title: A new sagittal parameter to estimate pelvic tilt using the iliac cortical density line and iliac tilt: a retrospective X-ray measurement study.
abstract: BACKGROUND
  When spinal kyphosis increases, the compensatory mechanism activates and the pelvic position changes. Increasing the pelvic tilt, which is the orientation of the pelvis with respect to the femoral head, is known to associate with the clinical symptoms in kyphosis in the aging population. It is often difficult to detect the femoral head on radiographs, limiting the ability to determine the pelvic tilt. Therefore, there is a need to establish another parameter independent of the femoral head which closely correlates with the pelvic tilt.
  
  
  METHODS
  Eighty-two adult patients with full-length lateral standing spine radiographs were recruited (mean age: 73.0 years). A new parameter, the iliac cortical density line (a component of the arcuate line of the ilium) and the iliac tilt (defined as the angle between the iliac cortical density line and the vertical), was analyzed to determine the correlation with the pelvic tilt.
  
  
  RESULTS
  Both the pelvic tilt (PT) and iliac tilt (IT) could be identified in 67 patients, and a significant correlation was observed between the PT and IT (r = 0.86, P < 0.0001). The PT could be estimated using the following formula: PT = IT - 12.9 (in females), PT = IT - 16.7 (in males).
  
  
  CONCLUSIONS
  The iliac tilt, which can be easily and directly measured using the iliac cortical density line, is a new parameter that can reliably estimate the pelvic tilt even when the femoral head is not detectable on the radiograph.
authors.affiliation: Department of Orthopaedic Surgery, Kyushu University Beppu Hospital, 4546 Tsurumi, Beppu, Oita, 874-0838, Japan. toshidoi@ortho.med.kyushu-u.ac.jp.
authors.forename: Toshio
authors.initials: T
authors.lastname: Doi
authors.affiliation: Department of Orthopaedic Surgery, Kyushu University Beppu Hospital, 4546 Tsurumi, Beppu, Oita, 874-0838, Japan. otohno@yahoo.co.jp.
authors.forename: Osamu
authors.initials: O
authors.lastname: Tono
authors.affiliation: Department of Orthopaedic Surgery, Kyushu University Beppu Hospital, 4546 Tsurumi, Beppu, Oita, 874-0838, Japan. kt99059@hotmail.com.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Tarukado
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan. harimaya@ortho.med.kyushu-u.ac.jp.
authors.forename: Katsumi
authors.initials: K
authors.lastname: Harimaya
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan. ymatsu@ortho.med.kyushu-u.ac.jp.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Matsumoto
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan. mitsu-38@ortho.med.kyushu-u.ac.jp.
authors.forename: Mitsumasa
authors.initials: M
authors.lastname: Hayashida
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan. seokada@ortho.med.kyushu-u.ac.jp.
authors.forename: Seiji
authors.initials: S
authors.lastname: Okada
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan. yiwamoto@ortho.med.kyushu-u.ac.jp.
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Iwamoto
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005270:Femur Head / Q000000981:diagnostic imaging* / Q000502:physiology*; D006801:Humans; D007085:Ilium / Q000000981:diagnostic imaging* / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010384:Pelvic Bones / Q000000981:diagnostic imaging / Q000502:physiology; D011187:Posture / Q000502:physiology*; D011859:Radiography; D012189:Retrospective Studies; D014965:X-Rays