Factors associated with occult acute rib fractures on chest CT after negative radiography in older fall patients

In older patients with fall-related injuries, chest computed tomography (CT) can detect acute rib fractures after chest radiography (CXR) showed no evidence of acute fracture. We evaluated clinical factors associated with CT-reported acute rib fracture within this clinician-selected imaging pathway. In this single-center retrospective observational study, we included patients aged ≥65 years who presented to the emergency department after a slip or fall between February 2021 and January 2024 and underwent same-visit chest CT after initial CXR without a definite, possible, or suspected acute rib fracture. The primary multivariable logistic model included age category (65–74, 75–84, or ≥85 years), male sex, fall from an elevated surface, non-alert mental status, head trauma, and localized chest wall pain. Covariates were entered simultaneously without automated selection, and all 739 patients were included. Sensitivity analyses examined alternative age specifications, sparse focal findings, and selectively ordered laboratory testing. Among 739 patients, 224 (30.3%) had a CT-reported acute rib fracture. Relative to ages 65 to 74 years, adjusted odds ratios (aORs) were 2.236 (95% confidence interval [CI], 1.443–3.465) for ages 75 to 84 years and 8.391 (95% CI, 4.354–16.172) for ages ≥85 years. Male sex (aOR, 1.791; 95% CI, 1.187–2.701), fall from an elevated surface (aOR, 2.415; 95% CI, 1.561–3.734), non-alert mental status (aOR, 1.891; 95% CI, 1.017–3.514), and localized chest wall pain (aOR, 11.541; 95% CI, 7.584–17.562) were also associated with acute rib fracture. Head trauma was not significantly associated with acute rib fracture. A 3-knot restricted cubic spline sensitivity analysis showed no evidence of departure from a linear age effect ( P  = .875); the estimate for non-alert mental status was attenuated when age was modeled continuously ( P  = .068). Within this clinician-selected CT pathway, older age, male sex, fall from an elevated surface, and localized chest wall pain were associated with CT-reported acute rib fracture after adjustment in the primary full-cohort model; the association with non-alert mental status was less stable across age specifications. These findings do not define a CT decision rule or support routine CT after negative CXR.