[Medial acetabular displacement and other pelvic displacements after Chiari osteotomy (author's transl)].

The authors have made a study of displacement after Chiari osteotomy in cadavers and in patients. In most of the cases, following osteotomy, there is movement not only at the pubic symphysis but also in the two sacro-iliac joints. Movement in the ipsilateral sacro-iliac joint is associated with upward and lateral displacement of the iliac crest giving an improved cover of the femoral head even though the acetabulum is not medially displaced. Movement in the controlateral sacro-iliac joint does result in medial displacement of the acetabulum but the whole of the opposite hemi-pelvis is also displaced so that the opposite acetabulum is displaced laterally and becomes more vertical. The authors attempt to draw conclusions on the biomechanical action of Chiari osteotomy on the opposite acetabulum.