CA2239801A1

CA2239801A1 - Hip joint prothesis

Info

Publication number: CA2239801A1
Application number: CA002239801A
Authority: CA
Inventors: Hartmut Kalberer; Hans-Georg Pfaff
Original assignee: Individual
Current assignee: Cerasiv GmbH Innovatives Keramik Engineering
Priority date: 1995-12-19
Filing date: 1996-12-06
Publication date: 1997-06-26
Also published as: TW386873B; EP0871418A1; WO1997022311A1; JP2000501965A; US6224633B1

Abstract

A hip joint prosthesis has a metallic shell (1) and an acetabular insert (2) with a spherical recess (3), as well as an intermediate element (4) made of plastics arranged between the shell (1) and the acetabular insert (2). To prevent osteolysis, the intermediate element (4) is made of an upper part (5) and a lower part (6) which can be linked to each other and the acetabular insert (2) is anchored between the upper part (5) and the lower part (6).

Description

Hip Joint Pro~hesis The invention relates to a hip ~oint prothe~s according to the preamble o~ claim 1.
A hip ~oin~ prothesis having ~hree spheric 1 calottes which lie one lnside the other is kno~n from the ut~lity model FR 2 715 828.
~he spherical outer calotte consistC of a bio-compstible, rigid material such as INOX-steel or titanium, and is provi~ed, on the outside, with radial depression~ ~or securing in the ar~ cavity o~ the pelvic bone.
The spheri~al inner calotte consi~ts of a hard, bio-compatible material, such as alum~nium o~;.~e lS ceramic, for example, or of a s~m~lar m~terial, ha~ing a low coe~ficient of ~riction in relation to the material o~ w~ich the head o~ the femur element, ~hich is ~ Le~ thereto, consists.
Th~ spherical intermediate calo~te consi~s of a ~0 semi-rigid material such as plastic6, ~n particular polyethylene.
A problem with inte~ te calottes or intermed~ ate elements made of plastias is that, as a ~esult of ~lgh a~rasion, they can trigger os~eol~sis i~
there ~ no form-lockin~ connect~on between the cl i~n~
shell and the p~astics coating. On the other hand, a form~ n~ co~ne~-tion can be ach~e~ed by melting the plastics coa~ing, as ~ bed in EP O 554 214 Al.
This can, h .~v~ , lead to destruction of the molecular structure and consequently can trigger ~ear.
The unde~lying ob~ect of the inven~ion is to lmpro~re a h~p ~oint p~ es~s accordlng ~o th~ prP~ Q
o~ o~ 1, in such a way that the danger o~ osteolysi~
is ~liminated to a considerable extent.
This ob~ect is achleved in accordance wlth the invention by the characterislng features o~ claim 1.

,, 2 As a result of the inLe~ ~ate element ~nSi sting of an upper portion and a lower portion, it being possible for upper portion and lower portion ~o be connected ~o each o~her, and the ca~ity i.,~e~L be~ng ret~ined between upper po~tion and lower portion, the wear o~ the intermediate element ~s avoided and consequently the danger o~ osteolysis $s r~uce~.
In a preferred o~hoA~ment~ the ca~ity insert is ~vele~ on all sides, with the exception of its spherical recess, by t~e intermediate ~ ~t, i.e. ~y the u~per portion and lower portlon, so that there are no free pl~ at which abrasion can occur~
~ he co~n~ tion o~ the ~ppe~ portion to ~he lower portion can be car~ied out in a whole ~ariety of ways.
15 Screw connections by way o~ a ~cre~ t~ead, snap nQn~ tions, p~r~n~r~, gluing or welding h~ve ~oven advantageous.
The cavit~ inser~ can be produced from metal or ce~amics. This invention is fa~ourabl~ suitable for ZO all ceramic cavity inser~s.
In an advantageous m~n~e~, there are provided in the cavi~y inse~t and in the ad~acent lowe~ portion, opposin~ opent~gs in ~-hich are placed inserts for protecting ayainst rotation. As a result of thls, t~e cavity inser~ sits in the intermediate elemen~ in a -~nQ~ such t~a~ it is fixed in $ts posit~on. ~he ins~3rtS Car~ be, for example, pins, slotting blocks and ~eather-key ~y~Lems respectively, or wedges an~ can be made, ~o~ example, from metal or plastlcs. For ;~ , the inserts ad~antageously fill the open~ng8 ~ ~tel~.
Further reatures of the i.,~ ion resul~ ~rom ~hQ
~gure~ . I.~h are des~ribed in the following.
Figure 1 shows, in section, a me~allic prothesis 5he~ ch can be implanted in the a~t~cu~ cavity (not shown) of a pelvic bone. For imp~oved ~etention, _3_ ribs or a scre~ t~read lO are ar~anged on the outside of the pr~hesis shell 1. Inserted into the prothesis shel~ 1 iQ an intermediate element 4 made of }~lastics, which in~e~- !d~ate element in tu~n covers a ceramic ca~ity inser~,2.
The outer cont~ur of the inter ,r ~ e ~l-- .F-t 4 iS
matohed to th~ shape of the pro~he~ s shell 1, and the inter~ediate element aonsists of an upper portion 5 and a lower portlon 6.
The lower portion 6 faces tbe ~emur bone and has a rec~s8 11 ~o~ mounting o~ the cav~y inse~t 2. ~n this conneation, the cavity inse~t 2 is covered ~ompl~ely by the intermediate element 4, wit~ the exception of its spher~cal recess 3. It should be emr~cified in 15 partlGular that th~ upper portion 6 (sic) also covers the su~ Ling surface 12 whi~h is adfacen~ to the recess 3. The upper por~ion 5 ~o~,s the cavity insert 2 on the rear side thereo~ and is connected to the lower portion ~ in a whole ~arie~ o~ ways. The r~pherical recess 3 is used to receive the hea~ of a femur element.
Flgure 1 shows a ~ n ~o~ the case that ~he patient has a dysrl~s~A, i~e- i~ the cavtty insert 2 has to be r~ asymmetrically in ~he proth-~c~ ~ s~o.t l. Fig~re 2 shows a ~y ~r ical lnse~tion o~ the ca~$t~ insert 2 into the pro~hesis ~he~
Ftgu~es 3 ~o.S show various connections of the upper portlon 5 to the lower portion 6. This con~lo~tion is denoted with X ln ~igures 1 and 2. Xr~
30 Figure 3, the upper portion 5 ~ s ~--- ec-tea or ~;r~w~l t o t~ wer po~tion 6 by w~y o~ ~ scre~ thread -:7.
Fig~e 8 ( slc ) shows a snap Cor~n~ct~ on 8 . For this purpose, ~ere are arranged on the upper portion 5 and lower portlon 6 small indi~dual p~o~eGtiOnS, ~~hl-:h 35 engage ln each other when the ~pper portion 5 ~ s fltted into t~e lower portion ~; and thus create a good .~ -4-r-o~n~-tion. Figure 5 shows pinning ~. For this purpose, a bore 13 is i~ od~ced into the lower port~on 6 and upper portion 5, in which bore a continuous pin 14 is inserted.
~he cavi~y insert 2 c~nsist~ of a ceramic material, such as an aluminium oxide ceramic, fo~
exa~ple. All other ceramic materials can also be used, however.
Figures 6 and 7 show l?~ho/~i~nents similar to those shown in Figures 1 and 2; 1~ J~L, t;here are addittnnall~ provided in the cavit~ insert.2.and in the ~d~acent lower portion 6 opposing openings 15 in ~hioh are r7 Ace~ inse~s 16 ~or protecting against ~o~ation.
ThesH inserts 1~ fill ~he o~n~ngs 15 completely and consist of metal or plastics.
Flgure 8 shOws a s~ot~on along th~ line A-A in Flgure 7 and Figure 9 shows a sectlon along the line B-B in ~igure 7. In Flgure 8, a pin 17, and in Figure 9 a slotting block 1~ whlch ls rectangula~ in cross-sec.tion, i~ pl~ce~ ln the opening 15.
With these lnserts 16, ~oL~lon against to~sion of the ca~ity insert 2 in the intermediate element 4 is ac~hi~Yed.
;

Claims

1. Hip joint prothesis having a metallic prothesis shell (1) with a cavity insert (2) having a spherical recess (3) and with an intermediate element (4) which is made of plastics and arranged between the prothesis shell (1) and the cavity insert (2), characterised in that the intermediate element (4) consists of an upper portion (5) and a lower portion (6), in that upper portion (5) and lower portion (6) can be connected to each other, and in that the cavity insert (2) is retained between upper portion (5) and lower portion (6).

2. Hip joint prothesis according to claim 1, characterised in that the cavity insert (2) in covered on all sides, with the exception of its spherical recess (3), by the intermediate element (4).

3. Hip joint prothesis according to one of the claims 1 or 2, characterised in that the connection of the upper portion (5) to the lower portion (6) takes place by way of a screw thread (7), snap connections (8), pinning (9), gluing or welding.

4. Hip joint prothesis according to one of the claims 1 to 3, characterised in that the cavity insert (2) consists of ceramic material.

5. Hip joint prothesis according to one of the claims 1 to 4, characterised in that there are provided in the cavity insert (2) and in the adjacent lower portion (6), opposing openings (15) in which are placed inserts (16) for protecting against rotation.

6. Hip joint prothesis according to claim 5, characterised in that the inserts (16) are pins (17), slotting blocks (18) or wedges.

7. Hip joint prothesis according to claim 5 or 6, characterised in that the inserts (16) fill the openings (15) completely.

8 . Hip joint prothesis according to one of the claims 5 to 7, characterised in that the inserts (16) are made of metal or plastics.