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Functional Evaluation of Motor Nerve Recovery in the Rat: A Comparison of the Sciatic Functional Index, Ankle Angles and Isometric Tetanic Force
Joo-Yup Lee, MD, PhD; Guilherme Giusti, MD; Huan Wang, MD, PhD; Patricia F. Friedrich, AAS; Allen T. Bishop, MD; Alexander Y. Shin, MD
Mayo Clinic, Rochester, MN, USA
Purpose: To correlate the sciatic functional index (SFI) and ankle angles in video gait analysis with isometric tetanic muscle force measurement to define the utility of these methods for evaluating functional motor recovery in the rat sciatic nerve defect model.
Methods: Forty male Lewis rats with 10 mm segmental defect in the sciatic nerve were randomly divided into two experimental groups: group I was repaired with reversed autograft; group II received a collagen conduit (NeuraGen® 1.5 mm, Integra LifeSciences Corp., Plainsboro, NJ). Video gait analyses were performed at 0, 4, 8, 12 weeks, and SFI and ankle angles in four different walking phases were recorded. Isometric tetanic force of the tibialis anterior muscle was also measured at 12 weeks, and correlated with video gait analysis data.
Results: The SFI results were statistically different between groups at 8, 12 weeks, but did not correlate with isometric tetanic force. Significantly, the SFI could not be measured in 26% of the rats at 8 weeks and 59% of the rats at 12 weeks secondary to toe contractures. Among various ankle angle measurements, only the ankle angle in toe-off phase demonstrated significant differences between groups at 8, 12 weeks, and correlated well with isometric tetanic force.
Conclusion: Toe contractures occurred more frequently in rats with better nerve recovery, and interfered with evaluation of the motor recovery using the SFI method. Ankle angle in toe-off phase measured from video gait analysis is a useful parameter which reflects functional recovery of the muscle force.
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