A Novel Surgical Approach for the Reconstruction of Critical-Size Mandibular Defects Using Calcium Sulphate/Hydroxyapatite Cement, BMP-7 and Mesenchymal Stem Cells-Histological Assessment

Abstract

A novel construct has been developed to induce bone formation within a pedicle muscle flap. A critical size defect (20 × 15 mm2) was created in the mandible of ten rabbits. The masseter muscle was adapted to fill the surgical defect and a combination of calcium sulphate/hydroxyapatite cement (CERAMENT™ | SPINE SUPPORT), BMP-7 and rabbits' mesenchymal stromal cells (rMSCs) was injected into the muscle tissue. Bone regeneration was evaluated 3 months after surgery. Limited areas of bone formation anatomically bridged the defect, despite the new bone forming throughout the muscle and within the connective tissue surrounding the remnants of the cement. The bone was thicker in the bucco-lingual direction compared to the contra lateral (non-operated) side. Quantitative histomorphometry assessment showed that the average bone surface area was 21.2 ± 6.0 mm2, this was significantly greater than that of the contra-lateral non-operated control side. The calculated amounts of residual cement and soft tissue or spaces were 20 ± 12% and 41 ± 10%, respectively. The average mineral apposition rate (MAR) was 1.92 μm/day. The findings demonstrated the remarkable potential of the use of local muscle flaps for injectable bio-cement loaded with BMP and seeded with rMSCs to induce bone formation for the reconstruction of bony defects.