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© 2001-2007 Joel M. Matta, M.D. Inc.,
Robert E. Klenck, M.D. Inc.
(About Periacetabular Osteotomy Continued)
In 1987 Prof. Ganz invited Dr. Matta to assist with several PAO surgeries in Bern and shortly following this Dr. Matta performed his first PAO surgeries in Los Angeles. Extensive prior surgical experience with the pelvis and hip was a prerequisite for all three of these surgeons to make the early development of PAO surgery successful.

"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.

As with any other major hip surgery, there is some risk of complications. Surgical wound infection and injury to major nerves or arteries is possible. Non-union (lack of healing) of the bone following the osteotomy is also possible. Dr. Matta's experience with this operation since 1987 however has shown PAO to be a relatively safe operation with the chance for any one of these complications to be less than one percent.

Patients begin physical therapy as soon as possible to improve hip motion and muscle function and to learn to use appropriate assistive devices such as crutches or a walker. During the first six weeks following surgery, the injured hip should bear no more than a limited weight of 30 pounds. Placing full weight on the operated side prior to bone healing can cause the screws to bend or break and the osteotomy to lose its position. Too vigorous exercise such as resistive exercise against weights can also cause failure. If failure occurs, re-operation may be necessary and the chance of developing arthritis is greatly increased.

X-rays will be taken at 2 or 3 days after surgery for a final assessment of the result.

Patients spend the two hours following surgery in the recovery room where nurses closely monitor them. The first night after surgery is typically spent in the intensive care unit to facilitate close monitoring and after that the patient is returned to the normal ward.

The same team of medical specialists cares for each patient pre- and post-operatively. Included among the team’s post-surgical priorities are pain management, preventing infection, and the prevention of deep vein thrombosis (blood clots in large veins), and pulmonary embolus (blood clots traveling through veins to the lungs).


Dysplastic acetabulum and femur after PAO.
Acetabulum and femur after healing of PAO and removal of two screws.
Hemi-pelvis with normal acetabulum and femur.
Hemi-pelvis with dysplastic acetabulum and femur.