Acetabular prosthesis

• US 4,778,474 A
• Filed: 07/22/1985
• Issued: 10/18/1988
• Est. Priority Date: 11/16/1984
• Status: Expired due to Fees

• Current Assignee: Tranquil Prospects Limited
• Original Assignee: Novamed Incorporated Houston TX
• Inventors: Homsy, Charles A.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Cannon, Alan W.
• Application Number:
  US06/757,150
• Time in Patent Office: 1,184 Days
• Field of Search: 623/22, 623/23, 623/16, 128/92 R, 128/92 XX, 128/92 XP, 427/2
• US Class Current: 623/22.14
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• CPC Class Codes: A61F 2/32 for the hip
• CPC Class Codes: A61F 2/34 Acetabular cups
• CPC Class Codes: A61F 2/36 Femoral heads ; Femoral endoprostheses
• CPC Class Codes: A61F 2/3662 Femoral shafts
• CPC Class Codes: A61F 2002/30011 differing in porosity
• CPC Class Codes: A61F 2002/30014 differing in elasticity, stiffness or compressibility
• CPC Class Codes: A61F 2002/3007 Coating or prosthesis-covering structure made of elastic material, e.g. of elastomer
• CPC Class Codes: A61F 2002/30072 Coating made of plastically deformable or self-moulding material
• CPC Class Codes: A61F 2002/30563 having elastic means or damping means, different from springs, e.g. including an elastomeric core or shock absorbers
• CPC Class Codes: A61F 2002/30673 Lubricating means, e.g. synovial pocket
• CPC Class Codes: A61F 2002/30827 Plurality of grooves
• CPC Class Codes: A61F 2002/30929 having at least two superposed coatings
• CPC Class Codes: A61F 2002/30973 Two joined adjacent layers having complementary interlocking protrusions and recesses
• CPC Class Codes: A61F 2002/3611 Heads or epiphyseal parts of femur
• CPC Class Codes: A61F 2002/3625 Necks
• CPC Class Codes: A61F 2002/3631 with an integral complete or partial peripheral collar or bearing shoulder at its base
• CPC Class Codes: A61F 2250/0018 differing in elasticity, stiffness or compressibility
• CPC Class Codes: A61F 2250/0023 differing in porosity
• CPC Class Codes: A61F 2310/00011 Metals or alloys
• CPC Class Codes: A61L 27/34 : Macromolecular materials
• CPC Class Codes: A61L 27/56 : Porous materials, e.g. foams or sponges
• CPC Class Codes: C08L 27/18 : Homopolymers or copolymers or tetrafluoroethene

Abstract

An improved acetabular prosthesis (14) is disclosed for use with a femoral head prosthesis (12). The acetabular prosthesis (14) comprises a cup (28) having, in use, sufficient strength to maintain its shape. The exterior surface of the cup (28) is substantially hemispherical. A coating (32) of sufficient thickness is provided on the exterior surface of the cup (28). The coating (32) is sufficiently deformable and has limited elastic memory to mold itself to the particular anatomic geometry or inner contour of the acetabulum. The coating (32) has grooves (36) on its external surfaces.

Claims

1. An improved acetabular prosthesis for fitting over a hemispherical ball of a femoral-head prosthesis and adapted to fit within the acetabulum in opposed contacting relation to the natural cartilage of the acetabulum;

said prosthesis comprising;

a generally rigid cup having an internal concave surface and a external convex surface;

a lining over the internal concave surface of said cup formed of a wear-resistant material and fitting against said hemispherical ball; and

a biocompatible pliant coating over the external convex surface of said cup formed of a deformable porous material having a porosity in the range of 40% to 90% and having interconnecting pores of a size from about 10 to 50 microns for minimizing the ingrowth of tissue into the pores;

said coating having a relatively low elastic memory and a relatively low modulus of elasticity generally similar to the cartilage of the acetabulum, said relatively low elastic memory and relatively low modulus of elasticity upon compression and deformation of the coating against the natural cartilage of the acetabulum permitting said coating to mold itself to the inner contour of the cartilage and natural acetabulum for continuously commodating the contour of the acetabulum, said relatively low elastic memory and relatively low modulus of elasticity providing sufficient softness in the coating so that the adjacent cartilage is not abraded or deteriorated therefrom.

2. A prosthesis according to claim 1, characterized in that said cup is made of a material selected from the group consisting of metal, polysulfone polymer, polycarbonate polymer, and polyacetal polymer.

3. A prosthesis according to claim 1, characterized in that the coating on said cup is porous polytetrafluoroethylene having a porosity in the range from 40% to 90%.

4. A prosthesis according to claim 3, characterized in that said coating has a porosity of approximately 60%.

5. A prosthesis according to claim 1, characterized in that said coating has a thickness in the range from 1 to 10 mm.

6. A prosthesis according to claim 1, characterized in that said coating has a plurality of grooves on its exterior surface to allow, in use, bulk movement of synovial fluid therethrough.

7. A prosthesis according to claim 3, characterized in that said coating is bonded to said cup with fluorinated ethylene propylene.

8. A prosthesis according to claim 1, characterized in that a layer of medical grade elastomer lies between the exterior of said cup and said coating.

9. A prosthesis according to claim 8, characterized in that said layer is mechanically interlocked to said cup and to said coating.

10. A prosthesis according to claim 8, characterized in that said layer is impregnated into the interior of said coating.

11. A prosthesis according to claim 8, characterized in that said layer is a medical grade silicone.

12. An improved acetabular prosthesis for fitting over a hemispherical ball of a femoral-head prosthesis and adapted to fit within the acetabulum in opposed contacting relation to the natural cartilage of the acetabulum;

said prosthesis comprising;

a generally rigid cup having an internal concave surface and an external convex surface;

a lining over the internal concave surface of said cup formed of a wear-resistant material and fitting in contact with said hemispherical ball; and

a biocompatible coating over the external convex surface of said cup formed of a deformable porous material having a relatively low elastic memory and a relatively low modulus of elasticity generally similar to the cartilage of the acetabulum to allow it to mold itself to the inner contour of the natural acetabulum, said coating having pores of a size between about 10 and 50 microns to minimize any tissue ingrowth from said acetabulum.

13. An improved acetabular prosthesis as set forth in claim 12 wherein said coating has an aggregate modulus of elasticity in compression less than around 4 MPa.

14. An improved acetabular prosthesis as set forth in claim 12 wherein a layer of medical grade elastomer is positioned between said convex surface of the cup and said coating.

15. An improved acetabular prosthesis as set forth in claim 13 wherein said coating is a porous polytetrafluoroethylene having a porosity in the range from 40% to 90% and a thickness in the range from 1 to 10 mm.

16. An improved acetabular prosthesis for fitting over a hemispherical ball of a femoral-head prosthesis and adapted to fit within the acetabulum in apposed contacting relation to the natural cartilage of the acetabulum;

said prosthesis comprising;

a generally rigid cup having an internal concave surface and an external convex surface;

a lining over the internal concave surface of said cup formed of a wear-resistant material and fitting in contact with said hemispherical ball;

a porous biocompatible coating over the external convex surface of said cup formed of a deformable material having a relatively low elastic memory and a modulus of elasticity generally similar to the cartilage of the acetabulum and less than around four megapascals (4 MPa) to allow it to mold itself to the inner contour of the natural acetabulum; and

a layer of medical grade elastomer positioned between the exterior of said cup and said coating, said elastomer having a thickness adequate to provide a predetermined resilience for said coating under a predetermined compression thereof.

17. An improved acetabular prosthesis as set forth in claim 16 wherein said porous coating has a porosity of between around 40% to 90% and has an internal pore size of around ten to fifty microns.

18. An improved acetabular prosthesis for fitting over a hemispherical ball of a femoral-head prosthesis and adapted to fit within the acetabulum in opposed contacting relation to the natural cartilage of the acetabulum;

said prosthesis comprising;

a generally rigid cup having an internal concave surface and an external convex surface;

a lining over the internal concave surface of said cup formed of a wear-resistant material and fitting against said hemispherical ball; and

a biocompatible pliant coating over the external convex surface of said cup formed of a deformable porous material having a relatively low elastic memory and a relatively low modulus of elasticity less than around 4 megapascals and generally similar to the cartilage of the acetabulum;

said coating having a porosity in the range of 40% to 90% and having interconnecting pores of a size from about 10 to 50 microns for minizing the ingrowth of tissue into the pores, said relatively low elastic memory and relatively low modulus of elasticity upon compression and deformation of the coating against the natural cartilage of the acetabulum permitting said coating to mold itself to the inner contour of the cartilage and natural acetabulum for continuously accommodating the contour of the acetabulum; and

means in said coating to permit the flow of synovial fluid into the adjacent cartilage even upon deformation of the coating.

19. An improved acetabulum prosthesis as set forth in claim 18 wherein said means in said coating to permit the flow of synovial fluid into the adjacent cartilage even upon deformation of the coating comprises a plurality of grooves on the external surface of the coating.