Background <p>Percutaneous iliosacral screw fixation is a widely used method for stabilizing posterior pelvic ring injuries, but anatomical variability, particularly sacral dysmorphism, can complicate screw placement. While global data suggest sacral dysmorphism prevalence varies by race and ethnicity, U.S.-based studies have largely focused on predominantly White populations. This study evaluated anatomical variation and sacral dysmorphism prevalence across sex, racial, and ethnic groups in a diverse U.S. trauma population.</p> Methods <p>A retrospective analysis was conducted at a Level 1 trauma center, including adults who underwent pelvic CT scans from 2018 to 2020. Exclusion criteria included pelvic/sacral pathology or prior surgery. Demographics collected were age, sex, race, and ethnicity. Sacral dysmorphism was assessed using qualitative criteria, and sacral safe zone dimensions were measured at the first three sacral segments. Statistical analyses included chi-square tests, <i>t</i>-tests, ANOVA, and unadjusted odds ratios (OR).</p> Results <p>Among 144 patients, 28% had sacral dysmorphism. Prevalence was significantly higher in Hispanic (44%) vs. non-Hispanic (21%) patients (OR = 3.86, <i>p</i> = 0.001). Men had larger safe zone dimensions than women at the first (<i>p</i> = 0.008) and second (<i>p</i> = 0.044) sacral segments. Compared to non-Hispanic women, Hispanic women had smaller dimensions at the first (<i>p</i> = 0.030) and larger at the third (<i>p</i> = 0.032) sacral segments. White males had significantly larger dimensions at the first (<i>p</i> = 0.006) and second (<i>p</i> &lt; 0.001) sacral segments than males of other races; White females had larger second sacral segment dimensions than females of other races (<i>p</i> = 0.008).</p> Conclusions <p>Sacral anatomy varies significantly by sex, race, and ethnicity. Recognizing these differences may aid preoperative planning and reduce the risk of malpositioned iliosacral screws.</p> Level of evidence III <p>Retrospective Cohort Study.</p>