Role of growth factors in the incorporation of unloaded bone allografts inthe goat

Revision of a failed total joint replacement often demands bone grafting me thods to restore deficient bone stock. However, impaired allograft incorpor ation can be the result of inadequate host or graft properties. The stimula tion of bone healing with growth factors could provide a new approach to de al with this problem. The repeated sampling bone chamber was used in the go at to investigate the properties of bone allografts enriched with transform ing growth factor-beta, recombinant human bone morphogenetic protein-2, and basic fibroblastic growth factor under unfavorable vascular and nonloaded conditions. Ten goats each had three bone chambers implanted in the medial proximal tibia, Different carrier allograft bone preparations were used for each growth factor based on convention and previously reported results, Th e period between implantation and chamber harvest was 8 weeks. The concentr ations of the growth factors used was 0, 1, or 10 mu g of transforming grow th factor-beta 2, 0, 1, or 5 mu g of bone morphogenetic protein-2, and 0, 1 0, or 200 ng of basic fibroblastic growth factor, The specimens were analyz ed histomorphometrically for the amount of soft tissue ingrowth, bone ingro wth, and the number of osteoclasts, In all specimens, a resorption front gr ew into the graft followed by fibrovascular tissue and, in some instances, bone, In the 5 mu g of bone morphogenetic protein-2 specimens, larger amoun ts of soft tissue and woven hone were present, whereas in the specimens tha t received 10 mu g of transforming growth factor-beta 2, there was a decrea se in the amount of tissue and bone ingrowth, Two hundred nanograms of basi c fibroblastic growth factor had a negative effect on soft tissue formation but increased the amount of vascular elements containing erythrocytes. The number of osteoclasts was higher in the 5-mu g bone recombinant human morp hogenetic protein-2 specimens, In the clinical at ena with absence of good perigraft vascularization and loading, bone morphogenetic protein-2 may hav e a strong stimulatory effect on bone graft incorporation.