title: Is the transverse acetabular ligament a reliable cup orientation guide?
abstract: OBJECTIVE
  It is controversial whether the transverse acetabular ligament (TAL) is a reliable guide for determining the cup orientation during total hip arthroplasty (THA). We investigated the variations in TAL anatomy and the TAL-guided cup orientation.
  
  
  METHODS
  80 hips with osteoarthritis secondary to hip dysplasia (OA) and 80 hips with osteonecrosis of the femoral head (ON) were examined. We compared the anatomical anteversion of TAL and the TAL-guided cup orientation in relation to both disease and gender using 3D reconstruction of computed tomography (CT) images.
  
  
  RESULTS
  Mean TAL anteversion was 11° (SD 10, range -12 to 35). The OA group (least-square mean 16°, 95% confidence interval (CI): 14-18) had larger anteversion than the ON group (least-square mean 6.2°, CI: 3.8 - 7.5). Females (least-square mean 20°, CI: 17-23) had larger anteversion than males (least-square mean 7.0°, CI: 4.6-9.3) in the OA group, while there were no differences between the sexes in the ON group. When TAL was used for anteversion guidance with the radiographic cup inclination fixed at 40°, 39% of OA hips and 9% of ON hips had more than 10° variance from the target anteversion, which was 15°.
  
  
  CONCLUSIONS
  In ON hips, TAL is a good guide for determining cup orientation during THA, although it is not a reliable guide in hips with OA secondary to dysplasia. This is because TAL orientation has large individual variation and is influenced by disease and gender.
authors.affiliation: Departments of Orthopaedic Medical Engineering, Osaka University Graduate School of Medicine, Osaka, Japan.
authors.forename: Hirohito
authors.initials: H
authors.lastname: Abe
authors.forename: Takashi
authors.initials: T
authors.lastname: Sakai
authors.forename: Toshimitsu
authors.initials: T
authors.lastname: Hamasaki
authors.forename: Masaki
authors.initials: M
authors.lastname: Takao
authors.forename: Takashi
authors.initials: T
authors.lastname: Nishii
authors.forename: Nobuo
authors.initials: N
authors.lastname: Nakamura
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Sugano
mesh_terms: D000077:Acetabulum; D019644:Arthroplasty, Replacement, Hip / Q000379:methods; D005260:Female; D005271:Femur Head Necrosis / Q000150:complications / Q000601:surgery*; D006618:Hip Dislocation, Congenital / Q000150:complications / Q000601:surgery*; D006621:Hip Joint / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008023:Ligaments, Articular / Q000033:anatomy & histology* / Q000601:surgery; D008297:Male; D015207:Osteoarthritis, Hip / Q000209:etiology / Q000601:surgery*