The Journal of Arthroplasty
Volume 24, Issue 3 , Pages 468-474, April 2009

Measurement of the Acetabular Cup Anteversion on Simulated Radiographs

  • Chen-Kun Liaw, MD

      Affiliations

    • Department of Orthopaedics, Tao-Yuan General Hospital, Taoyuan, Taiwan ROC
    • Institute of Computer Science and Information Engineering, National Taiwan University, Taipei, Taiwan ROC
    • Chen‑Kun Liaw and Rong‑Sen Yang contributed equally to this work.
    • ,
  • Rong-Sen Yang, MD, PhD

      Affiliations

    • Department of Orthopaedics, College of Medicine, National Taiwan University and Hospital, Taipei, Taiwan ROC
    • Chen‑Kun Liaw and Rong‑Sen Yang contributed equally to this work.
    • ,
  • Sheng-Mou Hou, MD, PhD, MPH

      Affiliations

    • Department of Orthopaedics, College of Medicine, National Taiwan University and Hospital, Taipei, Taiwan ROC
    • ,
  • Tai-Yin Wu, MD

      Affiliations

    • Taipei City Hospital, Renai Branch, Taipei City, Taiwan ROC
    • ,
  • Chiou-Shann Fuh, PhD

      Affiliations

    • Institute of Computer Science and Information Engineering, National Taiwan University, Taipei, Taiwan ROC
    • Corresponding Author InformationReprint requests: Chiou-Shann Fuh, PhD, Department of Computer Science and Information Engineering, National Taiwan University, Taipei 106, Taiwan ROC.

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).

Key words: hip arthroplasty, acetabulum, anteversion, protractor

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 This study was supported by the grant NSC96-2320-B-087-001, Taiwan, ROC.

PII: S0883-5403(07)00634-1

doi:10.1016/j.arth.2007.10.029

The Journal of Arthroplasty
Volume 24, Issue 3 , Pages 468-474, April 2009

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