The preosseous femoral head is thought to be vulnerable to compressive ischemic injury during the treatment of developmental dysplasia of the hip. The ossific nucleus has been proposed to increase the mechanical strength of the capital femoral epiphysis (CFE) and to decrease the risk of avascular necrosis. Sixty mixed-breed fetal and postgestational femoral head specimens were evaluated for structural stiffness in relation to the size of the ossific nucleus within the CFE. The structural stiffness of the CFE in the porcine model was found to increase exponentially with the size of the ossific nucleus. A finite-element model revealed that the presence of an ossific nucleus occupying 40% of the epiphyseal volume reduced the compressive strain in the region of the posterior-superior branch of the medial circumflex artery by an average of 54%. The results of this study support the hypothesis that the presence of the ossific nucleus may protect the CFE from compressive ischemic injury in the treatment of DDH.
Study conducted at The Milton S. Hershey Medical Center and The Pennsylvania State University College of Medicine, Hershey, Pennsylvania, U.S.A.
From the Department of Orthopaedics and Rehabilitation, The Pennsylvania State University College of Medicine, and *Cumberland Valley Orthopaedic Associates, Chambersburg, Pennsylvania, U.S.A.
Address correspondence and reprint requests to Dr. L. S. Segal, Department of Orthopaedics and Rehabilitation, Box 850, The Milton S. Hershey Medical Center, The Pennsylvania State University College of Medicine, Hershey, PA 17033, U.S.A.