Calcium phosphate scaffold and bone marrow for bone reconstruction in irradiated area: a dog study

Squamous cell carcinomas (SCC) of the upper aero-digestive tract are characterized by a high incidence of bone invasion; their treatment often requires large and damaging surgical resections and radiotherapy. Surgical and radiotherapeutic procedures generate irreversible effects on normal tissues, involving injuries on their reparation properties, especially on bone. The quality of life of patients undergoing major surgery and radiotherapy in maxillary and mandible areas is often reduced but could be improved by bone reconstructions. Bone reconstructions are rarely performed because surgery is complex and unsafe in irradiated bone. The aim of the study was to evaluate the bone reconstruction possibilities of macroporous biphasic calcium phosphate (MBCP™) associated to autologous bone marrow (BM) graft injected after irradiation. MBCP hollowed blocks were specially designed and implanted in tibia and femur bone before irradiation in a dog model. Implants were removed after 18 weeks. This is the first report of experiments performed after radiation delivery using high fractionated doses approximating usual treatment of SCC in human. The quality of the bone adjacent to implanted MBCP and the bone ingrowth's rates were evaluated. The qualitative and quantitative role of BM grafts associated with the MBCP implants was determined, using scanning electron microscopy linked to quantitative image analysis. A direct contact between newly formed bone and MBCP implants associated to BM graft was observed, without fibrous interposition. The new-bone formation was statistically increased inside the MBCP (P = 0.0126) by BM grafts. This study demonstrates that BM graft added to MBCP constitute an appropriate material to be considered in case of bone defect occurring in irradiated tissue, and could be foreseen for use after bone removal for oncologic obligations.