Characterization of the Vertical Stiffness Gradient in Cadaveric Human and Excised Canine Larynges.
Jacob Michaud-Dorko, Gregory R Dion, Charles Farbos de Luzan and 2 others
PMID 39244387WHAT IT FOUND
Both canine and human vocal fold tissue was stiffer at the lower edge than the upper edge.
In human tissue stiffness rose more toward the back than the front.
Key findings
01Canine and human vocal fold tissue showed a vertical stiffness gradient, with the inferior aspect stiffer than the superior aspect.
02At maximum indentation in the mid-coronal plane, unloading stiffness values were 4.6 kPa, 5.4 kPa, and 6.0 kPa for canine superior, medial, and inferior locations, and 3.2 kPa, 5.5 kPa, and 7.0 kPa for human locations.
03Stiffness increased away from the mid-coronal plane in both directions, and human vocal folds showed larger increases toward the posterior edge than toward the anterior edge.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study used only six canine and three human larynges, so the human findings may not represent a wide range of people. The human larynges came from older people with unknown exact age and gender, and tissue atrophy may have lowered measured stiffness. The tissue was tested after being cut and held in saline, not in a living person speaking, so the numbers may not match vocal fold behavior during phonation. The indentation measured stiffness under a slow press, not the fast air-driven vibration of speech. Cutting the larynx in half may have changed stiffness near the front of the vocal fold.
Declared interests
One author reported financial support from the National Institutes of Health under Grant No. R01DC009435. The other authors reported no known competing financial interests or personal relationships.
The easy way to misread this
Do not use these stiffness values to judge a patient's vocal fold health or choose a voice treatment. The study measured excised tissue under a slow mechanical press, not living vocal folds during speech.