title: Hypopharyngeal Wall Exposure within the Surgical Field : The Role of Axial Rotation of the Thyroid Cartilage during Anterior Cervical Surgery.
abstract: OBJECTIVE
  Esophageal/hypopharyngeal injury can be a disastrous complication of anterior cervical surgery. The amount of hypopharyngeal wall exposure within the surgical field has not been studied. The objective of this study is to evaluate the chance of hypopharyngeal wall exposure by measuring the amount of axial rotation of the thyroid cartilage (ARTC) and posterior projection of the hypopharynx (PPH).
  
  
  METHODS
  The study was prospectively designed using intraoperative ultrasonography. We measured the amount of ARTC in 27 cases. The amount of posterior projection of the hypopharynx (PPH) also was measured on pre-operative CT and compared at three different levels; the superior border of the thyroid cartilage (SBTC), cricoarytenoid joint and tip of inferior horn of the thyroid cartilage (TIHTC). The presence of air density was also checked on the same levels.
  
  
  RESULTS
  The angle of ARTC ranged from -6.9° to 29.7°, with no statistical difference between the upper and lower cervical group. The amount of PPH was increased caudally. Air densities were observed in 26 cases at the SBTC, but none at the TIHTC.
  
  
  CONCLUSIONS
  Within the confines of the thyroid cartilage, surgeons are required to pay more attention to the status of hypopharynx/esophagus near the inferior horn of the thyroid cartilage. The hypopharynx/esophagus at the TIHTC is more likely to be exposed than at the upper and middle part of the thyroid cartilage, which may increase the risk of injury by pressure. Surgeons should be aware of the fact that the visceral component at C6-T1 surgeries also rotates as much as when the thyroid cartilage is engaged with a retractor. The esophagus at lower cervical levels warrants more careful retraction because it is not protected by the thyroid cartilage.
authors.affiliation: Department of Neurosurgery, School of Medicine, Pusan National University, Busan, Korea.
authors.forename: Byung Kwan
authors.initials: BK
authors.lastname: Choi
authors.forename: Won Ho
authors.initials: WH
authors.lastname: Cho
authors.forename: Chang Hwa
authors.initials: CH
authors.lastname: Choi
authors.forename: Geun Sung
authors.initials: GS
authors.lastname: Song
authors.forename: Choongrak
authors.initials: C
authors.lastname: Kim
authors.forename: Hak Jin
authors.initials: HJ
authors.lastname: Kim