Optimization of chronic contact stress exposure to improve the mechanical environment of the dysplastic hip joint following periacetabular osteotomy

Hip dysplasia describes a skeletal deformity in which the hip socket (acetabulum) fails to adequately cover the ball side (femoral head) of the joint. This causes an unstable hip joint inside which very high mechanical stresses develop between the smaller contacting joint surfaces. While severe dysplasia is often addressed during childhood, less severe deformities may not be identified until the young adult years when patients present with activity-limiting hip pain and indications of early-onset hip arthritis resulting from many years of poor hip mechanics.

Treatment for young-adult dysplasia involves a major surgery to correct the orientation of the hip socket to better cover the femoral head and improve hip stability. However, even with treatment, most patients develop hip arthritis or need hip replacements within 30 years of their surgery. One potential reason for this may be that the surgery does not sufficiently reduce the high stresses in the joint, and high joint stresses have been linked to arthritis development.

In this work, 3D computer models of individual patients with hip dysplasia were used to identify stress levels associated with cartilage damage or future development of arthritis. These models were then used to simulate many possible surgical corrections in order to identify which hip socket orientation best reduces stresses below these damaging levels. A pilot study was then conducted in which the best socket reorientation for patients undergoing surgery was provided to the surgeon as a preoperative planning guide. The stresses calculated for a 3D model of the hip with the patient’s actual surgical correction were closer to those of the model with that patient’s best socket reorientation when the surgeon had access to this information preoperatively. Using a patient’s own hip anatomy to guide the surgeon to an individualized correction may provide the best opportunity to reduce that patient’s hip pain and likelihood of developing hip arthritis, thereby preventing their need for future hip replacement surgery.