The effect of intermittent local heating on fracture healing in the distal tibia of the rabbit.

Two series of controlled experiments were carried out to investigate the effect of intermittent local heating on fracture healing in the distal tibia of the rabbit. In the first series, the distal tibia was fractured in a reproducible manner and then treated by compression plate fixation. Nine animals received intermittent local heating around the fracture site for 6 weeks postoperatively in comparison with 5 control animals. The mechanical strength of the healed tibia was then measured in a standardized 3-point bend test. Intermittent local heating produced stronger bones than the untreated controls in 6 of the 9 cases, a result which was marginally significant (P = 0.055). In the second series of experiments, a reproducible bone defect was created by drilling a 2 mm diameter hole through the distal tibia; compression plate stabilization was not required. Fourteen animals received intermittent local heating around the fracture site for 3 weeks postoperatively in comparison with 7 control animals. Intermittent local heating produced stronger bones than the untreated controls in 8 of the 14 cases, a result which was not significant (P greater than 0.1). It is concluded that intermittent local heating of the type studied has too small an effect on accelerating the rate of fracture repair to be clinically useful.