GB2223174A

GB2223174A - Prosthetic implant

Info

Publication number: GB2223174A
Application number: GB8919697A
Authority: GB
Inventors: Carl H Jacobs; H Ravindranath Shetty
Original assignee: Bristol Myers Co
Current assignee: Bristol Myers Co
Priority date: 1988-09-08
Filing date: 1989-08-31
Publication date: 1990-04-04
Also published as: DE3930033A1; BE1003104A5; IT8921653A0; FR2635967A1; AU4123889A; NL8902242A; GB8919697D0; JPH02109555A

Description

2r (). '. A L x/- 3 -17 4 ATTACHMENT MECHANISM FOR SECURING AN ADDITIONAL

PORTION TO AN IMPLANT The present Invention relates to a prosthetic implant device, and more particularly to such implants which include at least two portions which need to be secured or attached together.

Heretofore, various types of attachment mechanisms have been utilized-.to 'secure two portions or layers of implants together.

U. 5. Fatent 4,205,400 to Shen et al. discloses a polytzhylene layer which is presumably molded onto a metallic support member via reverse tapered holes in the metallic member so that the polymeric layer is securely connected to the metallic member.

U.S. Patent 3,906,SSO to Rostoker et al. discloses a porous fiber metal structure adapted for attachment to a prosthesis. The fiber metal material is molded direct17 into the desired shape using dies and punchez. The fiber metal is then sintered together to form metallurgical bonds between the fibers.

U.S. Patent 3,605,123 to Hahn discloses a metallic bone implant having a porous metallic surface layer. The porous layer may be secured to the implant by plasma spraying the porous coating-thereto or by other suitable means. - 11 U.S. Patent 4,731,086 to Whiteside et al. discloses 'a shim to increase the effective thickness of a femoral knee. The pegs 18 and 181 on the femoral component may be inserted through openings 26 and 261 in the shim. I U.S. Patent 4,718,915 to Epinette discloses a hip prosthesis which includes two packing pieces attached thereto by a stud with a frustroconical head that engages a dovetail-shaped channel.

U.S. Patent 4,693,724 to Rhenter et al. discloses a femoral hip prosthesis in which the mounting of the neck 17 on the pin 1 has been achieved by means of a setting screw 23.

U.S. Patent 4,636,219 to Pratt et al. discloses a prosthesis including a porous surface comprised of a layered metal mesh structure and a process for fabricating the mesh screen structure for bonding to the prosthesis. The mesh may be bonded to a thin substrate which can then be cut or formed and applied to the body of a prosthesis on a flat surface as in F. 1g. 3 of Pratt et al. or contoured into specific shapes by processes such as creep forming.

U.S. Patent 4,570,271 to Sump discloses a prosthesis with a porous surface in which the porous coating is preformed directly into the desired shape which corresponds to the preselected surface of the prosthesis. The preform porous coating is then overlaid onto the preselected surface, compressed, and heated to adhere the preform to the prosthesis.

U.S. Patent 4,479,271 to Bolesky et al. discloses a prosthesis including porous surfaces which are either molded 1 and compressed directly into shape or c6ifipresSd-d -ind cut directly into shape. A polyethylene layer is molded onto the intermediate metal reinforcing layer and the porous bottom base layer. The porous layer is metallurgically bonded to 'the reinforcing layer. The attachment of the polyethylene layer is enhanced by penetration of the polyethylene into the porous material via openings in the reinforcing layer.

U.K. Patent Application GB 2 142 544 A to Medcraft discloses- a metho of akihj a surgical implant including diffusion bonding a mesh sheet to a substrate.

U.S. Patent 3,293,106 to Cocco et al. discloses a connectIon for attaching metal foil to a plastic substrate. The connection includes a support base with at least one recess formed therein and a second flat material positioned on the base and at least one protuberance formed from the second material and extending into the recess at an angle to the horizontal plane of the second material. The innermost end of the protuberance in the recess is apertured. An adhesive is utilized in each cavity/recess which is bonded to the base and extends from the recess through the aperture to cover all exterior surfaces of the protuberance substantially flush to the outer surface of the second material.

OBJECTS AND SUMMARY OF THE INVENTION

A principle object of this invention is to provide an attachment mechanism for securing an additional portion to the base portion of an implant.

Another object of this invention is to provide an attachment mechanism which is particularly suitable for securing materials having dissimilar bonding capabilities, although is not limited thereto.

A further object of the invention 'Is to provide a simple and effective mechanical attachment mechanism.

The present invention provides an attachment mechanism for securing an additional portion to a prosthetic impl'ant. The implant includes a base portion wit.'y a receiving surface and an additional -portion which is to be securely attached to the receiving surface. The additional portion includes an interfacing surface. At least one hole or cavity is included in either the receiving surface or the interfacing surface and the other of these two surfaces includes at least one corresponding post extending therefrom. The hole includes an opening and an inner wall extending therefrom having a reverse taper such that the hole widens as it extends into the surface that the hole' is in. The post is adapted to be received in the hole and is also adapted to be spread out to cause at least a portion of the post to become wider than the opening of the hole, thus resisting subsequent separation of the post from the hole to secure the additional portion to the base portion of the implant.

BRIEF DESCRIPTION OF THE DRAWINGS

These features and objects of the inventi.on, as well. as others, will become apparent to those skilled in the art by referring to the accompanying drawings:

Fig. 1 is a perspective view of a femoral knee implant component in accordance with the present invention; Fig. 2 is an exploded perspective:view--.of Che-femoral component of Fig. 1; Fig. 3 is an enlarged exploded partial cross -sectional view taken along lines 3-3 of Fig. 1; Fig. 4 is an assembled partial cross-sectional view of Fig.

3; Fig. 5 is a perspective view of an alternate embodiment of a femoral knee implant component ift accordance with the present invention.

Fig. 6 is an enlarged, exploded partial cross-sectional view taken along lines 6-6 of Fig. S; Fig. 7 is an enlarged, exploded partial cross -sectIonal view of an alternate embodiment taken along lines 6-6 of Fig. S; Fig. 8 is an assembled partial cross-sectional view of Fig.

6; 7; Fig. 9 is an assembled partial cross-sectional view of Fig.

Fig. 10 is a further alternate embodiment of a partial cross-sectional view taken along lines 6-6 of Fig. S; Fig. 11 is a partial cross-sectional vtew of the embodiment of Fig. 10 after the peg has been spread out by the plunger; Fig. 12 is an alternate embodiment- bE t. he addittonal- portion of Fig. 3; and Figs. 13 and 14 are further alternate embodiments of. the additional portion.

DETAILED DESCRIPTION OF THE INVENTION

Figs. 1-14 illustrate several particularly advantageous embodiments -of a 'prost'hetic implant according to the present invention. The invention will be described with reference to a femoral knee implant component 1 and is particularly suitable as such. However, it is understood that the principles of the invention may be utilized with other types of implants.

The prosthetic implant 1 of Figs. 1-4 includes a base portion 10 having a receiving surface 11 and an additional portion 20 which is to be securely attached to the receiving surface 11. The receiving surface 11 includes holes 14 therein with each hole 14 - including an openi'ng 17 on the receiving surface 11 and an inner wall 15 with a reverse taper extending therefrom such that the hole 14 widens as it progresses into the implant 1. The additional portion 20 includes a substrate 22 with a first or interfacing surface 28 and a second surface 29, with posts 32 exten.ding from the first surface 28 positioned and adapted to he received in the correspondingly located holes 14. For the femoral implant 1 shown, it is particularly advantageous for the holes 14 to be blind holes, so that the holes do not penetrate the articulating surface 4. Thus, the reverse tapered wall 15 of the blind hole 14 terminates at a bottom surface 16. The hole 14 as shown in Figs. 3-4 includes a means for spreading the post 32 such that upon insertion of the post 32 into the hole 14, the post is spread out to cause at least a portion of the post 32 to become wider than the opening 17 of the hole 14, thus resisting subsequent separation of the post 32 from the hole 14 to secure the additional portion 20 to the base portion of the implant 1. 1 The means for spreading the post 32 may be a protruding member 18 which extends from the bottom surface 16. The protruding member 18 may be a pointed cone such that the point of the cone is adapted to penetrate the post 32 upon insertion of 'the post 32 into the hole 14 thus spreading out the post 32. The post 32 is preferably spread out so that the post 32 securely contacts the reverse tapered walls 15 to resist the subsequent separation of the post 32 from the hole 14.

4 The additional portlon 20 may include a porous surface 24 on the second surface 29 of the substrate 22. The substrate 22 gives support to the porous surface 24. The porous surface 24 may be any. suitable porous material, such as a plasma sprayed porous surface or sintered beads or a wire-type mesh or screen material which may be prebonded or secured to the substrate 22 before attachment of the additional portion 20 to the base portion 10. This prebonding of the porous surface 24 to the substrate 22 may be done by diffusion bonding, by sintering, or by other suitable attachment means. A particularly advantageous porous material is the porous fiber metal structure of U.S. Patent 3,906,550 to Rostoker et al. This fiber metal material is preferably diffusion bonded to the substrate 22 to secure it thereto, although other suitable bonding methods could be used.

The receiving surface 11 on the base portion 10 of the implant 1 may be a recessed area 12 which is shaped to accept the additional- portion 20. The additional portion 20 may be substantially flush with the rim 13 of the base 10 as shown in Fig. 4, or it may be:raised up -hlghe-r,.,..t.,han,,t.he,-i-im or---be beldw the rim 13 depending on which is desirable for a given implant design.

The posts 32 may be solid studs which extend from the first surface 28 of the substrate 22 as shown in Fig. 3. The studs may be integrally formed with the substrate or may be secured to the substrate 22 by resistance welding or diffusion bonding or other suitable means. This would preferably be done prior to the attachment of ihe porOus surface 24 to the second surface 29 of the substrate 22. The solid' stud is impacted onto the protruding member 18 by appropriate setting tools arid fixtures, such as a break press and/or pneumatic and/or hydraulic devices (not shown).

Alternatively, the posts could be separate members such as shown in Figs. 5-9. The posts could be solid rivet members 34 as in Figs. 6 and 8 or hollow rivet members 36 with channel 40 therein as in Figs. 7 and 9. The separate members 34 or 36 each include a post portion 32 extending therefrom. The additional portion 20 in these embodiments includes post holes 38 therethrough adapted to receive the rivet members 34 or 36. The rivets 34 and 36 may include enlarged heads 35 and 37, respectively. Accordingly, the post holes 38 may include an enlarged portion 39 to accept the heads 35 or 37. In these alternate embodiments shown in Figs. 5-9, the heads 35 or 37 are exposed and substantially flush with the porous surface 24, whereas with the embodiment shown in Figs. 1-4, the porous surface 24 is not interrupted by the stud heads 35 and 36.

Thus, in the embodiment of Figs. 1-4, the amount of porous surface exposed or available without any interruption is maximized. Maximizing the exposed porous surface 24 is important since porous surfaces are generally used to enhance 1 the ingrowth of bone Into the porous surface when Implants are installed without any bone cement type of mater.lal as Is known in the art or is used to enhance the adherence of bone cement to the implant if such cement is used. If the separate rivets 34 or 36 are utilized rather than the extending stud-type post 32, the heads of the rivets 35 and 37 would ideally be sized to maximize the available porous surface area in designs where such a porous surface is utilized.

The hollow rivet 36 may utilize a similarly sized or slightly larger sized protruding '. member 18 as desired. The protruding member 18 in this embodiment would enter the channel and cause\ expansion of the internal diameter of the channel via the interference between the size of the protruding member 18 and the diameter of the channel 40 to expand the outside configuration of the hollow rivet 36 against the reverse tapered walls 15 to secure the hollow rivet 36 in the hole 14.

Fig. 12 shows an alternate embodiment of the additional portion 20 of Fig. 3 where the post 32 which extends from surface 28 of the substrate 22 is hollow and includes a channel 40.

A further alternate method of attaching the solid or hollow rivets 34 and 36, respectively, to the substrate 22 is shown in Figs. 13 and 14. In this method the rivet Is precisely positioned in a post hole 38 with enlarged portion 39 to accept heads 35 or 37 in the substrate 22. The porous surface layer (fiber metal pad or beads or other suitable porous material) 24 is positioned over the surface 29 to conceal the heads. The whole additional portion assembly 20 may be diffusion bonded or sintered prior to attachment of this assembly to the receiving surface 11 through the holes 14 of the implant 1. This enables 1 0 1 the exposed porous surface... 24-Ao - be uninterrupted: by- the heads35 or 37 since the rivet heads are concealed by the porous surface.

A further alternate embodiment of the hollow rivet 36 is shown in Figs. 10-11. In this embodiment, the means for spreading the post is not included in the hole as with the protruding member 18 of the other embodiments. Instead, the spreading means may be provided by a separate tool such plunger 50 which includes ap enlarged Up 1 with a tapered 52. The diameter I'd 1 11 - of the 'enlarged tip 51 of tool 50 slightly larger than the diameter I'd 2" of channel 40. enlarged tip 51 could also be spherically-erided (riot shown which the diameter of the sphere would be I'd 11.

as end is The in 1 Any other suitable plunger shape could be utilized. The plunger 50 is forced or impacted into the channel 40 which causes the upper portion of the channel 40 to deform, enlarging it to the "dill diameter.. This causes the outer diameter of the upper portion of the post portion of hollow rivet 36 to spread out or deform and thus contact a portion (contact height "h") of the tapered walls 15. The plunger 50 is then removed. The plunger 50 may be a manual instrument such as shown in Fig. 11 in which a hammer f orce is applied to the head 54 of the plunger. Alternatively, the plunger 50 may have a controlled force applied to it by a-n automated machine (riot shown) whIch impacts or forces the plunger into the channel 40 by controlled loads and feed rates. Such a plunger 50 may be constructed of hardened steel or other suitable material, such as carbide.

In any of the above-described embodiments, the additional portion 20 may include an integrilly formed, single substantially flat substrate 22. The substrate 22 may be conformed to the desired configuration which as shown in Fig. 2 k is a plurality of substantially flat-sekments-U.. -..'The segments26 may be integrally formed in one sheet or piece or they may be separate sections. The substrate may be a substantially flat plane, a series of substantially flat planes or an otherWise suitably contoured or formed member as desired. If a single segment or separate multiple segments 26 are utilized, each separate segment should include at least one post 32 adapted to be received in a corresponding hole 14. If the substrate 22 is formed of several segments 26 which are integrally formed it may not bi!-. necessary to incl.ule at. least one post 32 exteriding from each segment. The number of posts' 32 utilized would depend on the specific design configuration chosen.

The attachment mechanism of the present inveA"t!On is particularly suitable for the attachment of two portions having dissimilar bonding capabilities, although it is not limited thereto. Thus, the base portion 10 may be formed of one metallic material while the substrate 22 and porous surface 24 are each formed of a metallic material different from the one used for the base portion 10. For example, the base portion 10 may be formed of a cobalt-chrome material while the substrate 22 and porous surface 24 may be formed of titanium material or alloy. However, it is understood that this attachment mechanism may be utilized with any suitable material or combination of materials.

It it also noted that for certain implants. it may be appropriate for the posts 32 to extend from the base portion 10 with the corresponding holes 14 In the. additional portion 20, rather than have the posts 32 extend from the additional portion as described above. This variation is not shown in the Figs.

f a The corresponding method of securing the additional portion 20 to the base portion 10 includes providing the base portion 10 with a receiving surface 11 and then forming the holes 14 in the receiving surface 11 having openings 17 on the receiving surface 11 and each hole 14 having an inner wall 15 with a reverse taper extending from the opening 17 such that the hole 14 widens as it progresses into the implant. The substrate 22 is provided with corresponding posts 32 extending from its first surface 28. A means is provided for spreading the posts 32. This means may be provided within the holes -14 as with protruding member 18 or by use of an external tool such - ai plunger 50 as previously described. Upon insertion of the posts 32 into the correspondinA holes 14, the spreading means impacts the post 32 to cause at least a portion of the post 32 to become wider than the opening 17 of the hole 14, thus resisting subsequent separation of the post. 32 from the hole 14 to secure the additional portion 20 to the base portion 10 of the implant 1. The additional portion 20 may be provided with.a porous surface 24 on the second surface 29 of the additional portion 20 prior to the attachment of the additional -portion 20 to the base portion 10. Upon attachment of the additional portion 20 to the base portion 10, and thus upon insertion of the posts 32 -into the holes 14, the posts 32 are then spread so that the posts 32 securely contact the reverse tapered walls of the corresponding holes 14 to resist the subsequent separation of the posts 32 from the holes 14.

The base portion 10 is suitably sized and shaped in accordance with the prosthetic implant design desired. For the prosthesis 1 of Figs. 1-14. the recess 12 may suitably be about 2mm/0.079 in. deep, although the thickness of the prosthesis varies as the contours of the prosthesis vary.

i The substrate 22 may be made of thin sheet metal about 0.6 to l.Omm/0.024 to 0.0394 in. thick while the porous surface may be about 1.0 to 2.Omm/0. 0394 to 0.0788 in. thick. The posts 32 may be cylindrical prior to insertion into the hole 14 and substantially truncated cone-shaped after they have been spread out after contact with the spreading means. Accordingly, the holes 14 may have circular openings 17 just slightly larger (about 0.05mm/0.002 in. larger) than the diameter of the posts 32. The holes 14 widen 'as they progress into the implant 1 forming a truncated cone7shape. The openings 17 may be about 3.23mm/0.127 in. in diameter. while the posts 32 prior to insertion are about 3.18mm/0.125 in. in diameter (d 3) The portion 111.11 of the posts 32 which extends from the first surface 28 of the substrate 22 may be about O.Smm/0.020 in. or more shorter than the depth of the holes 14 prior to insertion of the post 32 therein. This allows room for the post 32 to extend as well as expand, if needed, as it mechanically deforms upon contact with the spreading means. The holes 14 may have a depth of about 3 to 4mm/0.118 to 0.158 in. The s I ope "all of the reverse tapered walls 15 may be about 2 to 15 degrees. The protruding member 18 may be a cone-shaped protrusion with a base diameter of about 1.9mm/0.07S in. and a height of about 1.27 to 3.81mm/0.050 to 0.150 in. Powever, for the hollow rivet design 36, the protruding member may have similar dimensions or it may be slightly larger if desirable for spreading of the posts 32.

The channel 40 in the hollow rivet may be about 1.27mm/0.050 in.

in diameter (d 2)' In the hollow rivet embodiment where plunger 50 is utilized, rather than a protruding member 18, the plunger 50 may have a diameter (d of 1.52mm/0-060 in. The outer dimensions of the posts 32 after insertion into the holes 14 generally spread out to conform to at least a portion of the shape of the reverse tapered holes 14. In Fig. 11, the contact height 11h" between the post portion 32 of hollow rivet 36 and the reverse tapered walls 15 may be about 1.27 to 2.54mm/0.050 to 0.100 in. The height "h" of the post/implant contact area is preferably maximized to in turn maximize the pull-out force (the force which would be required to start the post sliding out of the hole 14.) It is noted that other suitable geometries and specific dimensions may be utilized in keeping with the invention. Optimum dimensions will vary with the specific design requirements. destr6d. While this invention. has been described in terms of particularly advaritakeOUs embodiments, those skilled in the art can appreciate that modifications can be made without departing from the spirit and scope of this invention.

1 i 1,

Claims

CLAIMS:

1 1. A prosthetic implant comprising a first base portion including a receiving surface and a second additional portion which Is to be securely attached to the receiving surface wherein the receiving surface Includes at least uric hole therein, the hole including an opening on the receiving surface and an Inner wall with a reverse taper such that the hole widens as it progresses Into the implant and wherein the additional portion Includes a substrata with a first surface and a second surface wit h at least one post extending from the first surface, the at least one post adapted to be received in the at least one hole, the at least one hole including a means for spreading the at least one post suth that upon insertion of the at least one post into the at least one hole the post is spread out to cause at least a portion of the post to become wider than the open.ing of the hole, thus resisting subsequent separation of the post from the hole to secure the second additional portion-to the first base portion of te implant.

2. The prosthetic implant of Claim 1 wherein the additional portion Includes a porous surface on the second surface of the substrate.

3.

The prosthetic implant of Claim 1 or Claim 2 wherein the at least one hole is a blind hole and wherein the reverse,L-.apered wall tenninates at a bottem surface.

4. The prosthetic implant of Claim 3 wherein the means for spreading the post Is located on the bottom surface of the hole.

5. The prosthetic Implant of.Cl.aim, 4 -.whereih" the 'I ea i ":f oi m ns spreading the post is a protruding member which extends from the bottom surface.- 6. The prosthetic implant of Claim 5 wherein the protruding member is a pointed cone shape such that the point of the cone is adapted to enter the post upon insertion of the post into the hole and impaction of the post onto the protruding member, thus spreading out and widening the post.

The prv,-thetic inplant of any-prtecgdirig ilaim wherein_the post is spread out so that the post securely contacts at least a portion 'of the reverse tapered walls to resist the subsequent separation of the post from the hole, thus securing the additional portion to the base portion.

The prosthetic implant of any preceding claim wherein the post is integrally fonTed with the substrate.

g 9. The prosthetic implant of any preceding claim wherein the post.iF2..a-- solid stud.

10. The prosthetic implant of any one of Claims 1 to 8 wherein the post-. i,:s, a hollow post.

11. The prosthetic implant of Claim 1 wherein the additional portion includes at least one post hole therethrough wherein the at least one post is adapted to be received in the at least one post hole.

12. The prosthetic implant of Claim 11 wherein the post Is a solid post.

13. The prosthetic implant of Claim 11 wherein the -post Includes a channel therein.

14. The prosthetic Implant of Claim 2 wherein the subs%rate includes at least one post hole therethrough wherein the at least one post is adapted to be received in the at least one post hole and wherein the post includes an enlarged head which is seated in the substrate and wherein the porous surface is adapted to conceal the head when the porous layer is secured to- the substrate.

15. The prosthetic implant of any preceding claim wherein the receiving surface\of the base portion is a rec ess for accepting the additional portion.

16. The prosthetic implant of any preceding claim wherein the additicrial portion is comprised of an integrally formed single, - substantially flat substrate.

claim wherein the additional 17. The prosthetic implant of portion Is comprised of an integrally Eormed, single substrate which is conformed to the desired configuration.

The prosthetic Implant of any One of Claims 1 to 15 wherein the additional portion includes multiple separate segments, each segment including at least one Post extending therefrom and wherein the receiving surface of the base portion includes a corresponding hole for each at least one post for insertion of the post therein.

19. The prosthetic implant Of Claim 1 wherein the substrate is a porous layer with the at least one post extending from the porous layer.

20. The prosthetic implant of any preceding claim QIMIL'in-tI7P_JD_Me P37UM is formed of one metallic material and the substrate is formed of a different metallic material.

1 21. The prosthetic implant of Claim 2 wherein the base portion is formed of one metallic material and the substrate and porous surface are each formed of a metallic material different from the one metallic material.

22. The prosthetir- 'implant- of Claim 21 wherein the base port-Ion is formed of a cobalt-chrome material and the substrate and porous surface are each formed of a titanium material or alloy.

23. A prosthetic implant comprising a base portion including a receiving surface and an additional portion which is to be securely attached to the receiving surface, the aditional portion including an interfacing surface, and wherein one. of the two of the receiving surface and the interfacing surface includes a hole mearis thereln and the other surface including a post means extending therefrom, the hole means including an opening and an inner wall extending therefrom having a reverse taper such that the hole means widens as it extends into the surface that the hole means is in, the post means adapted to be received in the hole means, the hole means including a means for spreading the post means such that upon insertion of the post means into the hole means the post means 'is spread out to cause at least a portion of the post means to become wider than the opening of the hole means, thus resisting subsequent separation of the post means from the hole means to secure the additional portion to the base portion of the implant.

n t t 24. A prosthetic implant comprising a first base portion including a receiving surface and a second additional portion which is to be securely attached to the receiving surface wherein the receiving surface includes at least' one hole therein, the hole Including an opening on the receiving surface and an inner wall with a reverse taper such that the hole widens as it progresses into the implant and wherein the additional portion includes a substrate with a first surface and a second surface with at least one post extendinj from "the first surface, the at least one hole, and - 1. A, post adapted to be received in the at least one the at least one post adapted to be spread out by a spreadint means such that upon or subsequent to insertion of the at least one post into the at least one hole the post is spread out by the spreading means to cause at least a portion of the post to become wider than the opening of the hole, thus resisting subsequent separation of the post from the hole to secure the tecond additional portion to the first base portion of the Implant.

25. The prosthetic implant of Claim 24 where.in the spreadi.ng means is a protruding member within the hole extending from the base portion.

26. The prosthetic Implant of Claim 24 wherein the post includes a channel therethrough and the spreading means is a separate plunger tool which Is adapted to be impacted into the channel after the post has been inserted into the hole, said plunger adapted to cause the post to spread out and wherein the plunger is 3ubsequently removed.

27. A prosthetic implant comprising a base portion including a receiving surface and an additional portion which is to be securely attached to the receiving surface, the additional portion Including an interfacing surface, and wherein. one of the two of the receiving surface and the interfacing surface includes a hole means therein and the other surface including a post means extending therefrom, the hole means including an opening and an inner wall extending therefrom having a reverse taper such that the hole means widens as it extends into the surface.that the hole means is in, the post means adapted to - be Feceived in the hole means, thepost means further adapted to be spread out by a spreadin,g means such that upon or subsequent to insertion of the post means into the hole means the post means is spread out by the spreading means to cause at least a portion of the post means to become wider than the opening of the hole means, thus resisting subsequent separation of the post means from the hole means to secure the- additional portion to the bqse portion of the implant.

28. A prosthetic implant comprising a first metal base portion including a receiving surface and a second metal additional portion securely attached to the receiving surface wherein the receiving surface includes at least one hole therein, the hole including an opening on the receiving surface and a reverse tapered inner wall extending therefrom which widens as it progresses into the implant and wherein the additional portion includes a metal substrate with a first surface and a second surface with at least one metal post extending from the first surface into the at least one hole, the at least one post is spread out and mechanically deformed such that at least a portion of the post is wider 1 than the opening of the hole,' -"thus iiisistifii'--iubsequent separation of the post from the hole to secure the second additional portion to the ftrst base portion of the Implant.

29. A method of securing an additional portion which includes a substrate having a first surface and a second surface to a base portion of a prosthetic implant comprising:

a) providing the base portion with a receiving surface; b). forming at least. one hole in the receiving surface with an opening 'on the-,receiving surface and an inner wall with. a reverse taper such that the hole widens as it progresses into the implantf- C) providing the substrate with at least one post extending from the first surface; d) providing the at' least one hole with a means for spreading the at least one post; and.

e) inserting the at least one post into th6 at least one hole causing the spreading means to impact and enter the at least one post, thus causing at least a portion of the post to become wider than the opening of the hole, thus resisting subsequent separation of the post from the bole to secure the additional portion to the base portion of the implant.

30. The method of Claim 29 further Including providing a porous surface on the second surface ofthe additional portion.

31. The method of Claim 29 or CL-Am-30 further incllxlimg S'ng- the pot so that the post securely contacts at least a portion of the reverse tapered walls to resist the subsequent separation of the post from the hole.

32. The method of aW one of Claim 29 to 31 nzther including forming the base portion of one metallic material and forming the substrate out of a different metallic material.

33. A method of securing an additional portion which includes a substrate having a first surface and a second surface to a base portion of a prosthetic implant comprising:

lk- a) providing the base portion with a receiving surface; b) forming at least one hole in the receiving surface with an opening on the receiving surface and an inner wall with a reverse taper such that the bole wideris as it progresses into the implant; C) providing the substrate with at least extending from the first surface; d) Inserting the at least one post into the at least oil(.hole; and a) providing a means for spreading the at least one post to cause at least a portion of the Post to become wider than the opening of the hole after insertion of the post therein, thus resisting subsequent separation of the post from the hole to secure the additional portion to the base portion of the implant.

One ' post q 34. The method of Claii[i--3ftirther including providing the at least one hole with a 'bdttom surface and providing the bottom surface with a protruding member extending therefrom as the spreading means, and then upon insertion of the at least ore poz't. nto the at least one hole, impac.41..Ing the post onto the protruding member to cause at least a portion of the post to become wider than the opening of the hole.

35. The method of Claim 33 further including providing the post with a channel therethrough and providing a separate plunger tool as the spreading means and then impacting the plunger into the channel to cause at least a portion of the post to become wider than the opening of the hole, and then subsequently removing the plunger.

36. A prosthetic inPlant substantially as described with reference to,and as shayn in, Figures 1 to 4, or Figures 5, 6 and 8, or Figures 5, 7 and 9, or Figures 10 and 11, or any one of Figures 12, 13 and 14 of the accompanying drawings.

37. A mthOd of securing an additional portion to a base portion of a prosthetic implant, substantially as described.

Published 1990 atThe Patent Oface, State House,66171 High,10lbOrn 1oondonWClR4TP.FUTther copiesmaybe ObtOne"POm The Patento:mce. Sales Branch, St Mary Cray, OrpingtOn, Kent BT5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1.187