Background: Musculoskeletal plain radiographic imaging protocols are typically predicated on orthogonal views of the bone or joint being evaluated. Pelvic injury has been evaluated with 45° inlet and 45° outlet radiographs. While these views are perpendicular to each other, they may not be in the best plane to evaluate pelvic injury because of variable lumbopelvic anatomy. We hypothesized that inlet and outlet radiographic views optimized to examine the clinically relevant osseous landmarks vary substantially from routine 45° inlet and outlet views.
Methods: Sixty-eight consecutive patients without pelvic ring disruption who had undergone routine axial pelvic computed tomography scans were retrospectively identified. The optimal inlet and outlet angles required to profile the clinically relevant pelvic anatomy were quantified for each patient with use of sagittal computed tomography reconstructions.
Results: The optimal inlet angle to profile the anterior body of S1 required an average caudal tilt of 21°. The average outlet angle (cephalad tilt) perpendicular to the body of S1 was 63° and perpendicular to S2 was 57°. The optimal angles were the same for male and female patients and for patients with normal and dysmorphic pelves and were independent of patient age.
Conclusions: Screening inlet and screening outlet radiographs made at 25° and 60°, respectively, are recommended to provide accurate profiles of the clinically relevant posterior osseous pelvic anatomy.
1Department of Orthopaedic Surgery, Washington University School of Medicine, 1 Barnes Hospital Plaza, Suite 11300, St. Louis, MO 63110. E-mail address for W.M. Ricci: email@example.com
2Department of Orthopaedic Surgery, University of California, Irvine, 101 The City Drive South, Pavilion III, Building 29A, Orange, CA 92868