Bone Abstracts

Autogenous bone graft has been used in the treatment of a fracture, non-union, and bone defect. However, bone graft substitutes have been developed and used because of the limited amount or donor site morbidity of the autogenous bone graft. Many kinds of bone graft substitutes including osteoconductive materials and osteoinductive materials are used for improving bone healing. Osteoconductive materials help to provide a three-dimensional structure to support the ingrowth of the capillaries, perivascular tissues, and osteoprogenitor cells from the host bone. Osteoconductive materials are calcium phosphate ceramics such as hydroxyapatite, tricalcium phosphate and bicomposite of both materials, calcium sulfate and bioactive glass-ceramics. Osteoinductive materials induce the osteoprogenitor cells to form new bone by supporting mitogenesis of the undifferentiated perivascular mesenchymal cells. The most common osteoinductive materials are recombinant bone morphogenetic proteins.

The aim of this lecture is to introduce osteoconductive materials such as artificial hydroxyapatite, tricalcium phosphate, CaO-SiO₂-P₂O₅-B₂O₃ glass-ceramics, whose development I have been involved in. Artificial hydroxyapatite and tricalcium phosphate have been used as bone graft extenders. CaO-SiO₂-P₂O₅-B₂O₃ glass-ceramics can be used as intervertebral disc spacers for the interbody fusion surgery. In addition, E. coli-derived rhBMP-2 was produced. E. coli-derived rhBMP-2 has the advantage of lower manufacturing costs than the existing Chinese hamster ovary cell-derived rhBMP-2 because of mass production. We proved the osteoinductivity of E. coli-derived rhBMP-2 using various animal models such as the rabbit posterolateral fusion model, the mini-pig anterior lumbar interbody fusion model and the mini-pig lumbar posterolateral fusion model. Recently, we performed a clinical trial in patients with degenerative lumbar spine. Finally, the osteoinductivity of AB204, which was created from chimeric ligands of rhBMP-2 and activin-A with segmental gene cloning methods, was confirmed. The osteoinductivity of AB204 was significantly higher than that of rhBMP-2.