedly engaged to said endplate cylindrical portion.
33. The vertebral replacement implant according to claim 1, wherein some of said plurality of apertures extend through said first threads of said replacement body.
34. The vertebral replacement implant according to claim 7, wherein said replacement body includes a cylindrical wall defining a hollow interior, said cylindrical wall defining a plurality of apertures therethrough, said apertures being in communication with said hollow interior of said replacement body to facilitate tissue ingrowth into said replacement body.
35. The vertebral replacement implant according to claim 34, wherein some of said plurality of apertures extend through said external threads of said replacement body.

36. The vertebral replacement implant according to claim 28, wherein:
said engagement portion of said pair of endplates includes at least one threaded opening therethrough; and said means for fixing includes a set screw threaded into said threaded opening and into contact with said replacement body when said body is in threaded engagement with said endplate.