Osteopromotion by β-tricalcium phosphate/bone marrow hybrid implant for use in spine surgery

Study Design. Experimental animal study. Objective. Evaluate osteopromotive properties of a beta-tricalcium phosphate (TCP) implant with different osteogenic substances in an animal study. Summary of Background Data. Current research in spine surgery is focusing on resorbable bone implants because of the high morbidity after iliac crest graft harvesting. Therefore, several osteoconductive scaffolds are combined with osteoinductive substances. Methods. In 14 sheep, a critical size defect was performed on both tibiae. The sheep were randomized into 3 groups (4 sheep each) and a control group (2 sheep). In the treatment groups, the defects were filled with the beta-TCP scaffold impregnated with either venous blood, bone marrow from sternal aspiration, or a concentrated mononuclear cell suspension derived from sternal bone marrow aspiration. The sheep in each group were euthanized 6 and 12 weeks after the operation; the investigation included quantitative computerized tomography and histology. Results. The best bone formation occurred in the bone marrow group after 6 and 12 weeks, whereas no difference was found between the cell and venous blood groups. Only the bone marrow group showed bone formation inside the scaffold after 6 weeks. We conclude that a beta-TCP scaffold filled with bone marrow aspiration creates a biologic resorbable bone substitute with high osteopromoting capacity. Surprisingly, no better bone formation occurred in the concentrated cells group, which may be a result of technical reasons and needs to be further evaluated. Conclusions. The combination of beta-TCP and bone marrow has superior osteopromotive properties to venous blood or concentrated mononuclear cells and can be used effectively as a substitute to iliac crest graft.