title: Intraoperative assessment of the stability of the distal tibiofibular joint in supination-external rotation injuries of the ankle: sensitivity, specificity, and reliability of two clinical tests.
abstract: BACKGROUND
  This study was designed to assess the sensitivity, specificity, and interobserver reliability of the hook test and the stress test for the intraoperative diagnosis of instability of the distal tibiofibular joint following fixation of ankle fractures resulting from supination-external rotation forces.
  
  
  METHODS
  We conducted a prospective study of 140 patients with an unstable unilateral ankle fracture resulting from a supination-external rotation mechanism (Lauge-Hansen SE). After internal fixation of the malleolar fracture, a hook test and an external rotation stress test under fluoroscopy were performed independently by the lead surgeon and assisting surgeon, followed by a standardized 7.5-Nm external rotation stress test of each ankle under fluoroscopy. A positive stress test result was defined as a side-to-side difference of >2 mm in the tibiotalar or the tibiofibular clear space on mortise radiographs. The sensitivity and specificity of each test were calculated with use of the standardized 7.5-Nm external rotation stress test as a reference.
  
  
  RESULTS
  Twenty-four (17%) of the 140 patients had a positive standardized 7.5-Nm external rotation stress test after internal fixation of the malleolar fracture. The hook test had a sensitivity of 0.25 (95% confidence interval, 0.12 to 0.45) and a specificity of 0.98 (95% confidence interval, 0.94 to 1.0) for the detection of the same instabilities. The external rotation stress test had a sensitivity of 0.58 (95% confidence interval, 0.39 to 0.76) and a specificity of 0.96 (95% confidence interval, 0.90 to 0.98). Both tests had excellent interobserver reliability, with 99% agreement for the hook test and 98% for the stress test.
  
  
  CONCLUSIONS
  Interobserver agreement for the hook test and the clinical stress test was excellent, but the sensitivity of these tests was insufficient to adequately detect instability of the syndesmosis intraoperatively.
authors.affiliation: Division of Orthopedic and Trauma Surgery, Department of Surgery, Oulu University Hospital, P.O. Box 21, FI 90029 OYS, Oulu, Finland. harri.pakarinen@ppshp.fi
authors.forename: Harri
authors.initials: H
authors.lastname: Pakarinen
authors.forename: Tapio
authors.initials: T
authors.lastname: Flinkkilä
authors.forename: Pasi
authors.initials: P
authors.lastname: Ohtonen
authors.forename: Pekka
authors.initials: P
authors.lastname: Hyvönen
authors.forename: Martti
authors.initials: M
authors.lastname: Lakovaara
authors.forename: Juhana
authors.initials: J
authors.lastname: Leppilahti
authors.forename: Jukka
authors.initials: J
authors.lastname: Ristiniemi
mesh_terms: D000328:Adult; D016512:Ankle Injuries / Q000000981:diagnostic imaging / Q000601:surgery*; D000843:Ankle Joint / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D005500:Follow-Up Studies; D005593:Fracture Fixation, Internal / Q000379:methods; D050723:Fractures, Bone / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D057072:Intra-Articular Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D007430:Intraoperative Care / Q000379:methods*; D007593:Joint Instability / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011859:Radiography; D015203:Reproducibility of Results; D018570:Risk Assessment; D012399:Rotation; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D013484:Supination; D016896:Treatment Outcome