title: Accuracy and Measurement Error of the Medial Clear Space of the Ankle.
abstract: BACKGROUND
  Measurement of the medial clear space (MCS) is commonly used to assess deltoid ligament competency and mortise stability when managing ankle fractures. Lacking knowledge of the true anatomic width measured, previous studies have been unable to measure accuracy of measurement. The purpose of this study was to determine MCS measurement error and accuracy and any influencing factors.
  
  
  METHODS
  Using 3 normal transtibial ankle cadaver specimens, deltoid and syndesmotic ligaments were transected and the mortise widened and affixed at a width of 6 mm (specimen 1) and 4 mm (specimen 2). The mortise was left intact in specimen 3. Radiographs were obtained of each cadaver at varying degrees of rotation. Radiographs were randomized, and providers measured the MCS using a standardized technique.
  
  
  RESULTS
  Lack of accuracy as well as lack of precision in measurement of the medial clear space compared to a known anatomic value was present for all 3 specimens tested. There were no significant differences in mean delta with regard to level of training for specimens 1 and 2; however, with specimen 3, staff physicians showed increased measurement accuracy compared with trainees.
  
  
  CONCLUSIONS
  Accuracy and precision of MCS measurements are poor. Provider experience did not appear to influence accuracy and precision of measurements for the displaced mortise.
  
  
  CONCLUSIONS
  This high degree of measurement error and lack of precision should be considered when deciding treatment options based on MCS measurements.
authors.affiliation: 1 Harvard Combined Orthopaedic Surgery Residency Program, Boston, MA, USA.
authors.forename: Ogheneochuko
authors.initials: O
authors.lastname: Metitiri
authors.affiliation: 2 Beth Israel Deaconess Medical Center, Boston, MA, USA.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Ghorbanhoseini
authors.affiliation: 3 Boston Children's Hospital, Boston, MA, USA.
authors.forename: David
authors.initials: D
authors.lastname: Zurakowski
authors.affiliation: 2 Beth Israel Deaconess Medical Center, Boston, MA, USA.
authors.forename: Mary G
authors.initials: MG
authors.lastname: Hochman
authors.affiliation: 2 Beth Israel Deaconess Medical Center, Boston, MA, USA.
authors.forename: Ara
authors.initials: A
authors.lastname: Nazarian
authors.affiliation: 2 Beth Israel Deaconess Medical Center, Boston, MA, USA.
authors.forename: John Y
authors.initials: JY
authors.lastname: Kwon
mesh_terms: D000842:Ankle / Q000503:physiopathology*; D064386:Ankle Fractures / Q000503:physiopathology; D002102:Cadaver; D006801:Humans; D015588:Observer Variation; D000071066:Patient Reported Outcome Measures; D011859:Radiography; D012399:Rotation
keywords: accuracy; ankle fracture; medial clear space; mortise; syndesmosis