Functional assessment in the rat by ground reaction forces

Although the rat sciatic nerve model is used extensively in the investigati on of repair techniques, and a variety of evaluation methods utilized to as sess the results, a means to measure directly and accurately the return of Function in these animals is absent. Histologic, histomorphometric, and ele ctrophysiologic methods can be reliable indicators of nerve regeneration bu t do not correlate to functional recovery. The purposes of this study were to develop apparatus to continuously measure ground reaction forces (GRF) a nd use GRF parameters in the assessment of gait parameters in normal rats p reoperatively and following peripheral nerve severance and repair. Three ne urorrhaphy methods: direct sciatic nerve repair, direct tibial nerve repair and double sciatic nerve repair simulating autograft, as well as a non-rep aired tibial nerve transection were evaluated. The testing apparatus was de signed to measure the spontaneous and voluntary effort of the rat with obje ctive data. Three orthogonal components - vertical, craniocaudal (braking a nd propulsion), and mediolateral - of the ground reaction force were measur ed. Preoperative data showed that vertical forces were comparable among the four limbs but propulsion and braking forces displayed significant differe nces. At 12 weeks, functional recovery was most evident in the direct tibia l nerve repair group and absent in the non-repaired tibial defect group. Di rect sciatic nerve repairs and sciatic nerve grafts resulted in lesser degr ees of improvement. Results indicated that the propulsive force is the opti mal. GRF parameter for evaluating recovery of useful function. (C) 2000 Els evier Science Ltd. All rights reserved.