title: The reliability and validity of radiographic measurements for determining the three-dimensional position of the talus in varus and valgus osteoarthritic ankles.
abstract: OBJECTIVE
  To assess the most accurate radiographic method to determine talar three-dimensional position in varus and valgus osteoarthritic ankles, we evaluated the reliability and validity of different radiographic measurements.
  
  
  METHODS
  Nine radiographic measurements were performed blindly on weight-bearing mortise, sagittal, and horizontal radiographs of 33 varus and 33 valgus feet (63 patients). Intra- and interobserver reliability was determined with the intraclass coefficient (ICC). Discriminant validity of measurements between varus and valgus feet was assessed with effect size (ES). Convergent validity (Pearson's r) was evaluated by correlating measurements to the dichotomized varus and valgus groups. Obtained measurements in both groups were finally compared with each other and with 30 control feet.
  
  
  RESULTS
  Reliability was excellent (ICC > 0.80) in all but two measurements. Whereas frontal plane validity was excellent (ES and r > 0.80), horizontal and sagittal measurements showed poor to moderate validity (ES and r between 0.00 and 0.60). Four measurements were significantly different among all groups (p < 0.05). Talar positional tendency was found towards dorsiflexion or endorotation in the varus group and towards plantarflexion or exorotation in the valgus group. The frontal tibiotalar surface angle, sagittal talocalcaneal inclination angle, and horizontal talometatarsal I angle showed the best reliability, validity, and difference among the groups.
  
  
  CONCLUSIONS
  The frontal tibiotalar surface angle, sagittal talocalcaneal inclination angle, and horizontal talometatarsal I angle accurately determine talar three-dimensional radiographic position in weight-bearing varus and valgus osteoarthritic ankles. Careful radiographic evaluation is important, as these deformities affect talar position in all three planes.
authors.affiliation: Department of Orthopaedic Surgery & Traumatology, Kantonsspital Liestal, Rheinstrasse 26, 4410, Liestal, Switzerland. t.nosewicz@gmail.com
authors.forename: Tomasz L
authors.initials: TL
authors.lastname: Nosewicz
authors.forename: Markus
authors.initials: M
authors.lastname: Knupp
authors.forename: Lilianna
authors.initials: L
authors.lastname: Bolliger
authors.forename: Beat
authors.initials: B
authors.lastname: Hintermann
mesh_terms: D000015:Abnormalities, Multiple / Q000000981:diagnostic imaging*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000843:Ankle Joint / Q000002:abnormalities* / Q000000981:diagnostic imaging; D005260:Female; D006215:Hallux Valgus / Q000000981:diagnostic imaging*; D050488:Hallux Varus / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000000981:diagnostic imaging*; D011859:Radiography; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013628:Talus / Q000002:abnormalities* / Q000000981:diagnostic imaging*; D055815:Young Adult