Hip dysplasia is a skeletal deformity characterized inadequate coverage of the femoral head by a shallow acetabulum, which creates an unstable hip joint subjected to very high intraarticular contact stresses. The altered force transfer through the less congruent dysplastic hip joint frequently leads to activity-limiting hip pain and early-onset joint degeneration.

Treatment for young-adult dysplasia often involves a periacetabular osteotomy (PAO), a surgery which permits multiplanar reorientation of the acetabulum in order to increase femoral head coverage, improve joint stability, and alleviate hip pain. However, while PAO can achieve a radiographically “normal” hip joint, most patients still develop hip osteoarthritis (OA) or need total hip replacements within 30 years after correction. This may indicate that PAO insufficiently reduces the high contact stresses that have been linked to OA development.

In this work, discrete element analysis (DEA) of patient-specific models of individuals with hip dysplasia was used to identify thresholds of chronic contact stress-time exposure associated with cartilage degeneration or OA development. Two methods of computational optimization (brute-force and gradient-descent) were then developed to identify the acetabular reorientation that minimizes chronic exposures above those thresholds. Finally, a pilot study was conducted in which a patient-specific acetabular reorientation that optimizes that given patient’s chronic exposure was provided to the treating surgeon as a preoperative planning guide. The reduction in chronic exposures achieved with the actual surgical correction was closer to optimal in cases where the surgeon had access to this mechanical data preoperatively. Using a patient’s own hip anatomy to guide the surgeon to an individualized correction that optimizes contact stresses below damaging levels may provide the best opportunity to reduce that patient’s hip pain and likelihood of developing OA, thereby preventing their need for future total hip replacement.