title: Is transverse acetabular ligament a reliable guide for aligning cup anteversion in total hip arthroplasty?: A measurement by CT arthrography in 90 hips.
abstract: BACKGROUND
  Transverse acetabular ligament (TAL) has been used as a landmark for aligning cup anteversion. The use of TAL as a guide is based on the assumption that TAL version is distributed within the safe zone of acetabular cup. However, there was rarely reported to compare anteversion between TAL and acetabulum using direct measurement methods. The purpose of this study was to measure the anteversion of TAL in computed tomography arthrography (CTA) and compare it with Lewinnek's safe zone and anteversion of bony acetabulum.
  
  
  METHODS
  81 patients (90 hips) were selected among 204 patients (228 hips) who received CTA for hip pathology evaluation between March 2010 and June 2013. The anteversion of TAL measured at the lowest level of the acetabular notch and the anteversion of the acetabulum was measured at the level of femoral head center.
  
  
  RESULTS
  The mean TAL anteversion was 11.8° (SD 4.5, range 0-22.2). In eight hips (8.8%), TAL anteversion was outside the safe zone (15° ± 10°) as defined by Lewinnek. The mean acetabular anteversion was 13.3° ± 4.4° (range -1.0° to 22.6°). There was a strong correlation between TAL anteversion and acetabular anteversion (Pearson's correlation coefficient; 0.908, p < 0.001).
  
  
  CONCLUSIONS
  TAL anteversion has a large individual variation, and considerable portion of hips have TAL anteversion outside the safety zone of cup anteversion. TAL anteversion is influenced by acetabular anteversion. In hips with retroverted or pauci-anteverted acetabulum, TAL should be used cautiously because there is a risk of cup malposition.
authors.affiliation: Department of Orthopaedic Surgery, Inje University College of Medicine, Seoul Paik Hospital, Seoul, South Korea. Electronic address: cragy0215@naver.com.
authors.forename: Byung-Ho
authors.initials: BH
authors.lastname: Yoon
authors.affiliation: Department of Orthopaedic Surgery, Chung-Ang University College of Medicine, Seoul, South Korea. Electronic address: hayongch@naver.com.
authors.forename: Yong-Chan
authors.initials: YC
authors.lastname: Ha
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Seongnam, South Korea. Electronic address: ykleemd@gmail.com.
authors.forename: Young-Kyun
authors.initials: YK
authors.lastname: Lee
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Seongnam, South Korea. Electronic address: jis25@naver.com.
authors.forename: Woo-Lam
authors.initials: WL
authors.lastname: Jo
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Seongnam, South Korea. Electronic address: oasis100@empas.com.
authors.forename: Kyoung-Min
authors.initials: KM
authors.lastname: Lee
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Seongnam, South Korea. Electronic address: khkoo@snu.ac.kr.
authors.forename: Kyung-Hoi
authors.initials: KH
authors.lastname: Koo
mesh_terms: D000293:Adolescent; D000328:Adult; D001175:Arthrography / Q000379:methods*; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D008023:Ligaments, Articular / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult