CA2650756C

CA2650756C - Method and apparatus for replacing a damaged spinal disc

Info

Publication number: CA2650756C
Application number: CA2650756A
Authority: CA
Inventors: Edward C. Benzel; Isador H. Lieberman; Lee Strnad; James M. Kuras; Raymond S. Ross; Charles F. Birchall, Jr.; Keith Duke; Kari Zimmers
Original assignee: Axiomed Spine Corp
Current assignee: AXIOMED LLC
Priority date: 2003-12-10
Filing date: 2004-12-08
Publication date: 2012-01-31
Anticipated expiration: 2024-12-08
Also published as: EP1703869A2; CN101816596A; CN1901854A; WO2005058194A3; US7695517B2; US20050131542A1; EP1703869A4; AU2004299008A1; KR100753465B1; CA2650756A1; CA2549101C; US20050131543A1; EP1703869B1; US20050131544A1; US7128761B2; US7588600B2; JP2007513711A; EP2387976A1; CN101816596B; ATE534350T1

Abstract

A method for replacing a damaged spinal disc (10) between first and second vertebrae of a spinal column includes connecting a first mounting member (100) with the first vertebra of the spinal column. An artificial disc (10) is moved between the first and second vertebrae and into engagement with the first mounting member (100) to guide the artificial disc into position between the first and second vertebrae. The artificial disc includes a resilient core (90) having a first surface and a second surface, a first retaining member (20) connected to the first surface of the resilient core (90), and a second retaining member (60) connected to the second surface of the resilient core (90). The first retaining member (20) has an outer surface engageable with a first vertebra of the spinal column and an inner surface facing the first surface of the resilient core (90). The second retaining member (60) has an outer surface engageable with the second vertebra of the spinal column and an inner surface facing the second surface of the resilient core (90). An apparatus for replacing a damaged spinal disc in a spinal column includes a first retaining device (20) connected to the first surface of the resilient core (90). A second retaining device (60) is connected to the second surface of the resilient core (90). The second retaining device (60) has an outer surface engageable with a second vertebra and an inner surface facing the second surface of the resilient core (90). The inner surface of the first retaining device is spaced from the core (90). The core (90) deflects into engagement with the inner surface of the first retaining device (20) upon relative movement between the first and second retaining devices (20&60).

Description

METHOD AND APPARATUS FOR
REPLACING A DAMAGED SPINAL DISC
This is a divisional application of Canadian application Serial No. 2,549,101.

Field of Invention The present inventioii relates to a method and an apparatus for replacing a damaged spinal disc in a spinal colurnn, and more specifically, to an apparatus having a resilient core for replacing a damaged spinal disc in a spuzal colurrui.
Background of the Invention A laiown artificial disc meniber is disclosed in U.S. Patent No. 5,370,697.
U.S. Patent No. 5,370,697 discloses an artificial disc having upper and lower supports coiulected to adjacent vertebrae and an elastic separator. The separator has cover plates connected to opposite sides of an elastic core. The separator is a separate insert part that may be inserted between the upper and lower supports after the suppoi-ts are connected to the vertebrae. The separator does not engage the vertebrae.
A la-iown disc prosthesis is disclosed in U.S. Patent No. 6,419,706. U.S.
Patent No. 6,419,706 discloses a prosthesis having an elastic core and casings attached to the core. The casings engage vertebrae and partially cover the core.
Each of the casings has flaps and slcirts that exterid toward the opposite casing.
The flaps and skirts are spaced from the core when the prosthesis is an tulcompressed condition. The core engages the flaps and skirts upon maxiu-nuin coillpression of the prosthesis.

_2_ Summarv of the Invention A rnethod for replacing a damaged spinal disc between first and second vertebrae of a spuial colunul includes corll.-iectiiig a first mounting nzeinber with the first vertebra of the spinal column. An ai-tificial disc is moved between the first and second vertebrae and into engageinent witll the first mounting member to guide the artificial disc iuto position between the first and second vertebrae. The artificial disc includes a resilient core having a first surface and a second surface, a first retaining inember corulected to the first surface of the resilient core, and a seeond retainilZg melnber comlected to the second surface of the resilient core. The first retaining menlber has an outer surface engageable wit11 a first vertebra of the spinal column and an inner surface facing the first surface of the resilient core.
The second retairii.ng inenzber has an outer surface engageable witll the second vertebra of the spinal column and an iiuler surface facing the second surface of the resilient core.
AZ apparatus for replacing a dainaged spiilal disc in a spinal coluxmi of the present iuivention includes the artificial disc and the first inountiuig member comiectable witli the first vertebra and the artificial disc to position the artificial disc between the first and second vertebrae. The first inounting member is .
engageable with the artificial disc after beuig comiected to the first vertebra to guide movement of the artificial disc into position between the first and second vertebrae.
hz accordance with another aspect of the apparatus, a first retaining device is connected to the first surface of the resilient core. The first retaining device has an outer surface engageable with a first vertebra of the spinal colunui and an inner surface facing the first surface of the resilient core. A second retaining device is coiurected to the second surface of the resilient core. The second retail-iing device has ar. outer si .;rf?ce engageable with a second vertebra of the spinal colurnul and an iiuler surface facing the second surface of the resilient core. The iiuier surface of the first retaining device is spaced fronl the core. The core deflects into engagenzeiit with the iiuier surface of the first retaining device upon relative nzovement between the first and second retaining devices.

2a In accordance with another aspect, there is provided an apparatus for replacing a damaged spinal disc in a spinal column, said apparatus comprising: an artificial disc, said artificial disc including a resilient core having a first surface and a second surface, a first retaining member connected to said first surface of said resilient core, and a second retaining member connected to said second surface of said resilient core, said first retaining member having an outer surface engageable with a first vertebra of the spinal column and an inner surface facing said first surface of said resilient core, said second retaining member having an outer surface engageable with a second vertebra of the spinal column and an inner surface facing said second surface of said resilient core; and a first mounting member connectable with the first vertebra and said artificial disc to position said artificial disc between the first and second vertebrae, said first mounting member being engageable with said artificial disc after being connected to the first vertebra to guide movement of said artificial disc into position between the first and second vertebrae.
In accordance with another aspect, there is provided an apparatus for replacing a damaged spinal disc in a spinal column, said apparatus comprising: a resilient core having a first surface and a second surface; a first retaining device connected to said first surface of said resilient core, said first retaining device having an outer surface engageable with a first vertebra of the spinal column and an inner surface facing said first surface of said resilient core; and a second retaining device connected to said second surface of said resilient core, said second retaining device having an outer surface engageable with a second vertebra of the spinal column and an inner surface facing said second surface of said resilient core; said ;768-138 2b inner surface of said first retaining device being spaced from said core, said core deflecting into engagement with said inner surface of said first retaining device upon relative movement between said first and second retaining devices.

vVO 2005/058194 PCT/LIS200=4/()41402 ~
-~-Brief Description of the Drawinas The foregoing and other featlues of the present invention vlill beconle apparent to o11e skilled in the art to wllich tlie present invention relates upon consideratioll of tlle following descriptioll of the invention with reference to the accolnpanying drawings, in whicll:
Fig. 1 is a pictorial view of an apparatus to replace a damaged spinal disc constl-ucted in accordance with the present invention;
Fig. 2 is a sectional view of the apparatus of Fig. 1;
Fig. 3 is a pictorial view of an at-tificial disc of the apparatus of Fig. 1;
Fig. 4 is a schematic top view of the artificial disc of Fig. 3;
Fig. 5 is a pictolial view of a mountillg menlber of tlie apparatus of Fig. 1;
Fig. 6 is a schematic sectional view of the apparatus of Fig. 1 between adjacent vel-tebrae of a hunlan spinal colunl.n;
Fig. 7 is a scb.ematic sectional view of the apparatus of Fig. 1 between adjacent vertebrae of the spinal colunln showing the spillal colulnll in compression;
Fig. 8 is a schematic side view of an actuator for use in c=oiulecting mounting menlbers shown in Fig. 5 to adjacent vertebrae;
Fig. 9 is a pictolial view of insertion melnbers for use with the actuator of Fig. 8 to colulect the mounting members to adjacent vertebrae of the spinal colu11711;
Fig. 10 is a pictorial view of one of the insertion menlbers of Fig. 9;
Fig. 11 is a scllematic side view of the insertion meznber of Fig. 10;
Fig. 12 is a schematic top view of the insertion nzelliber of Fig. 10;
Fig. 13 is a sectional view of a portion of the insertion nlenlber taken along the line 13-13 in Fig. 12;
Fig. 14 is a pictorial vie'w of a slider cons3ectable to one of the insertion members of Fig. 9;
Fig. 15 is a pictorial view of a spring menlber for comlecting the lnountillg menlber to one of the insertion nlenlbers of Fig. 9;

Fig. 16 is a pictorial view of a surgical tool for use in insel.-ting the artificial disc of Fig. 2 between the adjacent vertebrae; and Fig. 17 is an enlarged view of a portion of the surgical tool of Fig. 16.
Description of the Invention The present invention relates to an apparatus or prosthesis to replace a damaged or degenerated spinal disc in a spinal column of a hunlan. Figs. 1-7 illustrate an apparatus or prosthesis 10 to replace a damaged or degenerated spinal disc in a spii7al colurnn. The apparatus 10 (Fig. 6) is used to replace a damaged spinal disc between adjacent tipper and lower vertebrae 12 and 14 of a hunzan spinal coluirui 16. The apparatus 10 (Figs. 17) includes an artificial disc 18 and mountia.ig members 100 that help connect the disc 18 to the adjacent vel-tebrae 12 and 14. The mounting members 100 also help position the disc 18 relative to the vertebrae 12 and 14.
The apparatus 10 (Fig, 1) includes an upper or first retaining device 20, a lower or second retaining device 60 and a resilient core 90 interposed between and adhered to the retaining devices. The upper and lower retaining devices 20 a1d are identical to each other and inchlde mounting melnbers 100. The apparatus is syrnnzetrical about a horizontally extending plane A (Fig. 3). The tenns "upper"
and "lower" are used herein with reference to the orientation of the apparatus when in the hunian body, as illustrated in Fig. 6, to distinguish the tivo identical retaining devices for reference puiposes.
The upper retaining device 20 includes ali upper or first retaining ring or ineniber 21 and a nlounting member 100. The al-tificial disc 18 includes the upper retaini.ng lnember 21. The upper retainiulg meniber 21 is 1-igid and made of a biocompatible material such as a biocompatible metal or polyn-ier. It is contemplated that the upper retaining member 21 could be made of a tital-liunl ~~ '=' ~ *~1= i_ alloy. The upper er reia1i1111g li1elil ~ b.. r ''1 ha5 an outer s u-face 22 en "aJeau ,,ie the vertebra 12. An inner concave surface 24 of the upper retaining nlember 21 is affixed or bonded to the resilient core 90. It is contemplated that the iruler surface 24 1nay have beads (not shown) sintered on the inner stirface or a texture rVO 2005/058194 PCT/US2004/041402 (not shown) etched onto the inner surface to help coiu-iect the upper retaining member 21 to the core 90.

A plurality of guides or ribs 26 (Figs. 3-4) and a central rib 2 8 extend from the oitter surface 22. Although the upper retaining n7ember 21 is shown as having four ribs 26, it is contemplated that the upper retaining member may have any nuinber of ribs 26. The ribs 26 engage the vertebra 12, as sliowil in Figs. 6-7, to retain the apparatus 10 in position between the vertebrae 12 and 14. The outer surface 22 may also have beads (not shown) sintered on the outer surface or a texture (not shown) etched onto the outer surface to further retaiul the apparatus 10 between the vei-tebrae 12 an.d 14.
The ribs 26 (Figs. 1-4) extend generally parallel to each other fiom a proximal side 30 of the disc 18 to an anterior side 32 of the disc. The central rib 28 exte7ds from the anterior side 32 of the disc 18 to an axially extending circular opening 36 in the upper retaining melnber 21. It is contemplated that the ribs and 28 may extend in any desired direction. The direction in which the ribs 26 and 28 extend is detenlziiled by the direction of insertion of the disc 18.
The axially extending opening 36 (Figs. 2-4) extends through the outer surface 22 and the iiuier surface 24 of the upper retaining member 21. The upper retaining meinber 21 has a fi-ustoconical surface 37 at least partially defuiing the opening 36. An upper poi-tion of the openi.ng 36 has a first diameter and a lower portion of the opening has a second diameter sinaller than the first diameter.
The opening 36 is centrally located between two of the ribs 26. Accordingly, there is no rib extending fi=om the proximal side 30 of the disc 18 to the opening 36.
Althougll tlie opening 36 is shown as being circular, it is conteznplated that the opening may have any desired shape.
A flange portion 38 extends from the upper retaining member 21 on tlie anterior side 32 of the disc 18. The flange portion 38 llas a recess 40 adjacent the central rib 28. The recess 40 is defined by a bottom surface 42 and side surfaces 44 and 46 extending upwardly fronz the bottom surface 42. An oval shaped slot 48 extends through the bottom surface 42 of the flange portion 38.
The slot 48 extends in a direction transverse to the direction iu1 wllich the rib extends.

WO 20(h-/U--)8194 PCT/US2004/041402 The ixuier concave surface 24 (Fig. 2) of the upper retaining menlber 21 is affixed oi- bonded to the resilient core 90. The upper retaining member 21 includes a peripheral flange portion 50 extending toward the lower retaining device 60.
The flange 50 encircles the core 90. The flange 50 has a radially iiu-ier surface facing the core 90. The surface 52 extends radially outvardly fi-om the concave surface 24 and toward the lower retaining device 60. The surface 52 on the flange 50 is spaced from the core 90, as shown in Fig. 6, until a predetei7liined load is applied to the apparatus 10.
The core 90 deflects toward the surface 52 on the flange 90 when a load is applied to the apparatus 10 to move the upper and lower retaining devices 20 and 60 relative to each other. When the predetermined load is applied to the apparatus 10, as shown in Fig. 7, the core 90 deflects into engagement witli the surface 52 on the flange 50. When the core 90 engages the flange 50, the core stiffens since fur111er deflection of the core is restricted by the flange 50.
The surface 52 of the flange 50 may have any desired configuration. The surface 52 inay have a first portion tliat extends closer to the core 90 than a second portion so that the core engages the first poi-tion of the surface 52 prior to engaging the second pol.-tion of the surface 52. Accordingly, the core 90 may engage different portions of the surface 52 as different loads are applied to the apparatus 10 to vary the stiffiless of the core at the different loads.
It is conteinplated that the retaining menlber 21 may have an inner surface (not shown) extending fiom the concave iluler surface 24 to t11e opening 36 a7d spaced from the core 90 until a predetennined load is applied to t11e apparatus 10.
'When the predeteizIlined load is applied to the apparatus 10, the core 90 deflects into engagenlent with the iiuaer surface (not shown) extending from the concave surface 24 to the opening 36. When the core 90 engages the iiu7er surface extending from the concave surface 24 to the openiizg 36, the core stiffens since filrther deflection of the core is restricted by the retaining nlenlber 21.

The lower retaining device 60 (Figs. 1-2) is ideiitical in configuration to the upper retaining device 20. The lower retaining device 60 includes a lower or second retaining menlber or ring 61 and a mounting member 100. The disc 1S
includes the lower retaiuiing nlenlber 61. The lower retaining meinber 61 is .NO 200,5/0,58194 PCT/US2004/041402 identical to the upper retaining member 21. Accordingly, the lower retaiuling inenlber 61 u7ill not be described in detail. The lower retaiidng meinber 61 is rigid and made from the same material as the upper retaiiling member 21, sttch as a titaniuin alloy. The lower retaining member 61 has an outer sttrface 62 engageable with the vei-tebra 14. A.i inner concave surface 64 of the lower retaining nleinber 61 is affixed or bonded to the resilient core 90. It is contemplated that the inner surface 64 may have beads (not shown) sintered on the iiu-ier surface or a texttire (not shown) etched onto the iizner surface to help coimect the lower retaining inember 61 to the core 90.
A plurality of guides or ribs 66 (Figs. 2 and 3) and a central rib 68 extend fronl the outer surface 62. The lower retaining tnember 61 may have any number of ribs 66. The ribs 66 engage the vertebra 14, as shown in Figs. 6 and 7, to retain the apparatus 10 in position between the vertebrae 12 and 14. The outer surface 62 may also have beads (not shown) sintered on the outer stuface or a texture (not shown) etched onto the outer stuface to fui-ther retain the apparatus 10 between the vertebrae 12 and 14.
The ribs 66 extend generally parallel to each other fiom the proxiinal side 30 of the disc 18 to the anterior side 32. The central rib 68 (Fig. 2) extends fioin the anterior side 32 to an axially extending circular opeiling 70 in the lower retaining nzen~.ber 61. It is contemplated that the ribs 66 and 68 may extend in any desired direction. The direction in which the ribs 66 and 68 extend is deteriniiied by the direction of insertion of the disc 18.
The axially extending openiizg 70 (Fig. 2) extends tluough tiie outer surface 62 and the iiuler surface 64 of the upper retaining nzenlber 61. The lower retaining men-ibe.r 61 has a frustoconical surface 71 at least partially defining the opening 70. A lower portion of the opening 70 has a first dianleter and an upper poi-tion of the openuzg has a second diameter smaller than the first diameter.
The opening 70 is centrally located between tvo of the ribs 66. Accordingly, there is no rib extending from the proximal side 30 of the disc 18 to the opening 70.
Although the opening 70 is described as being circular, it is contemplated that the openivig may have any desired shape.

A flanae portion 72 extends from the lower retaining nzember 61 on the anterior side 32 of the disc 18. The flatige portion 72 has a recess 74 adj acent the central rib 68. The recess 74 is defined by an upper surface 76 and side surfaces 78 and 80 extending do`viwardly fronl the upper surface 76. An oval shaped slot 82 extends through the upper surface 76 of the flange portion 72.
The slot 82 extends in a direction transverse to the direction in which the central rib 68 extends.
The inuer concave surface 64 (Fig. 2) of the lower retaining member 61 is affixed or bonded to the resilient core 90. The lower retaining nleinber 61 includes a peripheral flange portion 84 extending toward the upper retaining device 20.
The flange 84 encircles the core 90. The flange 84 has a radially im-ier surface facing the core 90. The surface 86 extends radially outwardly fiom the concave surface 64 and toward the upper retaining device 20. The surface 86 on the flange 84 is spaced fronz tlze core 90, as shown in Fig. 6, i.uitil a predetennined load is applied to the apparatus 10.
Tlze core 90 deflects toward the surface 86 on the flange 84 when a load is applied to the apparatus 10 to nlove the upper and lower retaining devices 20 and 60 relative to eacll other. When a predetez111ined load is applied to the apparatus 10, as shown in Fig. 7, the core 90 deflects into engageinent with the surface 86 on the flange 84. Wlien the core 90 engages the flange 84, the core stiffens since fiu-ther deflection of the core is restricted by the flange 84.
The surface 86 of the flange 84 lnay have any desired conf guration. The surface 86 may have a first poi-i:ion that extends closer to the core 90 than a second poi-tion so that the core engages the first portion of the surface 86 prior to engaging the second porlion of the surface 86. Accordingly, the core 90 may engage different portions of the surface 86 as different loads are applied to the apparatus 10 to vary the stiffi7ess of the core at different loads. It is also conteinplated that the flange 84 on the lower retaining inen7ber 61 may engage the flange 50 on the upper retaiiiing rnember 21 wlien a predeteniiined load is applied to the apparatus 10.
It is conteinplated that the retaining znember 61 may have an iiuler stuface (not shounl) extending froin the concave iiuler surface 64 to the openin` 70 and spaced from the core 90 until a predetermined load is applied to the apparatus 10.
Wheii the predeteiznined load is applied to the apparatus 10, the core 90 deflects into engagement ~x~ith the inner surface (not shown) exteriding fiom the concave surface 64 to the opening 70. W11en the core 90 engages the iiu-ier surface extending from the concave surface 64 to the opening 70, the core stiffens since fiu-t11er deflection of the core is restricted by tlie retaining member 61.
The resilient core 90 is one-piece and lnay be made of a urethane silicone blend manufactured by the Polymel- Teclulology Group located in Bericley, California. The resilient core 90 may be adhered or bonded to the upper and lower retaining inenlbers 21 and 61 in any maiuier lalown in the art. It is contemplated that the resilient core 90 could be insert molded, transfer molded or inj ection molded between the upper and lower retaining inenlbers 21 and 61. The core 90 may be molded betvtleen the upper and lower retaining members 21 aiid 61 by injecting the material for tlie core through one of the opeilirigs 36 or 70 in the upper and lower retaining members.
The resilient core 90 may be made of a polymer that is a silicone-polycarbonate-tuethane copolyiner by the nanie of CarboSilTM manufactured by the Polyiner Technology Group located in Berlcley, Califoznia. The resilient core 90 is prepared through a multi-step bullc synthesis during which polydimethylsiloxane is incorporated into the polyiner soft segnlent with aliphatic, hydroxyl-teilninated polycarbonate oligom.ers. The hard segment consists of an aromatic diisocyanate with a low molecular weight glycol chain extender. The copolylner chains are tezZninated with silicone.
The xnaterial of the resilient core 90 combines the bioconlpatibility and biostability of silicone elastom.ers with tlie processibility and toughness of thezrn.oplastic urethane elastoiners. The material of the resilient core 90 has a relatively high hard segnzent content that softens significantly upon reaching equilibrium with the body of a patient. The relevant equilibrium involves thermal equilibriun7 with the body at approximately 37 C and equilibrium water and solute uptalce by the polymer after beiulg implanted in the body. The material of the resilient core 90 has a decreased modulus at 37 C compared to that at room temperature. Accordingly, the higher duroineter polyiner can be used for its biostability, since conditions iu the hunlan body lower the modulus of the polyiner to the desired range of compressive stiffi7ess.
The resilient core 90 is wedge shaped. The upper retaining ineinber 21 is spaced from the lower retairiing member 61 a first dista.nce adjacent the proximal side 30 of the disc 18. The upper retaining member 21 is spaced from the lower retain.ing meniber 61 a second distance greater than the first distance adjacent the anterior side 32 of the disc 18. It is contenlplated that the upper retaiiiing member 21 ixiay be spaced from the lower retaining member 61 by any desired distances.
The core 90 has an upper or first convex surface 92. The upper convex surface 92 is affixed to the concave iimer surface 24 of the upper retaining niember 21. A lower or second convex surface 94 is affixed to the concave iruier surface 64 of the lower retaining member 61.
The core 90 includes a radially outer surface 96. Arcuate transition surfaces 98 extend between the radially outer stuface 96 and the upper and lower slufaces 92 and 94. The radially outer surface 96 is spaced from the flanges and 84 on the upper arid lower retaining meinbers 21 and 61 tmtil the predeteimined load is applied to the apparatZis 10.
The peripl7eral surface 96 and the transition surfaces 98 may have any desired configuration. The surfaces 96 and 98 may have first portions that extend closer to the flanges 50 and 84 thaii second portions so that the first portions eiigage the flanges 50 and 84 prior to the second portioils. Accordingly, the different portions of the surfaces 96 and 98 may engage tl-ie flanges 50 and 84 as different loads are applied to the apparatus 10 to vary the stiffiiess of the core 90 at different loads.
Each of the retaining devices 20 and 60 (Figs. 1-7) includes a mounting member 100 to help coiulect the disc 18 to the vertebrae 12 and 14. The inountiilg members 100 also help position the disc I S between the vertebrae 12 and 14.
The moiinting members 100 (Fig. 6) extend into the openings 36 and 70 in the retaining members 21 and 61 when the apparatus 10 is connected to the vertebrae 12 and 14.
The disc 18 is inserted between the vertebrae 12 and 14 after the nlounting members 100 are coiu-iected to the vertebrae. The ribs or guides 26 and 66 on WO 20055/0=+8194 PCT/US21)04/041402 sides of the openings 36 and 70 of the disc 1S engage the niotu7ting opposite members 100 to guide the disc in.to a desired position between the vertebrae and 14. The inounting members 100 are identical to each other. Accordingly, only one mounting member 100 will be described in detail.
The mounting naember 100 (Fig. 5) is rigid and made of a biocompatible material such as a biocompatible metal or polytner. It is contemplated thal:
the mounting member 100 could be made of a titanium alloy. The motultixlg nlenlber 100 has an outer surface 102 that faces the vertebra. An im.ler concave surface 104 of the motniting member 100 faces the resilient core 90. The iiuier concave surface 104 of the mounting member 100 of the upper retaining device faces the upper surface 92 of the core 90. The iiu-ier concave surface 104 of tlle mounting member 100 of the lower retaining device 60 faces the lower surface of tlie core 90.
The resilient core 90 deflects toward the concave stufaces 104 when a load is applied to the apparatus 10 to move the upper and lower retaining devices and 60 relative to each other. The core 90 deflects into the openings 36 and 70 in the upper and lower retaining members 21 and 61 and into engagement with the concave surfaces 104 when the spine 16 is subject to a predetenniuled load, as shovni i11 Fig. 7. When the core 90 engages the surfaces 104 of the mounting members 100, the resilient core stiffens since fw.-tlier deflection of the core toward the retaining devices 20 and 60 is restricted. It is conteinplated that the retaining member 100 may have a.n axially extending openi.ilg to penziit tlie escape of gas froin between the core 90 and the n7ountiuzg lnezriber.
The surfaces 104 of the motulting nieinber 100 may have any desired configuration. The core 90 may engage different portions of the surfaces 104 as different loads are applied to the apparatus 10 to vary the stiffiiess of the core 90 at different loads. It is also contemplated tl-iat the surface 104 of the znountiua.g menlber 100 of the retaining device 20 iilay have a different configuration than the surface 104 of the mounting men-iber 100 of t11e retaining device 61.
Projections 106 extend fiom the outer surface 102 of the mounting member 100. The projections 106 engage the vertebrae 12 and 14 to help retain the apparatus 10 in position between the vertebra 12 and 14. Although the niounting member 100 is shown having four proj ections 106, it is conten-iplated that the mounting member may have any number of projections. It is conteinplated that the projections 106 may have any desired shapes, sizes, and/or tip configurations. The projections 106 may include passages for bone inj owth, have barbs, and/or have hooks.
The mounting member 100 includes a circular body 110 from which the projections 106 extend. Althougli the body 110 of the mounting menzber 100 is shown as being circular, it is contemplated that the body 110 may have any desired configuration that penllits the inotuiting menlber 100 to slide into the openings 36 and 70 in the disc 18.
The body 110 of the nlounting member 100 has a radially outer filistoconical surface 112. A rounded transition surface 113 extends fiom the radially outer surface 112 to the concave surface 104. The body 110 has a first diaineter adjacent the outer surface 102 and a second diaineteir adjacent the transition surface 113 that is smaller than the first diameter. The radially outer surfaces 112 and/or the transition stu faces 113 of the mounting members 100 engage the ribs or guides 26 and 66 on the retaining members 21 and 61 to guide movement of the disc 18 in a first posterior direction relative to the motultii2g meinbers and tl-ie vertebrae 12 and 14. The central ribs 28 and 68 on the upper and lower retaining members 21 and 61 act as stops to prevent movement of the disc. 18 in the first direction after the disc has been inserted to a desired. depth.
The central ribs 28 and 68 engage the radially otiter surfaces 112 and/or the transition surfaces 1 l 3 on the motu-iting nzeinber 100. When the central ribs 28 and 68 engage the mounting inenibers 100, the radially outer surfaces 112 and/or the transition surfaces 113 guide relative lnovement between the n7ounting n7einbers and the retaiiling members 21 and 61 in second directions extending transverse to the first directions so that the mounting members move into the openings 36 a1d 70 in the disc 18.
The radially outer fi2istoconical surfaces 112 on the mounting meinbers 100 engage the fitiistoconical surfaces 37 and 71 on the upper and lower retainilig nien7bers 21 aild 61 when the nlounting members are in the opei-iuigs 36 and 70 i11 the disc 18. The engagement of the surfaces 112 with the stufaces 37 and 71 JVO 2005/05819-3 PCT/US200-4/04740~

creates interference fits between the mounting meinbers 100 and the disc 18.
Accordingly, the disc 18 is prevented from nzoving relative to the inounting mernbers 100.
The radially outer surface 112 has fotu= recesses 114, two of which are shown in Fig. 5. The recesses 114 are located at 90 relative to each other.
Although the mounting niember 100 is described as having four i-ecesses 114, it is contemplated that the mountivIg member 100 may have any number of recesses.
The mounting menzbers 100 may be connected to the vei-tebrae 12 and 14 using a surgical tool that includes an actuator 120 and a pair of insertion members 140 (Figs. 8 and 9). The moulzting members 100 are connected to the mernbers 140 and the actuator 120 moves the members away fiom each other to coilnect tlie inounting meinbers to the vertebrae. The actuator 120 (Fig. 8) may be a modular spine distractor manufactured by Friedrich Gn1bH of Solingen, Germany to wllich the nieinbers 140 are coiulected. The actuator 120 is l~tiown in the art and will not be described in detail.
The actuator 120 includes a pair of actuation handles 122 and a pair of separators 124 that are connectable to the meinbers 140. The haridles 122 are coiuiected to the separators 124 by a linkage systenl 126. Upon movement of the handles 122 toward each other, the linlcage system 126 causes the separators 124 to move away from each other. The actuator 120 also includes a loclcing mechanism 128 for loclcing the separators 124 at a desired distance fronl each otller.
The insertion members 140 (Figs. 9-13) are coiulectable to the separators 124. The members 140 are identical to each other. Accordingly, only one inember 140 will be described in detail.
The member 140 includes a cozuiecting end 144 that is insei-table into an opening (not shown) in one of the separators 124 of the actuator 120. The end includes a pair of projections 146. The projections 146 (Fig. 12) extend generally parallel to each other and defule a chauzel 148 between tlleni. The end 144 is insei-ted into the opening (not shown) in the separator 124 of the actuator 120 to connect the nlember 140 to the actuator in a lalown nlaiuler. The member 140 may be removed from the separator 124 in a laiown mazuzer. It is contemplated that the WO 2005/0-58194 PCTlUS2004l041-102 end 144 of the member 140 hay have any desired configuration to coiuiect the member to a desired actuator.

The projections 146 (Figs. 9-12) extend from a first end 150 of a central body 152 of the nlember 140. The central body 152 has an upper surface 154 and a parallel lower surface 156 extending from the first end 150 to a second end of the central body. The projections 146 extend at an angle to the surfaces and 156. It is conten7plated that the projections 146 may extend at any desired angle to the surfaces 154 and 156. The upper surface 154 has a scalloped recess 164.
Side surfaces 160 and 162 extend fron-i the upper surface 154 to the lower surface 156. A pair of longitudinally extending grooves 166 (Fig. 10) located in the side surfaces 160 and 162 extend along the body 152. The grooves 166 extend fioin the first end 150 to the second end 158.
A slider 168 (Figs. 9 and 14) may be connected to the body 152 of the nieinber 140. The slider 168 engages one of the vertebrae 12 and 14 to prevent further insertion of the mounting mernbers 100 in the proximal direction between the vertebrae. The slider 168 includes a main body portioi7 170 with a tlueaded opening 172. A pair of flanges 174 extend downwardly fronl the body portion 170. The flanges 174 (Fig. 14) extend generally parallel to each other and include portions 176 extending toward each other. The portions 176 are received in the grooves 166 in the body 152 of the member 140. The slider 168 includes a vertically extending groove 178 in a surface 179 that faces away from the coimecting end 144 of the member 140.
The slider 168 may be moved relative the body 152 toward and away from the end 144 of the member 140. A set screw (not shown) is tlu-eaded into the opening 172 and extends into the scalloped recess 164 to prevent movement of the slider 168 relative to tlae body 152. The scalloped recess 164 defines a plurality of positions for the slider 168 relative to the member 140.
An insertion end 180 (Figs. 9-13) of the member 140 extends fronl the second end 158 of the body 152. The insertion end 180 extends at an angle to the upper and lower surfaces 154 and 156 of the body 152 and generally parallel to the projections 146. It is contemplated that the insertion end 180 may extend at any WO 2005/0-5819 4 PCT/US2004/04140'-, desired angle relative to the surfaces 154 and 156. The insertion end 180 (Fig. 11) has a lower surface 182 that extends at an angle to the lower surface 156 of the body 152.
The insertion end 180 (Fig. 12) includes a recess 184 for receiving the mounthlg member 100. The recess 184 is generally U-shaped with an open end 186 througll which the rnounting meinber 100 nzay be inserted into the recess and removed from the recess. The recess 184 is defined by sidewalls 188 and intercoiuiected by a back wall 192. A bottom wall 194 extends generally peipendicular to the sidewalls 188 and 190 and the back wall 192.
The sidewall 188 has a. notcll 198 extending radially outwardly. The sideA-vall 190 includes a notch 200 extending radially outwardly. The back wall 192 has a notch 202 extending toward the body 152. A groove 206 (Figs. 10 and 13) is foniied in the sidewall 188 extending from adjacent the open end 186 to the notch 198. A groove 208 extends from the notch 198 to tlie notch 202. A
groove (not shown) similar to the groove 208 extending between the notch 202 and the notch 200 is forrn.ed in the sidewall 190. Another groove (not shovin) sin-iilar to the groove 206 extending from the notch 200 to adjacent the open end 186 is fornled in the sidewall 190.
A first circular opening 216 extends through the bottom wall 194 and is centrally located in the recess 184. The openi.ng 216 pennits removal of the mounting member 100 fi-om the recess 184 if needed. A second smaller circular opening 218 extends through the bottom wall 194 and is located in the notch 202.
A spring inember 230 (Figs. 9 and 15) is received in the recess 184 to hold the n7ounting mernber 100 in the recess. The spring menlber 230 is generally U-shaped and includes a pair of aims 232 and 234 extending from a base 236. A
projection 238 extends fi-on1 the base 236 in a directioil opposite fronl the anns 232 and 234. The projection 238 has a circular opening 240 for receiving a pin (not shown) to coiulect the spring inember 230 to the menlber 140. The pin (not shown) extends through the opening 240 in the spring menlber 230 and into the opening 218 in the member 140 to connect the spring member to the member 140.
The arm 232 includes an upwardly extending end 246 that engages the niounting nlember 100 to retain the mounting nleniber in the men7ber 140. The WO 200/0-5819-1 PC'I'/US20041047-10 2 end 246 has a radially invvardly extending projection 248. The projection 248 extends into one of the recesses 114 in the mounting member 100 to retain the nlounting member in the menzber 140.
The arn1234 has an upwardly extending end 252. The end 252 has a radially inwardly extending projection 254. The projection 254 extends itito one of the recesses 114 in the mounting member 100 to retain the mounting menlber in the member 140.
The spring member 230 is inserted into the recess 184 ti-irough the open end 186. The atnls 232 and 234 extend into the groove 206 in the sidewall 188 and the groove (not shown) in the sidewall 190 extending from the notch 200 to adjacent the open end 186, as tlle spring 230 is being iulserted into the recess 184.
The ends 246 and 252 of the anns 232 and 234 move toward each other. tiUhen the ends 246 and 252 are adjacent the notches 198 and 200, the ends 246 and 252 nlove away from each otlier.
When tl-ie sprulg 230 (Fig. 9) is inserted in the recess 184, tlie ann 232 extends into the groove 208 and the ann 234 extends into the groove (not shown) extending fiom the notch 202 to the notch 200 in the insertion end 180 of the member 140. The opening 240 in the projection 238 of the spring menlber 230 is aligned with the opening 218 in the insertion end 180. A pin (not shown) exteiids tluough the opening 240 in the spring meinber 230 and into the opening 218 to retain the spring member in the recess 184. The ends 246 and 252 extend upwardly into the notches 198 and 200 in the sidewalls 188 and 190.
Upon insertion of the motulting member 100 between the ends 246 and 252 of the spring 230, the ends move radially outv,Tardly away from each otlier into the notches 198 and 200 until the recesses 114 are aligned with the projections and 254. VAien the recesses 114 are aligned with the projections 248 and 254, tlie ends 246 and 252 move toward each other into the recesses to retain the mounting nZember 100 in the insertion end 180. The motmting member 100 may be removed fi-om the recess 184 by overcoming the retaining force applied by the spring member 230.
Aaz insertion tool 300 for inserting the disc 18 between the vertebrae 12 and 14 after the n7ounting members 100 are coiulected to the vertebrae 12 and 14 is WO 200-5/058194 PCT/US2004/04140~

illustiated in Figs. 16 and 17. The tool 300 (Fig. 16) resernbles a conunon pair of scissors and has a pair of legs 302 and 304 pivotally cormected to one another. The tool 300 includes a grasping end 306 foni7ed by a pair ofjaws 308 on tlie legs and 304. The jaws 308 (Fig. 17) include oval shaped projections 310 extendulg toward each other. The projections 310 are inserted into the openings 48 and 82 in the disc 18 to grasp the disc for insei-tion between the vertebrae 12 a1id 14.
The leg 302 (Fig. 15) has an enlarged end 312 opposite tlie jaw 308. The enlarged end 312 may be struck with a mallet to drive the disc 18 betlx7een the vertebrae 12 and 14 if needed. The leg 304 has a curved handle 314 opposite the jaw 308. The handle 314 is easily grasped by a surgeon for inanipulating the tool 300.
A locking inechanisnl 320 prevents the jaws 308 fron7 pivotiikg away from each other after the projections 310 have been inserted into the openings 48 and 82 in the disc 18. The loclcing mecha.nism 320 includes a rod 322 pivotally connected to a inounting portion 324 extending from the leg 304. The rod 322 has a tlueaded end 326 that extends through an opening 328 in the leg 302. A nut 332 tlu=eadably engages the end 326 of the rod 322 and engages the leg 302 to prevent the jaws 308 from pivoting away fron7 each other.
When the apparatus 10 is to be inserted between tlie vertebrae 12 a.nd 14, an anterior space adjacent the vertebrae is exposed using a retroperitoneal or transperitoneal approach. A midline reference is established. A midline marker, such as a K-wire, is placed to nzaintain a reference point to the center of one of the vertebrae 12 and 14. The space between the vertebrae 12 and 14 is distracted and the dan-iaged disc between the vertebrae is excised. After the daniaged disc is excised, the cartilaginous end plates are removed from the vertebrae 12 and 14.
The vertebrae 12 and 14 are then sculpted as desired.
The appropriate size apparatus 10 is deteinZined by using trial sizers. The trial sizers are similar to the disc 18. The trial sizers are iiiserted between the vertebrae 12 and .14 to detennine the desired footprint, wedge angle, azid disc height needed to replace the excised disc. The desired footprint, wedge angle and disc height are confinlied using fluoroscopy.

WO 2005/0S8194 PCT/TJS2004/04140-, The inounting members 100 are then inserted into the vertebrae 12 and 14.
The appropriate members 140 are selected based upon the desired wedge angle for use between the vei-tebrae 12 and 14. The mounting members 100 are inserted into the recesses 184 in the member 140. The insertion ends 180 of the members 140 are inserted between the vertebrae 12 and 14 until the nlidline marlcer extends into the groove 178 on the slider 168 and the slider 168 engages the anterior ridge of one of the vertebrae 12 and 14 directly under the midline marlcer. Once the insertion ends 180 of the members 140 have been inserted into the desired.
deptll, the insertion ends are moved away fi-on1 each other by the actuator 120 to insert the projections 106 on the nzounting meinbers 100 into the vertebrae 12 a.nd 14.
After the mountiuzg niembers 100 have been com7ected to the vertebrae 12 and 14, the members 140 are removed from between the vertebrae 12 and 141eaving the mountilig niembers beliind.
After the n7otmting nlenlbers 100 are coiulected to the vertebrae 12 and 14, a tzial sizer may be reinserted between the vertebrae. Verification of the position of the trial sizer is achieved using fluoroscopy. If it is detemiined that the mounting members 100 are not in the desired positions, the mounting nienlbers can be easily renloved and repositioned in the vertebrae.
After the mounting inembers 100 are connected to the vertebrae 12 an.d 14 in tlieir desired positions, the insertion tool 300 is coiulected with the disc 18. The disc 18 is then inserted between the vertebrae 12 and 14. During insertion of the disc 18, the ribs 26 and 66 on opposite sides of the openings 36 aiid 70 engage the surfaces 112 and 113 on the nlounting il7embers 100 to guide insertion of the disc.
The central ribs 28 and 68 engage the mounting members 100 when the disc 1.8 has been inserted to the desired depth between the vertebrae 12 and 14. The ribs 26, 28, 66, and 68 on the disc 18 guide insertion of the mounting members into the openings 36 and 70 in the disc 18.
Af1:er the disc 18 is placed into the desired position between the vertebrae 12 and 14, the tool 300 is removed fiozn the disc. The ribs 26, 28, and 68 on the disc 18 engage the vertebrae 12 and 14 when the motmting members 100 are inserted in the openings 36 and 70 in the disc 18. The inounting WO 200-5I0.5819-4 PCT/US200-4/04140~

n7embers 100 and ribs 26, 28, 66 and 68 retain the apparatus 10 in position between the vertebrae 12 and 14.
When the apparatus 10 is in use in the spinal coluinn 16, the upper retaining device 20 is affixed to the vertebra 12. The ribs 26 and 28 and the projections 106 on the mounting ir=.ember 100 resist relative movement between the upper retainin.g device 20 and vertebra 12. The lower retaining device 60 is affixed to the vertebra 14. The ribs 66 and 68 and the projections 106 on the nzounting member 100 resist relative movement between the lower retairung device 60 and the vertebra 14.
When the upper aiid lower retaining devices 20 and 60 move relative to each other, such as when the spine 16 is hi compression, as shown in Fig. 7, the resilient core 90 deflects toward the concave surfaces 104 on the mounting inenzbers 100. The resilient core 90 also deflects toward the surfaces 52 and 86 on the retaining members 21 and 61 when a load is applied to the apparatus.
Accordingly, the core 90 expends energy to reduce stress in the core upon relative movernent of the upper and lower retaining devices 20 and 60 to provide a relatively long fatigi.te life for the apparatus 10.
The resilient core 90 deflects uito engagement with the surfaces 104 of the mounting meinbers 100 when a predetermined load is applied. The core 90 also deflects into engagement with the surfaces 52 and 86 on the retaining nzeinbers 21 and 61 when a predetennined load is applied. Accordingly, the core 90 stiffens when the core engages the surfaces 104, 52, and 86 since fiutl.ler deflection of the core is restricted. It is contemplated that the core 90 may engage the surfaces 104, 52, and 86 at different applied loads.
Although the ribs 26 and 66 on the disc 18 are described as engaging the mounting members 100 to guide insertion of the disc between the vertebrae 12 and 14, it is conteinplated that the mounting members 100 may have grooves that ribs on the disc 18 extend into to guide insertion of the disc. It is also contemplated that the mounting members 100 nlay have ribs that extend into grooves in the disc 18 to guide insei-tion of the disc. Fui-t1leiinore, it is conteniplated that the disc 18 may be inserted between the vertebrae 12 and 14 without use of the mounting inembers 100. If the disc 18 is used without the WO 200---)/0'--)8194 PCT/US2004/041402 mountilig members 100, it is conteinplated that the retaining members 21 and 61 of the retaining devices 20 and 60 would include inner concave stufaces siunilar to the iiuler concave surfaces 104 of the mounting members. The core 90 would be spaced fl-om the inner concave surfaces on the retaining members 21 and 61 and deflect i.nto engagement with the inner concave surfaces when a predeternzined load was applied to the apparatus 10.
It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the ineaning and range of equivalents of the 1.0 appended claims. The presently disclosed enibodiments are considered in all.
respects to be illustrative, and not restrictive. The scope of the invention is indicated by the appended claims, rather tlian the foregoing description, and all changes that come witllin the meaning aild range of equivalence thereof are v.7tended to be embraced thereiil.

Claims

CLAIMS:

1. An apparatus for replacing a damaged spinal disc in a spinal column, said apparatus comprising:

a resilient core having a first surface and a second surface;

a first retaining device connected to said first surface of said resilient core, said first retaining device having an outer surface engageable with a first vertebra of the spinal column and an inner surface facing said first surface of said resilient core; and a second retaining device connected to said second surface of said resilient core, said second retaining device having an outer surface engageable with a second vertebra of the spinal column and an inner surface facing said second surface of said resilient core;

said inner surface of said first retaining device being spaced from said core, said core deflecting into engagement with said inner surface of said first retaining device upon relative movement between said first and second retaining devices.

2. An apparatus as defined in claim 1 wherein said core includes a radially outer surface extending between said first and second surfaces of said core, said radially outer surface facing a portion of one of said first and second retaining devices, said radially outer surface being spaced from said portion of said one of said first and second retaining devices, said core deflecting into engagement with said portion of one of said first and second retaining devices upon relative movement between said first and second retaining devices.

3. An apparatus as defined in claim 1 wherein said first retaining device includes a portion engageable with a surgical tool for inserting said first retaining device between the first and second vertebrae, said portion of said first retaining device including an opening into which a portion of the surgical tool extends.

4. An apparatus as defined in claim 1 wherein said first retaining device includes a first mounting member and a first retaining member, said first retaining member having said outer surface engageable with the first vertebra and an inner surface affixed to said first surface of said core, said first mounting member including said inner surface facing said core that said core engages upon relative movement between said first and second retaining devices, said first retaining member having an opening extending through said inner and outer surfaces of said first retaining member, said first mounting member being located in said opening.

5. An apparatus as defined in claim 4 wherein one of said first retaining member and said first mounting member includes a guide engageable with another of said first retaining member and said first mounting member to guide movement of said first retaining member into position between the first and second vertebrae.

6. An apparatus as defined in claim 1 wherein said first mounting member has a frustoconical surface engaging a frustoconical surface on said first retaining member, to prevent said first mounting member from moving relative to said first retaining member.