CA1332098C

CA1332098C - Bone implant

Info

Publication number: CA1332098C
Application number: CA000594279A
Authority: CA
Inventors: Roy Douglas Crowninshield; Thirumalai N.C. Devanathan; Howard C. Price; Abner K. Wang; Jack E. Parr
Original assignee: Bristol Myers Squibb Co
Current assignee: Bristol Myers Squibb Co
Priority date: 1988-03-22
Filing date: 1989-03-21
Publication date: 1994-09-27
Anticipated expiration: 2011-09-27
Also published as: IT8919842A0; GB2216425B; NL8900692A; GB2216425A; AU3162789A; GB8906098D0; BE1002983A5; FR2628966A1; JP2823585B2; DE3909545A1; IT1228684B; DE3909545C2; AU617159B2; JPH01317435A; FR2628966B1

Abstract

ABSTRACT OF THE DISCLOSURE

A bone implant includes a nonmetallic core and a metallic porous surface secured to the nonmetallic core. The nonmetallic core is designed to closely approximate the modulus of elasticity for bone and the metallic porous surface is intimately engaged with bone to enhance bone growth into the metallic porous surface.

Description

~ ~3~q8 The present invention relates to a bone implant wh~ch is used in a surgical proceeding to repair or reconstruct skeletal deformities. These bone implants have been utilized by orthopaedic surgeons in hip and knee arthroplasty to reconstruct articulating joints, as well as in trauma situations to secure fractured bones together.

Various ~etals ~ave been proposed to manufacture bone implants. Titanium and cobalt chrome, ~or example, are in wide spread use because of their biocompatibilit~ with bone tissue and their strength character~stics for carrying loads imparted to the skeletal structure following implantation. With a metal bone implant, U.S. Patents 3,605,123 and 3,900,~50 further provide a porous metallic surface to enhance fixation of the implant with a resected bone at the intramedullary canal.
Theso metals are strongor than bone; however, bone is somewhat flexible, and thc stif~ metals do not exactlr match ~he flexibility of bone~ As a result, numerous recent articles and pàtents are proposing the use of composites or nonmetals for the construct~on of bone implants in ordor to provide the implant with a modulus substantially the same as bone.

In United States Patent 4,662,887 a polyetheretherketone commonly referred to as PEE~ is disclosed for use as an orthopaedic device. The PEE~ polymer is blocompatible and sufficiently fle%ible in icinal form to approximate the anatomlc elasticitr of bone. In Hochman United States Patent 3,893,196, a composite hlp implant i~s provlded with a graphit~ fibor cor~, an outer layer of graphito fl~er circumscrlbing tho cor~ and a plastic skin enclosin~ all of the fibor and provid~ng a porous ~ 33~098 plastic surface to enable the bone to knit thcreto. In further support of Hochman is Patent 4,164,794, wherein a porous composite material is provided on the surface of a hip prosthesis to enhance fixation to bone.

Comparing the metal implant with the composite implant, advantages and disadvantages are apparent. With the metal implant, the stren~th characteristics of metals results in a stiff implant which may stress shield portions of the bone. To date, no composite implant has establis`hed the intimate bone association believed to be necessary for adherence to bone for long term fixation in spite of the numerous attempts to provide a porous composite surface for the composite implant. Further it is believed that polymsr surfaces may be insufficiently durable to transfer load and posses inadequate sbrasion resistance for long term fixation.

The present invention teaches an orthopaedic implant which incorporates the advantages of metal and composite materials.
Rather than relying upon a total composite or a total metal implant, the invention provides a composite core which closely approximates the flexibilitr of bone and a porous metallic surface sscured to the composite core so that bone growth and/or cement will readily penetrate and adhere to the porous metallic ~urface ~or long term fixation of the orthopaedic implant.

It is an advantage of the present invention that the composite/metal implant approximates the ~lexibllity of bone and provides a porous metallic surface which is r~adily compatible wlth bone to provide unrestrlcted lngrowth of bono into the porous surface and such porous metallic surfaco ~s ~ ~3~8 sufficiently strong and durable to provide for long term fixation. Moreover, the porous metallic surfac~ is provided by a metallic fiber metal pad which resists abrasion and remains integrally secured to the composite core during implantation as well as after implantatlon.

In the drawings, Figure 1 is a side view of a femoral component following implantation. Figure 2 is a cross sectional view taken along line 2-2 of Figure 1. Figure 3 is a cross sectional view taken along line 3-3 of Figure-l. Figure 4 is a cross sectional view of the porous fiber metal pad i~
separate from the composite stem, and Figure S is a view similar to Figure 3 showing an alternative embodiment of the ~ invention.
,~ , ~` The emoral component 10 is surgicallr i~planted into the intrametull-rr canal 12 o$ the femur 14. Tho intramedullary canal 12 is exposed by resection of the anatomlc femoral head (not shown). A head 16 is coupled to a neck 18 of the femoral component. ~he heat 16 is spherical in shape to provide for ` articulatidn with~n a socket 20 of an acetabulum 22.

The femoral component lO includes a core 24 comprising a plurality of lon~itudlnallr ex$ending fibers, an intermediate layer 26 comprising a braided sheath of fibers, a skin 28 onclosing the core 24 and intermediate larer 26, and a pair of porous fiber metal pads 30 and 31 securod to-the skin 28. In -- the drawings the intermediste layer 26 is shown as a larg~r fibercross section than the core 24 for lllustratlon purpocos only. Tho core 24 and intormediato layer 26 aro constructed from tho same fibers.

^3-~33~9~

The core 24, intermediate layer 26 and skin 28 extend from a distal end 33 to a proximal end 32 forming the neck 18 The porous fiber metal pads 30 and 31 are preferably disposed adjacent the neck 18 and on both sides, anteriorlr and posteriorly, of the femoral component The plurality of fibers forming the core 24 and the braided sheath of fibers forming the intermediate layer 26 are made of APC-2 as sold by FIBER~TE, an Imperial Chemical Industry affil~ate, see FIBERITE- Data Sheet 3a propriety data of aromatic polymer composite, APC-2/Hercules Magnamite-AS4 Carbon Fibre This material includes continuous carbon fibre with PE~K impregnated into the continuous carbon fibre~

The skin 28 is made of polyetheretherketone or PEE~ as taught b~ United States Patent 4,662,887 This material is available from Imperial Chemical Industri~s per the specification for Victrex- 450G polyetheretherketone (PEK~
natural color granular molding resin The ~iber metal pads 30 and 31 are disclosed in Un~ted States Patent 3,906,550 as short titaniu~ wires which are 20 - kinked in a sinusoidal pattern with a specific amplitude to period ratio of 24 Numerous short wires are sintered together to form a unitary porous pad for fixation to the skin In order to manufacture the femoral component lO, the longitudinal fibers for the coro 24 are bundled together and pullod through braidors for braiding a shsath or layer 26 over the core 24 Wlth the ~shoath or layor covering tha coro 24, a suitable length is cut and disposet in a mold so that the skin 1 3320q8 28 can be in~ectlon molded o~er the sheath 26 snd core 24. The PEEK material for the skin 28 is heatod in the ln~ection molding step ant readily attaches to the impregnated PEEK in the carbon fibers of the sheath 26 and the core 24. After the skin is cooled, a fiber metal pad as shown in Figure 4 is heated to a temperature sufficient to permit the skin to penetrate the heated pad. It is believed that a temperature of about 6000P suffices for penetration. A heated fiber metal pad is then forced into each side o~ the stem to penetrate via meltin~ into the skin 28 a predetermined distance. Preferably, ons-half of the thickness of the fiber metal pad is penetrated into the skin as seen in comparin~ Fi~ures 3 ant 4. When the fiber metal pad cools, the penetrated portion of the fiber metal pad is trapped within or secured to the skin 28 while an outer portion of the fiber metal pad remains porous or open ~or intimate contact with bone and the resulting bonr ingrowth that follows in view of the affinity for bone to associate with titanium wire.

In the alternative embodiment of Figure 5. a metal barrier 40 separates the fiber metal pads 30 into an inner fiber metal partion 42 and an outer fiber metal portion 44. The barrier 40 separates that portion of the pad intended for impregnation into the skin from that portion o the fiber metal pad intended .
for bony ingrowth.

Although the afore~oing description proceeds with roference to PEEK and titanium fibor metal pad, it is contemplatod that othor composite cores with or without iber roinforcement can bo utilized wlth othor types of motallic porous surfaces, o.g. beads, to gonerate a hybrld composite/motal bonc implant that lncludes ~ modulus ~ ~3~09~

su~stantially the equivalent of bone and a porous metallic surface to encourage bone ingrowth. Prosthotlc knoe components can also be ~ade by the composite/metal bone implant of the present invention. In addition, the composite bone lmplant with the porous metallic surface of the present invention, is also readily adapted for use in a cemented hip arthroplasty where PMMA bone cement is used to secure the implant to bone.

The material for the skin 28 is referred to hereinabo~e as ~ polyetheretherketone or PEEK; however, such material is also referred to as polyaryletherketone. As an alternative material, it is believed that polyetherketone tP~K) or polyetherketoneketone (PEK~) is suitable for forming the skin and as a matrix for the carbon fibers of the core ant braid.
The polyetherketone (PEK) is aYailable fro~ Imperial Chemical Tndustries and the polyetherketoneketone is available from DuPont as PEK~ polymer. As such this material is also includet in the in~rention claimed.

,

Claims

1. A femoral hip component for implantation within a femoral canal of a bone, the femoral canal being open at one end in response to resection of a femoral head of the bone, the femoral hip component comprising a nonmetallic core adapted to extend into the femoral canal and opposing the wall thereof to substantially fill the femoral canal, the nonmetallic core being flexible to substantially approximate the flexibility of the bone surrounding the femoralcanal, and a porous metallic component fixedly secured to the nonmetallic core for disposition at an outer surface of the nonmetallic core for use in intimate contact with the wall of the femoral canal to accommodate bone growth into the porous metallic component when the femoral hip component is implanted into the femoral canal so that the bone ingrowth into the porous metallic component secures the femoral hip component within the femoral canal.

2. The femoral component of claim 1 in which the nonmetallic core comprises a first set of fibers oriented in a longitudinal direction from one end to an opposite end for the femoral component, a second set of fibers forming a braided sheath covering the first set of fibers, and a polymer layer surrounding the first and second sets of fibers, and a polymer layer surrounding the first and second sets of fibers and engaging the porous metallic component.

3. A femoral hip component adapted to implantation within a femoral canal of a bone, the femoral canal being open at one end in response to resection of a femoral head of the bone, the femoral hip component comprising a nonmetallic core extending into the femoral canal and opposing the wall thereof to substantially fill the femoral canal, the nonmetallic core being flexible to substantially approximate the flexibility of the bone surrounding the femoral canal, and a porous metallic component fixedly secured to the nonmetallic core for disposition at an outer surface of the nonmetallic core in intimate contact with the wall of the femoral canal to accommodate bone growth when the femoral hip component is implanted into the femoral canal, the porous metallic component including a substantially nonporous barrierembedded therein and the nonmetallic core extends into the metallic porous surface component up to but not past the nonporous barrier.

4. A hip prosthesis comprising a core substantially forming a predetermined shape for the hip prosthesis adapted to fit into a femoral canal of the hip after a femoral head of the hip has been resected to expose the femoral canal, the core including a center component longitudinally extending from one end outside the femoral canal to another end inside the femoral canal and a nonmetallic skin secured to the center component, the core being flexible to closely approximate the flexibility of that portion of the femur defining thefemoral canal so that when the core is fitted into the femoral canal the core and that portion of the femur exhibit substantially the same degree of flexibility, and a metallic porous surface fixedly secured to the nonmetallic skin to accommodate bone growth into the metallic porous surface when the hip prosthesis is fitted into the femoral canal.

5. The prosthesis of claim 4 in which the porous metallic surface is formed from a fiber metal pad and the nonmetallic skin maintains the fiber metal pad in spaced relation to the center component.

6. A prosthetic component for implantation within a canal of a bone, the canal being open at one end, the prosthetic component comprising:
a flexible nonmetallic core adapted to extend into the canal and opposing the wall thereof to substantially fill the canal; and a metallic component fixedly secured to the nonmetallic core for disposition at an outer surface of the nonmetallic core for use in intimate contact with the wall of the canal.

7. The prosthetic component according to claim 6, wherein said metallic component is porous so as to accommodate bone growth into the porous metallic component when the prosthetic component is implanted into the canal so that the bone ingrowth into the porous metallic component secures the prosthetic component within the canal.

8. The prosthetic component according to claim 6, wherein said nonmetallic core has a flexibility which substantially approximates the flexibility of the bone surrounding the canal.

9. The prosthetic component of claim 6 in which the nonmetallic core comprises a first set of fibers oriented in a longitudinal direction from one end to an opposite end for the prosthetic component, a second set of fibers forming a braided sheath covering the first set of fibers, and a polymer layer surrounding the first and second sets of fibers, and a polymer layer surroundingthe first and second sets of fibers and engaging the metallic component.

10. A prosthetic component adapted to implantation within a canal of a bone, the canal being open at one end, the prosthetic component comprising:
a nonmetallic core extending into the canal and opposing the wall thereof to substantially fill the canal;
a metallic component fixedly secured to the nonmetallic core for disposition at an outer surface of the nonmetallic core in intimate contact withthe wall of the canal; and a substantially nonporous barrier embedded in the metallic component.

11. The prosthetic component according to claim 10, wherein said metallic component is porous so as to accommodate bone growth into the porous metallic component when the prosthetic component is implanted into the canal so that the bone ingrowth into the porous metallic component secures the prosthetic component within the canal.

12. The prosthetic component according to claim 10, wherein the nonmetallic core extends into the metallic component up to but not past the nonporous barrier.

13. The prosthetic component according to claim 11, wherein the nonmetallic core extends into the porous metallic component up to but not past the nonporous barrier.

14. The prosthetic component according to claim 10, wherein said nonmetallic core has a flexibility which substantially approximates the flexibility of the bone surrounding the canal.

15. A prosthesis comprising:
a flexible core substantially forming a predetermined shape for the prosthesis adapted to fit into a canal of a bone, the flexible core including a center component longitudinally extending from one end outside the canal to another end inside the canal and a nonmetallic skin secured to the center component; and a metallic surface fixedly secured to the nonmetallic skin.

16. The prosthesis according to claim 15, wherein said metallic surface is porous so as to accommodate bone growth into the metallic porous surface when the prosthesis is fitted into the canal.

17. The prosthesis according to claim 15, wherein the flexibility of the core closely approximates the flexibility of that portion of the bone defining the canal so that when the core is fitted into the canal the core and that portion of the bone exhibit substantially the same degree of flexibility.

18. The prosthesis of claim 15 in which the metallic surface is formed from a fiber metal pad and the nonmetallic skin maintains the fiber metal pad in spaced relation to the center component.

19. A prosthesis to engage a bone, comprising:
a core;
an exterior skin encompassing said core and forming an exterior layer, wherein said skin comprises a nonmetallic material; and a metallic layer attached to said exterior layer of said exterior skin to make intimate contact with said bone when said prosthesis engages said bone.

20. The prosthesis of claim 19, wherein said metallic layer is porous.

21. The prosthesis of claim 19, wherein said core comprises a central core and an intermediate layer encompassing said central core.

22. The prosthesis of claim 21, wherein said central core and said intermediate layer comprise the same material.

23. The prosthesis of claim 22, wherein said material forming said central core and said intermediate layer is nonmetallic.

24. The prosthesis of claim 23, wherein said material forming said central core and said intermediate layer is different than the nonmetallic material forming the exterior skin.

25. A femoral prosthesis to be in contact with a femoral bone, comprising:
a head shaped to engage a socket; and a femoral component shaped to be inserted in an intramedullary canal, wherein said femoral component comprises:

a core;
an exterior skin encompassing said core and forming an exterior layer, wherein said skin comprises a nonmetallic material; and a metallic layer attached to said exterior layer of said exterior skin to make intimate contact with said femoral bone when said femoral component is inserted in said intramedullary canal.

26. The femoral prosthesis of claim 25, wherein said metallic layer is porous.

27. The femoral prosthesis of claim 25, wherein said core comprises a central core and an intermediate layer encompassing said central core.

28. The femoral prosthesis of claim 27, wherein said central core and said intermediate layer comprise the same material.

29. The femoral prosthesis of claim 28, wherein said material forming said central core and said intermediate layer is nonmetallic.

30. The femoral prosthesis of claim 29, wherein said material forming said central core and said intermediate layer is different than the nonmetallic material forming the exterior skin.

31. A femoral hip component adapted to implantation within a femoral canal of a bone, the femoral canal being open at one end in response to resection of a femoral head of the bone, the femoral hip component comprising a nonmetallic core extending into the femoral canal and opposing the wall thereof to substantially fill the femoral canal, the nonmetallic core being flexible to substantially approximate the flexibility of the bone surrounding the femoral canal, and a porous metallic component fixedly secured to the nonmetallic core for disposition at an outer surface of the nonmetallic core in intimate contact with the wall of the femoral canal to accommodate bone growth when the femoral hip component is implanted into the femoral canal, the porous metallic component including a substantially nonporous barrierembedded therein and the nonmetallic core extends into the metallic porous surface component up to but not past the nonporous barrier.