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Periacetabular Osteotomy (PAO)

What is a periacetabular osteotomy (PAO)?
A “PAO” is a surgery used to correct a condition called hip dysplasia. Hip dysplasia is when there is insufficient coverage of the femoral head (ball) by an excessively shallow acetabulum (hip socket). During a PAO, the acetabulum is repositioned to cover more of the femoral head in order to improve the stability of the hip joint. The PAO surgery improves hip function, decreases hip pain, and stops the damage occurring inside of the joint that can lead to hip arthritis over time.

How is a PAO performed?
The PAO preserves the integrity of the pelvic ring, but allows precise and full correction of even severe hip dysplasia. It involves cutting the pelvis around the entire acetabulum, which is then repositioned into a position that better covers the femoral head. Usually, 3 or 4 screws are used to hold the acetabulum in its new position. Over time, new bone will grow where the cuts are made, fusing the acetabulum to the rest of the pelvis.


Image 1: The red arrow points to the dysplasia of the right hip. Compared to the normal left hip, the right femoral head is not covered by the acetabulum and is starting to slip upwards and out of the socket.


Image 2: The red arrow points to the right hip after a PAO has been performed. The femoral head is now properly covered, and moved downwards and into the acetabulum.

Occasionally, the hip joint may need to be opened or a hip arthroscopy may need to be performed at the same time as a PAO in order to repair damage inside of the joint, such as a labral tear.


Image 3: The red arrow points to the dysplasia of the right hip. Notice the decreased lateral coverage of the right femoral head by the acetabulum compared to the coverage of the left femoral head.


Image 4: The red arrow points to the right hip after a PAO has been performed. The femoral head is now properly covered.


Image 5: During the PAO surgery, a hip arthroscopy was performed, allowing visualization of the cartilage and labrum. The red arrow points to a labral tear.


Image 6:  The red arrow points to where the labral tear repaired.
If femoral deformity is also contributing to the hip dysplasia, then a PAO may be performed in conjunction with a femoral osteotomy. Usually, the femoral osteotomy is performed through a second incision over the side of the thigh.


Image 7: The red arrow points to the dysplasia of the right hip. Compared to the normal left hip, the right femoral head is not covered by the acetabulum and the femoral head is pointing excessively upwards.


Image 8: The red arrow points to the right hip after a PAO combined with a femoral osteotomy has been performed. The femoral head is now properly covered and the femoral head is pointing towards the center of the socket. The right hip appears more symmetric with the normal left hip.

What is the patient’s recovery like after a PAO?
The recovery and expectation for patients who have a PAO performed are:

  • In the hospital for 3-5 days after surgery
  • Walking and using crutches 1-2 days after surgery
  • Using crutches for 6-8 weeks after surgery
  • Most patients are completely healed and back to sports 3-6 months after surgery

What are the patient outcomes for a PAO?
Patients have reduced pain, improved hip function and increased activity level scores in short-term outcome studies two years after a PAO. The 10-year outcomes for the PAO procedure show that 80-90% of patients are free of end-stage osteoarthritis.

Call (650) 497-8263 for an appointment or more information on periacetabular osteotomies.