title: Variability in radiographic medial clear space measurement of the normal weight-bearing ankle.
abstract: BACKGROUND
  Medial clear space (MCS) width on mortise radiographs of the ankle is commonly used by clinicians for determining the competence of the deltoid ligament in the Weber B supination-external rotation ankle fracture. Significant variability exists in the current literature regarding methods of obtaining this measure and definition of a normal measure in comparison with a pathologic state.
  
  
  METHODS
  Seventy-three paired bilateral ankle mortise radiographs that were without ankle pathology were retrospectively reviewed. MCS width at two separate locations (oblique and perpendicular) and superior clear space (SCS) were measured on digital radiographs. A Student's t test was used to compare mean values.
  
  
  RESULTS
  Mean values (± SD) were 3.2 (± 0.7)~mm for MCS oblique, 2.6 (± 0.7)~mm for MCS perpendicular, and 3.3 (± 0.6)~mm for SCS. A significant difference (p < .001) existed for all three measures between males and females. MCS oblique was statistically different than MCS perpendicular (p < .001) for all patients and for males and females independently. The mean difference between paired bilateral radiographs was 0.3 (± 0.2)~mm for MCS oblique, 0.6 (± 0.6)~mm for MCS perpendicular, and 0.2 (± 0.2)~mm for SCS.
  
  
  CONCLUSIONS
  MCS width has variability based on the location chosen for measurement and gender. Contralateral radiographic comparison of MCS should be routinely used to identify pathologic widening versus normal anatomic variation.
  
  
  CONCLUSIONS
  Use of single threshold values for MCS width as an operative indicator may produce a false-positive diagnosis of deltoid incompetence in Weber B supination-external rotation ankle fractures and possibly lead to unnecessary surgery.
authors.affiliation: Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Murphy
authors.forename: Anish R
authors.initials: AR
authors.lastname: Kadakia
authors.forename: Todd A
authors.initials: TA
authors.lastname: Irwin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000843:Ankle Joint / Q000000981:diagnostic imaging* / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011859:Radiography; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012727:Sex Characteristics; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult