EFFECT OF CLODRONATE ON FRACTURE-HEALING IN DENERVATED RATS

The effect of clodronate on healing of the fracture of osteopenic bone was studied in rats. A total of 165 female rats (14+/-1 weeks, 216+/- 2 g) were divided into five fracture groups (n = 30), and a neurectomi zed group (n = 15). Osteopenia top) was induced by right sciatic neure ctomy 4 weeks before the fracture. Nonosteopenic (nop) rats were not o perated. A closed prepinned diaphyseal fracture of the right femur was done by three point bending method both to op and nop rats, and the l eft femur served as an unoperated control. All the fracture groups wer e divided into treatment (clodronate 10 mg/kg/day sc) and control (sal ine sc) groups, and the administration was continued throughout the st udy. The op rats were killed 2, 4, 8, and 12 weeks and nop rats 8 week s after the fracture. Fracture healing was examined by x-ray and bone- bending strength. Neurectomy reduced bone strength (p < 0.01) at 4 wee ks. Clodronate did not affect the bending strength of healing callus o f op rats at 2, 4, 8, or 12 weeks after fracture, but reduced the stre ngth of healing callus in nop rats (p < 0.05) at 8 weeks. Radiologic c allus width increased in clodronate-treated groups both in op (8 and 1 2 weeks, p < 0.001) and nop rats (8 weeks, p < 0.05) when compared wit h saline-treated groups. Clodronate did not affect normal bone strengt h. In conclusion, clodronate did not affect the bending strength of op fracture nor the strength of the control bones. The remodeling of the fracture was delayed with clodronate.