Effects of time lapse on results of partial nerve injury repair.

Partial nerve severance is a problem in peripheral-nerve surgery. It should be repaired without tension for a good functional result. There is usually no trouble in repairing acute injuries. But, as time passes, it may be difficult to establish a proper end-to-end repair, and this cause more tension at the repair sites. In this study, the critical time lapse for a deleterious effect was evaluated. Thirty rats were used, with partial nerve severance repaired immediately or at 10 or 20 days later. At 2, 4, 8, 12, 20, and 28 weeks, functional assessment of nerve regeneration was performed using walking-track analysis. Functionally, the sciatic index values were very close to each other in the immediate and 10-day-delay group, but the difference between these groups and the 20-day-delay group was statistically significant. The study suggests a critical period of about 2 weeks after partial nerve section before irreversible changes occur. Although this is not applicable to human models, it implies further work on a primate model for determining a reliable time-lapse period.