Distraction osteogenesis using IGF-I after nerve microreconstruction

The discipline of limb lengthening has undergone numerous advances over the last few years. The neurologic complications surrounding this procedure are well established and described in the clinical setting, and can be deleterious for the patients in distraction osteogenesis protocols. The specific aims of the reported project were: 1) to determine the ability of IGF-I to enhance nerve regeneration in repaired nerves that are subjected to distraction only 4 weeks after nerve repair, and 2) to determine if a low dose of IGF-I applied at the time of the repair is neuroprotective to repaired nerves at this early time window. Forty adult male Sprague-Dawley rats were randomized into eight groups (n=5). Four groups (Groups A to D) underwent distraction of the femoral bone following sciatic nerve repair, and four groups served as controls (Groups E to H). Nerve reconstruction was achieved by end-to-end nerve repair (four groups, two with distraction [A, B] and two without [E, F]) and by interposition nerve grafting (four groups, two with distraction [C, D] and two without distraction [G, H]). A low dose of IGF-I was administered at the time of nerve microreconstruction. Distracted groups, despite the administration of IGF-I, demonstrated no signs of nerve regeneration, as assessed by sciatic functional index (SFI), electrophysiologic studies, and quantitative and qualitative histologic studies. Non-distracted groups showed signs of nerve regeneration. The 4-week time interval between nerve repair and distraction did not provide enough time for nerve regeneration to be completed, even if the repair was exposed to a low dose of IGF-1.