A technique to quantitate motor recovery following nerve grafting

Sixteen patients were evaluated retrospectively following grafting of an upper extremity peripheral nerve injury. In addition to the standard subjective muscle grading, the force of reinnervated muscle groups was quantitatively measured using force transducers, and reported relative to the contralateral side. Patients recovered a median motor grade of M3, which correlated to a 32% recovery of muscle force of the contralateral side. M3 and M4 motor grades encompassed a large range of actual muscle force: M3 correlated with a recovered force that ranged from 17% to 42%, M4 with a range of 66% to 79%. The percent force of motor recovery decreased significantly with longer delays to nerve grafting, even when controlling for the severity of the injury. Similarly, recovery of muscle force decreased when longer segments of nerve grafts were used. Testing the return of muscle strength after peripheral nerve injuries with a standardized objective system that compares function to the uninjured side enhances the sensitivity of evaluating nerve regeneration and provides a measurement system that can facilitate the comparison of different nerve repair techniques.