title: Geometric morphometric shape analysis in an ovine model confirms that the upper esophageal sphincter is not round.
abstract: OBJECTIVE
  Dysfunction of the upper esophageal sphincter (UES) is a common cause of oral-pharyngeal dysphagia (OPD). Dilation is a primary treatment, although current techniques are subject to a high rate of failure and recurrence. Devices available for UES dilation are cylindrical and were designed to distend the round lumen of the esophagus. Our objective was to determine the cross-sectional dimension of the UES in an ovine model of OPD and compare it with that of the cervical esophagus.
  
  
  METHODS
  Prospective cadaveric animal study.
  
  
  METHODS
  Three-dimensional casts of the upper aerodigestive tract of 10 fresh cadaveric ewes were constructed using a platinum-cured liquid silicone polymer. Cross-sections at the level of the UES and cervical esophagus were digitized and mathematically compared using geometric morphometric shape analysis.
  
  
  RESULTS
  Consensus shape among all 10 animals revealed that the narrowest region of the maximally distended UES has a cross-sectional shape that resembles a kidney, whereas the cervical esophagus approximates a circle. The shape of the UES and cervical esophagus were significantly different (P < .0001), and surface area calculations demonstrated that an inscribed circle significantly underestimated the area implied by the kidney-shaped UES model.
  
  
  CONCLUSIONS
  Current dilators used to treat UES dysfunction are cylindrical and based on the assumption that the UES is round. This is the first report to empirically analyze the cross-sectional area of the UES utilizing an established ovine model. The data suggest that the cross-sectional area of the UES is shaped like a kidney, and currently available cylindrical dilators are suboptimal for UES distention.
authors.affiliation: Department of Otolaryngology/Head and Neck Surgery, University of California Davis, Sacramento, California 95817, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Cates
authors.forename: Emily K
authors.initials: EK
authors.lastname: Plowman
authors.forename: Omid
authors.initials: O
authors.lastname: Mehdizadeh
authors.forename: Kaicheng
authors.initials: K
authors.lastname: Yen
authors.forename: Amanda
authors.initials: A
authors.lastname: Domer
authors.forename: Michael
authors.initials: M
authors.lastname: Gilden
authors.forename: Peter C
authors.initials: PC
authors.lastname: Belafsky
mesh_terms: D000818:Animals; D003680:Deglutition Disorders / Q000473:pathology* / Q000628:therapy; D004106:Dilatation / Q000295:instrumentation; D004195:Disease Models, Animal; D016099:Endoscopy, Gastrointestinal; D004867:Equipment Design; D049631:Esophageal Sphincter, Upper / Q000473:pathology*; D005260:Female; D025341:Principal Component Analysis; D012756:Sheep