Effect of magnitude and direction of force on laryngeal abduction: Implications for the nerve‐muscle pedicle graft technique

Abstract

The nerve-muscle pedicle graft technique is a treatment for recurrent laryngeal neuropathy (RLN), but the optimal placement of the pedicles within the cricoarytenoideus dorsalis (CAD) muscle is unknown. The magnitude and direction of force placed on the muscular process of the left arytenoid cartilage affects the magnitude of laryngeal abduction. Five larynges were harvested from cadavers. Using increments of 0.98 N, a dead-weight force generator applied a force of 0-14.7 N for 1 min each to the left muscular process at 0, 10, 20, 30, 40, 50, 60 and 70 degrees angles. The rima glottis was photographed digitally 1 min after each force had been applied. Distances between biomarkers (Lines 1-4) and right to left angle quotient (RLQ) were used to assess the degree of left arytenoid abduction. Increasing force from 0-14.7 N progressively and significantly increased the length of all lines and RLQ, indicating abduction. Furthermore, there was a significant interaction between force and angles. Applying forces of 7.84 N or greater (Lines 2-4 and RLQ) or 11.76 N or greater (Line 1) at angles 0, 10, 20 and 30 degrees resulted in significantly greater abduction than applying the same forces at 40, 50, 60 and 70 degrees. Angles of 0-30 degrees correspond with the direction of pull exerted by the lateral compartment of the CAD muscle. In RLN, nerve-muscle pedicle grafts should be placed preferentially in the lateral rather than in the medial compartment of the CAD muscle. The information presented can be used to assist surgeons in the planning and application of the nerve-muscle pedicle graft procedure.