# Preoperative hypocalcemia predicts postoperative complications in older orthopedic patients: A multicenter cohort study

## TL;DR

Low calcium levels before surgery in older orthopedic patients are linked to higher postoperative complication risks, suggesting preoperative calcium correction could improve outcomes.

## Contribution

This study identifies preoperative hypocalcemia as an independent predictor of postoperative complications in elderly orthopedic patients.

## Key findings

- Low preoperative calcium levels are associated with a 79% higher risk of complications compared to high calcium levels.
- A threshold effect is observed at 2.4 mmol/L serum calcium, below which the risk of complications increases significantly.
- The association remains consistent across subgroups of age, gender, comorbidities, and surgical complexity.

## Abstract

Serum calcium, a key biochemical marker in the body, plays a crucial role in maintaining bone health. Nevertheless, research exploring the link between preoperative serum calcium levels and the occurrence of postoperative complications in elderly orthopedic patients is currently lacking.

This study sought to assess the ability of preoperative serum calcium levels to predict the occurrence of postoperative complications in geriatric orthopedic surgery.

We utilized multivariate logistic regression to identify correlations between serum calcium levels and complications. Generalized additive models to analyze the dose-response relationship with curve fitting and threshold effect evaluation. Subgroup analyses further evaluated the impact of other covariates.

This study included 690 elderly patients undergoing orthopedic surgery. Common postoperative complications primarily included infection, hypoalbuminemia, and electrolyte imbalance, etc. The study demonstrated that preoperative serum calcium levels were an independent protective factor against postoperative complications (OR: 0.24, CI: 0.07–0.76, P = 0.036). When comparing groups based on serum calcium tertiles, patients in the low calcium group exhibited a 79% higher risk of complications compared to the high calcium group (OR = 1.79, 95% CI: 1.12–2.78). Further nonlinear relationship analysis revealed a threshold effect between serum calcium and postoperative complication risk, with a turning point at 2.4 mmol/L. The association was statistically significant below this value but not above it. Subgroup analyses and interaction tests showed that age, gender, comorbidities, and medications, cognitive function, cardiac function, and surgical complexity were not significantly associated with this correlation (P > 0.05 for interaction).

Preoperative calcium screening and correction may represent a simple, low-cost strategy to reduce postoperative complications in elderly orthopedic patients. This study provides evidence for the importance of actively correcting calcium levels before surgery and establishes the value of serum calcium as an early warning indicator for poor prognosis.