Convergent end-to-end neurorrhaphy: An alternative technique for dual innervation of the gastrocnemius muscle in rats

Abstract

Introduction Muscle contraction generated by electrical impulses simultaneously originating from two different neural sources may be an interesting treatment alternative for long term facial palsy. An experimental model was designed to compare single and dual innervation of the gastrocnemius muscle (GM) in rats. Methods Fifty adult Wistar rats underwent transection of their right peroneal nerve and were divided into five groups (n = 10): control (C), tibial nerve section (TS), tibial nerve primary end-to-end neurorrhaphy (PEE), tibial nerve primary repair associated with end-to-side peroneal-to-tibial nerve transfer (PRES), and tibial nerve repair by convergent end-to-end (CEE) neurorrhaphy between the proximal stumps of the tibial and peroneal nerves to the distal stump of the tibial nerve. The outcomes were assessed 12 weeks after the experiment by walking track, electromyography, GM mass index, and histomorphometric analysis of the distal tibial nerve. Results The functional recovery of the PRES (-33.77 +/- 24.13) and CEE (-42.15 +/- 31.14) groups was greater (P < 0.003) than the PEE group (-80.26 +/- 17.20). The CEE group (18.35 +/- 7.84) showed greater amplitude (P = 0.006) than the PEE group (8.2 +/- 4.64). There was no difference in the muscle mass index among the reinnervation groups (P > 0.705). Histologic analysis revealed greater (P < 0.002) axonal density in the CEE group (126.70 +/- 15.01) compared to PEE (99.70 +/- 12.82) and PRES (92.00 +/- 19.17) groups. Conclusions The dual innervation techniques showed earlier and greater functional recovery of the GM than did the single innervation technique. The CEE group showed a 40% higher number of regenerated axons in the distal tibial nerve stump.