Stimulation of bone formation by recombinant fibroblast growth factor-2 in callotasis bone lengthening of rabbits

Bone lengthening by callotasis is one of the most useful methods not only for the treatment of short extremities but also for extensive bone defects; however, the procedure takes a long time especially for the consolidation of the distracted callus. In this study, effects of a single local injection of recombinant human fibroblast growth factor-2 (FGF-2 or basic FGF) on callotasis bone lengthening were examined in rabbits. Ten days after the osteotomy at the middle of the tibia and the installment of an external fixator, the osteotomized site was distracted at a rate of 1.4 mm/day for 7 days, resulting in 9.8 mm lengthening. On the final day of distraction, 200 microg of FGF-2 in 150 microl of saline solution or vehicle alone was injected into the center of the distracted callus. Injection of FGF-2 increased bone formation at the distracted callus radiologically and histologically. A significant effect on bone mineral content (BMC) at the callus was observed as early as 2 weeks, and FGF-2 increased the BMC about twofold at 5 weeks after a normal remodeling process. We conclude that the callotasis method in combination with FGF-2 injection at the consolidation step could be clinically beneficial to shorten the bone lengthening period.