In the past, there has been little research into leg length inequality (LLI) and its effect on hip arthroplasty bearing longevity. This investigation aimed to determine the effects of post-operative LLI on hip motions during gait and to postulate the subsequent influence on the wear of the artificial hip joint replacement. Motion data from a clinical gait analysis were processed with an in-house computational model to plot graphs showing the movement of loci of 20 points on the femoral head during one gait cycle for two cohorts: 19 LLI patients and 38 normal healthy patients. Loci paths were quantified by calculating the aspect ratio (AR) of the path shape. It was found that on average, LLI patients had a reduction in flexion/extension and abduction/adduction. Furthermore, the AR of LLI patients was found to be 8% smaller than the normal group. The shorter, more multidirectional, motion paths in LLI patients would suggest the potential for greater wear in a polyethylene bearing compared to an asymptomatic, non-LLI patient. The results have potential implications towards preclinical wear testing of joint replacements.
Keywords: Leg length inequality; arthroplasty; gait; hip; wear.