Electrical Muscle Stimulation (EMS) Does Not Influence Synkinetic Reinnervation In A Novel Rat Model Of Peripheral Nerve Injury And Repair
Joseph Catapano, MD, Michael P. Willand, MASc, PhD, Tessa Gordon, PhD, Gregory H. Borschel, MD.
University of Toronto, Toronto, ON, Canada.
Purpose: Recovery following nerve repair is limited by axon misdirection. Studies have shown that EMS following nerve repair reduces synkinetic reinnervation. Conclusions were based on functional measurements with no direct evidence. Here, we used a novel rat model to directly investigate whether EMS increases the proportion of motoneurons reinnervating original targets after injury.
Methods: The original soleus motoneuron pool was labeled with True-Blue. Following one-week, the right lateral gastrocnemius soleus nerve was transected and repaired, and the soleus muscle implanted with electrodes. One group received EMS with a natural activation paradigm. Two months later, the right soleus nerve was retrograde labelled with Fluoro-Ruby to label regenerated motoneurons. The contralateral uninjured lateral gastrocnemius and soleus nerves were labelled with True-Blue and Fluoro-Ruby respectively to compare the spatial distribution of the contralateral motoneuron pool with the injured side. The number of regenerated axons was counted with histomorphometry.
Results: 3D reconstructions of labelled motoneuron pools demonstrated the majority of motoneurons regenerating to the soleus muscle derived from the lateral gastrocnemius motoneuron pool. EMS did not increase the proportion of original soleus motoneurons regenerating towards the soleus muscle (EMS: 10.9±2.3% vs Sham: 15.5±9.9%). There were no differences in axons counts (EMS: 200±68 vs Sham: 163±47).
Conclusions: While studies suggest EMS reduces muscle atrophy, our model does not support the use of EMS to reduce axonal misdirection following nerve repair.
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