Preoperative Vitamin D Status in Adults Undergoing Spinal Fusion
– Source: Paper #45, Nov 3, 2011, North American Spine Society Annual Meeting
By Jacob Buchowski, MD, et al.
Background Context: Vitamin D plays a pivotal role in mineral homeostasis and musculoskeletal health. Deficiency in the hormone predisposes to osteoporosis and subsequent fracture.
It can also lead to generalized bone pain and muscle weakness, which may translate into higher VAS, NDI, and ODI scores [visual analogue scale, neck disability index, and Oswestry low back pain disability index].
Recently, 43% of an adult orthopedic surgery population was found to be vitamin D-insufficient preoperatively.
To our knowledge, despite this alarming result, the prevalence of preoperative vitamin D abnormality in a dedicated adult spine surgery population has yet to be investigated.
Purpose: We sought to characterize the prevalence of preoperative vitamin D inadequacy and deficiency in adults undergoing spinal fusion and to determine whether previously identified risk factors (i.e., black race and obesity) for vitamin D abnormality can be applied to our population.
We also attempted to compare VAS, NDI, and ODI scores between groups of patients with vitamin D inadequacy and normal levels of the metabolite.
Study Design/Setting: Prospective diagnostic study (Level I).
Patient Sample: 262 consecutive adults who had undergone spinal fusion.
Outcome Measures: Vitamin D inadequacy or hypovitaminosis D was defined as a serum 25-hydroxyvitamin D (25OHD) level of less than 32 ng/mL, and deficiency was defined as 25OHD less than 20 ng/mL.
Preoperative VAS, NDI, and ODI scores were recorded. Surgical data included the number and location of fused levels.
Methods: Serum 25OHD levels were measured prospectively in consecutive adults (18 years of age or older) undergoing spinal fusion at a single institution. Operative schedules were surveyed in order to identify these patients. Statistical analysis was performed, and subsets were compared with Fisher’s exact and nonparametric Mann-Whitney U tests. [Used to determine if difference exists between two ‘groups.’]
Results: The mean age and BMI of the population were 55.2 plus/minus 12.9 years and 28.7 plus/minus 5.8 kg/m2, respectively. Of the 262 patients, 55% were female, 94% were white, and 4.6% were black.
There were 44% cervical [neck], 38% thoracic [upper back], and 53% lumbar [lower back] fusions.
The mean vitamin D level was 28.6 plus/minus 13.0 ng/mL. The overall rates of vitamin D inadequacy and deficiency were 65% and 27%, respectively.
As expected, there were significantly higher rates of obesity (BMI plus/minus 30 kg/m2; p=0.025), black race (p=0.005), and smoking (p=0.023) in the vitamin D-inadequate subset.
The mean VAS pain score was higher (p=0.024), bone mineral density was lower (p=0.032), and neurologic deficits were more prevalent (p=0.094) in this group as well.
We generated a composite disability measure by pooling NDI and ODI scores of cervical and thoraco-lumbar patients, respectively.
Upon excluding 57 patients with previous vitamin D or multivitamin supplementation, the mean pooled NDI and ODI score was significantly higher in the inadequate cohort (p=0.003).
Our investigation revealed an alarmingly high rate of vitamin D abnormality in the analyzed population.
While certain previously identified risk factors were confirmed, validated indices of spine-related disability were higher in the presence of hypovitaminosis D [deficiency].
Since augmenting serum vitamin D is straightforward and inexpensive, and deficiency may predispose to fracture, pseudarthrosis [failure of spinal fusion surgery], and suboptimal surgical outcome, we advocate repletion for patients with documented deficiency.
FDA Device/Drug Status: This abstract does not discuss or include any applicable devices or drugs.
Source: Paper #45, Nov 3, 2011, North American Spine Society Annual Meeting. Buchowski J, Stoker G, Bridwell K, Lenke L, Riew D, Zebala L. Washington University in St. Louis; Washington University School of Medicine; Washington University Medical Center Department of Orthopedic Surgery; Barnes Jewish Hospital, St. Louis, Missouri, USA. (Reported in North American Spine Society press release, Nov 4: “Watch your back with easy, inexpensive Vitamin D.")