Viscoelastic measurements after vocal fold scarring in rabbits--short-term results after hyaluronan injection.
CONCLUSIONS
The scarring model resulted in significant damage and elevated viscoelasticity of the lamina propria. Hyaluronan preparations may alter viscoelasticity in scarred rabbit vocal folds.


OBJECTIVE
Vocal fold scarring results in stiffness of the lamina propria and severe voice problems. The aims of this study were to examine the degree of scarring achieved in the experiment and to measure the viscoelastic properties after injection of hyaluronan in rabbit vocal folds.


METHODS
Twenty-two vocal folds from 15 New Zealand rabbits were scarred, 8 vocal folds were controls. After 8 weeks 12 of the scarred vocal folds received injections with 2 types of cross-linked hyaluronan products and 10 scarred folds were injected with saline. After 11 more weeks the animals were sacrificed. After dissection, 15 vocal folds were frozen for viscoelastic measurements, whereas 14 vocal folds were prepared and stained. Measurements were made of the lamina propria thickness. Viscoelasticity was measured on intact vocal folds with a linear skin rheometer (LSR) adapted to laryngeal measurements.


RESULTS
Measurements on the digitized slides showed a thickened lamina propria in the scarred samples as compared with the normal vocal folds (p<0.05). The viscoelastic analysis showed a tendency to stiffening of the scarred vocal folds as compared with the normal controls (p=0.05). There was large variation in stiffness between the two injected hyaluronan products.
Hertegård
S
S
Department of Logopedics and Phoniatrics, Karolinska Institute, Huddinge University Hospital, Sweden. stellan.hertegard@klinvet.ki.se
Dahlqvist
A
A
Goodyer
E
E
D000276:Adjuvants, Immunologic / Q000627:therapeutic use*; D000818:Animals; D002921:Cicatrix / Q000188:drug therapy*; D004195:Disease Models, Animal; D004548:Elasticity / Q000187:drug effects; D006820:Hyaluronic Acid / Q000031:analogs & derivatives / Q000627:therapeutic use*; D020007:Implants, Experimental; D007820:Laryngeal Mucosa; D011817:Rabbits; D014783:Viscosity / Q000187:drug effects; D014827:Vocal Cords / Q000187:drug effects* / Q000293:injuries* / Q000503:physiopathology
D000276:Adjuvants, Immunologic; C445362:hylan-B gel; D006820:Hyaluronic Acid; C445361:Restylane