CA2121001A1

CA2121001A1 - Intervertebral prosthesis and a process for implanting such a prosthesis

Info

Publication number: CA2121001A1
Application number: CA002121001A
Authority: CA
Inventors: Walter Baumgartner
Original assignee: Sulzer Medizinaltechnik AG
Current assignee: Zimmer GmbH
Priority date: 1993-04-21
Filing date: 1994-04-11
Publication date: 1994-10-22
Also published as: CZ94694A3; HU9400863D0; CN1096440A; KR940023446A; US5702454A; JPH06319760A; AU673052B2; US5755797A; FI941831A0; FI941831A; AU6052094A; NO941428D0; EP0621020A1; HUT67437A; TW302277B; NO941428L

Abstract

Abstract An implant consisting of several support members (7), which are produced from an elastic plastic, is provided as a replacement for a part, which is no longer capable of bearing loads, of the core region of an intervertebral disk (3). The support members (7) are inserted one after the other into a central cavity (5) constructed in the core region by means of a tube (6) passing rough an outer annular region (4) of the intervertebral disk (3) until said cavity is filled. When the cavity (5) becomes clogged with the filling members (7), they becomes deposited on the boundary walls of the annular region (4) and against one another and are elastically deformed under stress.
Accordingly a universal implant which can be adapted to cavities (5) of any shape, and which forms a relatively compact, elastic support structure, can be achieved.

(Fig. 1)

Description

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StJT ZE~ dizi~c~i~G L C~8404 li~interthur, Switze:~l~d intex~v*:r~çe~ ostl3~esis aF~d a }?roc:ess fox implantin~ such ?. ~ros~5is ~he in~entic;n relates to an intervertebral prosthesis as speciied in the pres~haracterislng clause o:E laim 1 and als~ to a process for implanting such a prosthesis.
Known intervertebral pros~heses of the mentioned type contain implanl:s for in~ervertebral disks, which via a tube can be introduced through the outer ring ~ anulus f ibrosus ) .of ~he in~ervertebral ~isk in~o i'l:s core region ( nucle~s 20 pulposus ), in order to ac~ie~e a bearing action in the direction o~ the main load~ Thus EP-A-0 453 3g3 shows a hollow member which can be introduced into t}l,e core ~egion o the intervertebral disk, and which can be coiled in the sllape o~ a cpiral and which can be ~illed in the coiled 25 state with an incompressible fluid. Before the insertion of sueh an implant, the core region of the interYertebral ~isk, whic:}~ is no longer capable o~ bearing lo~ds, has tv be cleared out witll auxiliary tools through the hollow tube~ in order to replace ~he no longer loa~l-bearing ma~erial by the 30 implant~ As the surgeon has ~o work with determin~d implant sizes, he is forced tv produc:e a matching ca~ity in the core ~ceç~ion o ~he interver'cebral disk. The known implan~
requires a relatively expensive design of the hollow member, in order to guarantee a permanen~ tightAess against the 35 e~ress o~ ~luid, whic~ is required if the implant is to work optimally .

~' ~121001 The inventi~n is intended to counteract these disadvantages.

The object o~ the invention is to c~eate a universal, simple to apply implant, whi~h can be used as a support member o~
very varied cavi~ies ~ormed at rand~m.

This object is achieved in accordance with the invention in that the implant contains at lea~t three elas~ically de~ormable suppor~ ~ember which can be inserted into the central cavity and can be positioned therein.

One advantage of t~e invention lies in that when creating the cavity, the surgeon only has to remove t~e material o~
the nucleus which is no longer capable o~ load bea~ing and t~at the quantity ~ support members to be inser~ed is necessarily established when the support members are inserted. The implant, which consists of support members which can be positioned spaced apart or touching one anothe~
~nd which can be made ~rom a~ optional elastic material well ~olerated by the body, is consequently suitable ~or every intervertebral disX. When the central cavity becomes clogged with the s~ppo~t members, they abu~ the boundary wall~, so that a universal trans~e~ o~ compressive for~es and an optimal distribution in the central cavi~y can be achieved. During loading the support members are elastically deformed, and the compressive forces acting in the direction o~ the member axis are converted into edge stresses in the anulus fibrosus.
,,1 A process according to the invention for implanting such an intervertebral prosthesis is the subject matter of Claim 15.
'l Refinements of the subject matter of the invention are given ~ in the dependen~ ~laims.
:3 35 A~cording to a pre~erred embodiment according ~o the inv~ntion, the support members can be made from an elastic i '~1 .1 .'1 . .

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2~210~1 plastic. Accordingly an implant made from a suitable plastic material which can be well tolPrated by the body, which can be manufactured with low expenditure and is permanently dimensionally stable, ca~ be simply o~tained.

The support members may preferably be deslgned in the form o~ rotational solids, which enable an optimal, uniorm ~ranser o~ the compressive forces. In this re~pect spherical designs are par~icularly ad~antageous.
The packing density can be inc~eased by the use o support members having dif~erent dimensions. By pro~iding ducts in the support members, cavities can be produced, whic~ in con~rast to solid members permit a defined, greater elastic deormation. In order to con~rol the rigidity o~ the implant, 2 mixture o~ solid members and hollow members can be inserted. For the suppor~ members themselves there is a plurality o~ shapes, which ranges from the non-oriented spherical ~hape ~ia lenticular and bean-shaped members to oblong, cylindrical, sausage-shaped members.

SeYeral support members can be connected in chains to form a string-like, flexible support, whereby the distance between two support members advantageously corresponds at least to the diameter o~ one o~ the support members, in . order to enable deviations o~ 180 when inserting the ~upport members. Single-piece chains made ~rom the same material are also possible, in which the flexibl~
intermediate pieces are designed with a corresp~ndingly thin :1~ 30 shape. It is also possible ~o space support m~mbers with l, ~lexible tubing. The chain shape of the support members has .~ ~irstly the advantage ~hat a suppo~t member in a chain can not easily lea~e ~he central ca~i~y through an aperture and .:¦ secondly ~hat during ~illing ~he operation can not be ' 3~ reversed without great time loss by withdrawing the chain.
:" A similar retention action can be achieved o~ indi~idual ~ support members having elas~icall~ deformable expansion .~
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elemen~s, which during insertion through the tube are deformed in the lon~itudinal direction and during entry into the central cavity spring back and assumP a larger cross section.

A further method ~f dep~s?ting support members in a determine~ orien~ation liec in adapting the cross ~ection o~
the tube to ~uide faces o~ the support ~embers and depositing t~e support members purposefully ~ roughly like 10 an inseot laying i~s eggs - on determined sites of the central cavit~, by the support member being guided in the tu~e and being eject~d with a plunger~ A lenticular member ~ay be deposited so th~tt ~or example, its fla~ sides are directed again~t the adjacent vertebrae.
If the support members comprise a positional indicator, roughly in t~e form of an inclusion made from a material which i~ ~isible under X-ray examination, such as tantalum, for example, ~heir depositing and subseguent changes in 20 position can be controlled.

Polyurethane, for example, iç suitable as the plastic or such support members. The support members may also be made from anot~er material, e~g. a hydrogel. Corresponding 25 support members may also be made rom a suitable ~oam.
~nother design, in which each support member i5 formed by a j cocoon-type coil ~onsis~ing of a plastic ~hread or a me~al , ~hread, is also conceivable.
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i, 30 In order to incxease ~he safety for ~he insertion and Z reten~ion the support membe~s, be~o~e the insertion of ~h~
j suppor~ me~bers a bag made from a synthetic woven fabric or plastic film can be introduced through ~he tube into the central cavity, whereby the aperture of th2 bag remains ~, 35 outside the tube. The support memb~rs are now inserted through the aperture of this hag, which aperture is supported on the tube. When khe central cavity and the bag ,. ~

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2121BOl s is ~illed with support me~bers, the bag can be tied of~ with a clamp or wire, in order to prevent supp~rt members çoming out.

~urt~er features and details can be gathered ~rom the following descripti4n of exemplified embodiments o~ the invention, in conjunction with t~e claims, rep~esented diagrammatically in the drawings.

10 Fig. 1 shows a bod~ of a vertebra in a plan Yiew with a cross section through an intervertebral disk, which contains an implant of support members, which can be supplied via a tube;
~ig. 2 shows the interver~e~ral disk in longi~udinal section along line II II in Fig~ 1;

3 2 n Fig . 3 shows ~ cross section through an intervertebral disk, ha~ing an implant in a modiied embodimen~;

Fig. 3a shows a cross ~ection through a bag with 1 25 suppo~t memb~rs:

,I Fig. 4a - 4e show various embodimen~s o~ suppor~
members constructed in ~ccordance with t~e invention;

Fig~ 5 shows ~he s~ppoxt member shown in Fig. 4e in a position during inser~ion through a tube represented in a par~ial longitudinal sec~ion;

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Fig. 6, 7 and 8 show implants oonsisting o~ several support mem~ers conneoted to one another, in dif erent embodiments.

According to the representa~ion in Figures 1 and 2, an interver~ebral disk 3 positioned between two ver~ebral ~odies l comprises an intact outer annular region 4 o~
natural tlssue, which surrounds a central core reyion. In the core region is formed a cavit~ ~, which was previously created by the removal of t~e core of t~e damaged intervertebral disk ~hich is no longer load bearing - o~ a part ~hereof - and i necessary damaged parts of ~he outer annular region 4. T~e formatio~ o~ t-he cavity 5 and the removal o~' t~e tissue parts whieh are no longer capable of l~ad-bearing is performed in a known manner by a tubular guide part, as represented in the ~orm of a tube 6, which, as for example in EP-A-O 453 393 mentioned a~ the beginning, is inserted, passing through an aperture 30 in the outer annular region 4, in~o the core ~egion o~ the in~erver~ebral disk 3 ~y a relati~ely slight engagement from ~he dorsal side betwee~ the vertebral bodies l and 2~ A youge is inser~ed into the core region throu~h the inserted ~ube 6, by which the ~avity ~ is created and the cut out tissue parts are removed.
An intervertebral prosthesis in the form of an implant consiSting o~ several support members 7, which can be inserted one after the other in~o the cavity 5, and which are made fro~ a~ elastic plastic well tolerated by the body, e.g. polyurethanet is provided as a replacement for a~ least one part o~ the core region remoYed. The support members 7 ' are constructed as rotational solids, and in the ex~mple '~ r2presented in the form o~ balls, the dimensions of which are cho en so tha~ they ~an be inserted through the tube 6 into the cavity 5. The ~upport members 7 are pac~ed into ~e cavity S, i~ necessary by means o~ a plunger 8, until the cavity is subs~antially Eilled by the support members 7 ,~

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' .'i' '.' ., ' . '. ' ~ : . ~ . : ' " ' . , : '' ~ ~2~001 resting against one another and the supp~rt members 5 form a new core region of the intervertebral dis~ 3 capable o~
the transfer o compressive forces. The number and dimensions of the support members 7 can be varied at random 5 acc~rding to the dimensions gi~en and the shape o~ the ca~ity S to be filled and the c~oss sec~io~ of the tube 6.
Thus f~r example a design is possible whi~h requires fewer support members 7 than the design shown, e.g~ three supp~rt members 7 designed in appropriate sizesO The support mem~ers 7 can be designed with varying dimensions or, as represented, with the same diameters. A design is also possible with suppoxt members 7 disposed in a single layer, for exa~ple, which can be disposed at a distance or at varying distances ~rom one another.
When the cavity is completely full, which can be monitored, for example, by a secon~ tubular guide part, as rzpresented in the form of a tube 6', which can be inserted ~om She right hand side in Figure 1 dorsally through an aperture 30' into the cavity 5, the tube 6 is or both tubes 6, 6' are withdrawn in a known manne~ from the annular region 4, whereby the ~hrough-duct - aperture 30 and 30' respectivel~
- ~or the tube 6 and 6' respectively is closed accordingly ~in front o~ the last support member 7 inserted. This may be j25 provided, in a manner still to be des~ribed, wi~h retention means which make it di~ficult for suppor~ members to leave ~hrough the through-channel~

An observation instrume~t 9 can be inser~ed t~rough the tube 6' to monit~r the clearing o~ the ~a~ity ~ and/or the plantation operation ~r an auxiliary instrument (not ~lrep~esented) can be inserted ~o assist the clearing and '1implantation process. I~ is ob~ious that instead of the !Itubes 6, 6' represented, other sui~able prote~ti~e and~o~
:135 guide elements o~ any shape and design can also be used.

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In Figure 3 the corresponding parts are provided with the sam~ reference numbers. According to ~his embodiment the support members 7 can be disposed in a coveri~g surrounding them, and in the representation in a bag 10, which is inserted in ~he empty state through the tube 6 into the cavity S and is then filled wi~h the support members 7 t~rough the ape~ture remaining ~utside the tube 6. The bag 10 may be made ~rom a woven abric, a ~nitted ~b~ic o~
film made ~rom an elastic plastic well tolerated by ~he body, e.g~ also from pol~ethylene. When the bag 10 is filled and is connected to the suppo~t members 7 to form a compac~, elastic implant suitable for ~ransm~t~ing compressive ~orces between the verteb~al bodies 1 and 2, the bag 10 can be tied off by a ~ealing par~ 11, e.q. in the ~orm of a clamp or, as shown in the drawings, a previously inse~ted wire loop, in order to keep the support members 7 together. After his the end o~ the ~ag 10 is cut of~ and withdrawn toge~her wit~ ~he tube 6, As ~an be seen in particular ~rvm Figure 3a, the bag 10 can be adapted to any desired shape of the cavity 5 to be fille~
accor~ing to the anatomi~al condi~ions prevailing.

Numerous embodiments o~ support member 7 are pos~ible.
~5 ThuS, for example, instead of rota~ional solids, designs with polyhedral support members ~ are possible. As shown in ~i~ure 4a the spherical support members 7 in the desîgn ropresented - or at least ~ne or s~me of the support members 7 - may be designed with a closed cavity 12, which contain an insert 13 in the ~orm o~ a spherical inclusion made from a material whi~h is ~isible under X~ray examination, e.g~
tantalum, as a positional indicator for the respe~tive position o~ the support members 7. ~esigns without an insert 13 are possible, in whic~ case a co~respondingly greater elastic de~ormation o~ the support member can be ac~ie~ed by the cavity 12.

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As shown in Figure 4b, the or at least some of t~e support members 7 have different diameters D ox ~1 and~or are designed with a duct 14 passing through them, which is open, or as represented can be provided with ~ ~od-shaped insert as a positional indi~ator, whereb~ ~he respective orientation o t~e insert 15 ~an be seen.

~s shown in Figure ~c~ support members 7 can be designed wit~ substan~ially cylindrical shapes rounded o~f at ~h2 ends, which can also be provi~ed with a duct 14 andJor with a ~od-shaped i~clusion 15 - or for example wi~ two corresponding inclusi~ns, ocet against one another in ths axial direotion of the support member 7. These support members 7 may also have dif~erent diameters D or Dl and/or different lengths L or Ll.

As shown in Figure 4d, the or at least some of the support ~embers 7 can be lenticular, and in the example represented in the shape o~ a~ ellipsoid, and can ~e accordingly designed with deined support surfaces 16, which p~rmit the suppor~ members 7 ~o be deposited purposefully wi~h the support faces 16 directed against the adjacent vert2~ral bodies 1, 2. As can also be seen from Fi~ure 4d, the tube 6 can be designed with a corresponding cross section, which as represented is oval, and which orms guideways 17 ~or the support faces 16~

As shown in Figure 4e, at least one o~ the support members, e.g~ the last suppor~ member 7 to be inser~ed into ~he cavity 5, can be provided with at least one, and as shown four elastically de~ormable expansion elements 18, which in ~he expanded s~ate pro~rude laterally from the support member 7 ~nd which, as represented 1n Fiyure 5, are de~ormed when inser~ t~rough the tube 6 in the longitudina}
direction into stressed positions 18' and spring back, on lea~ing the tube 6, inside t~e cavity 5 in the expanded i , , ;.. , . , ~ ; .:

, ,.;,; . ' . !: . : ' : ' " ` ' - 2~2~01 state, and thus prevent the support mem~ers fro~ leaving t~e cavit~ 5 t~xough the through-aperture fox the tube 6.

As can be seen rom Figure 6, several support members can be disposed in the manner o~ pearls on a pearl necklace on a ~lexible, ribbon-liXe or string-like support 20 and be connected the~eto t~ orm a cohesive implant. The suppor~
20 may preferably be provided with stop parts 21 disposed ~etw~en the support members 7, as represented in the form o~
knots constructed on the support 20, which are di~posed so tha~ between the support members 7 a predetermined minimum distance ~ is observed, which corresponds at least approximately to the diameter o~ o~e of the support members 7 or - in designs in which the ~imensions o~ the support lS members 7 vary - t~e sum of the radii o~ the adjacen~
support members 7.

As shown in ~igure 7, the support members 7 and the support 20 are manu~act~red ~ro~ the same material and are connected ~o ~orm a single-piece implan~, whereby ~he support 20 acts as a spacer. According to the representation shown in Figure ~, a number of support members 7 can be dispo~ed in a coYering in t~e ~orm o~ tu~ing 22 tigh~ly surr~unding t~e support membe~s 7 and can be connected thereto t~ ~orm a cohesive implant. The tubing 22, jU5~ like the bag lO~ may be ~rmed from a corresponding woven fabric, a knitted ~ ~abric or a film.

:, To sum up, the inYen~iOn can consequently be described as :l. 30 follows:

An implant consisting o~ several support members 7, w~i~h ! are produced from an elastic plastic, is pro~ided as a ~, replacement ~or a par~ o~ the core region o~ an intervertebral dis~ 3 which is no longer capable o~ load 1, bearing. ~he support members 7 are inser~ed one a~ter the ' other into a central cavity 5 constructed in the core region :~
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: "~ , ~--, 2~10~1 b~ means of a tube 6 passing though an outer annular ~egion 4 o~ the interverkebral disk 3, until said cavity is filled.
When ~he cavity 5 is clogged wi~h the filling members 7, they become deposi~ed at the boundary walls o~ the annular region 4 and against one another and are elastically de~ormed under stress. Accordingly a uni~ersal im~lan~
which can ~e adapted to cavities S o any shape, and whi~h ~orms a relatively compact~ elastic suppor~ structure, can be achieved.

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Claims

1. An intervertebral prosthesis having an implant, which can be inserted into a central cavity (5) of a core region of the intervertebral disk (3) and which is suitable for the transfer of compressive forces, as a replacement for a part of this core region, characterised in that the implant contains at least three elastically deformable support members (7), which can be inserted into the central cavity (5) and can be positioned therein.

2. A prosthesis according to Claim 1, characterised in that the support members (7) are made from an elastic plastic.

3. A prosthesis according to Claim 1 or 2, characterised in that the support members (7) are designed in the form of rotational solids.

4. A prosthesis according to one of the preceding Claims, characterised in that the inserted support members (7) are designed with varying dimensions (D, D1, L
L1).

5. A prosthesis according to one of the preceding Claims, characterised in that at least one of the support members (7) is designed with a duct (14) passing through it.

6. A prosthesis according to one of the preceding claims, characterised in that at least one of the support members (7) is designed with a closed cavity (12).

7. A prosthesis according to one of the preceding Claims, characterised in that at least one of the support members (7) is designed with at least one insert (13, 15) made from a material which is visible under X-ray examination, e.g. tantalum.

8. A prosthesis according to one of the preceding Claims, characterised in that the support members (7) are disposed in the manner of a pearl necklace on a flexible, e.g. string-like, support (20), which comprises retention means for observing a predetermined minimum distance (A) between the support members (7).

9. A prosthesis according to Claim 8, characterised in that the minimum distance (A) between the support members (7) corresponds at least roughly to the diameter (D) of one of the support members (7).

10. A prosthesis according to Claim 8 or 9, characterised in that the retention means contain at least one stop part (21) mounted between the support members (7), e.g. in the form of a knot constructed in the flexible support (20).

11. A prosthesis according to Claim 8 or 9, characterised in that the support members (7) and the flexible support (20) are produced from the same material and are connected to form a single-piece implant.

12. A prosthesis according to one of the preceding Claims, characterised in that the support members (7) are disposed in a covering (10, 22) surrounding them.

13. A prosthesis according to one of the preceding Claims, characterised in that at least one of the support members (7) is provided with at least one elastically deformable expansion element (18) laterally protruding from a main part of the support member.

14. A prosthesis according to one of the preceding Claims, characterised in that at least one of the support members (7) comprises a defined support face (16), which is intended to interact with a guideway (17) constructed in a guide part (tube 6) and by which the support member (7) can be positioned in a defined position in the central cavity (5),

15. A process for implanting an intervertebral prosthesis, which contains an implant having at least three elastically deformable support members (7), which implant can be inserted into a core region of an intervertebral disk (3), characterised in that - in a first step in an outer annular region (4) of the intervertebral disk (3) there is mounted an aperture passing through said annular region towards the core region, - in a following step a gouge is inserted through the aperture (30) towards the core region and therein by cutting out tissue parts of the core of the intervertebral disk which are no longer load-bearing is created a central cavity (5) and the tissue parts cut out are removed through the aperture (30), - in a further step the support members (7) are introduced through the aperture (30) into the cavity (5), whereby the cavity is substantially filled and the support members (7) form a pressure-resistant support structure, and - in a following step, after the introduction of the last support member the aperture (30) is closed.

16. A process according to Claim 15, characterised in that into the aperture (30) passing through the outer annular region (4) is inserted a tubular protective and/or guide part (tube 6), through which the gouge and the support members (7) are inserted into the core region.

17. A process according to Claim 15 or 16, characterised in that in the outer annular region (4) is mounted a second aperture (30'), and in that through it is inserted a second guide part (tube 6') towards the core region, by which the clearing out out the cavity (5) and/or the introduction of the support members (7) can be monitored or influenced respectively.

18. A process according to one of Claims 15 to 17, characterised in that after clearing out the central cavity (5) a covering (10) for the support members (7) subsequently to be inserted is introduced into the cavity (5), whereby a filling aperture remains outside the outer annular region (4).