The effect of age on peripheral motor nerve function after crush injury in the rat

Objective: To determine the ontogeny of functional recovery after peripheral nerve crush injury. Design: Comparative study in rats of varying ages. Materials and Methods: Sixty-second crush injury was performed on the left posterior tibial nerve. Control animals underwent either nerve transection or sham procedure. Nerve function was evaluated 2, 4, and 8 weeks following injury by walking track analysis. Print length ratio (PLR), (ratio of normal right-sided print length to experimental left-sided print length), was used to evaluate functional recovery. Measurements and Main Results: Two weeks after crush injury, adult rats experienced significantly greater functional impairment than both 4-day-old and 3-week-old animals (p < 0.05). Four weeks after injury, the difference in function between 4-day-old and adult rats and between 3-week-old and adult rats became insignificant. Complete recovery had been achieved by 8 weeks in all groups. Conclusions: These results demonstrate faster functional recovery after nerve injury in immature rats than in adults.