Bone Formation Stimulated by Treatment with Healosmp52 in a Sheep Model of Avn

INTRODUCTION With varying and uncertain etiologies, avascular necrosis (AVN) of the femoral head is a degenerative disease that usually leads to hip joint destruction. The pathology of osteonecrosis is initiated by an ischemic event resulting in bone and marrow necrosis, inflammation, infarction of the lesion by fibrous scar tissue, stress fractures in the weakened subchondral bone, and collapse of the articular surface of the femoral head. To obviate end-stage hip arthroplasty, current treatment methods to preserve the femoral head include electrical stimulation to induce osteogenesis, core decompression to relieve marrow hyperpression, osteotomy to remove necrotic bony tissue, and bone grafting to strengthen the subchondral bone and facilitate healing. It has been proposed that the limited success of these treatments could be improved by the use of bone grafts that incorporate growth and differentiation factors to stimulate bone regeneration [1]. HealosMP52 is a mineralized collagen bone grafting material, Healos, containing growth/differentiation factor-5 (GDF-5), a member of the bone morphogenetic protein family [2]. New bone formation induced by HealosMP52 has been demonstrated in various animal models, wherein GDF-5 acts as the osteoinductive stimulus within the osteoconductive Healos scaffold [3,4,5]. The purpose of this study was to evaluate the ability of HealosMP52 to promote bone formation in a sheep model of avascular necrosis. Necrotic lesions simulating AVN were created in the femoral head and neck, and treated with HealosMP52. Treated defects were evaluated by gross observation, microradiography, and histological methods for bone formation at 6 and 12 weeks after treatment, in comparison to untreated lesions.