How the pemberton innominate osteotomy really works: an animal study

Conventional wisdom holds that the Pemberton innominate osteotomy improves acetabular coverage and decreases acetabular volume through hinging of the acetabular dome through the triradiate cartilage. The aim of this study was to identify the site of hinging through the triradiate cartilage and characterize any alteration in acetabular volume produced by this procedure. Pemberton innominate osteotomies were performed under fluoroscopic control on six fresh immature pig innominate bones. The site of hinging at the triradiate cartilage was identified through observation during the procedure. Just prior to and immediately after the procedure, the acetabular dimensions were measured and recorded. Hinging was observed to occur through the extra-articular portion of the ilioischial limb of the triradiate cartilage. No alteration of acetabular volume was observed following successful Pemberton innominate osteotomies. The Pemberton osteotomy improves femoral head coverage through redirection of the acetabulum rather than alteration of acetabular shape.