Polyethylene cross-linked with an anthocyanin

• US 20100036491A1
• Filed: 08/05/2008
• Published: 02/11/2010
• Est. Priority Date: 08/05/2008
• Status: Active Grant

• Current Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Original Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Inventors: Wang, Aiguo, He, Shulin, Yau, Shi-Shen
• Granted Patent: US 8,133,436 B2
• Time in Patent Office: Days
• US Class Current: 623/11.110
• CPC Class Codes: A61L 2/08 Radiation
• CPC Class Codes: A61L 2/14 Plasma, i.e. ionised gases
• CPC Class Codes: A61L 2/20 Gaseous substances, e.g. vapours
• CPC Class Codes: A61L 27/16 obtained by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: A61L 27/505 Stabilizers
• CPC Class Codes: C08F 10/02 Ethene
• CPC Class Codes: C08J 3/28 Treatment by wave energy or particle radiation
• CPC Class Codes: C08L 23/06 Polyethene
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C08L 53/00 Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers

Abstract

A method for manufacturing of ultrahigh molecular weight polyethylene (UHMWPE) for implants, where the implants have been machined out of UHMWPE blocks or extruded rods, has anthocyanin dispersely imbedded in the polyethylene. The implant is then exposed to γ ray or electron beam irradiation in an amount of at least 2.5 Mrad followed by a heat treatment to prevent the implant from becoming brittle in the long term as well as to improve strength and wear. The method includes mixing a powder or granulate resin of UHMWPE with an aqueous liquid that contains anthocyanin in a predetermined amount. The water is then evaporated in order to deposit the anthocyanin in a predetermined concentration on the polyethylene particles. The doped UHMWPE particles are compressed into blocks at temperatures in a range of approximately 135° C.-250° C. and pressures in a range of approximately 2-70 MPa. Medical implants are made from the blocks.

Claims

1. A method of forming a cross-linked ultra-high molecular weight polyethylene material comprising:

combining an anthocyanin material and ultra-high molecular weight polyethylene (UHMWPE) to form a doped ultra-high-molecular weight polyethylene; and

irradiating the doped ultra-high molecular weight polyethylene with γ

ray or electron-beam radiation to a total dose of at least about 2 MRad followed by heating to form a doped cross-linked ultra-high-molecular weight polyethylene.

2. The method of claim 1 wherein the amount of anthocyanin by making a combined blend of anthocyanin and UHWMPE powder is between about 0.005 w/w % and about 2.0 w/w %.

3. The method of claim 2 wherein the amount of anthocyanin combined in the blend is between about 0.005 and about 0.4 w/w %.

4. The method of claim 2 further comprising the step of heating the doped ultra-high molecular weight polyethylene after irradiating.

5. The method of claim 1 further comprising the step of forming the doped cross-linked ultra-high molecular weight polyethylene into an implant.

6. The method of claim 5 further comprising the step of sterilizing the implant during or subsequent to irradiating.

7. The method of claim 6 wherein the sterilizing step comprises contacting the implant with electron-beam radiation, gamma radiation, gas plasma or ethylene oxide.

8. The method of claim 1 further comprising the step of packaging the implant.

9. The method of claim 8 wherein the sterilizing step occurs during, after or both during and after packaging the implant.

10. The method of claim 1 wherein the ultra high molecular weight polyethylene anthocyanin blend is a substantially uniform blend.

21. The method as set forth in claims 1 wherein the anthocyanin is obtained from grapes or bilberries.

22. The method as set forth in claim 1 further comprising forming an acetabular bearing from the doped UHMWPE wherein the wear on the acetabular bearing is between 1.2 and 1.55 mm³/mc after 2×

10⁶ cycle on a standard hip stimulator.

23. The method as set forth in claim 1 wherein the anthocyanin doped UHMWPE is treated three times by irradiation followed by heating at below the melt with cooling between each irradiation step.

24. The method as set forth in claim 23 wherein the material exhibited no detectable oxidation after accelerated aging under ASTM 2102 for four (4) weeks.

11. A method of forming a sterilized packaged implant comprising:

forming an implant from a blend of ultra-high molecular weight polyethylene and anthocyanin;

packaging the implant; and

irradiating the packaged implant with γ

ray or electron-beam radiation to a total dose of at least about 2 MRad.

12. The method of claim 11 wherein the implant is packaged in an oxygen-deprived barrier package.

13. The method of claim 11 wherein the ultra-high molecular weigh polyethylene blend is a substantially uniform mixture.

14. A load bearing medical implant, comprising:

a solid UHMWPE material; and

a sufficient amount of anthocyanin compound doped into said polymeric solid material to produce a stable, oxidation resistant, matrix for forming a medical, load bearing implant.

15. The implant of claim 14 in which said anthocyanin compound is present in a range of from 0.002 to 2% by weight.

16. The composition of claim 14 in which said polymeric solid material is in a molded form.

17. An implant made of UHMW polyethylene, where the implant has been machined out of UHMW polyethylene blocks or extruded rods, wherein anthocyanin is dispersely imbedded in the polyethylene with a concentration K of 0.002%<

K<

2%, the implant be exposed to γ

ray or electron beam irradiation amounts of at least 2 Mrad to prevent the implant from becoming brittle in the long term and thereby wear and tear at contact locations.

18. A method for the manufacture of ultra high molecular weight polyethylene implants, where the implants have been machined out of UHMW polyethylene molded blocks or extruded rods comprising:

mixing a powder or granulate of UHMW polyethylene with an aqueous liquid that contains anthocyanin in a concentration of 0.002%<

K<

2% by weight;

evaporating the water in order to deposit the anthocyanin in a predetermined concentration on the polyethylene particles;

compressing the polyethylene particles into blocks at temperatures in a range of approximately 135°

C.-250°

C. and pressures in a range of approximately 2-70 MPa and

sequentially irradiating the doped UHMWPE at a dose 2-5 MRads for a total dose of 9-12 MRads followed by heating the doped UHMWPE below the melting point after each irradiation.

19. The method as set forth in claim 18 wherein the water consists of deionized water.

20. The method as set forth in claims 18 wherein the anthocyanin is obtained from grapes or bilberries.