Measurement of the Acetabular Cup Anteversion on Simulated Radiographs
Received 5 May 2007; accepted 28 October 2007. published online 04 April 2008.
Abstract
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° to 41° (mean ± SD = 28.0° ± 9.8°), and our methods, 5° to 51° (27.7° ± 13.2°). The mean ± SD of error by Widmer's protractor was 5.2 ± 2.5°, and our protractor, 0.8° ± 0.8° (Student t test, P < .0001). The interobserver study showed the difference between measurements less than 2° 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
†Institute of Computer Science and Information Engineering, National Taiwan University, Taipei, Taiwan ROC
‡Department of Orthopaedics, College of Medicine, National Taiwan University and Hospital, Taipei, Taiwan ROC
§Taipei City Hospital, Renai Branch, Taipei City, Taiwan ROC
Reprint requests: Chiou-Shann Fuh, PhD, Department of Computer Science and Information Engineering, National Taiwan University, Taipei 106, Taiwan ROC.
This study was supported by the grant NSC96-2320-B-087-001, Taiwan, ROC.
1 Chen‑Kun Liaw and Rong‑Sen Yang contributed equally to this work.
ABSTRACT