Periacetabular Osteotomy.A Prospective Study With Reference to Cartilage, Migration and Bone Density

The cause of osteoarthritis in hip dysplasia is thought to be attributable to increased joint contact pressures secondary to decreased acetabular coverage of the femoral head and/or incongruity of the articular surfaces. The investigators' hypothesis is that when periacetabular osteotomy is performed and contact pressure on cartilage reduced, additional joint degeneration will be slowed or prevented unless irreparable damage to the cartilage has happened at the time periacetabular osteotomy is performed. Hence, the purposes of this study are:

• to develop an unbiased and precise method for measurement of the thickness of the articular cartilage in the hip joint because such a method can be used to evaluate the effect of periacetabular osteotomy and also to give a more precise indication/contraindication for surgery;
• to evaluate the migration of the acetabulum postoperatively and 6 months after surgery by use of RSA to examine the stability of the osteotomy; and
• to examine bone mineral density in acetabulum 1 and 2 years after surgery in order to find out whether the change in load distribution will affect bone density of the acetabulum over time in a way that in the area where more load is applied, bone density will increase, and in areas with less load, bone density will decrease;
• to examine the labrum in the hip joint.

Inclusion criteria

• Patients with radiologically diagnosed hip dysplasia (CE-angle < 25°)
• Patients with osteoarthritis graded 0, 1 or 2 defined according to Tönnis' classification
• Patients with pain from hip
• Age > 18 years
• Minimum 110° flexion in hip joint and closed growth zones in the pelvic region
• Informed consent

Exclusion criteria

• Patients with neurological diseases
• Patients with calvé-Legg-Perthes syndrome
• Patients where a femoral intertrochanteric osteotomy is necessary
• Patients with medical sequelae after earlier hip surgery
• Females who are pregnant
• Patients with metal implants