Claims
- 1. A method to improve the wear resistance of an implant made of a polyethylene, said method comprising the steps of:
a) providing an oxidation-resistant implant; b) irradiating the oxidation-resistant implant at a radiation dose above standard sterilization dose but below about 100 Mrad in order to crosslink the implant to improve its wear resistance, wherein said oxidation-resistant implant is more resistant to oxidation than an implant machined from a reference preformed UHMWPE.
- 2. The method of claim 1, wherein the polyethylene is selected from the group consisting of: UHMWPE and HMWPE.
- 3. The method of claim 2, wherein the irradiation step also sterilizes the implant.
- 4. The method of claim 3, wherein the irradiation is by gamma irradiation.
- 5. The method of claim 3, wherein the radiation dose is from about 5 Mrad to about 100 Mrad.
- 6. The method of claim 5, wherein the radiation dose is from about 5 Mrad to about 25 Mrad.
- 7. The method of claim 6, wherein the radiation dose is from about 5 to about 10 Mrad.
- 8. The method of claim 3, wherein the implant is not melted or annealed after the irradiation step.
- 9. The method of claim 3, wherein the irradiation is conducted in a low oxygen condition.
- 10. The method of claim 2, wherein the oxidation-resistant implant is formed by directly molding the oxidation-resistant implant from polyethylene powder.
- 11. The method of claim 2, further comprising the step of: forming the oxidation-resistant implant from the oxidation-resistant polyethylene.
- 12. The method of claim 11, further comprising the step of modifying a polyethylene, made from fusion of polyethylene powder, to make oxidation-resistant polyethylene, and machining or directly molding the oxidation-resistant implant from the oxidation-resistant polyethylene, said modification comprises one or more of the steps selected from the group consisting of:
(a) mixing an anti-oxidant with the polyethylene powder and fusing the polyethylene powder to form an oxidation-resistant polyethylene or implant; (b) fusing the polyethylene powder at a pressure of about 10 Mpa or above, a temperature of about 175° C. or above, and/or for a period of time of about 30 minutes or longer, to produce an oxidation-resistant polyethylene or implant; (c) fusing the polyethylene powder and rapidly cooling the fused polyethylene to form an oxidation-resistant polyethylene or implant; (d) fusing the polyethylene powder in a low oxygen environment; and (e) placing a polyethylene powder in a container, and performing one of the following: (i) causing an inert gas to flow through the polyethylene powder to flush out the air that is mixed with the polyethylene powder; (ii) causing an inert gas to flow through the polyethylene powder to flush out the air that is mixed with the polyethylene powder, after the air has been flushed out then pressurizing the container with an inert gas for a sufficient time to force the inert gas into the polyethylene powder and displacing the air from the polyethylene powder; (iii) pressurizing the container with an inert gas for a sufficient time to force the inert gas into the polyethylene polyethylene powder and displacing the air from the polyethylene powder; (iv) following any one of steps (i), (ii), and (iii), with evacuating the container for a time sufficient to draw out oxygen that is mixed with or absorbed into the polyethylene powder; (v) evacuating the container for a time sufficient to draw out oxygen that is mixed with or absorbed into the polyethylene powder; (vi) following any one of steps (i), (ii), (iii), (iv) and (v) with fusing the polyethylene powder in a low oxygen environment.
- 13. The method of claim 2, further comprising the step of: fusing a polyethylene powder to produce an oxidation-resistant polyethylene of about 4-inch diameter or smaller, and machining the implant from the oxidation-resistant polyethylene.
- 14. The method of claim 12, wherein the oxidation-resistant polyethylene is of about 4-inch diameter or smaller, and the oxidation-resistant implant is machined from the oxidation-resistant polyethylene.
- 15. A wear-resistant implant made from any one of the methods of claims 1 to 14.
- 16. A method to improve the wear resistance of an orthopaedic material comprising a polyethylene, the method comprising the steps of:
(a) providing an oxidation-resistant polyethylene; (b) irradiating the oxidation-resistant polyethylene at a dose of from about 5 Mrad to 100 Mrad, without melting or annealing the irradiated polyethylene, wherein said oxidation-resistant polyethylene is more resistant to oxidation than a reference preformed UHMWPE, and wherein said radiation is by gamma radiation or electron beam radiation.
- 17. The method of claim 16, wherein the radiation dose is from about 5 to about 25 Mrad.
- 18. The method of claim 17, wherein the radiation dose is from about 5 to about 10 Mrad.
- 19. The method of claim 18, wherein the polyethylene is selected from the group consisting of: UHMWPE and HMWPE.
- 20. A wear-resistant orthopaedic material, comprising a polyethylene, made according to any one of the methods of claims 14 to 19.
Parent Case Info
[0001] This patent application is a continuation-in-part of U.S. provisional patent application serial No. 60/200,525, filed on Apr. 27, 2000, entitled “Oxidation-Resistant and Wear-Resistant Polyethylene for Human Joint Replacements”.
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/US01/13839 |
4/27/2001 |
WO |
|