Mechanical Degradation of Retrieved UHMWPE Tibial Components Characterized by the Small Punch Test
Abstract Miniature specimen testing techniques are necessary to characterize the mechanical behavior of UHMWPE components for total joint replacement after sterilization, shelf aging, and implantation. The small punch test has been shown to reproducibly characterize virgin and in vitro aged UHMWPE. The first goal of this study was to demonstrate the feasibility of applying this technology to UHMWPE components after retrieval from the human body. Six short-term retrievals of the same tibial design were characterized with the intent of comparing the mechanical behavior of conventional and enhanced UHMWPE having an extended chain crystalline morphology. Statistically significant relationships were observed between damage scores and the small punch test metrics of initial load, ultimate load, and work to failure. The results of this study support the hypothesis that the in vivo performance of tibial bearings is related to the large deformation mechanical behavior of UHMWPE.