The Contribution of the Ossific Nucleus to the Structural Stiffness of the Capital Femoral Epiphysis: A Porcine Model for DDH

Abstract

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.

The effect of long‐term methylprednisolone treatment on the femoral head in growing pigs

“…Also in clinical studies, increased fibrinogen plasma levels have been reported under steroid treatment [37]. Increased plasma fibrinogen is associated with enhanced hyperviscosity and hypercoagulability [30]. The porcine coagulation system essentially employs the same set of coagulation factors as found in all other mammals, including human [31].…”

“…Steroid treatment in this study was started at the age of 10 weeks. At this age, the ossific nucleus still occupies <100% of the FH epiphysis [30]. Histopathology in the present study revealed an irregularly shaped subchondral bone plate with chondrous lacunae mainly in the cranial area exclusively in the CS treated animals.…”

Post-closed Reduction Perfusion Magnetic Resonance Imaging as a Predictor of Avascular Necrosis in Developmental Hip Dysplasia

“…15,36 In further support of this compression mechanism, several studies have shown that the unossified femoral head with its decreased structural stiffness is particularly vulnerable to compressive ischemic injury. 10,15,36,37 In addition, there are other studies to support that a young age per se (G6 months) is associated with an increased incidence of AVN. 5,38 Although this was not the main object of the present study, we could not confirm these findings.…”

“…9 The mechanical stiffness of the femoral head increases dramatically with the size of the ossific nucleus, as shown in a porcine model. 10 Also in humans, it has been suggested that the increased stiffness provided by the ossific nucleus may protect against AVN. In a study of 49 children (57 hip dislocations) younger than 12 months old, the presence of the ossific nucleus before closed or open reduction for DDH was associated with a lower incidence of AVN.…”

Developmental dysplasia of the hip: Controversies and current concepts

“…Although there are several observational studies 74,75 which appear to support this theory advocating a delay in surgical reduction until the ossific nucleus appears, no randomised controlled trials exist. This involves opening the hip capsule to remove or correct potential obstacles to reduction which may include an inverted labrum, neolimbus, pulvinar, hypertrophied ligamentum teres and transverse acetabular ligament and a tight iliopsoas tendon.…”