title: Direct measurement of acetabular radiographic version using an ordinary goniometer: a precision study.
abstract: OBJECTIVE
  The acetabular version following total hip arthroplasty is an important prognostic factor. Computer navigation serves as a precise tool during hip arthroplasty, which requires precise measurement to verify the effect of the procedure. Wan and colleagues have reported an innovative method for measuring acetabular radiographic version with an ordinary goniometer. Our objective was to study the precision of this method.
  
  
  METHODS
  We derived the underlying mathematical principle of Wan's method and produced a correction formula and chart. Forty-eight computer-synthesized radiographs were used to study the method and its mathematical correction. Ten real radiographs were used to detect intra-observer difference. The paired t-test was used for statistical analysis.
  
  
  RESULTS
  There was a significant difference between synthetic acetabular radiographic version and the measurement obtained with Wan's method (p < 0.05), but there was no difference after mathematical correction (p = 0.15). For smaller radiographic version (<20(o)), there was no statistical difference using Wan's method (p = 0.054).
  
  
  CONCLUSIONS
  The method of Wan and colleagues can be used when acetabular radiographic version is less than 20°. For larger radiographic versions, however, mathematical correction is necessary to obtain precise results.
authors.affiliation: Department of Orthopaedics, Tao-Yuan General Hospital, Taiwan. d92008@csie.ntu.edu.tw
authors.forename: Chen-Kun
authors.initials: CK
authors.lastname: Liaw
authors.forename: Tai-Yin
authors.initials: TY
authors.lastname: Wu
authors.forename: Rong-Sen
authors.initials: RS
authors.lastname: Yang
authors.forename: Yuan-Nian
authors.initials: YN
authors.lastname: Hsu
authors.forename: Tai-Jung
authors.initials: TJ
authors.lastname: Wu
authors.forename: Sheng-Mou
authors.initials: SM
authors.lastname: Hou
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging* / Q000601:surgery*; D053587:Arthrometry, Articular; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D006622:Hip Prosthesis; D006801:Humans; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*