Prefabricated muscle flap including bone induced by recombinant human bone morphogenetic protein-2: an experimental study of ectopic osteoinduction in a rat latissimus dorsi muscle flap.

For skeletal reconstruction, a vascularised bone graft is both reliable and useful, but some sacrifice usually occurs at the skeletal donor site. In the search for our alternative, we investigated ectopic osteoinduction by bone morphogenetic protein in a rat muscle flap, to prefabricate a muscle flap that included bone. Right latissimus dorsi muscle flaps were prepared in 16 rats. Recombinant human bone morphogenetic protein-2 (rhBMP-2; 2, 10 and 50 micrograms) mixed with atelopeptide type I collagen (3 mg) as the carrier was wrapped with the tip of the latissimus dorsi muscle flap. Three weeks later, ectopic osteoinduction in the latissimus dorsi muscle flap was investigated radiologically, histologically and biochemically. A radiological oval shadow was observed in each animal in each rhBMP-2-implanted group. The volume of the oval shadow area in the muscle flap was dependent upon the dosage of rhBMP-2. It indicated that on ectopic osteoinduction by rhBMP-2 in the muscle flap, induced trabeculae were circularly constructed at the margins of the lump. The radio-opacity of the oval shadows was almost equal in all rhBMP-2-implanted groups, and the shadow areas depended on the dosage of rhBMP-2. The biochemical indices of osteogenesis, ALP activity and Ca content in the lump were dependent upon the dosage of rhBMP-2. This study showed that ectopic osteoinduction occurred in the rat latissimus dorsi muscle flap and depended upon the dose of rhBMP-2. Wrapping rhBMP-2 mixed with atelopeptide type I collagen with the tip of a latissimus dorsi muscle flap could create a prefabricated muscle flap that included bone.