Custom implants for medialization laryngoplasty: a model that considers tissue compression

Abstract

Objective: Unilateral vocal fold paralysis can be treated with surgical medialization with a carved silastic implant. One challenge to this approach is anticipating the dimensions of the implant for adequate medialization. The purpose of this study was to develop a predictive model for implant design based on a patient's unique laryngeal anatomy and considering compression of the vocal fold.

Study design: Retrospective chart review, prospective cadaver study, and prospective patient study.

Methods: A retrospective chart review was performed on patients who received silastic medialization laryngoplasty with favorable outcome and who had preoperative computed tomography. Data including Voice Handicap Index, maximum phonation time, and implant dimensions were collected from medical records, and laryngeal measurements were taken from preoperative imaging. Measurements were taken from computed tomography scans of three cadavers who underwent laryngoplasty for this study. Tissue compression (TC) was calculated and analyzed. A model to predict successful implant dimensions was developed and applied prospectively in 16 patients.

Results: Eleven patients from the chart review and three cadavers were included. Of all laryngeal metrics, width of the vocal fold at maximal medialization was most strongly correlated to TC (r = 0.728). Linear regression was performed (y = 0.50x - 1.2, R(2) = 0.53, P = 0.005, F = 12.39). Of the prospective patients, 15 of 16 demonstrated complete glottis closure with the premeasured silastic implant.

Conclusions: Vocal fold compression by silastic implants is linearly correlated with vocal fold-width at maximal medialization. A predictive formula was generated to anticipate TC and was successful in designing custom implants for patients.

Keywords: Medialization laryngoplasty; Silastic; Thyroplasty; Vocal fold paralysis.