Supercharge End-to-Side Motor Transfer to a Long Nerve Graft to Enhance Motor Regeneration: An Experimental Rat Study

Background: Long nerve grafts are prone to chronic denervation, often resulting in unsatisfactory clinical outcomes. The authors aim to investigate whether supercharge end-to-side (SETS) motor nerve transfers to a long nerve graft can potentially enhance nerve regeneration and functional outcomes. Methods: A reversed long nerve graft was interposed between the C6 and the musculocutaneous nerve in 48 rats. The motor nerves near the C6 proximally and the musculocutaneous nerve distally were chosen for SETS transfer to the long nerve graft. There were four groups: (A) nerve graft only, (B) proximal SETS transfer, (C) distal SETS transfer, and (D) proximal and distal double SETS transfers. A grooming test was assessed at 4, 8, 12, and 16 weeks postoperatively. Biceps weight, compound muscle action potential amplitude, tetanic contraction force, and histomorphometric analysis of the musculocutaneous nerve were evaluated at 16 weeks. Results: Long nerve grafts that received SETS transfers (groups B, C, and D) showed superior results compared with the control group. Proximal SETS transfer had significantly better outcomes than distal SETS transfer in electrodiagnostic parameters, whereas double SETS transfer had the highest axonal count and biceps compound muscle action potential amplitude. Conclusion: SETS motor transfers to long nerve grafts can effectively improve functional outcome and optimize nerve graft regeneration to the target nerve. Clinical Relevance Statement: Long nerve grafts yield suboptimal functional results. The experimental study showed that SETS motor transfer to a long nerve graft improves muscle functional outcomes. A double motor SETS transfer provides the best results. Proximal SETS transfer might have more benefits over distal transfer.