Factors associated with U-type sacral fractures in geriatric patients: A retrospective cohort study.

OBJECTIVES: To identify demographic and clinical factors associated with geriatric U-type sacral fractures. METHODS: Design: Retrospective cohort study. SETTING: Two Academic Level 1 trauma centers. Patient Selection Criteria: Patients ≥ 65 years with sacral fractures between January 2023 and January 2025 who underwent advanced imaging (CT or MRI) were included. Outcome Measures and Comparisons: The primary outcome was U-type sacral fracture morphology (AO/OTA 55C0, 54C3), defined as bilateral sacral ala fractures with a transverse fracture through the sacral body, consistent with spinopelvic dissociation. Factors associated with U-type morphology were evaluated using univariate logistic regression, followed by multivariable logistic regression to identify independent associations. RESULTS: 263 geriatric patients with sacral fractures were included, of whom 76 (28.9%) had U-type fractures. On multivariable analysis, spondylosis/spondylolisthesis (OR 2.08, 95% CI 1.10-3.98, p = 0.025), independent ambulation prior to injury (with assistive device use as the reference group; OR 2.18, 95% CI 1.13-4.29, p = 0.022), and an atraumatic mechanism of injury (with low-energy injury mechanism as the reference group; OR 2.34, 95% CI 1.05-5.27, p = 0.038) were independently associated with U-type fractures. CONCLUSIONS: Nearly one-third of geriatric patients with sacral fractures who underwent advanced imaging demonstrated U-type morphology. Compared with non-U-type sacral fractures, U-type morphology was independently associated with degenerative spinal disease, independent ambulation prior to injury, and atraumatic presentation, suggesting a distinct injury profile in relatively functional older adults with underlying spinal degeneration.