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Impact of Vertical Stiffness Gradient on the Maximum Divergence Angle
Author(s) -
Farbos de Luzan Charles,
Maddox Alexandra,
Oren Liran,
Gutmark Ephraim,
Howell Rebecca J.,
Khosla Sid M.
Publication year - 2021
Publication title -
the laryngoscope
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.181
H-Index - 148
eISSN - 1531-4995
pISSN - 0023-852X
DOI - 10.1002/lary.29345
Subject(s) - materials science , stiffness , phonation , coronal plane , closing (real estate) , fold (higher order function) , glottis , vocal folds , viscoelasticity , divergence (linguistics) , anatomy , composite material , larynx , medicine , mechanical engineering , political science , law , audiology , engineering , linguistics , philosophy
During vocal fold vibration, the medial surface of both folds forms a convergent shape during opening and a divergent shape during closing. A greater maximum divergence angle is associated with greater closing forces which will increase the closing speed of the glottis. An increased closing speed results in a greater acoustic intensity and greater vocal efficiency. Indentation testing showed that as the strain increases, the inferior aspect of the folds becomes stiffer than the superior aspect, resulting in the vertical stiffness gradient (VSG). We hypothesize that a reduction of the vertical stiffness gradient will reduce the maximum divergence angle. Methods Four excised canine larynges were tested. Stress–strain curves of the superior and inferior aspects of the fold in the mid membranous plane of the baseline larynges were taken using the indentation method. Calcium hydroxylapatite (CaHA) crystals were then injected into the superior aspect of the fold. The stress–strain tests were repeated. Particle imaging velocimetry (PIV) of the intraglottal velocity fields was performed in three larynges at different subglottal pressures in the mid coronal plane for the baseline and CaHA‐injected larynges. Results CaHA injection reduced the inferior–superior stiffness gradient in all larynges. The maximal divergence angle was markedly reduced. In some cases, there was not a divergent angle. Discussion Marked reduction of the vertical stiffness gradient significantly reduces the maximum divergence angle. Clinical implications will be discussed. Level of Evidence NA Laryngoscope , 131:E1934–E1940, 2021