Predictors of Pulmonary Complications After Rib Fractures: Systematic Review and Meta-Analyses.

INTRODUCTION: Pulmonary complications are the principal drivers of morbidity, mortality, and resource utilization after rib fractures, yet early risk stratification remains inconsistent because of uncertainty regarding independent predictors. Existing studies frequently report unadjusted associations or heterogeneous outcomes, limiting clinical applicability. This systematic review and meta-analysis aimed to identify and quantify multivariable-adjusted predictors of pulmonary complications following rib fractures. METHODS: A protocol-registered systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 and Synthesis Without Meta-Analysis guidelines. Four databases (Scopus, Web of Science, PubMed, and Lens.org) were searched from January 2010 to February 2026. Eligible studies enrolled adults with blunt rib fractures and reported multivariable-adjusted effect estimates for pulmonary complications. Random-effects meta-analyses using restricted maximum likelihood estimation were performed for prespecified predictors: displaced rib fractures, male sex, and fracture burden thresholds. Risk of bias was assessed with the Newcastle-Ottawa Scale, and the certainty of pooled evidence was rated using the Grading of Recommendations, Assessment, Development and Evaluations framework. Heterogeneity, publication bias, equivalence testing, subgroup analyses, and leave-one-out sensitivity analyses were conducted. Nonpoolable predictors were synthesized narratively. RESULTS: Twelve studies encompassing 72,380 patients from nine countries met the inclusion criteria. Three predictors demonstrated independent associations in pooled analyses. Displaced rib fractures conferred the greatest risk (pooled adjusted odds ratio [OR] 3.32, 95% confidence interval [CI] 1.78-6.19; I2 = 0%). An exploratory pooled estimate of rib fracture burden (combining heterogeneous threshold definitions and one delayed-outcome estimate) was approximately twofold (OR 2.10, 95% CI 1.20-3.67; I2 = 25%); this estimate should be interpreted as an exploratory summary of direction and approximate magnitude rather than a single clinically interchangeable threshold effect. Male sex was also independently associated with complications (OR 2.02, 95% CI 1.17-3.48; I2 = 0%). Narrative synthesis identified additional high-risk features, including age ≥65 y, chronic obstructive pulmonary disease, upper or midline fracture location, and bilateral involvement. Leave-one-out sensitivity analyses produced directionally consistent estimates, and no statistically significant publication bias was detected, although these tests are underpowered when k is small. Effects were directionally consistent across geographic regions and outcome types. Grading of Recommendations, Assessment, Development and Evaluations certainty was moderate for displaced rib fracture, low for male sex, and low for rib fracture burden. CONCLUSIONS: Displaced rib fracture, male sex, and greater rib fracture burden were associated with pulmonary complications in pooled analyses adjusted for confounders. The fracture burden estimate should be considered exploratory because thresholds and outcome definitions varied across contributing studies. Advanced age and chronic lung disease help further define a higher-risk patient profile in the narrative synthesis. These findings may inform triage, analgesia, monitoring, and surgical stabilization decisions, but prospective studies using standardized pulmonary outcome definitions and validated prediction models are needed.