title: Effect of head position on radiographic assessment of laryngeal tie-forward procedure in horses.
abstract: OBJECTIVE
  To assess the effect of head position on relative position of the larynx and hyoid apparatus in horses with palatal dysfunction, and to define a standard position for radiographic assessment of laryngeal tie-forward.
  
  
  METHODS
  Prospective clinical study.
  
  
  METHODS
  Adult horses (n=9) with palatal dysfunction.
  
  
  METHODS
  Left lateral radiographs of the larynx were obtained pre and postoperatively for 3 different head positions (flexed=90 degrees ; neutral=100 degrees ; extended=115 degrees ). Distance between thyrohyoid bone and thyroid cartilage was measured. Data were analyzed to investigate differences between head positions, and to compare differences between pre- and postoperative measurements.
  
  
  RESULTS
  Head position had a significant effect on relative position of the larynx and hyoid apparatus preoperatively. There was no significant difference in postoperative measurements of the 3 head positions. A significant difference between pre- and postoperative measurements was found with the head in the neutral or extended position whereas there were no significant differences between pre- and postoperative measurements using the flexed position.
  
  
  CONCLUSIONS
  Head position affects the relationship between the hyoid apparatus and larynx preoperatively, with greatest distance occurring when the head is extended. In a flexed position, it is not possible to ascertain whether laryngeal position has changed postoperatively.
  
  
  CONCLUSIONS
  A standardized head position is necessary when assessing the laryngeal tie-forward procedure radiographically. An extended head position is most useful for this assessment.
authors.affiliation: Department of Clinical Veterinary Science, University of Bristol, Bristol, UK. Laura.McCluskie@bris.ac.uk
authors.forename: Laura K
authors.initials: LK
authors.lastname: McCluskie
authors.forename: Samantha H
authors.initials: SH
authors.lastname: Franklin
authors.forename: J Geoffrey
authors.initials: JG
authors.lastname: Lane
authors.forename: W Henry
authors.initials: WH
authors.lastname: Tremaine
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Allen
mesh_terms: D000818:Animals; D005260:Female; D006734:Horse Diseases / Q000000981:diagnostic imaging* / Q000601:surgery; D006736:Horses; D007830:Larynx / Q000002:abnormalities / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D010160:Palate, Soft / Q000002:abnormalities / Q000000981:diagnostic imaging / Q000601:surgery; D010805:Physical Conditioning, Animal / Q000502:physiology; D011182:Postoperative Care / Q000662:veterinary; D011187:Posture / Q000502:physiology; D011300:Preoperative Care / Q000662:veterinary; D011446:Prospective Studies; D011859:Radiography; D015619:Respiratory System Abnormalities / Q000000981:diagnostic imaging / Q000601:surgery / Q000662:veterinary*