The Potential of Viable Cells in Autologous Bone Grafts in a Goat Transverse Process Model

Introduction: INTRODUCTION Posterior spinal fusion is a well-known, procedure in spinal surgery. The golden standard to achieve fusion remains autologous bone grafting. Although the exact mechanism of bone formation after grafting is unclear, there are some clues on the processes involved. New bone is originating and progressing from the decorticated processes by (a combination of ) osteoconduction, osteoinduction and osteogenesis. After months the bone frontiers meet to bridge the gap. An intriguing aspect regarding the functioning of the autologous bone graft is the role of the viable cells that are present. Some studies have shown the osteogenic potential of cells in bone chips and in clinically sized grafts after intramuscular implantation.1,2 However, since the grafted bone will be deprived of vascularization for weeks, it is likely that the majority of cells cannot survive. In addition, the inflammatory phase of the local bone healing response will probably remove most transplanted cells. With the emergence of cell-based bone tissue engineering, the role of the cells in clinically sized implants has gained new interest. Previously we investigated such constructs of bone forming cells with porous ceramics, in a goat transverse process model.3 In this model a cassette that contains several conditions is placed on the decorticated transverse process. Bone formation in these conditions is considered representative of the initial bone formation in intertransverse spinal fusion. We observed an obvious effect of added cells only at the muscular side of the implants where, contrary to the controls, abundant new bone had formed. On the side in contact with the transverse process, bone formation was hardly influenced by the cells. It was concluded that although viable cells do have the potential to yield bone, their presence may be irrelevant in tissue engineered spinal fusion. In the current study, we studied the role of viable cells specifically in the autologous bone graft. We investigated the yield and dynamics of bone formation in vital and devitalized grafts in the transverse process model.