Ganz Periacetabular osteotomy is most useful for patients with hip dysplasia. Procedures that realign the position of the acetabulum (socket) are called osteotomies. Many different types have been promoted in the past for young patients with hip dysplasia. 90% of dysplasia cases occur in young women. These women typically were born with mild hip deformities that do not cause problems when they are children.

The elements of the dysplasia deformity are: oval shallow socket, steeply oriented socket, flattened oval head, narrow, valgus and anteverted neck, hypertrophied labrum. Typically these women have extremely loose ligaments and have much higher than normal hip mobility. They gravitate towards gymnastics and ballet because of their extreme flexibility. They start exhibiting mild hip symptoms in their 20s and 30s.

The hips start to fail early for two reasons: incongruency and instability. A normal hip is a spinning sphere. When an oval dysplastic hip rotates, abnormal forces are experienced by the articular cartilage leading to deterioration. A shallow dysplastic hip is poorly contained. If the orientation is more vertical, the situation is worse. The labrum hypertrophies in an attempt to better contain the head.

The result is a hip that is highly mobile. But the labrum eventually gets overloaded and fails. The first symptoms usually appear in the 20s and 30s depending on severity of the deformity and possibly activity level. At this point the articular cartilage may still be relatively normal.

If their socket orientation is too steep, a Ganz periacetabular osteotomy can improve symptoms by reorienting the entire socket and thereby better containing the head. If socket orientation is acceptable, sometimes the early symptoms are coming from a tear of the hypertrophied labrum that can be repaired arthroscopically. Removing torn labrum in dysplasia is not advisable because this destabilizes the head and may speed up the hip degeneration.

Studies on acetabular osteotomies have shown over 90% success in symptom relief if there is only minor articular cartilage damage at the time of surgery. The hope is that the hip joint will be preserved by this intervention, but this has not yet been proven. The ideal patient for osteotomy surgery is under 40 years with minimal arthritic changes on their hip x-ray. The problem is that there is no way of completely correcting the deformity. There is no way to deepen the socket or make the bearing spherical without destroying the cartilage. A hip resurfacing does accomplish these goals, but this requires an artificial implant.

Experts in Ganz osteotomy that I can recommend are:

• Michael Millis – Boston MA
• Robert Trousdale – Rochester MN