引言：维生素D在保持骨骼健康上起着至关重要的作用，而后者是脊柱融合术成功的关键。此外，维生素D缺乏导致的骨软化和骨质疏松症易使术后出现拔钉和内固定失败。本研究的目的是确定成人脊柱融合术前维生素D缺乏的发生率以及判断先前发现的维生素D缺乏危险因素能否应用于我们的人群。

方法：测量在同一家单独机构行腰椎融合术的成年人（至少18周岁）血清的25-羟基维生素D（25ODH）水平。该横断面研究包含2010/1到2011/3的313名连续患者。我们设计出一个复合伤残量表来分别评价颈椎和胸腰椎疾病患者的颈部和Oswestry伤残指数分数。维生素D缺乏的可能危险因素使用费雪精确概率法、卡方检验、曼—惠特尼检验和多变项逻辑迴归分析等方法进行分析。

结果：25OHD的平均基线水平是29 ± 14 ng/mL。57%的患者存在维生素D不足（<30 ng/mL），27%存在维生素D缺乏（<20 ng/mL）。其中女性176例（占56%）。平均年龄和平均BMI分别是55 ± 13 岁 和 29 ± 5.8 kg/m^2。260例患者诊断为退行性疾病，99例为脊柱畸形，73例为翻修病例。颈椎融合者占48%，胸椎融合占39%，腰椎融合占51%。平均融合的运动节段为4.8 ± 4.7个。维生素D缺乏的患者更年轻(P = 0.009)且以小于50周岁者居多(P < 0.050)。研究无性别差异。维生素D缺乏的患者骨密度无降低（P = 0.734），其体质量指数（P = 0.001）和残障评分(P = 0.004)明显更高。同样，他们也比正常BMI的患者 (P = 0.001)更容易出现肥胖，同时其残障指数≥60的人数明显多于<60者(P = 0.005)。术前补充维生素D或者多种维生素的患者比未补充维生素的患者年龄明显更大（P < 0.001），而且年龄50岁者更多（P = 0.001）。多变量分析的结果显示：BMI的增高（OR = 0.92, 95% CI = 0.87 - 0.97, P = 0.003），残障评分的增高(OR = 0.97, 95% CI = 0.95 - 0.99, P = 0.028)以及维生素D或多维生素的缺乏(OR = 0.14, 95% CI = 0.05 - 0.39, P < 0.001)是重要的预测因子。也就是说，残障指数每增加1分就会使25OHD水平大于20 ng/mL的可能性降低3%。总之，术前维生素D给予量的不足会导致这些几率下降86%。

讨论与结论：我们的研究显示在被研究者中维生素D缺乏的发生率很高。我们建议有明显维生素D缺乏的脊柱疾病患者补充该元素，因为增高血清的25OHD直接且便宜，而且维生素缺乏导致的脊柱骨质疏松和骨软化会使手术效果不佳。尽管高龄是维生素缺乏的一个明确的危险因素，但是仍不能忽视对行腰椎融合术的年轻患者术前的维生素D筛查，因其更少在术前补充维生素。此外，由于这些经过验证的脊柱疾病相关性指标可预测维生素D缺乏，因此它们可能在存在其它已明确的生理危险因素的情况下，成为临床上识别高危患者的有效工具。

INTRODUCTION

Vitamin D plays a critical role in establishing optimal bone health, which, in turn, is vital to the success of spinal arthrodesis. Furthermore, deficiency-induced osteomalacia and osteoporosis predispose to postoperative screw pullout and instrumentation failure. The purpose of this study was to characterize the prevalence of preoperative vitamin D abnormality in adults undergoing spinal fusion and to determine whether previously identified risk factors for suboptimal vitamin D can be applied to our population.
METHODS

Serum 25-hydroxyvitamin D (25OHD) levels were prospectively measured in adults (at least 18 years old) undergoing spinal fusion at a single institution. Between 1/2010 and 3/2011, 313 consecutive patients were identified for inclusion in this cross-sectional investigation. We generated a composite disability instrument by pooling Neck and Oswestry Disability Index scores of cervical and thoracolumbar patients, respectively. Potential risk factors for vitamin D deficiency were analyzed using Fisher’s exact, chi-squared, and Mann-Whitney U tests as well as multivariate logistic regression.
RESULTS

The mean baseline 25OHD level was 29 ± 14 ng/mL. The prevalence of vitamin D inadequacy (<30 ng/mL) was 57%, and that of deficiency (<20 ng/mL) was 27%. There were 176 (56%) females. The overall mean age and BMI were 55 ± 13 years and 29 ± 5.8 kg/m^2, respectively. While 260 patients were diagnosed with degenerative disease, 99 had spinal deformity, and there were 73 revision cases. The cervical spine was included in 48% of fusion constructs; thoracic spine, 39%; lumbar spine, 51%. On average, 4.8 ± 4.7 motion segments were included. Deficient patients were younger (P = 0.009) and more likely to be <50 years old (P < 0.050). There was no gender difference. Bone mineral density was not lower in the setting of deficiency (P = 0.734). Deficient patients had significantly higher body mass index (BMI; P = 0.001) and disability scores (P = 0.004); likewise, they were more liable to be obese than of normal BMI (P = 0.001) and rate their disability greater than or equal to 60 than <60 (P = 0.005). The subgroup of patients with prior vitamin D and/or multivitamin supplementation was significantly older (P < 0.001) and more likely to be at least 50 years of age than those without prior repletion (P = 0.001). Increasing BMI (OR = 0.92, 95% CI = 0.87 - 0.97, P = 0.003), increasing disability scores (OR = 0.97, 95% CI = 0.95 - 0.99, P = 0.028), and a lack of prior vitamin D or multivitamin supplementation (OR = 0.14, 95% CI = 0.05 - 0.39, P < 0.001) remained significant predictors upon multivariate analysis. In other words, each one-unit increase in disability index equated to a 3% decrease in the likelihood of having 25OHD of at least 20 ng/mL. In contrast, a lack of prior supplementation conferred an 86% decrease in those odds.
DISCUSSION AND CONCLUSION

Our investigation revealed an alarmingly high rate of vitamin D abnormality in the analyzed population. Since augmenting serum 25OHD is straightforward and inexpensive, and hypovitaminosis-induced spinal osteoporosis and osteomalacia may predispose to poor surgical outcome, we advocate repletion for spine patients with documented deficiency. Although advanced age is a well-established risk factor for deficiency, young adults undergoing spinal fusion should not be overlooked with regard to preoperative vitamin D screening; younger patients are less likely to have been previously supplemented. Moreover, as validated indices of spine-related disability are predictive of vitamin D deficiency, these may be clinically useful tools in identifying at-risk patients in the absence of other well-established, physiologic risk factors.