Effect of distraction osteogenesis on the peripheral nerve: experimental study in the rat.

Distraction osteogenesis is the current method of choice for bone lengthening. Despite the gain in experience, various complications are reported, among them, adverse effects on peripheral-nerve function. In order to thoroughly investigate the effect of distraction on neural tissue, a distraction osteogenesis model in the rat was established, using the femur of 30 Sprague-Dawley rats. The animals were randomized in three groups, following different rates of distraction (0.5 mm, 1.0 mm, and 1.5 mm/day) for 50, 25, and 16 days, respectively, so that the final length of distraction was the same in all groups. The mean sciatic function index ranged near normal in all groups. All groups demonstrated decrease of conduction velocity and the area under the curve of the compound action potential, while morphologic alterations consisted of decrease in the number of axons and evidence of active degeneration. Animals in Groups 1 (0.5 mm/day) and 2 (1 mm/day) displayed comparable changes, while in Group 3 animals (1.5 mm/day), changes were significantly more adversely dramatic. The safest and fastest rate of distraction in this rat model was determined to be 1 mm/day.