Periacetabular osteotomies are performed to improve femoral head coverage in a variety of clinical conditions. The stability of the osteotomy fragment between Ganz's periacetabular osteotomy was compared with that of Tonnis's triple innominate osteotomy under simulated weight-bearing conditions with a variety of screw constructs using three-dimensional analysis of fragment displacement and angular rotation. Generally, small amounts of displacement (<2 mm) and angular rotation (<3 degrees) were encountered for each fixation technique. Because the Ganz procedure violates the triradiate cartilage, it is not feasible in the immature patient. Thus, an understanding of fixation requirements in other available osteotomies to maintain fragment position is necessary.