title: Functional pelvic orientation measured from lateral standing and sitting radiographs.
abstract: We prospectively obtained preoperative and 3-month postoperative lateral pelvic radiographs in the standing and sitting positions from 84 patients who underwent total hip arthroplasty. We measured pelvic orientation (flexion extension) using the anterior pelvic plane as defined by the anterior superior iliac spines and pubic tubercles as references. There was a trend towards upright pelvic alignment when standing, with a mean anterior pelvic plane angle of 1.2 degrees (range, -22 degrees - +27 degrees). In the sitting position the pelvis tended to extend posteriorly, with a mean anterior pelvic plane angle of -36.2 degrees (range, -64 degrees - +4 degrees). There was a wide variation in the arc of pelvic flexion extension as patients moved from standing to sitting, with are of pelvic motion in some patients as mobile as 70 degrees and in others as stiff as 5 degrees. There was no significant variation between males and females or between preoperative and postoperative pelvic flexion extension. There were substantial variations in pelvic orientation when comparing standing and sitting for an individual patient and between different patients. This variation can be unpredictable, and may influence implant alignment and stability after total hip arthroplasty.
authors.affiliation: Institute for Computer Assisted Orthopedic Surgery (ICAOS), The Western Pennsylvania Hospital, Mellon Pavilion, Suite 242, 4815 Liberty Avenue, Pittsburgh, PA 15224, USA. tony@icaos.org
authors.forename: Anthony M
authors.initials: AM
authors.lastname: DiGioia
authors.forename: Mahmoud A
authors.initials: MA
authors.lastname: Hafez
authors.forename: Branislav
authors.initials: B
authors.lastname: Jaramaz
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Levison
authors.forename: James E
authors.initials: JE
authors.lastname: Moody
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement; D010384:Pelvic Bones / Q000000981:diagnostic imaging; D010388:Pelvis / Q000503:physiopathology*; D011187:Posture; D011859:Radiography