Preoperative hyponatremia predicts 30-day complications after open reduction and internal fixation of proximal humerus fractures: A retrospective study

Introduction: Open reduction and internal fixation (ORIF) is a standard treatment for displaced proximal humerus fractures. Conventional risk stratification relies on comorbidities and demographics, yet biochemical abnormalities, such as hyponatremia, may serve as predictors of vulnerability. Hyponatremia has been linked to frailty, immune dysfunction, and reduced physiologic reserve. This study evaluated whether preoperative hyponatremia is associated with an increased risk of 30-day complications after proximal humerus ORIF. Materials and methods: A retrospective cohort analysis was performed using the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database. Adult patients undergoing ORIF were included as hyponatremic (<135 mmol/L) or normonatremic (135–144 mmol/L). Thirty-day postoperative complications were assessed. Binary logistic regression with backward stepwise elimination was used to identify independent predictors, incorporating demographic and comorbidity variables. Significance was defined as p < 0.05. Results: Hyponatremia was significantly associated with multiple adverse outcomes after ORIF. Hyponatremic patients had higher odds of urinary tract infection (OR 2.24; 95 % CI, 1.20–4.16; p = 0.011), blood transfusion (OR 1.72; 95 % CI, 1.29–2.28; p < 0.001), unplanned reoperation (OR 1.78; 95 % CI, 1.33–2.40; p < 0.001), readmission (OR 1.66; 95 % CI, 1.22–2.25; p = 0.001), and overall complication risk (OR 1.56; 95 % CI, 1.26–1.93; p < 0.001). Conclusion: Preoperative hyponatremia is associated with an increased risk of complications following proximal humerus ORIF. These findings suggest that serum sodium may function as a surrogate marker of systemic frailty and aid in perioperative risk stratification for patients undergoing ORIF for proximal humerus fractures. Level of evidence: III. Retrospective Cohort Comparison; Prognosis Study.