The effect of duration of muscle denervation on functional recovery in the rat model.

The effect of long-term denervation on neuromuscular recovery was studied in a rat hind limb model. The posterior tibial nerve was transected and repaired immediately or after denervation periods of 2 weeks, or 1, 3, 6, 9, or 12 months. Six months following reconstruction excellent axonal regeneration was seen across all nerve repairs irrespective of periods of denervation. However, there was a precipitous and profound decrease in the recovery of both muscle mass and integrated motor function if the reconstruction was delayed for longer than 1 month. Rather than a progressive change proportional to the length of the denervation period, significant, more discrete changes occurred sometime after 1 month of denervation that precluded a full recovery of muscle mass. Integrated motor function quantified using walking track analysis was impaired even after immediate nerve repair.