Radiation and melt treated ultra high molecular weight polyethylene prosthetic device and method

• US 6,641,617 B1
• Filed: 12/03/1999
• Issued: 11/04/2003
• Est. Priority Date: 02/13/1996
• Status: Expired due to Term

• Current Assignee: Centerpulse Orthopedics Incorporated
• Original Assignee: Massachusetts Institute of Technology, The General Hospital Corporation (Mass General Brigham, Inc.)
• Inventors: Venugopalan, Premnath, Harris, William H., Merrill, Edward W., Jasty, Murali, Muratoglu, Orhun, Bragdon, Charles R., OʼConnor, Daniel O.
• Primary Examiner(s): Shaver, Kevin
• Assistant Examiner(s): Priddy, Michael B.
• Application Number:
  US09/454,123
• Time in Patent Office: 1,432 Days
• Field of Search: 623/23.58, 623/18.11, 623/22.11, 623/22.15, 623/22.21, 623/20.14, 623/20.22
• US Class Current: 623/23.58
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• 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 2/36 Femoral heads ; Femoral endoprostheses
• CPC Class Codes: A61F 2/3662 Femoral shafts
• CPC Class Codes: A61F 2/4657 Measuring instruments used for implanting artificial joints for surgical instruments A61B90/06
• CPC Class Codes: A61F 2/468 Testing instruments for artificial joints for testing non-implantable prostheses A61F2/76
• CPC Class Codes: A61F 2002/30065 thermoplastic, i.e. softening or fusing when heated, and hardening and becoming rigid again when cooled
• CPC Class Codes: A61F 2002/30084 Materials having a crystalline structure
• CPC Class Codes: A61F 2002/30125 elliptical or oval
• CPC Class Codes: A61F 2002/30158 trapezoidal
• CPC Class Codes: A61F 2002/30324 differing in thickness
• CPC Class Codes: A61F 2002/30616 Sets comprising a plurality of prosthetic parts of different sizes or orientations
• CPC Class Codes: A61F 2002/30685 Means for reducing or preventing the generation of wear particulates
• CPC Class Codes: A61F 2002/30934 Special articulating surfaces
• CPC Class Codes: A61F 2002/3233 having anti-luxation means for preventing complete dislocation of the femoral head from the acetabular cup
• CPC Class Codes: A61F 2002/3462 having a frustoconical external shape, e.g. entirely frustoconical
• CPC Class Codes: A61F 2002/349 Shell having a wavy or undulated peripheral rim
• CPC Class Codes: A61F 2002/3493 Spherical shell significantly greater than a hemisphere, e.g. extending over more than 200 degrees
• CPC Class Codes: A61F 2002/3495 : Spherical shell significantly smaller than a hemisphere, e.g. extending over less than 160 degrees
• CPC Class Codes: A61F 2002/3611 : Heads or epiphyseal parts of femur
• CPC Class Codes: A61F 2002/3623 : Non-spherical heads
• 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 2002/365 : Connections of heads to necks
• CPC Class Codes: A61F 2002/4631 : the prosthesis being specially adapted for being cemented
• CPC Class Codes: A61F 2002/4666 : for measuring force, pressure or mechanical tension
• CPC Class Codes: A61F 2210/0071 : thermoplastic
• CPC Class Codes: A61F 2230/0008 : elliptical or oval
• CPC Class Codes: A61F 2230/0026 : trapezoidal
• CPC Class Codes: A61F 2250/0036 : differing in thickness
• CPC Class Codes: A61F 2310/00011 : Metals or alloys
• CPC Class Codes: A61F 2310/00017 : Iron- or Fe-based alloys, e.g. stainless steel
• CPC Class Codes: A61F 2310/00023 : Titanium or titanium-based alloys, e.g. Ti-Ni alloys
• CPC Class Codes: A61F 2310/00029 : Cobalt-based alloys, e.g. Co-Cr alloys or Vitallium
• CPC Class Codes: A61F 2310/00071 : Nickel or Ni-based alloys
• CPC Class Codes: A61F 2310/00179 : Ceramics or ceramic-like structures
• CPC Class Codes: A61L 2430/24 : for joint reconstruction
• CPC Class Codes: A61L 27/16 : obtained by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: B29C 2035/085 : using gamma-ray
• CPC Class Codes: B29C 2035/0877 : using electron radiation, e.g. beta-rays
• CPC Class Codes: B29C 43/00 : Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor by liberation of internal stresses B29C61/006
• CPC Class Codes: B29C 43/16 : Forging
• CPC Class Codes: B29C 71/02 : Thermal after-treatment B29C71/0063 and B29C71/0072 take precedence
• CPC Class Codes: B29C 71/04 : by wave energy or particle radiation , e.g. for curing or vulcanising preformed articles during moulding, e.g. in a mould B29C35/08
• CPC Class Codes: B29K 2023/0683 : UHMWPE, i.e. ultra high molecular weight polyethylene
• CPC Class Codes: B29K 2995/0087 : Wear resistance
• CPC Class Codes: B29K 2995/0089 : Impact strength or toughness
• CPC Class Codes: B29L 2031/7532 : Artificial members, protheses
• CPC Class Codes: C08F 110/02 : Ethene
• CPC Class Codes: C08F 2500/01 : High molecular weight, e.g. >800,000 Da.
• CPC Class Codes: C08F 2500/14 : Die swell or die swell ratio or swell ratio
• CPC Class Codes: C08L 23/06 : Polyethene
• CPC Class Codes: Y10T 428/31692 : Next to addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31855 : Of addition polymer from unsaturated monomers

Abstract

A medical prosthesis for use within the body which is formed of radiation treated ultra high molecular weight polyethylene having substantially no detectable free radicals, is described. Preferred prostheses exhibit reduced production of particles from the prosthesis during wear of the prosthesis, and are substantially oxidation resistant. Methods of manufacture of such devices and material used therein are also provided.

Claims

1. A medical prosthesis for use within the body, said prosthesis being formed of ultra high molecular weight polyethylene, which has been radiation treated and melted such that the ultra high molecular weight polyethylene has substantially no detectable free radicals.

2. The prosthesis of claim 1 wherein said radiation is selected from the group consisting of gamma radiation and electron radiation.

3. The prosthesis of claim 1 wherein said ultra high molecular weight polyethylene has a cross-linked structure, so as to reduce production of particles from said prosthesis during wear of said prosthesis.

4. The prosthesis of claim 1 wherein said ultra high molecular weight polyethylene is substantially not oxidized.

5. The prosthesis of claim 1 wherein said ultra high molecular weight polyethylene is substantially oxidation resistant.

6. The prosthesis of claim 1 wherein said ultra high molecular weight polyethylene has substantially no chain scission.

7. The prosthesis of claim 1, wherein the ultra high molecular weight polyethylene (UHMWPE) has cross-linking so that a portion of said UHMWPE does not dissolve in xylene at 130°

C. or DECALIN at 150°

C. over a period of 24 hours.

8. The prosthesis of claim 1 wherein said ultra high molecular weight polyethylene has an initial average molecular weight of greater than about 2 million.

9. The prosthesis of claim 1 wherein part of said prosthesis is in the form of a cup or tray shaped article having a load bearing surface.

10. The prosthesis of claim 9 wherein said load bearing surface is in contact with a second part of said prosthesis having a mating load bearing surface of a metallic or ceramic material.

11. The prosthesis of claim 1 wherein said prosthesis is constructed and arranged for replacement of a joint selected from the group consisting of a hip joint, a knee joint, an elbow joint, a shoulder joint, an ankle joint and a finger joint.

12. A method for making a cross-linked ultra high molecular weight polyethylene (UHMWPE) having substantially no detectable free radicals, comprising the steps of:

providing conventional UHMWPE having polymeric chains wherein said UHMWPE is a cup or tray shaped article for use in a prosthesis;

irradiating said UHMWPE so as to cross-link said polymeric chains;

heating said irradiated UHMWPE above the melting temperature of said UHMWPE so that there are substantially no detectable free radicals in said UHMWPE; and

cooling said heated UHMWPE to room temperature.

13. A method of making a medical prosthesis from ultra high molecular weight polyethylene which has been radiation treated and melted such that the ultra high molecular weight polyethylene has substantially no detectable free radicals, wherein said prosthesis results in the reduced production of particles from said prosthesis during wear of said prosthesis, wherein the method comprises the steps of:

providing ultra high molecular weight polyethylene which has been radiation treated and melted such that the ultra high molecular weight polyethylene has substantially no detectable free radicals; and

forming a medical prosthesis from said ultra high molecular weight polyethylene so as to reduce production of particles from said prosthesis during wear of said prosthesis, wherein

said ultra high molecular weight polyethylene forms a load bearing surface of said prosthesis.

14. A method of treating a body in need of a medical prosthesis, comprising:

providing a shaped medical prosthesis formed of ultra high molecular weight polyethylene which has been radiation treated and melted such that the ultra high molecular weight polyethylene has substantially no detectable free radicals; and

applying said prosthesis to said body in need of said prosthesis.

15. A medical prosthesis for use within a body, wherein the medical prosthesis comprises cross-linked ultra high molecular weight polyethylene (UHMWPE) prepared by irradiation and melting, wherein the cross-linked UHMWPE is oxidation resistant.

16. The medical prosthesis of claim 15, wherein the melting is caused by the irradiation.