Is sacral dysmorphism protective against spinopelvic dissociation? multicenter case series

Objectives: Investigate the incidence of sacral dysmorphism (SD) in patients with spinopelvic dissociation (SPD). Design: Retrospective case series. Setting: Two academic level 1 trauma centers. Patients/Participants: One thousand eight hundred fifty adult patients with sacral and pelvic fractures (OTA/AO 61-A, B, C). Intervention: Plain pelvic radiographs and CT scans. Main Outcome Measurements: Incidence of SD in patients with SPD. Secondary radiographic evaluation of fracture classification and deformity on sagittal imaging. Results: Eighty-two patients with SPD were identified, and 12.2% displayed features of SD, significantly less than reported in the literature. The S2 sacral body was the most common horizontal fracture location in patients with SD and nondysmorphic sacra (ND). Roy-Camille type I patterns were more common in ND (35%), versus type II in SD patients (40%). SD patients had lower body mass indexes (19.7 vs. 25.2, P = 0.001). Segmental kyphosis (22.5 degrees ND vs. 23.8 degrees SD, P = 0.838) and sacral kyphosis (26 degrees ND vs. 31 degrees SD, P = 0.605) were similar between groups. Percutaneous fixation was the most common surgical technique. Conclusions: We report a significantly lower prevalence of SD in patients with SPD than previously reported in the literature. This suggests that variations in sacral osseous anatomy alter force transmission across the sacrum during traumatic loading, which may be protective against certain high-energy fracture patterns. Preoperative evaluation of sacral anatomy is critical, not only in determining the size and orientation of sacral segment safe zones for screw placement, but also to better understand the pathomechanics involved in sacral trauma.