The cause of Legg-Calve Perthes disease, 97 years after its original description remains undefined. In the present study we examined factors, which were correlated with a favourable or negative impact on the outcome of surgical treatment.

From a total of 98 children, treated during the period 1994–2006, we studied 20 cases (classified as Catterall III and IV), treated surgically. The average age was 7.4 years (4–13 years). We studied in comparison the most common procedures performed: these were the varus femoral osteotomy (12) and the lateral shelf acetabuloplasty (7). The subtrochanteric osteotomy yielded superior radiological results Stuhlberg I–II (I:6, II:6), than the lateral shelf procedure Stuhlberg II–IV (II:3, III:3, IV:1). The clinical results were similar between the two groups according to the Barrett scale, excellent or good.

Regarding the subtrochanteric osteotomy the most important factor was the precise varisation of the femoral neck and secondly the timing of surgical treatment early during the fragmentation stage of the disease, before the femoral head is significantly distorted. The most important positive factor regarding the lateral shelf procedure appears to be the accuracy of the surgical technique, in order that the graft coverage of the femoral head is accurately placed on the hip capsule. Negative factor for the lateral shelf procedure in one case was early weightbearing, which resulted in collapsing of the femoral head. It appears that with extensive necrosis (Caterall IV) the femoral head isn’t biomechanically enough resistant with this procedure to resist loads that result from early ambulation.