The Effect of Bone Morphogenetic Protein-2 and Hydroxyapatite Granules on the Incorporation of Autoclaved Femoral Autografts in Sprague-Dawley Rats

Introduction.Numerous methods of limb salvage surgery have been utilized in musculoskeletal tumors, one of them being autoclaved autograft. Apart from killing tumor cells, autoclaving of autograft will also inevitably damage the inherent osteoblasts and bone morphogenetic proteins, thus impeding bone healing and graft incorporation. Bone Morphogenetic Protein-2 has been proven to accelerate fracture healing. Only few studies have investigated the effect of Bone Morphogenetic Protein-2 on the incorporation of autoclaved autografts. In this study we investigated the effect of Bone Morphogenetic Protein-2 on the incorporation of autoclaved autografts in Sprague-Dawley rats. The objective of the study is to evaluate the effect of Bone Morphogenetic Protein-2 with hydroxyapatite granules on healing or incorporation of autoclaved autografts. Materials and methods.Twenty Sprague-Dawley rats were randomized into three groups: control group, hydroxyapatite group, and Bone Morphogenetic Protein-2 group. All animals underwent osteotomy of the femoral shaft, and the resulting autograft fragments were autoclaved for 15 minutes under a temperature of 134o Celsius. Autoclaved autografts were then re-implanted and fixed with intramedullary Kirschner wires. hydroxyapatite granules were added into the fracture sites of animals belonging to hydroxyapatite group. In the Bone Morphogenetic Protein-2 group, hydroxyapatite granules that had been immersed in Bone Morphogenetic Protein-2 solution were added to the fracture sites. Meanwhile, rats from the control group received neither Bone Morphogenetic Protein-2 nor hydroxyapatite granules. Anteroposterior and lateral radiographs of the osteotomized femurs were taken eight weeks later, after which all animals underwent euthanasia. Osteotomized femurs were harvested and sent for histopathological examinations. Lane-Sandhu radiological score and Salkeld-Marino histological scores were calculated. Results.The median distal radiological scores in control, hydroxyapatite and Bone Morphogenetic Protein-2 groups were 0.5, 1 and 2, respectively (p=0.011). Proximal radiological scores did not differ between groups (p=0.160). The median proximal histological scores in control, hydroxyapatite and Bone Morphogenetic Protein-2 groups were 3, 4 and 13, respectively (p=0.004); and distal histological scores were 3, 1 and 13, respectively (p=0.001). Post-hoc analysis revealed that significant differences in histological scores and distal radiological score were found between control and Bone Morphogenetic Protein-2 groups, as well as between hydroxyapatite and Bone Morphogenetic Protein-2 groups. Scores did not differ between control and hydroxyapatite groups (p<0.05). Proximal radiological and proximal histological scores were not correlated (r = 0.267, p>0.05). Distal radiological and distal histological scores, however, were moderately correlated (r = 0.567, p<0.05). Conclusions. Bone Morphogenetic Protein-2 with hydroxyapatite granules accelerated the incorporation of autoclaved autograft in Sprague-Dawley rats, while hydroxyapatite granules alone did not