title: Dynamic Stress Testing Is Unnecessary for Unimalleolar Supination-External Rotation Ankle Fractures with Minimal Fracture Displacement on Lateral Radiographs.
abstract: BACKGROUND
  This study aimed to identify factors from standard radiographs that contributed to the stability of the ankle mortise in patients with isolated supination-external rotation fractures of the lateral malleolus (OTA/AO 44-B).
  
  
  METHODS
  Non-stress radiographs of the mortise and lateral views, without medial clear space widening or incongruity, were prospectively collected for 286 consecutive patients (mean age, 45 years [range, 16 to 85 years]), including 144 female patients (mean age, 50 years [range, 17 to 85 years]) and 142 male patients (mean age, 40 years [range, 16 to 84 years]) from 2 trauma centers. The radiographs were analyzed for fracture morphology by 2 orthopaedic surgeons, who were blinded to each other's measurements and to the results of external rotation stress radiographs (the reference for stability). Factors significantly associated with ankle mortise stability were tested in multiple logistic regression. Receiver operating characteristic analyses were performed for continuous variables to determine optimal thresholds. A sensitivity of >90% was used as the criterion for an optimal threshold.
  
  
  RESULTS
  According to external rotation stress radiographs, 217 patients (75.9%) had a stable injury, defined as that with a medial clear space of <5 mm. Independent factors that predicted stable ankle mortise were female sex (odds ratio [OR], 2.5 [95% confidence interval (CI), 1.4 to 4.6]), a posterior diastasis of <2 mm (corresponding with a sensitivity of 0.94 and specificity of 0.39) on lateral radiographs (OR, 10.8 [95% CI, 3.7 to 31.5]), and only 2 fracture fragments (OR, 7.3 [95% CI, 2.1 to 26.3]). When the posterior diastasis was <2 mm and only 2 fracture fragments were present, the probability of a stable ankle mortise was 0.98 for 48 female patients (16.8%) and 0.94 for 37 male patients (12.9%).
  
  
  CONCLUSIONS
  Patients with noncomminuted lateral malleolar fractures (85 patients [29.7%]) could be diagnosed with a stable ankle mortise without further stress testing, when the fracture line widths were <2 mm on lateral radiographs.
  
  
  METHODS
  Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: 1Department of Surgery, Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland 2Division of Orthopedics and Traumatology, Department of Trauma, Musculoskeletal Surgery and Rehabilitation, Tampere University Hospital, Tampere, Finland.
authors.forename: Simo
authors.initials: S
authors.lastname: Nortunen
authors.forename: Hannu-Ville
authors.initials: HV
authors.lastname: Leskelä
authors.forename: Heidi
authors.initials: H
authors.lastname: Haapasalo
authors.forename: Tapio
authors.initials: T
authors.lastname: Flinkkilä
authors.forename: Pasi
authors.initials: P
authors.lastname: Ohtonen
authors.forename: Harri
authors.initials: H
authors.lastname: Pakarinen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D064386:Ankle Fractures / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010808:Physical Examination; D011859:Radiography; D012399:Rotation; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D055815:Young Adult