Long-Term Effects of Fat Injection Laryngoplasty in Relation to the Injected Fat Volume in Patients With Unilateral Vocal Fold Paralysis

Published:September 17, 2022DOI:



      To evaluate the improvements in vocal function and glottal form before and after autologous fat injection laryngoplasty in relation to the injected total fat volume in patients with unilateral vocal fold paralysis.


      Clinical study.


      Seventy-three patients with unilateral vocal fold paralysis received fat injection laryngoplasty and were divided into low-volume injection (<3 mL; average, 2.0 mL) and high-volume injection (≥3 mL; average, 4.3 mL) groups. Voice function before and after fat injection laryngoplasty were examined by aerodynamics evaluations, pitch and intensity measurements, and acoustic analyses. The glottal form before and after fat injection laryngoplasty was determined by measuring the ratio of vocal fold bowing (bowing ratio) and the ratio of lengths between bilateral vocal process (width ratio) at an easy phonation under laryngeal endoscopic examination. The postoperative parameters were evaluated for a median period of four years after fat injection laryngoplasty. The differences between pre- and postoperative parameters were examined separately for each group by the paired t-test. For each variable, a comparison of the effects of surgery was conducted using an analysis of covariance model with the change between the pre- and postoperative values as a dependent variable and the preoperative value as a covariate.


      In both groups, all parameters of voice function and glottal form after surgery significantly improved in comparison to those before surgery. Maximum phonation time, amplitude perturbation quotient, and normalized noise energy for 0 to 4 kHz in the high-volume group improved more significantly in comparison to those in the low-volume group.


      As a rough guide for males, injection of more than 3 mL of autologous fat to the vocal muscle layer is recommended for reliable improvement of voice function in patients with unilateral vocal fold paralysis.

      Key Words


      AA (Arytenoid adduction), ANCOVA (Analysis of covariance), APQ (Amplitude perturbation quotient), BR (Bowing ratio), FIL (Fat injection laryngoplasty), HV (High volume), LV (Low volume), MFR (Mean flow rate), MPT (Maximum phonation time), NNEa (Normalized noise energy for 0 to 4 kHz), PPQ (Pitch perturbation quotient), RLNP (Recurrent laryngeal nerve paralysis), SPL (Sound pressure level), TP (Thyroplasty type I), UVFP (Unilateral vocal fold paralysis), WR (Width ratio)
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