The Effect of Interposition Nerve Graft Length on Outcomes of Laryngeal Reinnervation

ABSTRACT Objective To evaluate the impact of interposition graft lengths on the efficacy of laryngeal reinnervation. Methods In an in vivo rabbit model, unilateral recurrent laryngeal nerve (RLN) resection was performed followed by immediate re‐anastomosis using interposition graft lengths of 0, 2, 4, and 6 cm ( N = 2 animals per length). After 4 months, thyroarytenoid (TA) muscles and RLNs were harvested and analyzed. Muscle fiber area was assessed using hematoxylin–eosin staining. Neuromuscular junctions (NMJs) were identified by immunohistochemistry for post‐synaptic acetylcholine receptors and categorized morphologically as pretzel shape (normally innervated), fragmented (partially innervated), or plaque‐like (degenerated). Axons within RLN segments were visualized using FluoroMyelin lipid‐fluorescent staining. Results Muscle fiber area tended to be decreased on the experimental side but did not differ significantly across graft lengths. Normal contralateral muscles showed 100% pretzel morphology. NMJ morphology progressively worsened with increasing graft length: 0 cm grafts (62% pretzel; 38% fragmented; 0% plaque), 2 cm (23%; 69%; 8%), 4 cm (15%; 54%; 31%), and 6 cm (18%; 36%; 46%). Axon count in the distal RLN segment as a percentage of axons in the proximal RLN segment similarly declined with graft length: 0 cm grafts (mean 136%), 2 cm (51%), 4 cm (19%), and 6 cm (17%). Conclusion Longer interposition grafts were associated with reduced axonal counts and increasingly abnormal NMJ morphology. These findings suggest longer interposition graft lengths may reduce laryngeal reinnervation outcomes. Level of Evidence n/a.