Assessing Injectate Volume in Injection Laryngoplasty Using Low-Cost Handheld Ultrasonography: Feasibility Study in an Ex Vivo Porcine Model.

Objectives/hypotheses: To evaluate the utility of low-cost handheld ultrasound in measuring volumes of injected material in injection laryngoplasty (IL) using an ex vivo porcine model.

Study design: Feasibility study.

Methods: Two different injection volumes (0.375 and 0.75 mL) and two types of materials (hyaluronic acid (HA) and calcium hydroxyapatite (CaHA)) were injected under direct visualization into porcine vocal folds. Seven replicates were performed for each of the four experimental groups. Cross-sectional longest and shortest dimensions were measured with ultrasound in the paramedian position. The correlation between injected volume and measured cross-sectional area by material type was assessed by ANCOVA.

Results: Injections of HA and CaHA into porcine vocal folds were able to be observed with US. Measured cross-sectional area significantly increased with greater volumes of injectate (0.375 mL: 0.29 ± 0.11 cm², 0.750 mL: 0.38 ± 0.16 cm²; P = 0.0151). While measured cross-sectional areas were marginally lower for HA compared to CaHA at both levels of volume injected, this was not statistically significant (P = 0.0875). Similarly, material type did not affect the relation between measured area and injected volume (P = 0.8805).

Conclusions: Ultrasound measurements may be feasible in assessing the injectate amount in vocal folds injection augmentation. This may be useful in situations where residual injectate amount in the vocal folds is important for clinical decisions, such as timing of thyroplasty after IL. Further clinical studies may elucidate the utility of ultrasound measurements of vocal fold injectate in relation to voice outcomes and stroboscopic findings.

Level of evidence: 5: