title: Diagnosing chronic diastasis of the syndesmosis: a novel measurement using computed tomography.
abstract: BACKGROUND
  Chronic diastasis of the syndesmosis has been recognized as a cause of persistent pain and dysfunction after a rotational ankle injury. Recently, there has been an increased effort to define the use of computed tomography (CT) imaging in making this diagnosis; however, no clear consensus has been reached on the best way to assess the anatomical integrity of the syndesmosis. In this retrospective case series, we have evaluated the diagnostic capability of 2 novel CT-based measurements.
  
  
  METHODS
  Fourteen patients with symptomatic syndesmotic instability received a bilateral ankle CT scan. Two measurements were performed. The first measurement was the angle subtended by 2 lines drawn tangent to the anterior and posterior surfaces of the distal tibia and lateral malleolus 1 cm above the talar dome. The second measurement was the area bound by these lines, the lateral tibia and the medial aspect of the lateral malleolus. The injured and contralateral sides were compared using a Wilcoxon rank sum test with a significance set at P ≤ .05.
  
  
  RESULTS
  When comparing the injured to the contralateral ankle, we found a significant decrease in the angular measurement of the syndesmosis (63.4 ± 6.1 degrees vs 68.4 ± 6.6 degrees; P = .018) and a significant increase in the area measurement (1.71 ± 0.44 cm(2) vs 1.21 ± 0.25 cm(2); P = .00003). Eleven of 14 patients had a smaller angular measurement, and all 14 had a larger area measurement in the injured ankle. All patients were confirmed to have instability via manual testing intraoperatively.
  
  
  CONCLUSIONS
  This study suggests that a comparison of angular and area measurements will help identify a diastasis of the syndesmosis in patients with persistent pain after a rotational ankle fracture. These measurements are straightforward to perform and rely on landmarks that are easy to identify.
  
  
  METHODS
  Level IV, diagnostic.
authors: University of Chicago Medical Center, Department of Orthopaedic Surgery and Rehabilitation Medicine, Chicago, Illinois.
authors: Gautam
authors: G
authors: Malhotra
authors: James
authors: J
authors: Cameron
authors: Brian C
authors: BC
authors: Toolan
mesh_terms: D000328:Adult; D016512:Ankle Injuries / Q000000981:diagnostic imaging*; D000843:Ankle Joint / Q000000981:diagnostic imaging*; D002908:Chronic Disease; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
keywords: ankle instability; computed tomography; diagnosis; diastasis; syndesmosis; trauma