title: Computed tomography for the detection of distal radioulnar joint instability: normal variation and reliability of four CT scoring systems in 46 patients.
abstract: OBJECTIVE
  The diagnosis of distal radioulnar joint (DRUJ) instability is clinically challenging. Computed tomography (CT) may aid in the diagnosis, but the reliability and normal variation for DRUJ translation on CT have not been established in detail. The aim of this study was to evaluate inter- and intraobserver agreement and normal ranges of CT scoring methods for determination of DRUJ translation in both posttraumatic and uninjured wrists.
  
  
  METHODS
  Patients with a conservatively treated, unilateral distal radius fracture were included. CT scans of both wrists were evaluated independently, by two readers using the radioulnar line method, subluxation ratio method, epicenter method and radioulnar ratio method. The inter- and intraobserver agreement was assessed and normal values were determined based on the uninjured wrists.
  
  
  RESULTS
  Ninety-two wrist CTs (mean age: 56.5 years, SD: 17.0, mean follow-up 4.2 years, SD: 0.5) were evaluated. Interobserver agreement was best for the epicenter method [ICC = 0.73, 95 % confidence interval (CI) 0.65-0.79]. Intraobserver agreement was almost perfect for the radioulnar line method (ICC = 0.82, 95 % CI 0.77-0.87). Each method showed a wide normal range for normal DRUJ translation. Normal range for the epicenter method is -0.35 to -0.06 in pronation and -0.11 to 0.19 in supination.
  
  
  CONCLUSIONS
  DRUJ translation on CT in pro- and supination can be reliably evaluated in both normal and posttraumatic wrists, however with large normal variation. The epicenter method seems the most reliable. Scanning of both wrists might be helpful to prevent the radiological overdiagnosis of instability.
authors.affiliation: Department of Surgery-Trauma Surgery, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands. mmewijffels@hotmail.com.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Wijffels
authors.affiliation: Department of Radiology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
authors.forename: Wouter
authors.initials: W
authors.lastname: Stomp
authors.affiliation: Department of Surgery-Trauma Surgery, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
authors.forename: Pieta
authors.initials: P
authors.lastname: Krijnen
authors.affiliation: Department of Radiology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
authors.forename: Monique
authors.initials: M
authors.lastname: Reijnierse
authors.affiliation: Department of Surgery-Trauma Surgery, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
authors.forename: Inger
authors.initials: I
authors.lastname: Schipper
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D001175:Arthrography / Q000379:methods; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D011884:Radius / Q000000981:diagnostic imaging*; D011885:Radius Fractures / Q000000981:diagnostic imaging*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014457:Ulna / Q000000981:diagnostic imaging*; D014954:Wrist Injuries / Q000000981:diagnostic imaging*; D014955:Wrist Joint / Q000000981:diagnostic imaging*; D055815:Young Adult
keywords: CT scan; Distal radioulnar joint; Distal radius fracture; Instability; Normal values