Vitamin D Status and Supplementation in Patients Undergoing Spine Surgery: A Systematic Review and Meta-analysis

Background Vitamin D may influence bone healing and recovery after spine surgery, but its clinical effects remain uncertain. Objective To evaluate clinical, functional, and bone-related outcomes associated with vitamin D status and supplementation in patients undergoing spine surgery. Methods This systematic review and meta-analysis was registered in PROSPERO (CRD420261467482) and reported according to PRISMA 2020. PubMed/MEDLINE, Scopus, Web of Science, Embase, and the Cochrane Library were searched from inception through 1 June 2026. Random-effects meta-analyses used mean differences (MDs) for continuous outcomes and risk ratios (RRs) for dichotomous outcomes. Direct supplementation analyses were prioritized, while analyses combining supplementation, baseline vitamin D status, or co-interventions were considered exploratory. Risk of bias was assessed using design-specific Joanna Briggs Institute tools. Results Thirteen studies were included. Four supplementation studies involving 177 participants showed no significant reduction in postoperative pain (MD -0.82, 95% CI -2.50 to 0.86; I2 = 84.3%). Three studies involving 277 participants showed lower Oswestry Disability Index scores in an exploratory analysis (MD -6.40, 95% CI -10.41 to -2.39; I2 = 96.8%). Three supplementation studies involving 128 participants showed no significant improvement in fusion rate (RR 1.17, 95% CI 0.78 to 1.74; I2 = 31.5%). An exploratory four-study fusion analysis was also not statistically significant (RR 1.24, 95% CI 0.98 to 1.57; I2 = 45.5%). Conclusion Current evidence does not establish that vitamin D supplementation independently improves postoperative pain or fusion rates after spine surgery. Possible benefits for disability and other bone-related outcomes remain uncertain because of small study numbers, heterogeneity, co-interventions, and residual confounding. Larger randomized trials stratified by baseline vitamin D status are needed.