Assessment of bone regeneration with calcium phosphate-based biomaterials in an osteonecrosis animal model

Abstract

Osteonecrosis of the femoral is a musculoskeletal disorder that has been described as a loss of subchondral bone integrity caused by an irreversible loss of osteocytes. Although there exist several pathogenic mechanisms apparently leading to osteonecrosis, the com- mon pathway involves impaired osteogenesis and angiogenesis throughout the lesion. If the underlying causes are not relieved, osteonecrosis usually progresses until producing a subchondral fracture and hip degenerative changes. In this study, two joint-preserving techniques based on calcium phosphate grafts loaded with growth factors (BMP-2) and bone marrow were assessed in vivo in an experimental sheep model. In order to assess bone regeneration, several quantitative methods based on µ-CT image processing were used to characterize bone morphometry, mineral density and composition. In addition, histological analysis with fluorescence microscopy and compression assays were carried out to analyze both bone mineralization and stiffness against compression. Obtained re- sults provided evidence of light bone regeneration surrounding the area of treatment as early as six weeks. Such osteogenesis was characterized by an increase of bone volume, trabecular thickness and mineral density. Scaffolds loaded with bone marrow provided lower osteoconductive but higher osteogenic properties. As opposed, carriers loaded with BMP-2 were more chemically stable but induced lower bone regeneration in the adjacent cancellous bone.