Periacetabular Osteotomy (PAO) is a surgical treatment for Acetabular Dysplasia  that preserves and enhances the patient's own hip joint rather than replacing it with an artificial part. The goal is to alleviate the patient's pain, restore function, and maximize the functional life of their dysplastic hip.

PAO is a procedure that was developed and first performed in 1984 in Bern, Switzerland by Professor Reinhold Ganz with the assistance of Jeffrey Mast, M.D. (an American surgeon from Sparks, Nevada who was spending a year's sabbatical leave with Prof. Ganz). Dr. Joel Matta's personal association with Prof. Ganz and Dr. Mast made him aware of the very good initial results of this innovative procedure.

“Periacetabular" means around the acetabulum. "Osteotomy" means to cut bone. Simply put, the PAO cuts the bone around the acetabulum that joins the acetabulum to the pelvis.

Once the acetabulum is detached from the rest of the pelvis by a series of carefully controlled cuts, it is rotated to a position of ideal coverage as dictated by the specific acetabulum's unique anatomy. PAO thereby reorients the acetabulum by changing its rotational position. The dysplastic roof that incompletely covers the femoral head is brought over the head to give the head a normal coverage and also brings the roof from an oblique to a horizontal position. Other subtle changes typically also occur. Anterior coverage may increase. Also the shortening of the extremity and lateralization of the joint which are often a part of acetabular dysplasia can also be improved

Individual cases of dysplasia however present with their own unique deficiencies and the PAO must often be tailored to solve these unique problems. X-rays taken during surgery confirm the correct position of the acetabulum and screws (typically 3) are inserted into the bone to maintain the acetabulum's new corrected position during bone healing.

A proximal femoral osteotomy (cutting and repositioning the bone of the upper femur) is also advisable in about one out of 10 patients who undergo PAO surgery in order to correct abnormalities related to the femur. The indication for this is not always known until during the PAO operation. The femoral osteotomy is then completed during the same surgery though a second incision is necessary.