Indications for intertrochanteric osteotomy after periacetabular osteotomy for adult hip dysplasia.

Residual hip dysplasia in the adult is characterized by deficient anterior and lateral acetabular coverage with subsequent hip joint incongruity and instability. The frequency of periacetabular osteotomy for the treatment of residual hip dysplasia is increasing. In certain morphologic conditions preoperative abduction or intraoperative radiographs reveal that congruency after a periacetabular osteotomy is not optimum; at this point the surgeon may consider the addition of an intertrochanteric osteotomy. In a retrospective study, the radiographs of 25 patients who had a femoral osteotomy with or after periacetabular osteotomy were analyzed and the results were compared with a control group of 34 patients who had periacetabular osteotomy without a femoral osteotomy. The analyzed parameters included: the femoral head extrusion index and the acetabular index, before and after periacetabular osteotomy; the femoral neck shaft angle; the presence of femoral head deformity; the presence of osteoarthrosis; the presence of a secondary acetabulum; the influence of previous ipsilateral hip surgery; the effect of hip adduction or abduction on joint congruency; and the age of the patient. The variables that had a statistically significant association with the performance of an intertrochanteric osteotomy included a femoral head extrusion index and an acetabular index after periacetabular osteotomy outside the normal limits, a neck shaft angle outside the limits of the control group, a deformed femoral head, an osteoarthritic hip, a secondary acetabulum, and a joint space height and congruency dependent on position of the proximal femur. When using statistically significant variables, a discriminant analysis predicted the correct group (periacetabular osteotomy with femoral osteotomy, or periacetabular osteotomy without femoral osteotomy) for 89% of the cases.