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Stephen Duncan, M.D.
Orthopedic Surgeon
Hip Preservation
Hip Resurfacing
Primary and Revision Hip Replacement
Primary and Revision Knee Replacement

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Periacetabular Osteotomy (PAO)

In a “normal” hip, the head (ball) of the femur (thigh bone) is covered adequately and well seated in the acetabulum (hip socket). The hip socket is “cup shaped.” In contrast, a dysplastic hip has incomplete or inadequate coverage of the femoral head. The dysplastic hip is more “dish shaped.” Because of the inadequate coverage of the femoral head in a dysplastic hip, the weight across the hip is distributed on a smaller surface area resulting in excessive load along the rim of the hip socket. Over time, this increased load along the rim of the socket will lead to degeneration of joint cartilage and formation of osteoarthritis. Patients with this condition frequently seek medical attention due to activity-related hip pain (discomfort in the groin or side of the hip). Prolonged sitting or walking can also increase these symptoms and a sensation of catching or popping may also occur. As these symptoms continue to increase, a slight limp may be noticed and more strenuous activities may become difficult. PAO surgery is a hip preservation surgery performed to correct a congenital or developmental deformity of the acetabulum known as acetabular dysplasia. If this condition remains untreated, secondary arthritis commonly develops. Therefore, in order to relieve symptoms and improve the prognosis of the hip, this surgery is done to correct the bony anatomy and help normalize the load across the joint. “Periacetabular” means around the acetabulum (hip socket). “Osteotomy” means to cut bone. Therefore, PAO means to cut the bone around the acetabulum and reposition the hip socket. The PAO is a very effective procedure for the treatment of symptomatic acetabular dysplasia.  Dr. Duncan, his colleagues and healthcare team have an extensive experience in the evaluation and treatment of patients with hip dysplasia. At surgery, controlled cuts are made to loosen the acetabulum from the pelvis, and the acetabulum is repositioned.  An incision is made across the front of the hip joint to allow exposure of the hip and surrounding pelvis. The use of x-ray during surgery helps direct the bony cuts and confirm the correct reorientation of the socket. The acetabulum is fixed in the new position with three or four screws. In most uncomplicated cases the surgery takes two to three hours.