Long-term acoustic comparison of thyroplasty versus autologous fat injection

Medialization by thyroplasty or intracordal autologous fat injection provides voice improvement in patients with unilateral vocal fold paralysis. Thyroplasty is considered a "permanent" medialization, whereas fat injection is considered "temporary" because of reabsorption. The objective of this study was to compare the evolution of acoustic parameters for these procedures over 1 year and to evaluate the results of fat injection at 2 years.

From 1994 to 1998, 46 consecutive patients (17 women and 29 men) were treated exclusively by intracordal injection of autologous fat, and then from 1999 to 2002, 48 consecutive patients (19 women and 29 men) were treated with the Montgomery Thyroplasty Implant System or Gore-Tex thyroplasty. Each patient's voice was prospectively recorded before operation and at 1,3, 12, and 24 months after operation. Six patients (13%) in the injection group underwent a second injection, and 1 patient (2%) in the thyroplasty group underwent revision surgery. Jitter, shimmer, and noise-to-harmonics ratio (NHR) were calculated for a 1000-ms midvowel segment of the vowel /a/.

One month after operation, jitter, shimmer, and NHR were significantly improved in both groups (Wilcoxon's test, p < 0.05 in all cases). Jitter and shimmer did not change significantly between 1 and 3 months or between 1 and 12 months (p > 0.05). The NHR had improved at 12 months in both groups (injection, p = 0.0004; thyroplasty, p = 0.0178) and at 24 months in the injection group (p = 0.0076). No significant difference was noted between the two techniques before operation or at 1, 3, or 12 months after operation (Mann-Whitney test, p > 0.05). Jitter and shimmer had not changed significantly after 24 months in either group. At 24 months, there was no difference in acoustic parameters between the two treatment groups.

The two techniques provided comparable objective acoustic voice improvement. At 2 years, autologous fat injection provides long-term acoustic voice improvement comparable to that of thyroplasty, but it has a higher rate of revision surgery.