title: Reliability of the Radiographic Sagittal and Frontal Tibiotalar Alignment after Ankle Arthrodesis.
abstract: Accurate measurement of the tibiotalar alignment is important in radiographic outcome assessment of ankle arthrodesis (AA). In studies, various radiological methods have been used to measure the tibiotalar alignment leading to facultative misinterpretation of results. However, to our knowledge, no previous study has investigated the reliability of tibiotalar alignment measurement in AA. We aimed to investigate the reliability of four different methods of measurement of the frontal and sagittal tibiotalar alignment after AA, and to further clarify the most reliable method for determining the longitudinal axis of the tibia.
  
  
  
  Thirty-eight weight bearing anterior to posterior and lateral ankle radiographs of thirty-seven patients who had undergone AA with a two screw fixation technique were selected. Three observers measured the frontal tibiotalar angle (FTTA) and the sagittal tibiotalar angle (STTA) using four different methods. The methods differed by the definition of the longitudinal tibial axis. Method A was defined by a line drawn along the lateral tibial border in anterior to posterior radiographs and along the posterior tibial border in lateral radiographs. Method B was defined by a line connecting two points in the middle of the proximal and the distal tibial shaft. Method C was drawn "freestyle"along the longitudinal axis of the tibia, and method D was defined by a line connecting the center of the tibial articular surface and a point in the middle of the proximal tibial shaft. Intra- and interobserver correlation coefficients (ICC) and repeated measurement ANOVA were calculated to assess measurement reliability and accuracy.
  
  
  
  All four methods showed excellent inter- and intraobserver reliability for the FTTA and the STTA. When the longitudinal tibial axis is defined by connecting two points in the middle of the proximal and the distal tibial shaft, the highest interobserver reliability for the FTTA (ICC: 0.980; CI 95%: 0.966-0.989) and for the STTA (ICC: 0.997; CI 95%: 0.996-0.999) is provided. Intergroup analysis for FTTA measurements revealed a statistically significant difference between the method in which the lateral border of the tibia was used to determine the longitudinal axis of the tibia, and the other methods in which the longitudinal axis was defined by bisecting the tibia.
  
  
  
  When the longitudinal axis of the tibia is defined by connecting two points in the middle of the proximal and the distal tibial shaft for measuring the FTTA and STTA, the most favorable interobserver reliability is provided. Therefore, this method can be recommended for evaluating the frontal and the sagittal alignment on anterior to posterior and lateral radiographs after ankle arthrodesis.
authors.affiliation: Department of Orthopaedics, Vienna General Hospital, Medical University of Vienna, Vienna, Austria.
authors.forename: Madeleine
authors.initials: M
authors.lastname: Willegger
authors.affiliation: Department of Orthopaedics, Vienna General Hospital, Medical University of Vienna, Vienna, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Holinka
authors.affiliation: Department of Orthopaedics, Vienna General Hospital, Medical University of Vienna, Vienna, Austria.
authors.forename: Elena
authors.initials: E
authors.lastname: Nemecek
authors.affiliation: Foot and Ankle Unit, Orthopaedic Hospital Vienna-Speising, Vienna, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Bock
authors.affiliation: Department of Orthopaedics, Vienna General Hospital, Medical University of Vienna, Vienna, Austria.
authors.forename: Axel Hugo
authors.initials: AH
authors.lastname: Wanivenhaus
authors.affiliation: Department of Orthopaedics, Vienna General Hospital, Medical University of Vienna, Vienna, Austria.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Windhager
authors.affiliation: Department of Orthopaedics, Vienna General Hospital, Medical University of Vienna, Vienna, Austria.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Schuh
mesh_terms: D000328:Adult; D000368:Aged; D000842:Ankle; D000843:Ankle Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D001174:Arthrodesis / Q000295:instrumentation / Q000379:methods* / Q000534:rehabilitation; D001863:Bone Screws; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011859:Radiography; D015203:Reproducibility of Results; D013977:Tibia / Q000000981:diagnostic imaging* / Q000601:surgery; D016474:Weight-Bearing