AP pelvis radiograph is insufficient for diagnosis of U-type sacral fractures

We investigated the sensitivity of a screening test for pelvic ring disruption, the AP pelvis radiograph, for clinically serious U-type sacral fractures which merit consultation with an orthopedic trauma specialist and may require transfer to a higher level of care.

Retrospective clinical cohort of 63 consecutive patients presenting with U-type sacral fractures at one level 1 trauma referral center from January 2006 through December 2019. The sensitivity of the first AP pelvis radiograph obtained on admission, interpreted without reference to antecedent or concomitant pelvis computed tomography (CT) by a radiologist and a panel of three blinded orthopedic traumatologists, was determined against a reference diagnosis made from review of all pelvis radiographs, CT images, operative reports, and clinical documentation.

Sensitivity of AP pelvis radiograph for U-type sacral fractures was 2% as interpreted by a radiologist and mean 12% (range 5-27%) as interpreted by orthopedic traumatologists with poor inter-rater agreement (Fleiss' κ = 0.11). 94% of sacra were at obscured by radiographic artifact.

The sensitivity of an AP pelvis radiograph is poor for U-type sacral fractures, whether interpreted by radiologists or orthopedic traumatologists. Pelvis CT should be considered as a screening test to rule out sacral fracture when the patient reports posterior pelvic pain, even if plain radiography demonstrates no injury or a minimally displaced pelvic ring disruption.

Diagnostic level III.