Abstract:
"Contact Stress Assessment of Conventional and Highly Crosslinked Ultra High Molecular Weight Polyethylene Acetabular Liners with Finite Element Analysis and Pressure Sensitive Film"
This study investigates the mechanical performance of conventional and highly crosslinked ultra-high molecular weight polyethylene (UHMWPE) acetabular liners used in total hip replacement (THR). Using a combination of finite element analysis (FEA) and pressure-sensitive film, the research examined stress magnitudes and distributions under a simulated single-leg stance. The study's hypothesis was that using large femoral heads with thinner, highly crosslinked polyethylene liners would result in excessive stress, but this hypothesis was not supported by the data. The FEA results showed that the highly crosslinked liners consistently experienced lower von Mises stresses at the articulating surface compared to conventional polyethylene, across all sizes tested. Specifically, even the thin, 3-mm thick highly crosslinked liners with large 38-mm and 46-mm heads had lower stresses than the conventional 22-mm head with a 5-mm thick liner, a combination with a long-established clinical record. Furthermore, the study found that tolerance stack dimensions, representing manufacturing extremes, elevated stresses at both the articulating surface and the backside of the liner, particularly at the rim where failure has been observed clinically. The overall findings suggest that, from a biomechanical perspective focused on stress states, the use of large heads with highly crosslinked polyethylene is advantageous. However, other factors like wear rates and implant-specific designs must be considered before recommending minimum liner thickness.
