Femoral head anteposition after surgery of congenital dislocation of the hip. A computerised tomography study of 22 hips suspected of anterior dislocation.

A new term called "femoral head anteposition" to describe the clinical appearance of a hip operated on because of CDH and suspected of anterior dislocation, has been introduced. CT scans of both the horizontal and sagittal planes of 22 hips suspected of iatrogenic anterior dislocation were made from 22 children. These had been operated on because of CDH by the open reduction method with derotation varus osteotomy of the femur and transiliac osteotomy by Dega. An evaluation of the CT scans combined with clinical examination allowed the differentiation of the homogeneous clinical appearance from the "anteposition". It was then possible to establish one or several coexisting reasons to the situation. These were: anterior dislocation of the hip, coxa magna after avascular necrosis, gluteal muscle fibrosis or periarticular ossifications.