Small Punch Testing of Artificially Aged Gamma-Sterilized Polycarbonate Urethane Acetabular Components

INTRODUCTION: Polycarbonate urethane (PCU) has been investigated as a candidate bearing material for total acetabular replacement and unicondylar knee replacement [1-4], and is currently being used in a pliable acetabular component (AIC Acetabular Buffer: Active Implants Corp., Memphis, TN). However, the susceptibility of PCU to post-irradiation aging is not yet fully understood. Furthermore, due to the reduced thickness of the PCU acetabular components, specialized testing techniques are necessary to directly evaluate their mechanical behavior from final fabricated implants. The objectives of this study were two-fold: (1) to determine the applicability of the small punch test to characterize PCU implants; and (2) to evaluate the susceptibility of PCU acetabular implants to degradation of mechanical behavior following gamma irradiation in air and accelerated aging. In this study, we characterized the small punch mechanical behavior of unirradiated and gamma sterilized AIC acetabular buffers before and after a standard accelerated aging protocol. We hypothesized that the gamma sterilized PU materials would exhibit less oxidative stability than unirradiated controls after accelerated aging.