Effects of Gait Patterns on the Viscoelastic Squeeze-Film Lubrication of Hip Replacements

The present study investigated the influence of various gait patterns on the viscoelastic squeeze-film lubrication characteristics of UHMWPE-based artificial hip replacements. Different gait loads (slow walking, normal walking, slow running) measured by Bergmann et al. were adopted in the present lubrication simulation. A comprehensive squeeze-film lubrication model for UHMWPE hip replacement was developed and numerically solved to determine the spatial distributions of film thickness and pressure profiles. The results showed that physiological loads had a negligible impact on the minimum film thicknesses during the stand phases. However, they significantly enhanced the minimum film thicknesses in both the elastic (1.16–1.31 times) and viscoelastic models (1.43–2.85 times) during the swing phases when compared to constant loads. This improvement was notably more pronounced in the viscoelastic model than in the elastic model. The slow-running gait, characterized by its higher frequency, demonstrated a more pronounced enhancement in squeeze-film lubrication of UHMWPE artificial hip joints compared to both normal-walking and slow-walking gaits. Specifically, the minimum film thicknesses during slow running were found to be 1.15 to 1.35 times greater than those observed during normal walking and 1.33 to 1.66 times greater than those during slow walking, highlighting the superior lubrication performance in the slow running case.