Dynamic nanomechanical analysis of the vocal fold structure in excised larynges

Objectives/Hypothesis: Quantification of clinical outcomes after vocal fold (VF) interventions is challenging with current technology. High-speed digital imaging and optical coherence tomography (OCT) of excised larynges assess intact laryngeal function, but do not provide critical biomechanical information. We developed a protocol to quantify tissue properties in intact, excised VFs using dynamic nanomechanical analysis (nano-DMA) to obtain precise biomechanical properties in the micrometer scale. Study Design: Experimental animal study. Methods: Three pig larynges were bisected in the sagittal plane, maintaining an intact anterior commissure, and subjected to nano-DMA at nine locations with a 250-μm flat-tip punch and frequency sweep load profile (10–105 Hz, 1,000 μN peak force) across the free edge of the VF and inferiorly along the conus elasticus. Results: Storage, loss, and complex moduli increased inferiorly from the free edge. Storage moduli increased from a mean of 32.3 kPa (range, 6.5–55.38 kPa) at the free edge to 46.3kPa (range, 7.4–71.6) 5 mm below the free edge, and 71.4 kPa (range, 33.7–112 kPa) 1 cm below the free edge. Comparable values were 11.6 kPa (range, 5.0–20.0 kPa), 16.7 kPa (range, 5.7–26.8 kPa), and 22.6 kPa (range, 9.7–38.0 kPa) for loss modulus, and 35.7 kPa (range, 14.4–56.4 kPa), 50.1 kPa (range, 18.7–72.8 kPa), and 75.4 kPa (range, 42.0–116.0 kPa) for complex modulus. Another larynx repeatedly frozen and thawed during technique development had similarly increased storage, loss, and complex modulus trends across locations. Conclusions: Nano-DMA of the intact hemilarynx provides a platform for quantification of biomechanical responses to a myriad of therapeutic interventions to complement data from high-speed imaging and OCT. Level of Evidence: NA Laryngoscope, 127:E225–E230, 2017.