Selection of the donor nerve for end-to-side neurorrhaphy.

Object. The authors of other studies have reported that the selection of an agonistic donor nerve is required for recovering voluntary motor control after end-to-side nerve repair. In this experimental investigation, the authors' goal was to verify this assumption by performing end-to-side neurorrhaphy of the rat median nerve on its antagonistic radial nerve. Methods. The left median nerve in 10 adult female rats was repaired by end-to-side neurorrhaphy after epineuriotomy on the radial nerve at the middle of the brachium. The time course of median nerve functional recovery was then assessed using the grasping test until postoperative Week 30. Before removing the nerve, the surgical site was carefully explored to exclude contamination by the proximal nerve stump, and the functional anatomy of median and radial nerves was assessed by electrical stimulation. Repaired nerves were then processed for resin embedding, and semithin sections were obtained for nerve fiber histomorphometry by using the dissector method. Results. Repaired median nerves were repopulated by nerve fibers regenerating from the radial donor nerve as previously shown. Moreover, voluntary motor control of the flexor muscles innervated by the median nerve was progressively recovered beginning in postoperative Week 10 and reaching 42% of normal by Week 30. Conclusions. Contrary to previously reported data, recovery of voluntary motor function after end-to-side nerve repair can also be expected when an antagonistic nerve is used as a donor nerve.