Effect of magnitude and direction of force on laryngeal abduction: implications for the nerve-muscle pedicle graft technique.

The research article explores how the direction and strength of force applied on a crucial larynx component affects the treatment of recurrent laryngeal neuropathy through the nerve-muscle pedicle graft technique.

Objective and Methodology

• The objective of the researchers was to determine how the magnitude and direction of force applied on the muscular process of the left arytenoid cartilage influenced laryngeal abduction, a crucial aspect of treating recurrent laryngeal neuropathy.
• To conduct this study, the researchers used five larynges harvested from cadavers. They used a dead-weight force generator to apply a force at increments of 0.98N, ranging from 0 to 14.7 N onto the left muscular process. Each force was applied for a minute at different angles: 0, 10, 20, 30, 40, 50, 60, and 70 degrees.
• The researchers then digitally captured images of the rima glottis one minute after each force application. They evaluated the degree of left arytenoid abduction by measuring the distances between named biomarkers (‘lines 1-4’) and the right-to-left angle quotient (RLQ).

Findings

• The results showed that increasing the force progressively from 0 – 14.7N significantly lengthened all lines and increased the RLQ, suggesting an increase in abduction.
• The study found a significant interaction between the force applied and the angles. Application of forces greater than 7.84N (for lines 2-4 and RLQ) or beyond 11.76N (for line 1) at angles of 0, 10, 20, and 30 degrees led to significantly greater evasion than when the same forces were used at angles of 40, 50, 60, and 70 degrees.
• In terms of direction, the angles 0-30 degrees were found to be in line with the pull direction exerted by the lateral compartment of the CAD muscle, which plays a role in this study’s context.

Conclusions and Implications

• Based on the findings, it was concluded that in treatments of RLN using nerve-muscle pedicle grafts, the grafts should preferably be placed in the lateral compartment of the CAD muscle rather than in the medial compartment. This directive is based on the fact that greater laryngeal abduction was achieved with force directions conforming to those of the CAD muscle’s lateral compartment.
• The research provides valuable insights that can be used to guide surgeons in planning and implementing the nerve-muscle pedicle graft procedure more effectively. This potentially improves treatment outcomes for patients with recurrent laryngeal neuropathy.