Maximum intraoperative elongation of the rat sciatic nerve with tissue expander: functional, neurophysiological, and histological assessment.

The purpose of this study was to assess the maximum rapid intraoperative elongation of the rat sciatic nerve with the use of tissue expander, and its possible functional recovery. One hundred and eight rats were divided into five groups, and their right sciatic nerves were expanded with a 10-cc, 12-cc, 14-cc, 16-cc, and 18-cc expander, respectively, for 1 h. The functional recovery of the nerve was assessed at intervals up to 3 months, using the sciatic function index (SFI), neurophysiological indices, and histology. The maximum intraoperative elongation was observed in group IV (16-cc volume of tissue expander), at about 23.83%. SFI decreased between the first and seventh postoperative days, but gradually recovered, reaching preoperative values in all groups according to the formulas of De Medinaceli et al. (Exp. Neurol. 77:634-643, 1982) and Bain et al. (Plast. Reconstr. Surg. 83:129-136, 1989). Latency and motor conduction velocity demonstrated deterioration after expansion, which peaked after surgery. Recovery was gradually completed by the end of the experiment. The histological findings indicated minor aberrations immediately after expansion and maximal demyelination with axonal disruption on day 15. The reparative process started by day 30 and continued until day 90, when almost no histological changes were observed. In conclusion, intraoperative nerve expansion successfully elongates the rat sciatic nerve up to 23.83%. But it causes functional and morphological abnormalities, which are of moderate to severe degree, are of short duration, and are reversible. Intraoperative nerve expansion might be a valuable solution in the treatment of short nerve gaps, but its clinical application still needs to be evaluated.