Structural, mechanical and wear resistance assessment of UHMWPE orthopedic components

The long-term survival of total joint prostheses is influenced by many factors. Among these factors, the most critical one is the presence of wear debris, particularly from the joint articulating surfaces. While ultra high molecular weight polyethylene (UHMWPE) has shown to be extremely promising in vitro and short-term clinical results, shelf-aged, oxidized components have been extremely unsuccessful clinically. Although shelf-aged components have been frequently tested in the laboratory, few studies have compared the properties of clinical retrievals to shelf-aged UHMWPE components. In this study, a thorough analysis method was developed and applied to both UHMWPE components retrieved at the time of revision, and non-implanted, shelf-aged UHMWPE components with the aim to understand better the significance of the in vivo factors on the material properties of the retrievals. The UHMWPE components were analyzed and characterized by visual observation of the surfaces, mechanical properties were assessed by small punch tests, wear resistance was analyzed by a multidirectional pin-on-disk test, and the oxidation level was detected by the Fourier transformed infrared (FT-IR) technique. The results indicated a strong correlation between the UHMWPE oxidation level, mechanical properties and wear resistance.