PEER-REVIEW REPORTS
Prevalence of Vitamin D Deficiency in Patients Undergoing Elective Spine Surgery: A Cross-Sectional Analysis Vijay M. Ravindra1, Jakub Godzik2, Jian Guan1, Andrew T. Dailey1, Meic H. Schmidt1, Erica F. Bisson1, Robert S. Hood1, Wilson Z. Ray2
Key words Degenerative spondylosis - Fusion - Insufficiency - Osteoporosis - Pseudarthrosis - Spinal instrumentation - Spine - Vitamin D deficiency -
Abbreviations and Acronyms BMD: Bone mineral density BMI: Body mass index NDI: Neck disability index ODI: Oswestry disability index OR: Odds ratio From the 1Department of Neurosurgery, Clinical Neurosciences Center, University of Utah, Salt Lake City, Utah and 2Department of Neurosurgery, Washington University in St. Louis, St. Louis, Missouri, USA To whom correspondence should be addressed: Wilson Z. Ray, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2015) 83, 6:1114-1119. http://dx.doi.org/10.1016/j.wneu.2014.12.031 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2015 Elsevier Inc. All rights reserved.
- 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 (18 years with a diagnosis of degenerative spinal spondylosis or spinal instability treated with spinal fusion were included. Risk factors for vitamin D deficiency (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%e57% of adults living in the United
1114
www.SCIENCEDIRECT.com
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
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.12.031
PEER-REVIEW REPORTS VIJAY M. RAVINDRA ET AL.
PREOPERATIVE VITAMIN D DEFICIENCY
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. METHODS 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 patients during the perioperative period (within 48 hours of surgical intervention). Surgical details including the length and location of the fusion construct, the number of motion segments, the use of graft material and bone morphogenic protein-2 (BMP-2), the instrumentation type, and the revision status were recorded. Data Collection Medical records were reviewed to identify patient demographic information, medical comorbidity information, medication use, and history of vitamin D supplementation. Specific variables thought to influence vitamin D levels were recorded, including age (60 years), race when available (white or other), and sex.
Figure 1. Representation of the physiology of vitamin D3 and its activation process through the liver and kidneys and the resultant effect on body calcium homeostasis. PTH,parathyroid hormone.
Previous studies have shown that intestinal absorption capacity declines with age, and increasing amounts of adipose tissue may sequester fat-soluble vitamins, thus diminishing their bioavailability (13); therefore, the body mass index (BMI) was recorded when available. Information on additional comorbidities, such as previous diagnosis of diabetes (type I or type II), endocrine dysfunction, and psychiatric, cardiovascular, and pulmonary disease, was collected. Smoking status, either current or significant smoking history (within 6 months of surgery), was recorded because of the known association between cigarette smoking and attenuation of calcium absorption and promotion of bone loss (16). In previous studies, smoking has been extrapolated as a marker for dietary habits and potential suboptimal micronutrient intake (13). In addition, the use of steroids for chronic disease (e.g., rheumatoid arthritis), use of vitamin D supplementation preoperatively (and preoperative vitamin D levels, if measured), and preoperative disability indices were recorded.
WORLD NEUROSURGERY 83 [6]: 1114-1119, JUNE 2015
Statistical Analysis Data were summarized using means and standard deviations for continuous variables and counts and frequencies for categorical variables. Univariate statistical analysis was performed to identify the unadjusted association of basic demographic and medical comorbidity covariates with the presence of vitamin D deficiency. Between-group comparisons were analyzed using a Fisher exact test for categorical variables and Student’s t-test for continuous variables. Colinearity between covariates was examined using Pearson’s correlation coefficients. Those covariates satisfying the statistical entry criteria (P < 0.2) on univariate analysis were included in the logistic regression model; steroid use and smoking were also included in the model. Multiple logistic regression analysis was performed to assess independent patient-level risk factors for preoperative vitamin D deficiency. The HosmerLemeshow test was used to check goodness-of-fit of the model, and the predictive value of the multivariate model was
www.WORLDNEUROSURGERY.org
1115
PEER-REVIEW REPORTS VIJAY M. RAVINDRA ET AL.
PREOPERATIVE VITAMIN D DEFICIENCY
Table 1. General Demographics and Health Characteristics of Patients Undergoing Elective Spine Fusion (n ¼ 230) Characteristic
Table 2. Surgical Characteristics of Patients Undergoing Elective Spine Fusion Vitamin D Level Overall Population (N [ 230)
Deficient (
Prevalence of Vitamin D Deficiency in Patients Undergoing Elective Spine Surgery: A Cross-Sectional Analysis Vijay M. Ravindra1, Jakub Godzik2, Jian Guan1, Andrew T. Dailey1, Meic H. Schmidt1, Erica F. Bisson1, Robert S. Hood1, Wilson Z. Ray2
Key words Degenerative spondylosis - Fusion - Insufficiency - Osteoporosis - Pseudarthrosis - Spinal instrumentation - Spine - Vitamin D deficiency -
Abbreviations and Acronyms BMD: Bone mineral density BMI: Body mass index NDI: Neck disability index ODI: Oswestry disability index OR: Odds ratio From the 1Department of Neurosurgery, Clinical Neurosciences Center, University of Utah, Salt Lake City, Utah and 2Department of Neurosurgery, Washington University in St. Louis, St. Louis, Missouri, USA To whom correspondence should be addressed: Wilson Z. Ray, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2015) 83, 6:1114-1119. http://dx.doi.org/10.1016/j.wneu.2014.12.031 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2015 Elsevier Inc. All rights reserved.
- 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 (18 years with a diagnosis of degenerative spinal spondylosis or spinal instability treated with spinal fusion were included. Risk factors for vitamin D deficiency (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%e57% of adults living in the United
1114
www.SCIENCEDIRECT.com
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
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.12.031
PEER-REVIEW REPORTS VIJAY M. RAVINDRA ET AL.
PREOPERATIVE VITAMIN D DEFICIENCY
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. METHODS 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 patients during the perioperative period (within 48 hours of surgical intervention). Surgical details including the length and location of the fusion construct, the number of motion segments, the use of graft material and bone morphogenic protein-2 (BMP-2), the instrumentation type, and the revision status were recorded. Data Collection Medical records were reviewed to identify patient demographic information, medical comorbidity information, medication use, and history of vitamin D supplementation. Specific variables thought to influence vitamin D levels were recorded, including age (60 years), race when available (white or other), and sex.
Figure 1. Representation of the physiology of vitamin D3 and its activation process through the liver and kidneys and the resultant effect on body calcium homeostasis. PTH,parathyroid hormone.
Previous studies have shown that intestinal absorption capacity declines with age, and increasing amounts of adipose tissue may sequester fat-soluble vitamins, thus diminishing their bioavailability (13); therefore, the body mass index (BMI) was recorded when available. Information on additional comorbidities, such as previous diagnosis of diabetes (type I or type II), endocrine dysfunction, and psychiatric, cardiovascular, and pulmonary disease, was collected. Smoking status, either current or significant smoking history (within 6 months of surgery), was recorded because of the known association between cigarette smoking and attenuation of calcium absorption and promotion of bone loss (16). In previous studies, smoking has been extrapolated as a marker for dietary habits and potential suboptimal micronutrient intake (13). In addition, the use of steroids for chronic disease (e.g., rheumatoid arthritis), use of vitamin D supplementation preoperatively (and preoperative vitamin D levels, if measured), and preoperative disability indices were recorded.
WORLD NEUROSURGERY 83 [6]: 1114-1119, JUNE 2015
Statistical Analysis Data were summarized using means and standard deviations for continuous variables and counts and frequencies for categorical variables. Univariate statistical analysis was performed to identify the unadjusted association of basic demographic and medical comorbidity covariates with the presence of vitamin D deficiency. Between-group comparisons were analyzed using a Fisher exact test for categorical variables and Student’s t-test for continuous variables. Colinearity between covariates was examined using Pearson’s correlation coefficients. Those covariates satisfying the statistical entry criteria (P < 0.2) on univariate analysis were included in the logistic regression model; steroid use and smoking were also included in the model. Multiple logistic regression analysis was performed to assess independent patient-level risk factors for preoperative vitamin D deficiency. The HosmerLemeshow test was used to check goodness-of-fit of the model, and the predictive value of the multivariate model was
www.WORLDNEUROSURGERY.org
1115
PEER-REVIEW REPORTS VIJAY M. RAVINDRA ET AL.
PREOPERATIVE VITAMIN D DEFICIENCY
Table 1. General Demographics and Health Characteristics of Patients Undergoing Elective Spine Fusion (n ¼ 230) Characteristic
Table 2. Surgical Characteristics of Patients Undergoing Elective Spine Fusion Vitamin D Level Overall Population (N [ 230)
Deficient (
