title: Modulating phonation through alteration of vocal fold medial surface contour.
abstract: OBJECTIVE
  1) To test whether alteration of the vocal fold medial surface contour can improve phonation and 2) to demonstrate that implant material properties affect vibration even when implantation is deep to the vocal fold lamina propria.
  
  
  METHODS
  Induced phonation of excised human larynges.
  
  
  METHODS
  Thirteen larynges were harvested within 24 hours postmortem. Phonation threshold pressure (PTP) and flow (PTF) were measured before and after vocal fold injections using either calcium hydroxylapatite (CaHA) or hyaluronic acid (HA). Small-volume injections (median, 0.0625 mL) were targeted to the inferomedial aspect of the thyroarytenoid muscle. Implant locations were assessed histologically.
  
  
  RESULTS
  The effect of implantation on PTP was material dependent. CaHA tended to increase PTP, whereas HA tended to decrease PTP (Wilcoxon test, P = .00013 for onset). In contrast, the effect of implantation on PTF was similar, with both materials tending to decrease PTF (P = .16 for onset). Histology confirmed implant presence in the inferior half of the vocal fold vertical thickness.
  
  
  CONCLUSIONS
  Taken together, these data suggested the implants may have altered the vocal fold medial surface contour, potentially resulting in a less convergent or more rectangular glottal geometry as a means to improve phonation. An implant with a closer viscoelastic match to vocal fold cover is desirable for this purpose, as material properties can affect vibration even when the implant is not placed within the lamina propria. This result is consistent with theoretical predictions and implies greater need for surgical precision in implant placement and care in material selection.
authors.affiliation: Departments of Otolaryngology-Head and Neck Surgery, University of Texas Southwestern Medical Center, Dallas, Texas, USA. ted.mau@utsouthwestern.edu
authors.forename: Ted
authors.initials: T
authors.lastname: Mau
authors.forename: Joseph
authors.initials: J
authors.lastname: Muhlestein
authors.forename: Sean
authors.initials: S
authors.lastname: Callahan
authors.forename: Roger W
authors.initials: RW
authors.lastname: Chan
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D017886:Durapatite / Q000494:pharmacology; D005260:Female; D006801:Humans; D006820:Hyaluronic Acid / Q000494:pharmacology; D007821:Laryngeal Muscles / Q000502:physiology; D007830:Larynx / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009092:Mucous Membrane / Q000502:physiology / Q000601:surgery; D010699:Phonation / Q000502:physiology*; D011312:Pressure; D019736:Prostheses and Implants; D018709:Statistics, Nonparametric; D020858:Tissue and Organ Harvesting; D014732:Vibration; D014827:Vocal Cords / Q000473:pathology / Q000502:physiology* / Q000601:surgery*; D014833:Voice Quality
chemical_list: D006820:Hyaluronic Acid; D017886:Durapatite