Osteotomy means that the bone is divided and shifted to a better alignment. Osteotomy on the socket side of the hip is called “acetabular osteotomy” or “pelvic osteotomy.” The peri-acetabular osteotomy (PAO) is the most common procedure for young adolescents (click the image below to view a video of this procedure). This is also called the Ganz osteotomy because it was developed by Professor Ganz in Berne, Switzerland. Osteotomy on the ball side of the hip is called “femoral osteotomy”. Sometimes osteotomy is recommended on both the socket and the ball side of the hip.
Peri-Acetabular Osteotomy (PAO) Procedural Video
This surgery involves cutting the pelvis around the hip joint and shifting it into a better position to support the stresses of walking. After the hip is re-positioned, it is held in place with screws until the bone heals. After the bone heals, the screws can be removed, but this is not usually necessary.
As you might imagine, this operation is complex and is usually performed in specialized centers that do this procedure on a frequent basis. After the operation, patients should not put full weight on their leg for up to three months, so crutches or walkers are often recommended along with a wheel chair for longer distances until the bone has healed in its new position.
Life After PAO Surgery
Long-term improvements in pain relief and quality of life are reported by 90% of patients after recovery from PAO surgery. This includes lasting improvements in sports participation, social life, and sex-life. Also, PAO surgery patients who eventually need a total hip replacement can expect the same success rates as people with arthritis from other causes. Even pregnancy and childbirth have similar success rates after PAO surgery when compared to other women.
Additional Resources to Learn More About Life After PAO Surgery
Determining Success Rates
The PAO operation is most likely to be successful in patients younger than 35 years and when the joint is shallow but has matching shapes on the ball and socket sides of the joint. This is called joint congruency and means that the curvature of the socket is the same as the curvature of the femoral head. When the joint space is thinner than 2mm thick (normal thickness is about 4 mm), then the joint may be too worn down for a PAO.
An MRI may be helpful to reveal whether the surface of the joint is healthy enough for the PAO to have a reasonable chance for success. There are a few techniques to look at cartilage health; on is called a dGEMRIC scan and another is called T2 mapping. dGEMRIC stands for delayed gadolinium-enhanced MRI of cartilage. When the dGEMRIC index is low, then the chance of success is decreased. The dGEMERIC index is not the only factor for predicting success, but it may help reveal when the joint surface is already damaged. More severe dysplasia when the top of the thigh bone is partly out of the hip socket also worsens the chances for success, but the PAO may still be the best choice for some patients.
Femoral osteotomy (the ball side of the joint) has also been reported with some success and is performed on a small percentage of patients. In this procedure, the upper femur is re-aligned to change the mechanics and allow weight-bearing on a fresh part of the femoral head. Femoral osteotomy is rarely used as the only procedure in the USA although promising results have been reported in Europe and other parts of the world. Usually, femoral osteotomy is combined with pelvic osteotomy when there is deformity of the upper femur from abnormal growth and development.
Other Pelvic Osteotomies
There are also other types of osteotomies on the hip socket side of the joint. In Japan, a modification of the PAO may be preferred. That modification cuts a circle around the hip socket and rotates the socket itself. This is called a “rotational” or “spherical” osteotomy. Other pelvic osteotomies that have had some success are the “triple innominate osteotomy,” “Chiari osteotomy,” and procedures that create a deeper socket or re-align the existing socket.
There are always risks to any operation, such as infection, blood clots, incomplete healing of the bone, nerve or artery injury. In addition, the hip may still develop arthritis over time even when the operation is successful.
Osteotomy is still the preferred treatment in young adolescents to postpone the need for hip replacement as long as possible.