• Vijay M Ravindra, Jakub Godzik, Andrew T Dailey, Meic H Schmidt, Erica F Bisson, Robert S Hood, Andrew Cutler, and Wilson Z Ray.
• *Department of Neurosurgery, Clinical Neurosciences Center, University of Utah, Salt Lake City, UT †Department of Neurosurgery, Barrow Neurological Institute, Phoenix, AZ ‡University of Florida School of Medicine, Gainesville, FL; and §Department of Neurosurgery, Washington University in St. Louis, St. Louis, MO.
• Spine. 2015 Oct 1; 40 (19): 1536-41.

Study DesignProspective observational study.ObjectiveTo investigate the association of perioperative vitamin D levels and nonunion rates and time to fusion in patients undergoing elective spine fusion.Summary Of Background DataAlthough there is a clear link between bone mineral density and the risk of osteoporosis, it is unclear whether low vitamin D levels affect rates and timing of spinal fusion.MethodsSerum 25-OH vitamin D levels were measured perioperatively in adults undergoing elective spinal fusion between 2011 and 2012. Vitamin D levels <20 ng/mL were considered deficient. Univariate and multivariate logistic regression were performed to identify independent predictors of pseudarthrosis/nonunion within a minimum follow-up period of 12 months. Kaplan-Meier analysis was used to compare time to fusion between groups.ResultsOf the 133 patients, 31 (23%) demonstrated vitamin D deficiency. Mean patient age was 57 ± 13 years; 44% were female and 94% were Caucasian. The cervical spine was fused in 49%, the lumbar spine in 47%, and the thoracic spine in 4%. Mean construct length was 2 levels (range 1-16). At 12-month follow-up, 112/133 (84%) patients demonstrated fusion (median time to fusion 8.4 mo). Nonunion at 12 months was associated with vitamin D deficiency (20% of patients with adequate vitamin D level vs. 38% of vitamin D-deficient patients, P = 0.063). Kaplan-Meier survival analysis demonstrated time to fusion was significantly longer in the vitamin D-deficient group (12 vs. 6 mo, P = 0.001). On multivariate analysis, vitamin D deficiency was an independent predictor of nonunion (odds ratio 3.449, P = 0.045) when adjusted for age, sex, obesity, fusion length, location, graft type, smoking, and bone morphogenetic protein use.ConclusionVitamin D levels may affect nonunion rate and time to fusion. These results offer insight into the importance of the metabolic milieu for bony fusion as well as a potential avenue for therapeutic intervention.Level Of Evidence3.

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