How Long Does Muscle Reinnervation Take? Results Of Long Term Follow Up After Distal Nerve Transfers
Julie C Beveridge, MD1; Jaret Olson, MD2; Michael J Morhart, MD, M.Sc2; K. Ming Chan, MD3
1University of Alberta, Edmonton, AB, Canada, 2Division of Plastic and Reconstructive Surgery, University of Alberta, Edmonton, AB, Canada, 3Division of Physical Medicine & Rehabilitation, University of Alberta, Edmonton, AB, Canada
Introduction: It is common belief that peripheral nerves have the capacity to regenerate only up to 2 years after injury. Consequently, the follow up period in many clinical studies examining distal nerve transfers or grafts is less than 2 years. Furthermore, nerve repair cases with incomplete reinnervation after 2 years are often considered failures and a secondary procedure is subsequently performed. The goal of this study is to systematically evaluate the extent of reinnervation and functional recovery through long term follow up beyond the two-year postoperative period in distal nerve transfer patients.
Materials & Methods: Through retrospective chart review, we identified distal nerve transfer patients with post-operative follow-up periods of three years or more at a single academic center. Electrophysiological techniques were used to evaluate the presence of persistent muscle denervation, recent reinnervation and extent of motor unit recruitment. Functional recovery was quantified by evaluating MRC strength grade.
Results: Sixteen patients met the above criteria and were included in the study. Eleven of the 16 patients (69%) demonstrated evidence of progressive reinnervation of target muscles beyond the first two years post surgery. There was a statistically significant increase in electrophysiological changes reflective of reinnervation across all time points, as well as a significant increase in motor unit recruitment from 1 to 2 year (p=0.002) and between 3 and great than 3 year (p=0.022). These electrophysiological changes correlated with a statistically significant increase in MRC strength grade across all time points.
Conclusions: This study demonstrates continual muscle reinnervation and functional improvement after the first 2 years in patients with distal nerve transfers, which is much longer than traditionally believed. This data points to the importance of following patients for sufficiently long periods of time before the effects of distal nerve transfers can be fully judged. Consequently, sufficient follow up of patients with distal nerve transfers would help to avoid the pitfall of performing unnecessary secondary procedures.
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