Here is some information that shows how a PAO works:
STEP #1: In this drawing of a pelvis (hips) and two femurs (the large leg bone), the dotted line on the right side of the pelvis shows where the acetabulum (the socket into which the head of the femur sits) will be broken. Dysplasia is insufficient coverage of the femoral head. The acetabulum is cut out of the pelvis so that it can be repositioned.
STEP #2: In this drawing, the acetabulum has been broken out of the pelvis and the arrow shows how it has rotated so that it now covers more of the head of the femur.
STEP #3: Once the acetabulum is rotated into the correct position, long and short screws are used to hold the acetabulum in place. These screws will remain indefinitely as the pelvis heals and may be removed once the hip is fully healed if an individual feels pain or they start to unscrew.
STEP #4: Finally, once the bone has grown back together, the hip is back to a solid unit. This process takes many weeks to months.
Click on this link http://www.hss.edu/animation-PAO-periacetabular-osteotomy.htm to watch an ANIMATED video (NOT gruesome, I promise) of how a PAO surgery works.