A new treadmill-type motorized walking belt machine for video recording of the rat's gait and sciatic functional index measurement. A comparative study with other methods

The sciatic functional index (SFI) is a remarkable tool to assess dysfunction and functional recovery of the sciatic nerve of rats. Usually measured on hind foot imprints on paper, a new method is now being proposed, by direct analysis of video recorded foot sole images obtained with a treadmill-type walking belt machine functioning with gait speed control (G1). Results were compared with the SFI measured on imprints on paper (G2) and on video recorded foot sole images obtained with a static see-through runway (G3). The right sciatic nerve of 19 adult female Wistar rats was crushed by the application of a controlled load. Impressions/images obtained both preoperatively and at weekly intervals for eight consecutive postoperative weeks were digitized, stored and analyzed in a computer loaded with specific software, the SFI being automatically calculated after measuring the appropriate parameters. SFI differed significantly between G1 and G2 and G1 and G3 (p < 0.05), but not between G2 and G3 (p > 0.05) during the first and second postoperative weeks, nonsignificant differences (p > 0.05) being observed for any comparison between groups during the third through eighth postoperative weeks. We conclude that the three methods yielded equivalent results from the third week onward, but both video recording methods (G2 and G3) permitted a more adequate early evaluation (first and second weeks), since the SFI parameters were more easily identifiable. Images obtained with the walking belt machine are more uniform and sharper, thus contributing to reduce the influence of biases observed with imprints on paper.