Preliminary clinical study of the arytenoid cartilage abduction grades after prosthetic laryngoplasty with cricoarytenoideus dorsalis myectomy in racehorses.

Overview

• This study evaluates the effects of adding a cricoarytenoideus dorsalis (CAD) muscle removal (myectomy) to standard prosthetic laryngoplasty surgery in racehorses suffering from recurrent laryngeal neuropathy (RLN).
• The main focus was to compare the arytenoid cartilage abduction grades after surgery both short-term and long-term between horses treated with the standard surgery and those treated with the modified surgery including CAD myectomy.

Background

• Recurrent laryngeal neuropathy (RLN) is a common condition in racehorses causing paralysis of the arytenoid cartilage, resulting in respiratory noise and impaired performance.
• The standard surgical treatment is prosthetic laryngoplasty (PL), which helps abduct the arytenoid cartilage to improve airflow.
• The cricoarytenoideus dorsalis (CAD) muscle is responsible for arytenoid abduction; however, in RLN its function is impaired.
• This study investigates whether removing the CAD muscle during surgery (CAD myectomy) improves postoperative arytenoid abduction by reducing dynamic forces on the prosthesis over time.

Methods

• Records from January 2019 to December 2023 were reviewed retrospectively.
• Horses with RLN were grouped into two: those treated with standard prosthetic laryngoplasty (PL) and those with a modified procedure including complete CAD muscle myectomy (modified myectomy laryngoplasty).
• Endoscopic arytenoid abduction grades were assessed after anesthetic recovery at two time points: short term (7-10 days post-op) and long term (80-90 days post-op).
• A telephone questionnaire was used to gather additional clinical data about athletic performance and return to racing.

Key Findings

• Older horses (4-5 years) presented with significantly higher grades of RLN compared to younger horses (2-3 years), although age did not affect long-term outcomes post-surgery.
• Horses treated with the modified procedure (PL + CAD myectomy) showed:
  • Significantly better long-term arytenoid abduction grades compared to those treated with PL alone.
  • 62.6% maintained a grade 2 abduction long-term, indicating better airway patency.
  • Mean abduction grade in the modified myectomy group was 2.38 versus 3.13 in the standard PL group, demonstrating superior functional retention.

Conclusions and Clinical Implications

• Removing the CAD muscle during laryngoplasty likely reduces the mechanical impact on the prosthetic suture over time, aiding sustained arytenoid abduction.
• This modified surgical technique may decrease the risk of early and long-term loss of arytenoid abduction and improve clinical outcomes in racehorses with RLN.
• The study provides useful clinical reference data for future research examining how CAD muscle dynamics contribute to postoperative loss of arytenoid function.

Limitations and Future Directions

• This was a retrospective study and could be influenced by selection bias and limited control over variables.
• The study relied on endoscopic grading and telephone questionnaires rather than objective performance metrics alone.
• Further prospective, controlled studies including biomechanical analysis are needed to fully quantify the role of CAD muscle in prosthetic failure and abduction loss.
• Longer follow-up and larger sample sizes could help confirm clinical benefits and safety of CAD myectomy additions.