PERI-ACETABULAR OSTEOTOMY (PAO)
Another tool in the preservation of the natural hip, is surgery aimed at the acetabulum or socket of the hip joint. Some people are born with sockets that are very shallow (Developmental Dysplasia of the Hip or DDH). Also some sockets are pointing too far backwards or too far forwards resulting in a relative Dysplasia despite having a normal depth. This is something that one is born with and can run in families to varying degrees.
Many people have these problems and are unaware of them until there is pain that results in the taking of an X-ray, and even then the radiologist or even the orthopaedic surgeon may miss the underlying problem if they are not familiar with the latest intricacies of hip pathology. In fact I recommend that all aspiring athletes should at least have a plane pelvis X-ray so that a predisposition to premature wear and tear arthritis (Osteoarthritis) can be noted. This may lead to surgery or even just an adjustment of sporting activity so as to minimize the risk.
What does a PAO Involve?
This surgery is aimed at reorientating the socket or acetabulum so that the surface area of contact between the femoral head (the ball), and the socket weight bearing zone is optimized.
To do this the surgeon has to cut the bone in such a way so as to isolate the socket, which is then moved under x-ray guidance and direct vision, to the desired position in order to fulfill the above criteria. This needs to be done while preserving the blood supply to the socket bone and cartilage , and must be done without penetrating the joint. Also the integrity of the pelvis is preserved so that early weight bearing on the leg is possible immediately after surgery. After the socket is repositioned, it is fixed with screws and the bone heals as with any fracture. Crutches are required for at least 6 weeks and early range of motion exercises are encouraged including driving within a week or two. Patients remain in the ward till they are negotiating a flight of stairs with their crutches, the average being 5 days.
This surgery is not for the faint hearted, and I’m talking about the surgeon. The surgery takes place very close to the main arteries and nerves as they track toward the leg past the hip joint. These structures are therefore at risk and great care is taken to protect them throughout the surgery.
Possible complications are the same as those for arthroscopic and open hip dislocation surgery but to a greater extent. Once again, the surgical techniques have been refined so that this surgery can be performed through an incision that is half of what it used to be historically, but despite this the cut is still approximately 10cm depending on the size of the patient.
Often the PAO is preceded by an arthroscopic evaluation of the hip joint cartilage quality, as it does not make sense to perform hip preserving surgery if the cartilage is already very worn.
Usually patients with DDH present in their thirties with hip pain and studies have shown that a PAO can prevent the need for hip replacement surgery or at the very least allow the patient to continue to run, for example, and take part in high level sport for a decade or two before needing a hip replacement. Remember that after a hip replacement you are not able to run anymore and 1 per 100 hip replacements have a complication requiring further surgery.
A very important point is that the repositioning of the socket, with a PAO, will often make any eventual hip replacement if required more easy to perform, giving a better result . This is especially the case for patients with DDH where the PAO places the bone in a better position to accept the artificial socket of a hip replacement.