The contribution of the ossific nucleus to the structural stiffness of thecapital femoral epiphysis: A porcine model for DDH

The preosseous femoral head is thought to be vulnerable to compressive isch emic injury during the treatment of developmental dysplasia of the hip. The ossific nucleus has been proposed to increase the mechanical strength of t he capital femoral epiphysis (CFE) and to decrease the risk of avascular ne crosis. Sixty mixed-breed fetal and postgestational femoral head specimens were evaluated for structural stiffness in relation to the size of the ossi fic nucleus within the GEE. The structural stiffness of the CFE in the porc ine model was found to increase exponentially with the size of the ossific nucleus. A finite-element model revealed that the presence of an ossific nu cleus occupying 40% Of the epiphyseal volume reduced the compressive strain in the region of the posterior-superior branch of the medial circumflex ar tery 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 compress ive ischemic injury in the treatment of DDH.