Prosthetic polyethylene bearing having enhanced wear properties

• US 6,146,426 A
• Filed: 11/01/1996
• Issued: 11/14/2000
• Est. Priority Date: 11/02/1995
• Status: Expired due to Term

• Current Assignee: Stryker European Operations Holdings, LLC (Stryker Corporation)
• Original Assignee: Howmedica International Incorporated
• Inventors: Doyle, Christina
• Primary Examiner(s): Willse, David H.
• Application Number:
  US08/742,540
• Time in Patent Office: 1,474 Days
• Field of Search: 623/23.51, 623/23.58, 623/23.59
• US Class Current: 623/23.58
• CPC Class Codes: A61F 2/30 Joints
• CPC Class Codes: A61F 2/3094 Designing or manufacturing processes
• CPC Class Codes: A61F 2/32 for the hip
• CPC Class Codes: A61F 2/34 Acetabular cups
• CPC Class Codes: A61F 2/3662 Femoral shafts
• CPC Class Codes: A61F 2/3868 with sliding tibial bearing
• CPC Class Codes: A61F 2/389 Tibial components A61F2/3868 takes precedence
• CPC Class Codes: A61F 2/468 Testing instruments for artificial joints for testing non-implantable prostheses A61F2/76
• CPC Class Codes: A61F 2002/30084 Materials having a crystalline structure
• CPC Class Codes: A61F 2002/30841 Sharp anchoring protrusions for impaction into the bone, e.g. sharp pins, spikes
• CPC Class Codes: A61F 2002/30878 with non-sharp protrusions, for instance contacting the bone for anchoring, e.g. keels, pegs, pins, posts, shanks, stems, struts
• CPC Class Codes: A61F 2002/3611 Heads or epiphyseal parts of femur
• CPC Class Codes: A61F 2310/00011 Metals or alloys
• CPC Class Codes: A61L 27/16 obtained by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: B29C 55/22 of tubes B29C61/08 takes precedence
• CPC Class Codes: B29K 2023/0683 UHMWPE, i.e. ultra high molecular weight polyethylene
• CPC Class Codes: B29K 2995/0054 multi-axially
• CPC Class Codes: B29L 2031/7532 Artificial members, protheses
• CPC Class Codes: C08L 23/06 Polyethene

Abstract

A prosthetic bearing element having a bearing surface is made from an ultra-high molecular weight polyethylene with a molecular weight greater than 1,000,000 with a multi-axially molecular orientation. From tests which have been applied to such material, it has been found that the wear rate is lowered and preferably the direction of one of said axial molecular orientations extends parallel with or along the length of the bearing surface.

Claims

1. A prosthetic bearing element having a bearing surface, said bearing surface made from a polyethylene material taken from close to the internal diameter of a drawn polyethylene tube, said tube made from polyethylene having a molecular weight greater than 1,000,000, said tube subjected to a single solid phase deformation in two directions to cause an orientation of the polymeric chains parallel to a bearing surface of said bearing element in only two perpendicular directions in the same area of the bearing surface, said deformation in two directions, having a deformation ratio of 1.3 to 1.9.

2. The prosthetic bearing element as claimed in claim 1 in which said deformation ratios in each direction are 1.5 to 1.6.

3. The prosthetic bearing element as claimed in claim 2 wherein the polyethylene has a molecular weight greater than 4,000,000.

4. The prosthetic bearing element as claimed in claim 1 wherein a first of said two solid phase deformations includes a deformation performed in a lengthwise direction of the tube and a second deformation is performed in a substantially transverse direction thereto.

5. The prosthetic bearing element as claimed in claim 4 in which the second deformation is greater than the first.

6. The prosthetic bearing element as claimed in claim 5 wherein the tube is a hollow tube and passed over a forming die of increasing cross-sectional area, the second deformation taking place in a circumferential direction.

7. The prosthetic bearing element as claimed in claim 6 in which the tube is passed over said forming die without applying an external force to the tube.

8. The prosthetic bearing element as claimed in claim 5 wherein the tube is solid.

9. The prosthetic bearing element as claimed in claim 8 wherein the tube has a square or rectangular cross-section.

10. The prosthetic bearing element as claimed in claim 5 wherein the tube is drawn through a die.

11. The prosthetic bearing element as claimed in claim 5 wherein the tube is passed through a die.