Recent Advances of Mechanical Performance and Oxidation Stability in Ultrahigh Molecular Weight Polyethylene for Total Joint Replacement: Highly Crosslinked and .ALPHA.-Tocopherol Doped

Abstract

Ultrahigh molecular weight polyethylene (UHMWPE) is the popular material of choice for use as a bearing surface in total joint replacement (TJR). Despite an extremely low friction coefficient of UHMWPE to metals with liquid lubrication, however, wear and fatigue fractures are major problems limiting the durability of implanted UHMWPE components. Although highly crosslinked UHMWPE has been intensively studied for decades, its use in orthopedic implants has been limited to relatively low stress and multidirectional load applications, such as acetabular cups in hip joint replacements (HJR). This is mainly because highly crosslinked UHMWPE requires thermal treatment process, indispensable for eliminating the residual free radicals, which leads to a decrease in crystallinity resulting in the reduction of fatigue performance of highly crosslinked UHMWPE. By contrast, recently α-tocopherol doped UHMWPE has been viewed seriously as a novel orthopedic UHMWPE. The α-tocopherol doped UHMWPE exhibits excellent wear and fatigue performance and can be applicable to high stress and linear motion applications, such as total knee replacements (TKR). This paper comprehensively reviews recent advances in the mechanical properties and oxidation stability of medical grade UHMWPE, particularly focusing on highly crosslinked UHMWPE and α-tocopherol doped UHMWPE.