The effect of increased distraction frequency on soft tissues during limb lengthening in an animal model.

The purpose of this study was to compare the effect of distraction frequency on soft tissues. Ten rabbits underwent high-frequency, automated distraction at 1,440 increments per day, whereas five rabbits were manually distracted at a low frequency of three increments per day. The tibias were lengthened approximately 20% at a rate of 1.05 mm/day. The results indicate that all animals had decreased range of motion of the ankle; however, the high-frequency group fared better compared with the low-frequency group (p<0.01). In addition, the P1 latency of the somatosensory evoked potentials did not change in the high-frequency group, but was statistically higher for the low-frequency group (p<0.05). There was no significant difference found in the histologic studies of muscle of either group. Thus increasing the distraction frequency resulted in better range of motion of the ankle joint and maintained normal somatosensory evoked potentials.