Acetabular coverage of the femoral head after triple pelvic osteotomy: no relation to outcome in 51 hips followed for 8-15 years.

In developmental dysplasia of the hip in adolescents and young adults, pelvic osteotomies aim to improve acetabular coverage of the femoral head by reorienting the acetabulum. We determined whether acetabular coverage is related to long-term clinical results after triple osteotomy of the pelvis. We used a previously published computer program (Konishi and Mieno 1993) which calculates three-dimensional coverage of the femoral head from plain anteroposterior radiographs. We studied the pelvic radiographs of 51 hips in 43 patients and the results were correlated with studies on clinical outcome (de Kleuver et al. 1997). Total acetabular coverage improved from a mean of 56% to 70%. We did not find a relationship between total acetabular coverage and long-term outcome, nor could we determine an optimal coverage. Reduced coverage of the posterolateral quadrant of the femoral head was related to a reduced score for walking ability (p = 0.03), and therefore care should be taken not to overcorrect the acetabulum forwards when attempting to improve the deficient anterior coverage. We challenge the concept that total acetabular coverage is a prerequisite for a good long-term outcome after triple pelvic osteotomy, and hypothesize that other factors such as the change in load across the hip are probably more important in determining the outcome.