Potential of an ultraporous β-tricalcium phosphate synthetic cancellous bone void filler and bone marrow aspirate composite graft

Abstract.

Autogenous cancellous bone is considered to be the best bone grafting material. Autogenous bone grafts provide scaffolding for osteoconduction, growth factors for osteoinduction, and progenitor stem cells for osteogenesis. However, the procurement morbidity, limited availability, and expense associated with the use of autogenous bone grafts are significant disadvantages. Allografts and xenografts lack the osteoinduction and osteogenesis properties of autogenous bone, and they introduce the potential for both transferring disease and triggering a host immune response. Synthetic bone grafts [hydroxyapatite or tricalcium phosphate(TCP)], while good platforms for osteoconduction, lack any intrinsic properties of osteoinduction and osteogenesis. A composite graft that combines synthetic scaffold with autogenous osteoprogenitor cells from bone marrow aspirate (BMA), a low-morbidity procedure, could potentially deliver the advantages of autogenous bone grafts without the disadvantages. A new ultraporous β-TCP construct, engineered using solution-derived nano-particle technology, may prove to be an ideal carrier for BMA in such a composite. The unique, interconnected macroporosity, mesoporosity, and microporosity of this synthetic cancellous bone void filler allows it to wick in cells and nutrients via enhanced capillarity. Preliminary canine data support this expectation, demonstrating bone formation that suggests good penetration of cells and nutrients. These results suggest that BMA cells, absorbed into such a scaffold, may remain viable, thereby potentially making such a composite a true synthetic replacement for autogenous cancellous bone.