CA1325078C

CA1325078C - Intervertebral disk endoprosthesis

Info

Publication number: CA1325078C
Application number: CA000601800A
Authority: CA
Inventors: Gerhard Fuhrmann; Ulrich Gross; Bertram Kaden; Herman-Josef Schmitz; Thomas Fritz; Curt Kranz
Original assignee: Individual
Current assignee: SCHMITZ HERMAN JOSEF
Priority date: 1988-06-06
Filing date: 1989-06-05
Publication date: 1993-12-14
Anticipated expiration: 2010-12-14
Also published as: EP0346269A2; JPH02111358A; ATE95684T1; EP0346269B1; DE8807485U1; EP0346269A3; DE58905879D1; US5002576A

Abstract

A B S T R A C T

An intervertebral disk endoprosthesis is filled with viscoelastic material and provided with cover plates at its end faces. The disc comprises a circular or elliptical corrugated tube surrounding and contiguous with the viscoelastic material and terminated by the cover plates. The cover plates are rigid, and the corrugated tube allows for less constrained tilting of the cover plates and further accommodates the compressive bulging of the viscoelastic material.

Description

BACKGROUND OF TH~ INYENTION

,~ The present invention relates to an endoprosthesis of the type defined in the preamble of Claim 1.
~, German Patent No. 2,203,242 discloses such a prosthesis.
,' 5 Its drawback is that the elastic material applied between the cover plates is not completely compatible with the human ~ody ~ since harmful long-term reactions with the surrounding body ¦ ~ tissue cannot be permanently excluded~
! ~ Moreover, U.S. Patent No. 4,759,766, discloses an ¦ ~ 10 intervertebral disk prosthesis in which a rigid spacer is provided between two symmetrical end plates. The end plates are movable relative to one another by the interaction of meshing pairs of convex and concave faces.
~ ~ Here again there exists the drawback that the surfaces s .~ :, -~ 15 rubbing against one another create abrasion particles.
, ~ ~
S~ R~ OF THE INVENTIQN
It is the object of the present invention to provide an endoprosthesis of the above-mentioned type in which better ' 3 compatibility with the human body is provided and whicha~ditionally prevents material particles from being released due to frequent alternating stresses and moving around.
~i , Thi~ is accomplished by the present inventlon, which , pxovides an intervertebral disk endoprosthesis filled with ~-~ viscoelastic material and provided with cover plates at its end faces, comprising a circular or elliptical corrugated tube surrounding and contiguous with the viscoelastic material and '', ~ ...
- :--. ', ' ' ~

terminated by the cover plates, wherein said cover plates are rigid, and wherein said corrugated tube allows for less constrained tilting of said cover plates and further accommodates the compressive bulging of said viscoelastic material.
The present invention also provides an intervertebral disk . endoprosthesis filled with viscoelastic material and provided with cover plates at its end faces, comprising a circular or elliptical corrugated tube surrounding and contiguous with the -~ viscoelastic material and terminated by the cover plates, wherein at least one of said cover plates is provided with a flange, and wherein said corrugated tube allows for less constrained tilting of said cover plates, and further accommodates the compressive bulging of said viscoelastic material.
The invention is based on the realization that a cuff in the form of a corrugated tube, preferably made of titanium, surrounding the viscoelastic material, on the one hand, provides a body-compatible exterior surface and, on the other hand, a hermetically sealing inclusion.
The corrugated tube is here preferably incorporated in the elastic properties in such a manner that it prevents excessive bulging of the interior body upon compression and thus contributes to its form stability. In particular, the suppression of bulging also prevents painful contact with adjacent nerves.
By filling the viscoelastic material entirely or partially with oriented or unoriented fibers, the viscosity of the elastic interior body can be controlled. An increase .

, ,, _ .

::.: . ,: . - - . .- . .

:

in the degr~ or ~ill reduces compres~lbillty. The Arr~ng :~ ment, whlch 1~ o~lented perpendic~alarly to the directlon of the load ana p~rpondloularly to the directlon of the gra~ien~
of fill l~vel chAnges, cu~ve~ under a load . suitable dis--~ 5 trl~ution, for oxa~ple by increasing ~he degree of flll in th~ c~ntar, al~o per~its the or~atlon of ~n arr~ngement in whlch the ~rontal ~ace~ for~ a type of "rucker" which is s~le to tilt to all ~ido~. Wlth ~n asy~m~trio~l a~rangemen~ o~
thQ r~lling, an a~ymme~riaal, pr~e~ential tiltlng or pu~hlng .-~. 10 behavior can also ~e realized. :
In partioular, ~hc viscoela~tic materlal filling the corrugated ~ub~ i~ compoQed of a polymerizable mat~rial which i~ in~oduced in liquid form into a ~111 op~nlng dur~ng manufacture. Additionally, th~re 1~ ~dvan~ageously pro~la~d --a ven~llatlng ~pening. A slliaon~ adhs~ive a8 it is e~ployed to glue ~ogether blood v~s~els i5 particularly ~uitable as ~ :~
i the vl8coelA~tl~ ~ater~al.
- The ~ndoprosths~ie according to the ~nvention i~
I pre~r~bly employa~ ln ~uch a ~anner tha~ th~ adjacent ver-20 tebrae ar~ ~llled down ~o thAt thQ thsn exposed spongy tl~ue ::
--:t '. grows ~ nto r~glono of the cover pla~o whlah are provided w~ th a poroua ~nd pa~tiçularly bio~ctive surface.
-~ Scrsw-type cla~plng devices or weld qonnect~ onR are favorable ~o~ Sa~tonlng the cove~ plat~s and the corrugated ,' ~' ''~`
- 4 ~

.. . .

tube. A connection by m~an~ of ~ ten~lcn ring i~ o o~
~` adVAn~Ag~e .
- Acoor~lng to a ~lr~t advantageou~ embodlmon~, the :.- interv~rt~br~l dlo~ endopro~hesi~ 1~ compo~ed o~ a Glo~ed . 5 spring body which i~ d ln lt~ lnterlor wlth a vi3~0ela~-y tic material ~hat 1~ relnforced wlth ~iber~ to di~erent ~.
~, degrees. At both lt~ ~nd~, the ~prlng body i~ ~ealingly and - flrmly oonnectea wl~h planar cover plates made o~ a bloa~tlve ato~lal.
i ~ 19 In ano~h~r ~bod~ment, ~he intervertebral di~k andopro3-th~sls i~ composQd o~ a clos~d sprlng ~o~y whlch is filled in ~-it~ lnterlor with ~ viscoela~ti4 material that i~ reingorced ::
wlth flb~r~ to al~rent ~egr~es in di~e~ent areas. At bo~h , ~ lts end~, thi~ sprlng body 1G also ~ealing~y an~ ~lrmly ;~ 15 aonneated wlth rlgld cover plates who~e sur~aces are adapt~d ts the vertebrae and are provided with laterally di~po~d ' ~ tab~ ~'or the a¢oo~odatlon Or ~a~tening ~crsw~ that act a~
ten~lon ecrew~.
A~vantag~40us moalfica~ionæ of ~he lnventlon are d~ined 20 in ~he dependent claims and w~ll be de~cribed in greater detall ~elow in connection wlth a de~cri~tion o~ the p~-~err~d e~o~ nt o~ the invention an~ wlth rs~erence to th~
, . dra~ing ~igu~

,.. .
~:
i _ 5 _ :

~' .:

1.;, ,:~ " , :., ,. : .~ , . . : ' :'; ' .

1 32501~

. BRIEF DESCRIPTION OF THE DRAWI~S

. J ;
Figure 1 1~ ~n enlarged slde vl~ o~ a ~lr~t embo~iment o~ the inv~n~ion.
Flgure 2 i8 a corre~pondln~ uRtration of a ~econd : ~ 5 e~bodimont.
. Flgur~ 3 ~n~ 4 are enlarged dfftail views o~ variations Or ~he ~mbo~ nt.

~, In the fir~t embodiment 3hown in Figure 1, the inter~er- `.
~ lO t~bral d~k en~opro~thQsis i5 compo~q~ o~ a spring body in J the fo~m of a olo~ed corrug~ted tube 1 fille~ ln it~ in~erior ~:
with a vi~coelaatlc material 2 and se~lingly and ~irmly conn~oted at ~oth i~5 end~ wl~h planar cover plates 3 and 4 ~ ;
~f ~ bioactive ~a~xisl or a m~t~rifll providod with a ~ 15 bioaotlve coating. In principle, ~h~ corrugat~d tube is e ~lmllar to correcponding spring elem~nt~ a~ th~y are ~mployed ln barometric preo~ure gaugcs or the like.
~ho vlsco~la~tic material 1~ pre~erably compos~d o~
~dy-co~patible 8~ licone~ Thu~ th~ ~p~ing body ~orm8 a 20 ~table bur~sr ele~nt which can be compre~sed and dero~me~
without its axlal croe~ section ah~nging su~An~ ally Bince .

lt $8 enclo~ed by th~ flexible corrughted tube. HoweYer, in addltion to compres~ive ~ovemen~, tllting, shear and, to a ted ext~nt, al80 tereional move~ente are possi~le without the croes oect~on of the 3prlng bcdy being enlarged. The ~prlng body i~ ~table with re~pect to 1~ sur~ace charac~
teristic6 ~nd 18 not ~ub~ect to ~ny w~ar. In order to adapt ~he lmplant6 to ~pecial requirement~, it 1~ prov~ded that the ela8t~c~ty ch~ra~t~rletlc~ of ~aterlal 2 and pos31bly al~o ~f corrugate~ tube 1 dlffer locally. For thiq purpose, a varia~ $ber rein~otcement is provlded for ~aterial 2 whlch lo~ally ch~nge8 its comp~essibility in such a way that compres~lon cau~es ~ "rolling o~" to the ragion equlpped .. wlth the fibQr ~ill. Local weakening of the corrugatQd tube ~rroundin~ the rilling ~arves to ~urther augment thle 15 a~eot aauesd by th~ ~ nhomogeneity o~ the epriny body. Th~
exterlo~ ~Ace~ 5 an~ 6 o~ cover platee 3 and 4 are either . adapted ~o the shape o~ ~he ad~acent n2tural vertebrAe or are made plan~r~ ~aa-~ 5 and 6 Are prsvlded wlth a bio ct~ve ; coatlng - n~t ~hown ln detail - whlch snhan~es ~he in-growth , ~0 o~ body ti~u~. Such coatings are hydroxyl apatite, o~ramic -~ HIP ~aterial or polylac~id~. Resor~Abl~ mat~rial 1~ pre-ferably applied in~o s~condary por~B to wh1~h the bone grows once the r6~0rb~bla material hs~ bee~ catabolized. Thi~ ~180 suppre~se~ in~ections. A porou4 ~ur~a~e of the ~etalllc ..

.

,,. ~ . .

ba31c body of ~over pl~tes 3 and 4 can be re~lizsd, for exa~pl~, by sand-bl~ting. The ln-g~owth o~ the VertebraQ i9 enhanced by mllllng down the bone e~rrace 50 th~t th~ ~p~ngy -~ ti~ue i8 expo8ed and a - pra~er~bly planar - contaat aur~ace on the bon~ v~ilablQ whlch i~ adapt~d to ~c~ 5 and 6, re3pectlvely. Th~ ~e~Alllc ~omponent~ of the lmplRn~ are uni~ormly made o~ tl~Anium t or #o~ o~hor 5ul~1¢ ~orlal, . ~uch as ~tainle~s Bteel 3uitable tor implantation purpo es) 80 a3 to ensure ~h¢ be~ pos6i~1e ~o~y ~ompatlblll~y and 8xolude corro~on.
In a ~econd Qmbodlmen~ whi~h i8 $11ustrat~d in Figure 2, the interver~obral ~lsk endopro~th~io 1~ ~gain compc~d of a clo~ed ~prlng body ln the rorm o~ a corrugated tube 1' whlch i8 fllled ~n ite int~rior wl~ a visco~lastic mater~al 2' th~t is rein~orced wlth ~ib~r~ to dif~erent degrees and i8 ~eal~ngly and rlrmly clo~e~ at bo~h i~R en~ by means o~
rigid co~er pl~ts~ 3' and 4'. Later~lly disposed, tab-like 21ange~ 7 and 8 ~ro conneated ~lth ao~er plates 3' ~nd 4' and are oriented perpendicularly to the surface3 ot ths cover plates. The ~lange~ are provided with hole~ 9 an~ 10 ~or ~he pas6ag~ of bon~ ~crews 11 a~d 12. ~h~ hol~s a~ orianted in ~uch a w~y that ~crews 11 and 12 in~r~ed ~ro~ the ou~side sp~ead ~pen ln ~ scrQw-ln dir~ctlon and thu~ constltuta ~-~
ten~lon cr~ws ror cover plat~ 3' an~ 4'. ~olco 9 ~nd 10 ' : ~

, ~ .

,, -:- -. ~ ~ :

. .: . ~ . . ~: . : . .

~ 1 325078 a~6 provlded wlth wldened portions 1~ and 14 to accommodate the heads of conventlonal bon~ screw~ 60 that the latter c~n be coun~erounk. ~y mean~ o~ flange~ 7 an~ 8 ~nd bone ~crews .. 11 and 12, th~ lmplant~ are ~crewed onto the v~r~ebrae ~rom th~ ~ront. The ~on~ ~orews are al80 composed ~f th~ m~t~llic materlal o~ the romaindex of ~h~ lmp~ant.
The varlAtton o~ the embodiment ~hown ln Flgur~ 3 i5 an enlarged datall Or the embodiment o~ Flgure 2 ~een along the ~ection llne ~r~d III in tha~ ~lgure. Groov~s 15 ar~ made in cover pla~4 3' to ~orm guide~ durlng con~aot with the adjacent vertebra and take care o~ arting lnarea~ed ~tr~ngth to the connectlon when tension 3crew~ 11 and 12 of :~, Figur~ 2 are ~Ight-n~d.
F~gur~ 4 shows part o~ anoth~r varia~lon o~ the e~bodi-ment whlch ~0r~8, ror example, a modi~lcstion of the ~mbodi-ment ~hown in ~lgure 1. Her~, ~orruga$ed tu~e 1 i~ connected with cover plat~ 3'' ~y means o~ a cl8mping rlng 16 whlch i8 aonflgured a~ a ~lvl~od rlng in whose thread engage~ a scr~w ! 17 that has b~oen ln~srtsd ~rom the exterior facQ oP the cover ~, ~l~ 20 plate and who~ h~d 18 supported ln A aorreYponding rece~
18 aocommoda~ing ~he hea~ of ~he screw. ~he edge region 1~ : -o~ corrugat~d tube ~ ~8 thus clamp~ ln ~etween the unde~sld~
o~ ~over plato 3'', which is there provi~e~ wlth a r~gion 20 ~ ehapod a8 ~ p~tial recek~ in clAmplng ring 16 ~nd can thue ,, .-~ ~ - . . . . ................... . ~ . -- ...
.- . . . . - . ~ . .

-~ 1 325078 .~ be ~nstalled e~lly~ The ~trength o~ the oonne4tlon i~ ~
c en~ured under all ~tree6e~ to ~e expac~od. ::
A pa~ge opnn$ng 21 in covor plate 3'' ~rves to ~
the interior wlth v~3~0ela~tic mAtorla~ - or, toge~her wl~h a 5 ~imll~r openlnq, as ventilation~
'' ~he pre~ent invontion 15 no~ 11mi~ed in its embo~ n~ to th~ above-de~crLbed pr~erred embodiment.
Rather, a numb-r or varl~tlon~ ~e ~nc~ivable which take advantage o~ the d.~wri~e~ eolutlon even for b~1aally . ~ 10 di2~erent configur~tlcn~
i It will b~ understood that the above de3crlptlon o~ ~he ~ :
pre3ent lnv~ntlon lg euscepti~le to ~Ar~ou~ mo~ifi~ati~nfir , -~
; ~ ~hangos ~nd ad~pt~tion~, and the 3a~e ~re intended to be , comprehend~d wlthln the m~aning and r~nge o~ egyivalent~ ofj 15 the appende~ alai~ .
~3 ,. , -..

. . .
s,-, :;

S'" ,,- - 10 -, ~
!

Claims

1. An intervertebral disk endoprosthesis filled with viscoelastic material and provided with cover plates at its end faces, comprising a circular or elliptical corrugated tube surrounding and contiguous with the viscoelastic material and terminated by the cover plates, wherein said cover plates are rigid, and wherein said corrugated tube allows for less constrained tilting of said cover plates and further accommodates the compressive bulging of said viscoelastic material.

2. Endoprosthesis as defined in Claim 1, wherein the corrugated tube is composed of biocompatible metal.

3. Endoprosthesis as defined in Claim 1, wherein the viscoelastic material is filled completely or partially with oriented or unoriented fibres.

4. Endoprosthesis as defined in Claim 3, wherein the filling is inhomogeneous, such that compressibility increases in the direction toward at least one edge region.

5. Endoprosthesis as defined in Claim 1, wherein the viscoelastic material includes hardenable, originally liquid, components.

6. Endoprosthesis as defined in Claim 5, wherein at least one of the cover plates and the corrugated tube are provided with at least one of a closable fill opening and a ventilation opening.

7. Endoprosthesis as defined in Claim 1, wherein the corrugated tube is fastened to at least one cover plate by a screwable clamping device.

8. Endoprosthesis as defined in Claim 7, wherein the clamping device is a clamping ring.

9. Endoprosthesis as defined in Claim 1, wherein the corrugated tube is welded to at least one cover plate.

10. Endoprosthesis as defined in Claim 1, wherein the corrugated tube has a wall thickness which is variable in one of a transverse direction or the longitudinal direction.

11. Endoprosthesis as defined in Claim 1, wherein at least one of the outwardly oriented end faces of the cover plate is provided with at least one of spurs, radial grooves, and circumferential grooves.

12. Endoprosthesis as defined in Claim 1, wherein at least one of the outwardly oriented end faces of the cover plates and of the corrugated tube is provided with at least one of a porous, surface area enlarging coating, surface configuration, and surface regions.

13. Endoprosthesis as defined in Claim 1, wherein at least one of the outwardly oriented frontal and side faces is provided with embedments of a bioactive material.

14. Endoprosthesis as defined in Claim 13, wherein the bioactive face is composed of at least one of hydroxyl apatite, polylactide or HIP material.

15. An intervertebral disk endoprosthesis filled with viscoelastic material and provided with cover plates at its end faces, comprising a circular or elliptical corrugated tube surrounding and contiguous with the viscoelastic material and terminated by the cover plates, wherein at least one of said cover plates is provided with a flange, and wherein said corrugated tube allows for less constrained tilting of said cover plates, and further accommodates the compressive bulging of said viscoelastic material.

16. Endoprosthesis as defined in Claim 15, wherein the flange extends parallel to the centre axis of the corrugated tube.

17. Endoprosthesis as defined in Claim 16, wherein the flange is provided with a bore.

18. Endoprosthesis as defined in Claim 17, wherein the direction of the bore diverges from the cover plate toward the centre axis of the corrugated tube so that a screw passing through the bore constitutes a tension screw.

19. Endoprosthesis as defined in Claim 17, wherein, on the side facing away from the centre axis of the corrugated tube, the bore is provided with a recess for a screw head.

20. Endoprosthesis as defined in Claim 15, wherein the exterior face of the cover plate is provided with grooves which are oriented perpendicularly to the flange.

21. Endoprosthesis as defined in Claim 1, wherein the exterior of at least one of the cover plates is configured in such a way that it is adapted to the end faces of an adjacent vertebra.