Anterior Sacroiliac Fracture Dislocation: A Comparative Radiologic analysis of Crescent Fractures in Pelvic Ring Injuries: A Retrospective Study.

Background and Objectives: Anterior sacroiliac fracture dislocation (ASFD), also known as locked pelvis, is a rarely reported diagnosis. The types of ASFDs are often misdiagnosed as lateral compression fractures due to the presence of crescent fractures. In this study, we distinguished ASFD from lateral compression fractures (LC 2) and studied their characteristics. Materials and Methods: This is a retrospective study involving patients from a Level 1 trauma center. Fifty-nine patients under the age of 65 years with crescent fractures caused by a high-energy mechanism were investigated. Results: The incidence of ASFD was 25% (15 of 59) in patients with crescent fractures. Among the 15 patients, 6 had override of the ilium over the sacrum, inhibiting reduction in the sacroiliac joint. Pre-operative radiographic evaluations revealed that vertical displacement of the ASFD was larger than that of lateral compression fracture (LC 2) in the outlet view (mean 9.5 vs. 1.9 mm, p = 0.013), and the pelvic asymmetry ratio was larger in ASFD (mean 7.8 vs. 4.1, p = 0.006) in the pelvis AP view. All patients achieved union after surgery. Post-operative radiography showed no significant vertical displacement difference. There was no difference in vascular injury or hemodynamic instability requiring embolization or preperitoneal pelvic packing (PPP) between the two groups. Conclusions: Patients with ASFD have greater vertical displacement and asymmetry compared to patients with LC 2 fractures. These fractures must be distinguished for appropriate reduction and anterior plate fixation.