Measurement of the acetabular cup anteversion on simulated radiographs.
Widmer (J Arthroplasty 2004;19:387) reported a protractor for measuring the anteversion of acetabular cups on radiographs but with limited precision. We intended to improve its precision by trigonometric mathematics. We measured the anteversion of the acetabular cups on 336 simulated radiographs using aforementioned 2 methods. The anteversion measured by Widmer's protractor ranged from 7 degrees to 41 degrees (mean +/- SD = 28.0 degrees +/- 9.8 degrees), and our methods, 5 degrees to 51 degrees (27.7 degrees +/- 13.2 degrees). The mean +/- SD of error by Widmer's protractor was 5.2 +/- 2.5 degrees, and our protractor, 0.8 degrees +/- 0.8 degrees (Student t test, P b .0001). The interobserver study showed the difference between measurements less than 2 degrees for each method. Therefore, the smaller error of our method than that of Widmer implicated a potentially precise measurement of the anteversion (level of evidence: diagnostic study, level II).
Department of Orthopaedics, Tao-Yuan General Hospital, Taoyuan, Taiwan ROC.
Chen-Kun
CK
Liaw
Rong-Sen
RS
Yang
Sheng-Mou
SM
Hou
Tai-Yin
TY
Wu
Chiou-Shann
CS
Fuh
D000077:Acetabulum / Q000000981:diagnostic imaging* / Q000601:surgery; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D017755:Prosthesis Fitting; D011859:Radiography