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Pearls and Pitfalls of Motion Analysis: Is There a Place for it in the Functional Evaluation of Sciatic Nerve Injury and Repair?
Jing Rui, MD; M. Brett Runge, PhD; Robert J. Spinner, MD; Michael J. Yaszemski, MD, PhD; Anthony J. Windebank; Huan Wang, MD, PhD
Mayo Clinic, Rochester, MN, USA
Purpose: Rat sciatic nerve injury is the dominant model used in peripheral nerve research. Video assisted gait kinetics analysis has gained much attention and shown ankle angle measurement during the gait cycle to be a sensitive method to assess function. In conduit repair of sciatic nerve defects, we found that previously reported kinematic measurements failed to be a sensitive indicator of function, due to the fact recovery in conduit repair is inferior and joint contracture is inevitable. The current study aims to explore the role of physiotherapy in mitigating joint contracture and to seek motion analysis indices that can sensitively reflect motor function.
Methods: Data were collected from 26 rats that underwent left sciatic nerve transection and conduit repair with a 1-cm gap. Postoperatively manual passive planter and dorsi-flexion of the ankle joint was applied twice a day with 100 repeats each time for a total of 8 weeks. High-speed video recording of gait kinetics was obtained preoperatively and at regular postoperative intervals using PeakMotus motion analysis system. Parameters regarding step length, phase duration and ankle angle were acquired and analyzed. Passive range of motion (PROM) of the ankle joint was measured with a goniometer.
Results: At each time point, maximum PROM of the left ankle was smaller than that of the right ankle. Stride length ratio (SLR, uninjured foot/injured foot) significantly decreased at immediate postop comparing to baseline (0.55± 0.11 vs 1.00±0.03). This parameter gradually recovered to 0.76±0.10 at endpoint evaluation and had a strong correlation with the postoperative time course. Percent swing of the normal paw (PSN, % of the total stride duration that the uninjured paw is in the air) reduced from baseline 50±2% to 40±3% immediate postop and gradually increased to 46±3% at endpoint. Propulsion angle (PA, ankle angle at opposite initial-contact minus ankle angle at mid-stance) was based solely on plantarflexor strength. This angle changed from 53.3±8.1° preop to 10.0±6.7° immediate postop and recovered to 22.8±10.9° at 20 weeks. Clearance angle (CA, ankle angle change from toe-off to mid-swing), which depended solely on dorsiflexor strength, dropped from 75.5±7.7° preoperatively to 0 after surgery and increased to 11.7±6.3° at 20 weeks.
Conclusions: Ankle joint contracture persisted despite rigorous physiotherapy. Parameters acquired from a 2D motion analysis system (i.e. SLR, PSN, PA and CA) could sensitively reflect nerve function impairment and recovery in the rat sciatic nerve conduit repair model despite the existence of joint contractures.
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