title: Radiographic measurement of anterior talar translation in the ankle: determination of the most reliable method.
abstract: BACKGROUND
  Although most would agree that stress radiography is an important research tool to evaluate the integrity of the ankle ligaments in studies of chronic ankle instability, there is little agreement with regard to the best technique to make these measurements. The primary objective of this study was to establish the most reliable method for measuring anterior displacement of the talus relative to the tibia using stress radiographs of the ankle. This information is necessary to standardize radiographic evaluation of injured ankles and for biomechanical studies of the ankle joint, but has never been investigated.
  
  
  METHODS
  This study examined the reliability of four available methods by measuring the intra-observer repeatability and inter-observer reproducibility of three different investigators. Lateral radiographs were obtained while the ankle was supported in the Telos device with the joint unloaded, and then with a 150 N anterior directed load applied to the calcaneus. At two separate time intervals, the radiographs were read by three different observers using four measurement techniques. For each technique, the measurement of the unloaded ankle was subtracted from the loaded ankle to obtain anterior talar translation.
  
  
  RESULTS
  The method that measured the shortest distance between the posterior lip of the distal tibia and the talar dome (designated Method I in the current series) was significantly more reproducible between readers and within readers across repeated measurements than the other methods tested.
  
  
  CONCLUSIONS
  Based on the findings from this study, it can be concluded that measurement of the distance between the posterior lip of the distal tibia and the talar dome is the method of choice to characterize the position of the talus relative to the tibia in stress radiography. In order to standardize the radiographic evaluation of ankle injuries, this method should be the one employed to measure anterior talar translation.
authors.affiliation: Department of Orthopaedics and Rehabilitation, McClure Musculoskeletal Research Center, University of Vermont, Burlington, VT 05405, USA. bruce.beynnon@uvm.edu
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Beynnon
authors.forename: Gavin
authors.initials: G
authors.lastname: Webb
authors.forename: Bryan M
authors.initials: BM
authors.lastname: Huber
authors.forename: Charles N
authors.initials: CN
authors.lastname: Pappas
authors.forename: Per
authors.initials: P
authors.lastname: Renström
authors.forename: L D
authors.initials: LD
authors.lastname: Haugh
mesh_terms: D016512:Ankle Injuries / Q000000981:diagnostic imaging*; D000843:Ankle Joint / Q000000981:diagnostic imaging; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging*; D015588:Observer Variation; D010808:Physical Examination / Q000379:methods*; D010812:Physical Stimulation / Q000379:methods; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013180:Sprains and Strains / Q000150:complications / Q000000981:diagnostic imaging*; D013628:Talus / Q000000981:diagnostic imaging*; D013977:Tibia / Q000000981:diagnostic imaging*