Freedom of acetabular fragment rotation following three surgical techniques for correction of congenital deformities of the hip.

Femoral head coverage achieved with an acetabular osteotomy for hip dysplasia is achieved by acetabular rotation that can be restricted by osteotomy orientation and soft tissue attachments to the acetabular fragment. Procedures that allow excess rotation or motion in an undesirable direction (especially external rotation) may have undesirable consequences. Rotational aspects of these procedures have not been well described and are not well appreciated radiographically. This study examined the angular motion related to three operative techniques for redirectional acetabular osteotomies. The freedom of motion allowed for the Ganz periacetabular, Carlioz triple, and Tonnis triple osteotomies was quantified using three-dimensional motion measurement. The Ganz osteotomy allowed the greatest amount of motion. The Carlioz osteotomy allowed statistically less motion and depicted the "coupled motion" phenomenon in which a maximal angular rotation in one plane (abduction) is associated with a predicted angular change in another plane (external rotation). The Tonnis osteotomy allowed freedom of motion similar to the Ganz osteotomy without coupled motion.