Isolated Unilateral Posterior Sacroiliac Dislocation With an Intact Anterior Pelvic Ring: Case Report of an Unusual Injury Pattern.

Unstable pelvic ring injuries usually present with pubic symphysis and/or pubic rami disruption, in association with fractures or fracture-dislocations affecting the posterior iliac, sacroiliac joint, and/or the sacrum. Involvement of the strong posterior osteoligamentous complex with an intact anterior pelvic ring is extremely rare, with only a limited number of cases previously documented. We report the case of a 15-year-old male who sustained high-energy trauma after being struck in the back by a heavy metal structure. He presented with a unilateral posterior sacroiliac dislocation and an intact anterior pelvic ring, which is believed to represent a previously unreported injury. The patient underwent closed reduction with percutaneous fixation using a 7.0 mm partially threaded cannulated iliosacral screw. This case highlights an unusual pelvic injury pattern not fully addressed by current classification systems and emphasizes the importance of carefully assessing anterior ring integrity in high-energy posterior pelvic trauma.