Importance of crossover innervation in digital nerve repair demonstrated by nerve isolation technique.

This study was conducted to determine how testing of nerve repair using nerve isolation techniques compares with standard testing. Nerve isolation consisted of double-gloving, leaving the study finger free, and administering local anesthetic blocks to all other sensory contributions in the exposed digit. Ten patients with 13 single digital nerve repairs of equally severe injuries were studied at a mean of 41 months postoperatively. Standardized tests yielded an excellent result in 77% for static two-point discrimination (S2pd), 85% for moving two-point discrimination (M2pd), and 46.2% for Semmes-Weinstein monofilaments (SWMF). The same studies combined with nerve isolation yielded an excellent result in only 43% for S2pd, 43% for M2pd, and 0% for SWMF. These results indicate a statistically significant difference and the importance of crossover innervation from intact nerves in the long-term result of digital nerve repair. Nerve isolation study techniques are an important adjunct in assessing the outcome of nerve repair and are the only method of evaluating the true end result of nerve regeneration following neurorrhaphy.