title: Vitamin D Levels and 1-Year Fusion Outcomes in Elective Spine Surgery: A Prospective Observational Study.
abstract: METHODS
  Prospective observational study.
  
  
  OBJECTIVE
  To investigate the association of perioperative vitamin D levels and nonunion rates and time to fusion in patients undergoing elective spine fusion.
  
  
  BACKGROUND
  Although 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.
  
  
  METHODS
  Serum 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.
  
  
  RESULTS
  Of 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.
  
  
  CONCLUSIONS
  Vitamin 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.
  
  
  METHODS
  3.
authors.affiliation: *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.
authors.forename: Vijay M
authors.initials: VM
authors.lastname: Ravindra
authors.forename: Jakub
authors.initials: J
authors.lastname: Godzik
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Dailey
authors.forename: Meic H
authors.initials: MH
authors.lastname: Schmidt
authors.forename: Erica F
authors.initials: EF
authors.lastname: Bisson
authors.forename: Robert S
authors.initials: RS
authors.lastname: Hood
authors.forename: Andrew
authors.initials: A
authors.lastname: Cutler
authors.forename: Wilson Z
authors.initials: WZ
authors.lastname: Ray
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D002574:Cervical Vertebrae / Q000378:metabolism / Q000601:surgery*; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000378:metabolism / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013123:Spinal Fusion / Q000379:methods; D014808:Vitamin D Deficiency / Q000378:metabolism*; D014815:Vitamins / Q000378:metabolism*
chemical_list: D019485:Bone Morphogenetic Proteins; D014815:Vitamins