CA1300811C

CA1300811C - Prosthetic implant with wrapped porous surface

Info

Publication number: CA1300811C
Application number: CA000567349A
Authority: CA
Inventors: Arden Rex Zolman; Phillip J. Andersen; Steven T. Bayne
Original assignee: Bristol Myers Co
Current assignee: Bristol Myers Squibb Co
Priority date: 1987-08-24
Filing date: 1988-05-20
Publication date: 1992-05-19
Anticipated expiration: 2009-05-19
Also published as: GB2208800B; FR2619707B1; AU613922B2; JPH0614943B2; IT8821727A0; IT1226850B; AU1814288A; JPS6456050A; GB2208800A; DE3822154A1; DE3822154C2; FR2619707A1; GB8814268D0

Abstract

ABSTRACT

A prosthetic implant including a porous pad separate from the stem of the implant and in which the pad is adapted to be wrapped around the stem for attachment thereto. The pad is first precontoured into a preliminary shape and is then wrapped about the stem in a second and final shape corresponding to the shape of the stem portion about which it is wrapped and subsequently secured.

Description

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ZMOll9 ~ Y~ THETIC l P~ RAPPED POROUS SURFAC8 ¦ BACKGROUND OF THE INVENTION

The present invention relates to a prosthetic implant device and more particularly to xuch implants including porous surfaces thereon. This invention is particularly suitable for use as a femoral component for ~ hip prosthesis, although is not limited thereto.

¦ Heretofore, various types of porous surfaces have been incorporated into prosthetic implants. Such porous implants are often implanted without the use of any type of bone cement material so that the porous surface will be in direct contact with the bone surface. After a period of time, bony ingrowth occurs in and around the porous sur~ace to ~ologically affix or ~urther secure the implant in th~ bono. Alternatively, an implant ha~ing a porous surface ~a~ b~ implanted with bone cement, such that the penetration of the bone ce~ent into the porous sur~ace of the prosthesis will enhance the ~i~ation oi.' the prosthesis. ~ ~ ~

The following U.S. paten~s disclos~ prosthe~ic i~pl~nts which include various types of porous suraces : ~ ' U.S. Patent 3,906,550 to Rostoker et al. discloses a porous ~iber metal structure adapted for attachment to a prosthesis.
The ~iber metal ~aterial is molded directly into the desired precise sh~pe using dies and punches.
~: :
U.S. Patent 4,479,271 to Bolesky e~ al. discloses a p~osthes includlne porous surfaces ~hlch are al50 either 1l ~3~0811 '-' I
molded and compressed dlrectly lnto shape or compressed and cut ¦
directly into shape.
Il I
IU.S. Patent 4,536,894 to Galante et al. discloses a ¦
: pros~hesis including porous surfaces in which the porous ¦
surfaces are porous pads which are compressed and cut directly to the desired shape and then adhered to substantially ~lat surfaces.
I
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 preselec~ed 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. The preform may be produced by conventional multi-layer knitting, braiding, winding, weaving, or other continuous wire processes.

U.S. Patent 4 9 58g,883 to Kenna discloses a prosthesis including a porous surface in which the porous coating is compr~sed of spherical particles which appear ~o have been directly bonded to the prosthesis stem.

: ~ l U.S. Patent 4,636,219 to Pra~t e~ al. discloses ia prosthesis including a porous sur~ace comprised of a layered metal mesh structure. The mesh may be bonded to a thin su~strate (on the ord~r o 0~010 to 0.012 inch) whlch thin substrate can ~hen be cut or ormed and applied to the body of a prosthesis on a flat surface as in Fig. 3 of Pratt et al. or contoured into spec~fic shapes by processes such as creep ~formine.

U.S. Patent 4,660,755 to Farling et al. discloses a method for constructing a surgical implant in which a porous layer is ~bonded to a substrate in the absence of a furnace, the bonding ~¦occurring via an electrode.

U.K. Patent Application GB2059267A to Ducheyne discloses a type of porous metal wire mesh suitable for use on a prosthesis, U.K. Paten~ Application GB2142~30A to Brown et al.
discloses a prosthetic implant having a porous surface provided by a perforated micro-contoured sheet.

U.~. Patent Application GB2153233A to Lee et al. disclsses a prosthetic implant which utilizes wed~es to wedge between the bone cavity wall and the prostbesis stem in which the wedges may Include a porous surface.

European Patent Application ~P0178650A2 to Ducheyne ¦discloses a porous flexible metal fiber material for implantation in con~unction with a prosthesis in which one or more l~yers of:the porous sheet material are pressed aga.inst the bone~ surface wlth a 18yer of bone eement then betwe~n the : implant and the po~ous sheet material.
-OBJECTS AND SU~MARY OF THE IN ~NTION
::
: : A pr~nciple ob~ect of this invention is to provide a :prosthetic implant which lncludes a porous pad separate from ~he prosthesis stem which ls adapt~d for wrapping around the stem ¦~for attachmen thereto.

~3~8~3~

Another object of the invention is to provide a prosthetic implant which includes a porous pad separate from the fixation ~surface base portion such that the porous pad has a first preliminary precontoured shape. The porous pad is adapted for wrapping about the fixation surÇace base portion in a second and final shape corr~sponding to the shape of the fixation surface ¦base portion about which it is wrapped.

A further objec~ of the invention is ~o provide such a ¦prosthetic implant in which the pad is wrapped about at least two adjaccnt sides.

A still further object of the invention is to provide a process for wrapping a porous pad about a prosthesis stem in wbich the pad has a first preliminary, substantially flat precontoured shape which is subsequen~ly wrapped about the stem into a second and final shape for attachment ~o the s~em.

The present invention accomplishes the above o~ec~s and as such provides a prosthetic implant which includes a porous pad which is pre~iminarily formed into a first shape and then wrapped and/or formed about the stem of ~he implant to confor~
to the shape of the implant in a second and final shape.~ The pad ls then adhered to the stem. The inven~ion also provides a process for prepaFlng the porous pad and for convenientl~

wrapping th~ pad about the stem.

BRIEF DESCRIPTION OF TH~ DRAWINGS

These fea~ures and obj~cts of the in~ention, 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 component for a lhip prosthesis according to the present invention;
¦I Fig. 2 is an anterior side elevational view thereof;
¦ Fig. 3 is a lateral side elevational view thereof;
Fig. 4 is a medial side elevational view ~hereof;
Fig. S is a cross-sectional view taken along lines 5-5 of Pi~. 2;
Fig. 6 is a cross-sectional view taken along lines 6-6 of Fig. 2;
I Fig. 7 is a side view of a femoral component according to ¦the present invention located in a forming fixture with the fixture shown in 8 cross-sectional view taken along lines 7-7 of ~ ~ig. ~c;
Fig. 8 is a cross-sectional view of the forming fixture taken along lines 8-8 of Fig. 7;
Figs. ~a, 8b, and 8c are cross-sectional views taken along lines 8-8 of Flg. 7 of the forming ~ixture illustrating various jaws in act~vated posi~ions about the femoral component stem;
Fig. 9 is a top view o a pressed and prebonded shee~ of porous material;
: Fig. 10 is a top view of~ the sheet of Fig. 9 illustrating a ; I cut;out portion;
~: Fig. 11 is a top view of the porous pad formed from the cut : out of Fig. 10;
: ~ ~ Fig. 12 i5 a side view of~a femoral compvnen~ ac~ording to the prssent lnvention located in a ~onding ixture with the ; : ~ixture shown in a cross-sectional view taken along lines 12-12 . of ~ie- 13;
Fig. 13 is a cross-sec~ional view o~ the bonding fixture ~a~en along lines 13-13 of Fig. 12;
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j Fig. 14 is an anterior side elevational view of an alternate embodiment of a femoral component, Fig. lS is posterior side view of the component of Fig. 14;
I and ¦ Fig. 16 is an alternate embodiment for a porous p~d to be ¦ used in conjunction with the component of Fig. 14.

; DETAIL~D DESCRIPTION OF TH~ NY~NTIGN

Figs. 1-13 illustrate a particularly advanta~eous embodiment of a prosthetic implant according to the present invention. The invention will be described with reference to a femoral component 10 of a hip prosthesis and is particularly sui~able as such. Howcver, it is understood that the principles of the invention may be suitable for other implants having elongated fixation stems. In addition, it is noted for ref~rence that the partlcular femoral component 10 described herein is desi~ned for i~plantation in a right femur, while a : corresponding f~moral component (not shown) for implantation ina l~ft femur woul~d be a ~irror i~age of tbe:~femoral;~component 10 : shown or the ri~ht femur.

1 ;~ The f~moral component lO~of Figs. 1 6 includes a distal end : ~ a~nd a proximal :en~ 14. As ~is well known, the ~emoral componen~ 10 is intended to ~it within th* intramedullary canal ~ ~ ~ : of a femur (not shown) such~ tha~ ths proxi~al end ex~ends i~ outwardly from the intramedullary canal o~ tha f0mur to cooperate with an acotabulum or acetabular prosthetlo mcmber via a ball or the like carricd at the proximal end 14. A dlstal ~portion 16 y includo a plurallty of grooves 18 extending ¦

~: ~
longitudinally. A proximal portion 24 includes a porous surface¦
or pad ~6 encircling the femoral component 10. The distal~
portion 16 and the proximal portion 24 comprise the stem portion 20 of the femoral component 10. A neck 28 extends from the !
proximal portion 24 a~d is adapted to carry a ball 30 sho~n in phantom lines in Fig. 1. An aperture 31 adjacent the neck 28¦
accommodates a tool for removing the femoral component 10 romj the intramedullary cana~ should removal be necessary. Thel porous psd 26 is desi~ned to extend outwardly from the proximal¦
portion 24 albeit a small extension of about O.Smm psst the¦
adjacent smoo~h surface of the proximal portion 24.
,, Figs. 2, 3, and 4 illustrate a chamfer 32 on the anterior side of the femoral component which may be included to avoid lmpingement o~ the distal end 12 into th0 bo~e surrounding the intramedullary canal at ~hat loca~ion.

As shown in Figs. 1-4, ~he proximal portion 24 includes a lateral side 34, a posterior slde 3~ a medial side 38, ~nd an ant~rior side 40. A porous pad 26, as shown ln the embodiment of Figs. 1-6, is oircumferentiallr wrapped around the`~-~proximal ~portion 24 of the ~tem portion 20. The pad 26 may be formed of an~ suitable porous material that is adapted to be preliminarily pressed into a first shRpe and th~n subsequently wrapped about the stem portion 20 into a s~cond shape con~orming to the shaple of the stem portion 20. One suoh suit~ble material is the fiber metal structure disclosed in U~S. Patent 3,906,S50 to Rostoker and ~alante, although it is noted tha~ the Rostoker et al.
patent t~aches that thc fi~er metal ~aterial ls molded directly into the desired shap~, ratber than providing a first preliminary shape which is then subsequently wr~pped or for~ed ;WQ~3~3 ~about a pros~hetic implant into the second and final shape in ¦¦accordance with the present invention. It is understood that ¦any suitable porous material, particularly fibrous (wire-type) ¦Iporous structures which are adaptable to be practiced in ¦laccordance with the present invention, may be utilized. The material for the porous pad may be titanium wire having a diameter of 0.010 inches t and the material for the femoral component may also be titanium. Again it is understood that any suit~ble materials may be utili~ed.

The shape of the porous pad 26 may have any desirable configuration, although preferably the pad is first formed in or pressed into a substantially flat sheet 126 (see Figs. 9-11).
~The outer boundary of the pad 26 mar have any suitable contour.
¦The porous pad 26 is separate from the stem portion 20. The psd 26 is adapted for wrapping around the stem portion 20 for ~ttachment thereto. The porous pad 26 has a first preliminarr precontoured shape as shown i~ Fig. 11 and is then subsequentlr wrapped and/or formed about the stem portion 20 for attachment thereto in a second and final shape corresponding to the shape~
of the s~em portion 20 as shown ln Figs. 1-4. The porous pad 26 is wrapped around at least~two eo three adjacent sides, althoug~i preferabl~ is wrapped around all four ~sidss 34, 36, 38, ~nd 40 to~ form a continuous porous surface circumferentially about the stem portion 20.
:
The porous material, such as a kinked titanium fiber metal, is prass formed into D sheet 126 of porous material. The sheet : 126 may have any desired thickness or dimensions. The di~ensions of the sh~et 126 may be adapted to cut out ~ single ~pad 26 havi 8 a desired outer boundarr or adapted to cut out ~ O~

¦multiple pads 26 from a sin~le sheet. The sheet 126 is prebonded in a vacuum furnace by holding the sheet for a suita~le length of time at a temperature sufficient to create metallurgical bonds at the points of contact of the fibers of the porous material within the sheet 126. A porous pad 26 having the desired outer contour ls then cut from the sheet leaving a correspondin~ cut out 226 in the sheet 126.
Prebonding ~he fiber metal sheet prior to cutting it creates mechanical integrity in the sheet 126 so that the fiber material is more easily formable and holds its shape better.

The porous pad ~6, shown in Fig. 11 which is subsequently applied to the femoral component 10 of Figs. 1-4, lncludes a medial pad side 1~8 to correspond to the medial stem side 38, posterior and anterior pad sides 136 and 140 each extending from or adjacent to the medial pad side 138 and adapted to correspond to the posterior and anterior s~em sides 36 and 40, respectively, and first and second tabs 120 and 122 extendin~
~rom the posterior and anterior sides, respecti~ely. The two tabs together comprise the lateral pad sid~ 13d which will oorrespond to the lateral stem side 34 of the emoral component 10. The pad 26 may be asymmet~i~ as shown with the pos~erior porous pad surface 136 having greater surface area than the ~n~erior porous pad surface 140 ~nd with ~he medial pad surface 138 being longer than the lateral pad surface 134. However, ~he pad 26 could readily be made symmetrically, if desired, as any appropriate shspe may be utilized for the pad 26.

The pad 26 is then ready to be wrapped about the stem psrtion 20. The proximal portion ~4 of the s~em portion 20 includes a recess 74 (see Fig. ~) having a shape corresponding 3a30~

to the pad 26 and adapted to receive the pad 26 for subsequent ¦
attachment thereto. The pads 26 can be shaped to conform to any desirable and suitable implant stem or fixation surface , configuration. The proximal portion 24 of the stem portion 20 ~
of the femoral component shown has an asymmetric noncircular !
cross-section as shown in Figs. S and 6.
.
The process for wrapping the porous pad 26 may be accomplished by placing the femoral component 10 (without pad 26) in a forming fixture $0 as shown in Figs. 7 and 8. The fixture 60 has a plurality of forming jaws 61, 6~, 63, and 64.
The forming jaws are each operated by corresponding rod 161, 162, 163, and 164, respectively, which operatively connects the jaws to cylinders 261, 262, 263, and 264, respectively. The cylinders 261, 262, 263, and 264 may be air operated cyllnders or hydraulic cylinders or any other suitable activation mechanism. The ~aws, rods, and cylinders may be made of tool ste~l, or any other suitable material strong enough to form tbe porous pad 26 about ths femoral component 10.

The neck 28 o~ the femoral component 10 is seated in a cylindrical bushing 66 within base pla~e 68 of fixture 60 to hold the femoral component 10 in place. A sliding locating pin 69 may be ~placed ~hrough the aperture 31 to keep the femoral component 10 from rotating while the form~ng is taking place.
The bushing 66 may suitably be made rom a nonmetallic material such as delrin so as not to scra~ch ~he neck ~. Th~ base plate I may be made of aluminum or s~eel. Other suitable means of holding the emoral component 10 s~curely in the forming fix~ure 60 could also be utili~ed.

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\ l ¦ The jaws 61, 62, b3, and 64 are each in a retrac~ed ¦~ position about the femoral component 10. The precut substantially flat porous pad 26 is placed in position between ¦ the jaws and the implant 10 with the ~edial pad portion 138 ¦ aligned with the corresponding medial side 38 of the s~em ~por~ion 20. The jaws, which have interfac~ng surfaces corresponding to the desired pad and stem configuration, are ,then activated in a predetermined sequence to form the pad 26 ~about the implant conforming the pad 26 to the shape of the implant lQ as shown in Figs. 8a, ~b, and 8c. In Fig. 8a the first forming jaw 61 is activated from its retracted position to a position in which the first jaw 61 is pressed up against the~
medial porous pad surface 138 which is thus pressed against the corresponding medial side 38 of the stem portion 20 shaping and ¦locating the respective portion of the pad ~6 thereto. The first jaw 61 is then held in its activated position agains~ the stem portion 20.

Alternatively, the medial porous pad surface 138 c~uld be preformed to the shape of th~ medlal side 38 by utilizing a correspondingly shaped separate forming dye (not shown) for just the medial side (rather than forming this ~edial side UsiDg the saquential fixture ~0). The separate dye would include a substantially U-shaped depression such as that shown in the cross-sact1on of ~aw 61 in Fig. 8a and a corresponding U-shap~d projecti~n corresponding to the outer contour of the medial side of the emor~1 component; which when brought together with the : pad 26 ln ~etween would preform the pad 26 into $he substantlally U-shaped conf~guration, such as tSat ach~avsd using th~ first ~aw bl of the s~qu~ntial orming fixture 60~ If such a separate dye is used, the pad 26 having the preformed ".. ~ . ~;~UD~311' '' (U-shaped) medial pad surface 138 would then ~e plac~d in position in the forming fixture 60 between the jaws and the implant 10 with the preformed medial pad 138 ali~ned with the medial side 38 of the stem portion 20. The jaw 61 would be activated to hold the pad 26 having the preformed medial pad surface against the stem portion 20. The remaining se~uential activation of the jaws would then continue.

The second and third jaws 62 and 63 may ~e then ac~iv~ted simultaneously as shown in Fig. 8b to press the posterior and anterior porous pad surfaces 136 and 140, respectively, against the posterior and anterior sides 36 and 40 of the stem portion thus shaping the respective portions of the pad thereto.
Jaws 61, 62, and 63 are then held in this activated position against the stem portion 20.

The fourth ~aw 64 is then activated as shown in Fig. 8c to press the first and second tabs 120 and 122 of the lateral porous pad surface 134 against the lateral side 34 of the stem portion 20 thus shaping the respective portions o~ the pad thereto. The tabs 120 and 1~2 mate together on the later~l side ~ ,~
34 to form a flush interface 27, thus providing a continuous circumferential porous surface connecting the ~nterior, medial, posterior, and lateral sides.

The forming ~aws are ~en released from their ac$ivated positions, and thus retracted sway from the stem portion 20.
The ~moral component lO wi~h the conformed pad 26 surrounding it is remov~d from th~ forming fixture 60. The femoral component lO is then placed in ~n appropriate bonding fixtur~ 80 such as ln Figs. 12-13 in which the porous pad is held s~curely l;~UOl~

ln place against the s~em por~ion ~0. The pad 26 is positioned~
securely in the recess 74 which corresponds to the wrapped shape of the pad 26. The porous pad 26 is then bonded to the stem ¦~portion 20 to securely att~ch i~ thereto. Th~ bonding may bel achieved by diffusion bonding the pad to the stem portion ~ !
holding the pad securely thereagainst at a sufficient temperature for a sufficient length of ~ime to achieve secure bonding. However, it is understood that other bonding processes¦
such as sintering or other suitable bonding methods may be utilized.

Although any appropriate bonding fixture or holding mechanism may be used for bonding the pad 26 to the stem portion, 20, Figs. 12 and 13 illustrate such a suitable fixture 80. The fixture 80 includes a support frame 86 with a pluralit~ of holding or bonding blocks or jaws 81, 82, 83, and 84 which surround thc porous pad 26 on the proximal portion 24 and which conform ~o the shape of tbe stem portion 20 about whicb they are positioned. The bonding blocks which hold the pad 26 in place against the stem portion 20 are suitabl~ made of a carbon material, as is the rame 86. The bonting blocks 81, ~2,~ 8~, and 84 are placed under sufficient pressure evenlr holding the pad 26 agains~ the stem por~ion 20 ~ia scr~ws 88.

Alternatively, rakher than orming the substantially 1at first preliminarily shaped pad 26 about the stem portion 20 ln~o its second and final contoured shape, the pad 26 can be formed about a man~rel (not shown) whlch has a shape which corresponds to the portion of the i~plAnt to which th~ pad i~ to be ~ttached. This formln~ about a ~andrel can b~ done with a fixture 60 such as that described aboYe used or ~orming the l~V~l~
, subs~antlally flat or medially preformed pad 26 about the ¦
implant itself. Then the formed pad 26 which has been shaped i about the m~ndrel is removed from the mandrel and placed about the femoral component 10. The pad 26 can then be securely bonded to the stem portion 20 as described above.

An alternate embodiment for a femoral component 400 is shown in Figs. 14-16 in which the porous pad 426 is adapted to fit in recess 474. Figs. 14 and 15 show the component 400 without the porous pad 426 thereabout. The pad 426 is adap~ed to be wrapped about t1lree ad~acent sides including the lateral, medial, and anterior sides 36, 38~ and 40 to form a continuous porous surface interconnecting these three sides. Since the pad 426 does not completely surround all sides of the implant, the pad 426 may be conveniently formed from its substantially flat first preliminary shape (as shown in Fig. 16) to its second and final contoured shape which corresponds to the shape of the recess 474 in the stom portion 20 either by using a correspondingly shaped (substantially U-shaped for tbe embodi~ent shown in Figs. 14-16) s~parate sin~le forming dye (not shown), or R orming fixture 60 wi~h multiple sequ~atially operated forming jaws such as previously described. The formed pad 426 can then be bonde~ to th~ s~em por~ion 20 in a similar manner as previously describ~d for tbe p~d 2S which circumferentially surrounds the stem portion.

The prosthetic implant of the present in~ntion provides an implant ha~ing a wrapped porous pad and a method o wrapping such pad about a prosthetic stem portion. T~ pr~sent invention proYides for a substantially flat pad having a predetermined outer ~oundary to be su~sequently wrapped about a prosthesis ~31~0~11 stem to conform to the shape of the stem and to be attached ¦
thereto. While this invention has been described and exemplified in terms of particularly advantageous embodiments, those skilled in the art can appreciate that modifications can be made without departing from the spirit and scope of this lnvention

Claims

1. A prosthetic implant including a stem portion having a plurality of sides and wherein the implant includes a porous pad separate from the stem portion, the pad adapted for wrapping around and conforming to the shape of a portion of the stem portion for attachment thereto.

2. The prosthetic implant of Claim 1 wherein the pad has a preliminary substantially flat precontoured shape which is subsequently wrapped around the stem in a nonflat second and final shape corresponding to the shape of the stem portion about which the pad is wrapped.

3. The prosthetic implant of Claim 1 wherein the pad is wrapped about a portion of at least two adjacent sides.

4. The prosthetic implant of Claim 1 wherein the pad is wrapped about all sides forming a continuous circumferential porous pad surface about the stem portion.

5. The prosthetic implant of Claim 1 wherein the porous pad is made from a fiber metal material.

6. The prosthetic implant of Claim 5 wherein the porous pad of fiber metal material is prebonded prior to wrapping of the pad about the stem portion.

7. The prosthetic implant of Claim 5 wherein the porous pad of fiber metal material is prepressed into a substantially flat blanket having a desired thickness and prebonded prior to wrapping of the pad about the stem portion.

8. The prosthetic implant of Claim 1 wherein the stem portion includes a recess corresponding to the shape of the porous pad for placement of the pad in the recess.

9. The prosthetic implant of Claim 1 wherein the portion of the stem portion about which the pad is wrapped has a noncircular, asymmetric, cross-sectional configuration.

10. The prosthetic implant of Claim 1 wherein the implant is a femoral component for a hip prosthesis.

11. The femoral component of Claim 10 wherein the stem portion has a proximal portion and a distal portion and wherein the stem portion includes a medial, a posterior, an anterior, and a lateral side.

12. The femoral component of Claim 11 wherein the porous pad is locator substantially in the proximal portion of the hip prosthesis.

13. The femoral component of Claim 12 wherein the proximal portion has a noncircular, cross-sectional configuration.

14. The femoral component of Claim 12 wherein the porous pad is wrapped about a portions of the anterior, medial, and posterior sides forming a continuous porous surface connecting these three sides.

15. The femoral component of Claim 12 wherein the porous pad is wrapped about a portion of the anterior, medial, posterior, and lateral sides forming a continuous porous surface connecting these four sides thus circumferentially surrounding the stem portion.

16. The prosthetic implant of Claim 7 wherein the separate porous pad has a predetermined outer boundary defining a desired contour for the porous pad.

17. The prosthetic implant of Claim 1 wherein the porous pad is a single pad.

18. A femoral component for a hip prosthesis having a fixation surface base portion having a plurality of distinct sides and wherein the implant includes a porous pad separate from the base portion, and wherein the porous pad has a first, preliminary precontoured shape, the porous pad adapted for wrapping about a portion of at least two of the plurality of sides for attachment thereto in a second and final shape.

19. A method of constructing a prosthetic implant comprising the following steps:

(a) providing a base implant including a stem portion having a plurality of sides;
(b) precontouring a separate porous pad having a first desired configuration; and (c) wrapping the pad around the stem portion for attachment thereto in a second configuration conforming to the shape of the stem about which the pad is wrapped.

20. The method of Claim 19 further including the step of bonding the pad to the stem portion while holding the pad against the stem portion in a suitable bonding fixture.

21. The method of Claim 19 further including the steps of press forming and prebonding a sheet of porous material prior to precontouring the pad.

22. A method of constructing a prosthetic implant comprising the following steps:

(a) providing a base metal implant including a stem portion having a medial, a posterior, an anterior, and a lateral side;
(b) forming a sheet of porous fiber metal material;
(c) prebonding the sheet to bond the fiber metal material together;
(d) cutting a porous pad from the sheet to provide the pad with an outer boundary defining a desired contour; and (e) wrapping the pad around the stem portion ant conforming the pad to the shape of the stem portion about which the pad is wrapped for attachment thereto.

23. The method of Claim 22 wherein the process for wrapping the pad around the stem portion further includes the step of forming the pad to conform to the shape of one side of the stem portion first and then sequentially forming the pad to correspond to the shape of the remaining sides.

24. The method of Claim 22 wherein the process for wrapping the pad around the stem portion further includes the step of forming the pad, to correspond to the shape of the stem portion to which it is to be attached by placing the prosthetic implant in a fixture having a plurality of forming jaws, each in a retracted position away from the prosthetic implant; placing the porous pad in a desired location between the jaws and the implant, then activating the jaws against the fiber metal and the implant in a predetermined sequence to form the porous pad about the implant, conforming the pad to the shape of implant.

25. The method of Claim 24 wherein the process for wrapping the pad around the stem portion further includes the step of providing four forming jaws to be operated in the following sequence:

(a) activating the first jaw to press the porous pad against one of the sides of the implant and maintaining the first jaw in this activated position;
(b) activating the second and third jaws to press the porous pad against the two sides adjacent the one side of the implant and maintaining the second and third jaws in these activated positions; and (c) activating the fourth jaw to press the porous pad against the remaining side enabling the porous pad to be conformed to the shape of the stem portion and fully surround the stem portion.

26. The method of Claim 25 wherein the process further includes the steps of:

(a) releasing the jaws from their activated positions;

(b) removing the stem with conformed pad surrounding it from the fixture;
(c) placing the stem in an appropriate bonding fixture in which the porous pad is held securely in position against the stem; and (d) bonding the porous pad to the stem to attach it securely thereto.

27. The method of Claim 22 wherein the process further includes the step of:

(a) forming the pad to correspond to the shape of the stem portion to which it is to be attached by shaping the porous pad about a mandrel which has a shape which corresponds to the portion of the implant to which the pad is to be attached;
(b) removing the formed pad from the mandrel;
(c) placing the formed pad about the prosthetic implant;
and (d) attaching the pad securely to the stem.

28. A prosthetic implant having a nonflat fixation surface wherein the implant includes a porous pad separate from the fixation surface, and wherein the porous pad has a first preliminary substantially flat preformed shape, the porous pad adapted for subsequently forming about the nonflat fixation surface for attachment thereto in a nonflat second and final shape corresponding to the shape of the fixation surface to which it is attached.