Highly crystalline cross-linked oxidation-resistant polyethylene
The present invention relates to methods for making highly crystalline cross-linked polymeric material, for example, highly crystalline cross-linked ultra-high molecular weight polyethylene (UHMWPE). The invention also provides methods of making antioxidant-doped highly crystalline cross-linked polymeric material using high pressure and high temperature crystallization processes, medical implants made thereof, and materials used therein.
1. A medical implant comprising an oxidation resistant, cross-linked polymeric blend made by a process comprising the steps of:
a) mixing a polymeric material with an antioxidant to form a polymeric blend, wherein the mixing is in the absence of a supercritical fluid, and wherein the polymeric material is polymeric resin powder, polymeric flakes, polymeric particles, or a mixture thereof;
b) consolidating the polymeric blend;
c) irradiating the polymeric blend by ionizing radiation at an elevated temperature that is above room temperature and below the peak melting point of the polymeric blend, thereby forming a cross-linked polymeric blend;
d) mechanically deforming the cross-linked polymeric blend at a temperature below its melting point, thereby forming a mechanically deformed cross-linked polymeric blend;
e) annealing the mechanically deformed cross-linked polymeric blend, thereby forming an oxidation resistant cross-linked polymeric blend; and
f) machining the oxidation resistant cross-linked polymeric blend, thereby forming the medical implant.
2. The medical implant of claim 1 , wherein polymeric material is selected from a group consisting of a low-density polyethylene, high-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene (UHMWPE), or a mixture thereof.
3. The medical implant of claim 1 , wherein the polymeric material is compression molded to another piece or a medical implant prior to heating the polymeric material, thereby forming an interface or an interlocked hybrid material.
4. The medical implant of claim 1 is packaged and sterilized by ionizing radiation or gas sterilization, thereby forming a sterile medical implant.
5. The medical implant of claim 1 , wherein the antioxidant is an α-tocopherol.
6. The medical implant of claim 1 comprises medical devices selected from the group consisting of acetabular liner, shoulder glenoid, patellar component, finger joint component, ankle joint component, elbow joint component, wrist joint component, toe joint component, bipolar hip replacements, tibial knee insert, tibial knee inserts with reinforcing metallic and polyethylene posts, intervertebral discs, sutures, tendons, heart valves, stents, and vascular grafts.
7. The medical implant of claim 1 , wherein the mechanically deformed cross-linked polymeric blend is annealed at a temperature that is above or below the melting point of the polymeric material.
8. The medical implant of claim 1 , wherein the annealing is carried out in air for at least for one minute to about 5 hours or more at about 130° C.
9. A method of making a medical implant comprising an oxidation resistant cross-linked blend of polymeric material, wherein the oxidation resistant cross-linked blend of polymeric material is made by a process comprising the steps of:
a) blending the polymeric material with an antioxidant, wherein the blending is in the absence of a supercritical fluid, and wherein the polymeric material is polymeric resin powder, polymeric flakes, polymeric particles, or a mixture thereof;
b) consolidating the blend;
c) irradiating the blend of polymeric material with ionizing radiation at an elevated temperature that is above room temperature and below the melting point of the blend of polymeric material, thereby forming a cross-linked blend of polymeric material; and
d) machining the cross-linked blend of polymeric material, thereby forming the medical implant.
10. The method of claim 9 , wherein the antioxidant is an α-tocopherol.
11. The method of claim 9 , wherein the antioxidant concentration is about 0.01 wt/wt %, 0.02 wt/wt %, 0.05 wt/wt %, 0.1 wt/wt %, 0.2 wt/wt %, 0.5 wt/wt %, or 1.0 wt/wt %.
12. The method of claim 9 , wherein polymeric material is selected from a group consisting of a low-density polyethylene, high-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene (UHMWPE), or a mixture thereof.
13. The method of claim 9 , wherein the polymeric material is irradiated at a temperature between about room temperature and less than about 155° C.
14. The method of claim 9 , wherein the blend of polymeric material is irradiated at a temperature of about 90° C., about 100° C., about 110° C., about 120° C., about 130° C., or about 135° C.
15. The method of claim 9 , wherein the radiation dose is between about 25 and about 1000 kGy.
16. The method according to claim 9 , wherein the implant comprises medical devices selected from the group consisting of acetabular liner, shoulder glenoid, patellar component, finger joint component, ankle joint component, elbow joint component, wrist joint component, toe joint component, bipolar hip replacements, tibial knee insert, tibial knee inserts with reinforcing metallic and polyethylene posts, intervertebral discs, sutures, tendons, heart valves, stents, and vascular grafts.
17. The method of claim 9 , wherein the medical implant is packaged and sterilized by ionizing radiation or gas sterilization, thereby forming a sterile medical implant.
18. A method of making a medical implant comprising an oxidation resistant cross-linked and interlocked hybrid material, wherein the oxidation resistant cross-linked and interlocked hybrid material is made by a process comprising the steps of:
a) blending the polymeric material with an antioxidant, thereby forming a polymeric blend, wherein the blending is in the absence of a supercritical fluid, and wherein the polymeric material is polymeric resin powder, polymeric flakes, polymeric particles, or a mixture thereof;
b) compression molding the polymeric blend to the counterface of a second material, thereby forming an interlocked hybrid material having an interface between the polymeric blend and the second material;
c) irradiating the interlocked hybrid material with ionizing radiation at an elevated temperature that is above room temperature and below the melting point of the polymeric blend, thereby forming a cross-linked and interlocked hybrid material; and
d) machining the cross-linked interlocked hybrid material, thereby forming the medical implant.
19. The method of claim 18 , wherein the second material is porous, metallic, a metallic mesh or back, a non-metallic mesh or back, a tibial tray, a patella tray, or an acetabular shell.
20. The method of claim 18 , wherein the polymeric material is a polyolefin, a polypropylene, a polyamide, a polyether ketone, or a mixture thereof.
21. The method of claim 18 , wherein polymeric material is selected from a group consisting of a low-density polyethylene, high-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene (UHMWPE), or a mixture thereof.
22. The method of claim 18 , wherein the interlocked hybrid material is irradiated at a temperature between about room temperature and less than about 155° C.
23. The method of claim 18 , wherein the interlocked hybrid material is irradiated at a temperature of about 90° C., about 100° C., about 110° C., about 120° C., about 130° C., or about 135° C.
24. The method of claim 18 , wherein the radiation dose is between about 25 and about 1000 kGy.
25. The method of claim 18 comprises medical devices selected from the group consisting of acetabular liner, shoulder glenoid, patellar component, finger joint component, ankle joint component, elbow joint component, wrist joint component, toe joint component, bipolar hip replacements, tibial knee insert, tibial knee inserts with reinforcing metallic and polyethylene posts, intervertebral discs, sutures, tendons, heart valves, stents, and vascular grafts.
26. The method of claim 18 , wherein the medical implant is packaged and sterilized by ionizing radiation or gas sterilization, thereby forming a sterile medical implant.
27. The method of claim 18 , wherein the antioxidant is an α-tocopherol.
28. The method of claim 27 , wherein the antioxidant is a vitamin E.
29. The medical implant of claim 5 , wherein the antioxidant is a vitamin E.
30. The method of claim 10 , wherein the antioxidant is a vitamin E.