The use of a detailed video-based locomotor pattern analysis system to assess the functional reinnervation of denervated hind limb muscles

Abstract

BackgroundSpinal cord injuries induce a critical loss of motoneurons followed by irreversible locomotor function impairment. Surgical approaches combined with neuroprotective agents effectively rescue the damaged motoneurons and improve locomotor function. Our aim was to develop a reliable method which is able to provide quantifiable and in-depth data on the locomotor recovery during skeletal muscle reinnervation. New methodSprague-Dawley rats underwent lumbar 4 ventral root avulsion and reimplantation followed by riluzole treatment in order to rescue the injured motoneurons of the damaged pool. Control animals were operated, but received no riluzole treatment. The locomotor pattern of the hind limb was recorded biweekly on a special runway equipped with high resolution and high speed digital cameras producing both lateral and rear views simultaneously. All together 12 parameters of the hind limb movement pattern were evaluated by measuring specific joint angles, footprints and gait parameters in single video frames. Four months after the operation Fast Blue, a fluorescent retrograde tracer was applied to the L4 spinal nerve in order to label the reinnervating motoneurons. ResultsOur results confirmed the sensitivity of our arrangement and established strong relationship between the functional improvement and the morphological reinnervation. Moreover, we developed a correction method to make the system tolerant to the differences in the weight, step duration and step length. Comparison with existing methodsThere are no commercially available cheap, multi-parametric analysing equipment to characterise the gait in its complexity. ConclusionsOur system offers a modular, adaptable and expandable analysis on the reinnervation of the limb musculature in rodents.