Medical implant or medical implant part and method for producing the same

Abstract

The invention provides a medical implant or medical implant part comprising a body and a surface layer, wherein the surface layer comprises a mixture comprising at least one hydrophilic polymer and ultrahigh molecular weight polyethylene having a weight average molecular weight of about 400,000 atomic mass units or more. The invention also provides a method for producing such a medical implant or medical implant.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This is a divisional of co-pending U.S. patent application Ser. No. 10 / 675,047, filed Sep. 30, 2003, the disclosure of which is incorporated by reference in its entirety.FIELD OF THE INVENTION [0002] This invention pertains to medical implants or medical implant parts comprised of ultrahigh molecular weight polyethylene and methods of producing and using the same. BACKGROUND OF THE INVENTION [0003] Ultrahigh molecular weight polyethylene (“UHMWPE”) is commonly used in making orthopaedic implants, such as artificial hip joints. In recent years, it has become increasingly apparent that tissue necrosis and osteolysis at the interface of the orthopaedic implant and the host bone are primary contributors to the long-term loosening failure of prosthetic joints. It is generally accepted by orthopaedic surgeons and biomaterials scientists that this tissue necrosis and osteolysis is due, at least in part, to the presence of microscopic particles ...

AI Technical Summary

Benefits of technology

"The invention provides a medical implant or part with a surface layer made of a mixture of a hydrophilic polymer and ultrahigh molecular weight polyethylene. This mixture is produced by dispersing the hydrophilic polymer in the ultrahigh molecular weight polyethylene and then filling the compression mold with the mixture. The resulting medical implant or part has improved mechanical properties and can be easily produced."

Problems solved by technology

In recent years, it has become increasingly apparent that tissue necrosis and osteolysis at the interface of the orthopaedic implant and the host bone are primary contributors to the long-term loosening failure of prosthetic joints.

Eventually, the orthopaedic implant becomes painful and / or loose and must be revised and / or replaced.

However, the free radicals formed upon irradiation of UHMWPE can also participate in oxidation reactions which reduce the molecular weight of the polymer via chain scission, leading to degradation of physical properties, embrittlement, and a significant increase in wear rate.

Moreover, the three-dimensional network produced by the cross-linking reaction can reduce the mechanical properties of the UHMWPE.

Moreover, while the cross-linking of the UHMWPE and other known methods can increase the wear resistance of a medical implant or medial implant part comprising UHMWPE, such implants or implant parts can still produce microscopic wear particles of UHMWPE that can lead to the eventual failure of the medical implant or medical implant part.