Elsevier

World Neurosurgery

Volume 83, Issue 6, June 2015, Pages 1114-1119
World Neurosurgery

Peer-Review Report
Prevalence of Vitamin D Deficiency in Patients Undergoing Elective Spine Surgery: A Cross-Sectional Analysis

https://doi.org/10.1016/j.wneu.2014.12.031Get rights and content

Objective

Decreased bone density secondary to osteoporosis and osteomalacia represents a significant risk factor for bony fracture and spinal instrumentation failure. We evaluated the incidence of vitamin D deficiency in patients undergoing elective spinal instrumentation to investigate which patient-level risk factors are associated with deficient vitamin D levels.

Methods

Serum 25-OH vitamin D levels were evaluated postoperatively (<72 hours) in patients undergoing elective spinal fusion from 2011 through 2012. Patients >18 years with a diagnosis of degenerative spinal spondylosis or spinal instability treated with spinal fusion were included. Risk factors for vitamin D deficiency (<20 ng/mL) were analyzed using univariate and multiple logistic regression to identify independent predictors of deficiency.

Results

The mean preoperative neck and Oswestry disability indexes of the 230 consecutive patients (mean, 57 ± 13.9 years) were 21.0 ± 9.8 and 22.2 ± 8.5, respectively. Mean 25-OH vitamin D level was 25.9 ± 12.4 ng/mL (range, 6–77 ng/mL). Sixty-nine (30.0%) patients had laboratory-confirmed vitamin D deficiency and 89 (38.9%) had laboratory-confirmed vitamin D insufficiency (20–30 ng/mL). The risk of vitamin D deficiency was greater in men (odds ratio [OR] 2.53; P = 0.009), patients aged 40–60 years (OR 2.45; P = 0.018), and those who had body mass index >40 (OR 7.55; P = 0.004), an existing diagnosis of diabetes (OR 3.29; P = 0.019), or no vitamin D supplementation (OR 4.96; P = 0.043).

Conclusions

Vitamin D deficiency was common in patients with degenerative spondylosis undergoing spinal fusion. Middle-aged patients, men, the morbidly obese, those with a history of diabetes, and those with no history of supplementation had a higher incidence of vitamin D deficiency.

Introduction

Decreased bone density secondary to osteoporosis and osteomalacia represents a serious risk factor for both bony fracture and spinal instrumentation failure 5, 8, 11, 21, 24. One of the most common and potentially treatable causes of pseudarthrosis or instrumentation failure in patients undergoing spinal fusion is poor bone mineral density (BMD) resulting from age-related vertebral osteoporosis (7). Numerous studies have shown that low serum vitamin D levels lead to greater bone resorption and turnover, predisposing patients to vertebral osteoporosis 14, 22, 23.

The National Osteoporosis Foundation estimates that 52 million Americans have osteoporosis or low bone mass (http://nof.org/articles/7), whereas an estimated 25%–57% of adults living in the United States have a deficiency of vitamin D 10, 12. Osteoporosis is a bony condition defined by a decreased density of normally mineralized bone. Reduced bone density compromises the mechanical strength of bone, increasing the risk of bony fracture (11). Vitamin D is a secosteroid that plays a key role in bone and calcium metabolism. The active form of vitamin D is vitamin D3 (cholecalciferol). The cutaneous synthesis of vitamin D3 is the major source of vitamin D. Cutaneous vitamin D3, along with that from nutritional sources, is conjugated in the liver to 25(OH) vitamin D and the kidneys to the active form of 1,25(OH)2 vitamin D (20). Vitamin D causes increased calcium absorption from the intestines and the kidneys and acts on osteoblasts to increase BMD (Figure 1) (20).

Nearly one third of patients older than 50 years of age undergoing spinal surgery have osteoporosis (5). Stoker et al. (26) demonstrated an insufficiency rate of 57% and a deficiency rate of 27% in preoperative 25-OH vitamin D levels in 313 patients undergoing elective spinal fusion. Despite this high incidence of osteoporosis and its association with serum vitamin D, the preoperative assessment of BMD and vitamin D levels is not routine among most spinal surgeons (7). Although there is a clear link between BMD and the risk of osteoporosis, it is not clear whether aggressive treatment of low vitamin D levels leads to improved spinal fusion and decreased incidence of instrumentation failure. With increased scrutiny of all spinal fusion procedures, low-cost testing that helps predict the potential risk for subsequent nonfusion and need for revision surgery may have substantial cost-saving benefits. Because of the compelling evidence suggesting a high incidence of unrecognized vitamin D deficiency, studies examining the precise role of these measures in humans undergoing spinal fusion procedures are necessary (26).

In the present study, we evaluated the incidence of vitamin D deficiency in patients scheduled to undergo elective spinal instrumentation procedures to investigate which patient-level factors are associated with deficient vitamin D levels. The information gathered will provide an understanding of risk factors and will allow surgeons an opportunity to preoperatively assess bony health and metabolism before surgery.

Section snippets

Patient Population

A cross-sectional observational analysis was designed to evaluate patients undergoing elective spinal fusion at a single academic, tertiary referral institution between November 2011 and December 2012. The Institutional Review Board approved the study. Patients older than 18 years undergoing elective spinal fusion were eligible. To maintain population uniformity, patients with traumatic spinal fracture or injury treated with stabilization were excluded. Vitamin D levels were assessed in all

Patient Characteristics

Two hundred thirty patients underwent elective spine surgery during the study period. The mean age of the patients was 57 ± 13.9 years (range, 18–90 years), with 42.2% of patients older than 60 years (Table 1). More than half (56.1%) of the population were men, and nearly all patients were white (95.9% of 221 patients). BMI was categorized into three groups, <30 representing nonobese patients, 30–40 indicating obesity, and >40 signifying morbidly obese; the mean BMI of the 223 patients for whom

Discussion

In 2006, approximately 343,000 spinal fusion procedures were performed in the United States alone. A common and potentially treatable cause of delayed complication after spinal fusion is pseudarthrosis and spinal instrumentation failure (19). Although pseudarthrosis or instrumentation failure cannot always be linked to a single entity, a known contributor is poor BMD or osteoporosis (9). Decreased BMD is a known predictor of instrumentation failure, and with an aging population, an increased

Acknowledgments

We thank Kristin Kraus, M.Sc., for editorial assistance in preparing this article, Jennie Williams, M.F.A., for illustrations, and Richard H. Schmidt, M.D., Ph.D., and Joel D. MacDonald, M.D., for their participation in this study.

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    Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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