Claims
- 1. A preformed material for subsequent production of a medical implant with improved wear resistance comprising a polyethylene cross-linked at least twice by irradiation and thermally treated by annealing after each irradiation.
- 2. The preformed material as set forth in claim 1, wherein the material is cross-linked by a total radiation dose from about 2 to about 100 MRad.
- 3. The preformed material as set forth in claim 2, wherein the total radiation dose is between about 5 to about 10 MRad.
- 4. The preformed material as set forth in claim 3, wherein three radiation doses are applied with an incremental dose for each irradiation is between about 2 and about 5 MRad.
- 5. The preformed material as set forth in claim 1, wherein three radiation doses are applied with an incremental dose for each irradiation being between about 2 and about 5 MRad.
- 6. The preformed material as set forth in claim 5, wherein the total radiation dose is between about 5 to about 10 MRad.
- 7. The orthopedic preformed material as set forth in claim 1, wherein the polyethylene has a weight average molecular weight of greater than 400,000.
- 8. The preformed material as set forth in claim 1, wherein the annealing takes place in air at a temperature greater than 25° C.
- 9. The preformed material as set forth in claim 8, wherein the annealing takes place for a time and temperature selected to be at least equivalent to heating said irradiated material at 50° C. for 144 hours as defined by Arrhennius equation (14).
- 10. The preformed material as set forth in claim 9, wherein said material is heated for at least about four hours.
- 11. The orthopedic preformed material as set forth in claim 1, wherein the polyethylene is at room temperature for each irradiation.
- 12. The preformed material as set forth in claim 1, wherein the polyethylene is cross-linked three times by irradiation and thermally treated by annealing after each irradiation at a temperature between 25° C. and 135° C. for at least 4 hours.
- 13. A method for increasing the wear resistance of a preformed polyethylene comprising:
irradiating the preformed polyethylene in the solid state at least two times; and annealing the preformed polyethylene after each irradiation.
- 14. The method for increasing the wear resistance as set forth in claim 13, wherein the material is cross-linked by a total radiation dose from about 1 to about 100 MRad.
- 15. The method for increasing the wear resistance as set forth in claim 14, wherein the total radiation dose is between about 5 to about 10 MRad.
- 16. The method for increasing the wear resistance as set forth in claim 15, wherein an incremental dose for each irradiation is between about 2 and about 5 MRad.
- 17. The method for increasing the wear resistance as set forth in claim 16, wherein an incremental dose for each irradiation is between about 2 and about 5 MRad.
- 18. The method for increasing the wear resistance as set forth in claim 17, wherein the total radiation dose is between about 4 to about 10.5 MRad.
- 19. The method for increasing the wear resistance as set forth in claim 18, wherein the weight average molecular weight of the polyethylene is greater than 400,000.
- 20. The method for increasing the wear resistance as set forth in claim 19, wherein the annealing takes place at a temperature greater than 25° C.
- 21. The method as set forth in claim 29 wherein the annealing takes place between 110° C. and 135° C.
- 22. The method for increasing the wear resistance as set forth in claim 20, wherein the annealing takes place for a time and temperature selected to be at least equivalent to heating said irradiated material at 50° C. for 144 hours as defined by Arrhennius equation (14).
- 23. The method for increasing the wear resistance as set forth in claim 23, wherein said material is heated for at least about 4 hours.
- 24. The method as set forth in claim 13 further including the step of machining the preformed polyethylene into a medical implant.
- 25. The method as set forth in claim 13, wherein the material polyethylene is cross-linked three times by irradiation and thermally treated by annealing after each irradiation at a temperature between 25° C. and 135° C. for at least about 4 hours.
- 26. A medical device comprising a polyethylene material irradiated at least two times and annealed at a temperature lower than the melting point of the material after each irradiation.
CROSS-REFERENCED TO RELATED APPLICATIONS
[0001] This application is based on U.S. Provisional Application No. 60/386,660 filed on Jun. 6, 2002, the teachings of which are incorporated herein by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60386660 |
Jun 2002 |
US |