title: Reliability of the assessment of lower limb torsion using computed tomography: analysis of five different techniques.
abstract: OBJECTIVE
  Various methods have been described to define the femoral neck and distal tibial axes based on a single CT image. The most popular are the Hernandez and Weiner methods for defining the femoral neck axis and the Jend, Ulm, and bimalleolar methods for defining the distal tibial axis. The purpose of this study was to calculate the intra- and interobserver reliability of the above methods and to determine intermethod differences.
  
  
  METHODS
  Three physicians separately measured the rotational profile of 44 patients using CT examinations on two different occasions. The average age of patients was 36.3 ± 14.4 years, and there were 25 male and 19 female patients. After completing the first two sessions of measurements, one observer chose certain cuts at the levels of the femoral neck, femoral condylar area, tibial plateau, and distal tibia. The three physicians then repeated all measurements using these CT cuts.
  
  
  RESULTS
  The greatest interclass correlation coefficients were achieved with the Hernandez (0.99 intra- and 0.93 interobserver correlations) and bimalleolar methods (0.99 intra- and 0.92 interobserver correlations) for measuring the femoral neck and distal tibia axes, respectively. A statistically significant decrease in the interobserver median absolute differences could be achieved through the use of predefined CT scans only for measurements of the femoral condylar axis and the distal tibial axis using the Ulm method. The bimalleolar axis method underestimated the tibial torsion angle by an average of 4.8° and 13° compared to the Ulm and Jend techniques, respectively.
  
  
  CONCLUSIONS
  The methods with the greatest inter- and intraobserver reliabilities were the Hernandez and bimalleolar methods for measuring femoral anteversion and tibial torsion, respectively. The high intermethod differences make it difficult to compare measurements made with different methods.
authors.affiliation: Trauma Department, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany. manoliodakis@yahoo.gr
authors.forename: Emmanouil
authors.initials: E
authors.lastname: Liodakis
authors.forename: Iosifina
authors.initials: I
authors.lastname: Doxastaki
authors.forename: Kongfai
authors.initials: K
authors.lastname: Chu
authors.forename: Christian
authors.initials: C
authors.lastname: Krettek
authors.forename: Ralph
authors.initials: R
authors.lastname: Gaulke
authors.forename: Musa
authors.initials: M
authors.lastname: Citak
authors.forename: Mohamed
authors.initials: M
authors.lastname: Kenawey
mesh_terms: D000328:Adult; D000465:Algorithms; D005260:Female; D005269:Femur / Q000002:abnormalities* / Q000000981:diagnostic imaging*; D006801:Humans; D007719:Knee Joint / Q000002:abnormalities* / Q000000981:diagnostic imaging; D008297:Male; D015588:Observer Variation; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013977:Tibia / Q000002:abnormalities* / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014102:Torsion Abnormality / Q000000981:diagnostic imaging*