Spine Surgery Patients Need Adequate Vitamin D Levels

Lara C. Pullen, PhD

November 11, 2011

November 11, 2011 (Chicago, Illinois) — Spine-related disability is higher in patients with low levels of vitamin D. A new study found that 65% of patients undergoing spinal fusion had vitamin D inadequacy (<32 ng/mL), which can delay recovery. Low levels of vitamin D predispose to fracture pseudarthrosis and suboptimal surgical outcome.

The results of the study were presented here at the North American Spine Society 26th Annual Meeting. The work was performed by Jacob M. Buchowski, MD, and orthopedic surgeons at Washington University School of Medicine and Barnes-Jewish Hospital in St. Louis, Missouri. The study was chosen as one of the meeting's best papers.

Dr. Buchowski noted that "it was alarming to see that so many patients have inadequate or deficient vitamin D levels, especially when vitamin D is so readily available and inexpensive." He suggested that it is reasonable to screen patients scheduled for surgery for vitamin D levels, and those with a documented deficiency should be given vitamin D supplements.

Dr. Buchowski was initially prompted to perform the study because he had a patient in her 40s who experienced a slow recovery after spinal fusion therapy. During examination, the patient mentioned that she had recently been diagnosed with vitamin D deficiency. Dr. Buchowski and colleagues at Barnes-Jewish Hospital now routinely screen all patients undergoing spinal fusion surgery for vitamin D deficiency.

The study consisted of 313 patients undergoing spinal fusion surgery, which involved the removal of the discs between 2 or more vertebrae. The average age of the study population was 55.2 ±12.9 years (55% female, 41% obese, 94% white, and 4.6% black). Overall, 44% of the fusions were cervical, 38% were thoracic, and 53% were lumbar.

The mean vitamin D level in the study population was 28.6 ± 13.0 ng/mL, and 27% of the patients were vitamin D deficient (<20 ng/mL).

The subset of patients with inadequate vitamin D had a higher rate of obesity (body mass index, ≥30 kg/mm²; P = .025), black race (P = .005), and smoking (P = .023). They also had a higher mean visual analog scale pain score (P = .024), lower bone mineral density (P = .032), and more prevalent neurologic deficits (P = .094).

The authors generated a composite disability measurement by pooling the Neck Disability Index and Oswestry Disability Index scores of cervical and thoracolumbar patients. When the 57 patients who had had previous multivitamin or vitamin D supplementation were excluded, the mean pooled disability score was significantly higher in the inadequate cohort (P = .003).

Although a previous study showed inadequate vitamin D levels in 43% of patients undergoing orthopedic procedures, this is the first study to look solely at patients undergoing spine surgery.

In discussing the limitations of the study, Maxwell Boakye, MD, FACS, from the Stanford School of Medicine, in California, told Medscape Medical News that "rigorous multivariate analysis was not performed to control for potential confounders, and selection bias could explain the differences in outcomes. The results may not necessarily generalize to other populations, and need to be confirmed in other geographic populations and settings."

Vitamin D helps with calcium absorption, and patients with a deficiency can have difficulty producing new bone. Low vitamin D levels are known to be common in elderly patients. Dr. Buchowski and colleagues found, however, that many younger patients also have vitamin D deficiency. The researchers found that the main risk factors for inadequate vitamin D are smoking, obesity, disability prior to surgery, and never having taken vitamin D or multivitamin supplements.

Sun exposure is one of the best ways to get the body to produce vitamin D. Vitamin D is also easily stored in the body. To maintain bone health and normal calcium metabolism, the Institute of Medicine established a recommended daily allowance for vitamin D of 600 IU.

Dr. Buchowski reports consulting for Stryker and CoreLink, and has a speaking and/or teaching arrangement with Stryker. Dr. Boakye has disclosed no relevant financial relationships.

North American Spine Society (NASS) 26th Annual Meeting: Abstract 45. Presented November 3, 2011.