The term “lateral acetabular osteotomy” means that unlike in Pemberton and Salter procedures osteotomy of the acetabular roof is directed from the lateral extracapsular rim in a medial direction. Controlled by fluoroscopy, the surgeon should chisel bone to the most medial and posterior part of the triradiate cartilage, but stop 3 mm before reaching it. After complete osteotomy is performed from the sciatic notch to the anteroinferior iliac spine, the acetabular roof can be turned down separately to a normal angle. Therefore, the joint obtains its normal radius and stability immediately. Even extremely shallow acetabuli can be treated successfully as long as the cartilage is not consolidated. Follow-up investigations until the end of growth in 90 hip joints have shown that acetabular measurements were normal or slightly pathologic in 82–93% of patients according to our grading system of normal values and degrees of deviation. When varus osteotomy was performed simultaneously, measurements of femoral neck and head were normal to slightly pathologic in only 47–50%. For this reason, we have avoided varus osteotomies in the last decade. No complications have occurred at the triradiate cartilage.