title: Using tomography to diagnose occult ankle fractures.
abstract: OBJECTIVE
  To determine the incidence of occult ankle fractures and to determine whether an ankle effusion identified radiographically correlated with the presence of an occult fracture.
  
  
  METHODS
  Attending physicians in the emergency department of a university hospital prospectively identified patients with acute ankle injuries that produced ecchymosis or edema over two or more major ligaments of the ankle. Plain radiographs of these patients demonstrated ankle effusions without fractures. A consecutive sample of patients with acute ankle injuries was selected. Thirty-six of 1,151 patients were eligible to enter the study; 2 of these patients subsequently were excluded from the data analysis. All eligible patients underwent plain ankle tomography at 3-mm intervals in the coronal and sagittal planes. The types and frequencies of occult ankle fractures identified on plain film tomography were noted. The distention of the ankle joint capsule of enrolled patients was measured to determine if the degree of effusion correlated with the presence of an occult fracture.
  
  
  RESULTS
  The minimum incidence of occult fractures in the general population with ankle injuries was 1%. Twelve of 34 patients (35%) with acute, severe injuries had occult fractures. Depending on the size, an effusion was correlated with the presence of an occult fracture in 35% to 85% of the study population.
  
  
  CONCLUSIONS
  Plain film tomography should be used when evaluating ankle injuries if both edema or ecchymosis over two or more stabilizing ligaments and radiographic evidence of an effusion are present simultaneously.
authors.affiliation: Department of Emergency Medicine, Vancouver Hospital, British Columbia, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Ho
authors.forename: D G
authors.initials: DG
authors.lastname: Connell
authors.forename: D L
authors.initials: DL
authors.lastname: Janzen
authors.forename: A
authors.initials: A
authors.lastname: Grunfeld
authors.forename: T W
authors.initials: TW
authors.lastname: Clark
mesh_terms: D000208:Acute Disease; D000328:Adult; D016512:Ankle Injuries / Q000150:complications / Q000000981:diagnostic imaging*; D004438:Ecchymosis / Q000209:etiology; D004487:Edema / Q000209:etiology; D005122:Exudates and Transudates; D005260:Female; D050723:Fractures, Bone / Q000000981:diagnostic imaging*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013639:Tarsal Bones / Q000293:injuries*; D014057:Tomography, X-Ray Computed