Peter D. Gibson, Mark R. Adams, Kenneth L. Koury, M. K. Shaath, Michael S. Sirkin, Mark C. Reilly

To determine the quantifiable difference in pubic symphysis diastasis when comparing CT scan and pelvic radiographs in individuals with anterior pelvic ring injuries. Retrospective chart and radiographic review SETTING:: Level 1 trauma centerPatients/Participants: Between 2002 and 2013 all individuals requiring internal fixation of the anterior pelvic ring were reviewed. Out of 163 patients, 72 met inclusion criteria. Patients with a symphysis dislocation were included if the pelvic radiograph and CT scan were performed without a pelvic binder and imaging was adequate for required measurements. Symphyseal diastasis was measured on the initial pelvic radiograph, the CT scout and axial views. Comparison of measured symphyseal diastasis on CT scan and pelvic radiographs. Seventy-two patients met inclusion criteria. Ninety-seven percent (70/72) had a reduction of their symphysis diastasis in the CT with an average reduction of 6.6 mm (Range -2.6 to 35.5 mm). The average diastasis on radiograph was 26.3 mm compared to 19.7 mm on CT scout (P<0.001). Fourteen patients (19.2%) had a reduction from greater than 25 mm to less than 25 mm - a traditional cut off for operative intervention. The AP pelvis radiograph remains an important part of the workup for trauma patients. Reliance on CT scan alone may underestimate the true degree of pelvic displacement. Failure to obtain pelvic radiographs in the acute setting limits the information in which the medical team can base both immediate and definitive decisions in regards to pelvic ring injuries. Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.