Prevalence and Clinical Implications of Vitamin D Deficiency in Spine Surgery Patients: A Large-Scale Clinical Study.

STUDY DESIGN: Retrospective study. OBJECTIVE: To determine the prevalence of vitamin D deficiency in patients undergoing spine surgery and to evaluate its distribution across demographic characteristics, bone mineral density (BMD), and spine disease categories. A secondary objective was to examine the associations between serum 25-hydroxyvitamin D (25(OH)D) levels and bone turnover markers (BTMs). SUMMARY OF BACKGROUND DATA: Vitamin D is essential for musculoskeletal health. Although previous studies have reported a high prevalence of vitamin D deficiency among patients undergoing spinal surgery, most have been limited by small sample sizes, and large-scale investigations remain scarce. METHODS: Patients aged ≥40 years who underwent spine surgery between January 2021 and March 2024 were retrospectively reviewed. Preoperative evaluation included BMD measured by dual-energy X-ray absorptiometry and serum measurements of 25(OH)D and BTMs, including β-cross-linked C-telopeptide of type I collagen (β-CTX), procollagen type I N-terminal propeptide (PINP), and osteocalcin. Patients were stratified by age, sex, BMD status, and spine disease category. The correlation between serum 25(OH)D and BTMs was evaluated. RESULTS: A total of 1388 patients were included. Vitamin D deficiency was present in 43.4% of patients, and 39.2% had insufficient levels. Deficiency was more common in females (50.1%) than males (29.9%) and was most prevalent among patients aged 40-59 years. Patients with osteoporosis had the lowest mean 25(OH)D levels and the highest β-CTX, PINP, and osteocalcin levels. Among disease categories, patients with osteoporotic vertebral fractures showed the lowest vitamin D levels and the highest β-CTX and PINP levels. Serum 25(OH)D levels were negatively correlated with β-CTX and PINP. CONCLUSIONS: Vitamin D deficiency remains highly prevalent among patients undergoing spine surgery, particularly in females and younger individuals. Lower vitamin D levels are associated with increased bone turnover activity, suggesting that routine assessment and management of vitamin D status may help optimize bone health. LEVEL OF EVIDENCE: Level III.