Department of Orthopaedic Surgery, Hospital for Special Surgery, Weill Cornell Medicine, New York, NY, USA; Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany.
Department of Orthopaedic Surgery, Hospital for Special Surgery, Weill Cornell Medicine, New York, NY, USA.
Spine J. 2022 Oct;22(10):1642-1650. doi: 10.1016/j.spinee.2022.05.008. Epub 2022 Jun 5.
Osteoporosis is a risk factor for instrumentation failure in spine surgery. Bone strength is commonly assessed by bone mineral density (BMD) as a surrogate marker. However, BMD represents only a portion of bone strength and does not capture the qualitative dimensions of bone. Recently, the magnetic resonance imaging (MRI)-based vertebral bone quality (VBQ) score was introduced as a novel marker of bone quality. However, it is still unclear if the VBQ score correlates with in-vivo bone microstructure.
The aims of the study were (1) to demonstrate differences in MRI-based (VBQ) and in-vivo (microcomputed tomography; μCT) bone quality between osteopenic/osteoporotic and normal bone, (2) to show the correlation between VBQ, bone microstructure and volumetric BMD (vBMD), and (3) to determine the predictive value of the VBQ score for the prevalence of osteopenia/osteoporosis.
STUDY DESIGN/SETTING: Retrospective cross-sectional study.
267 patients who underwent posterior lumbar fusion surgery from 2014 to 2021 at a single academic institution. Bone biopsies were harvested intraoperatively in 118 patients.
VBMD, VBQ score, and bone microstructure parameters derived from μCT.
Quantitative computed tomography (QCT) measurements were performed at the lumbar spine and the L1/L2 average was used to categorize patients with a vBMD ≤120mg/cm as osteopenic/osteoporotic. The VBQ score was determined by dividing the median signal intensity of the L1-L4 vertebrae by the signal intensity of the cerebrospinal fluid using sagittal T1-weighted MRI scans. Intraoperative bone biopsies from the posterior superior iliac spine were obtained and evaluated with μCT. VBQ scores and μCT parameters were compared between the normal and the osteopenic/osteoporotic group. Correlations between VBQ score, μCT parameters and vBMD were assessed with Spearman's correlation (ρ). Receiver operating characteristic (ROC) analysis was performed to determine the VBQ score as a predictor for osteopenia/osteoporosis. Multiple linear regression analysis with vBMD L1/L2 as outcome was used to identify independent predictors from VBQ, μCT parameters and demographics.
267 patients (55.8% female, age 63.3 years, BMI 29.7 kg/m; n=118 with bone biopsy) with a prevalence of osteopenia/osteoporosis of 65.2% were analyzed. In the osteopenic/osteoporotic group the VBQ score, structured model index (SMI), and trabecular separation (Tb.Sp) were significantly higher, whereas bone volume fraction (BV/TV), connectivity density (Conn.D) and trabecular number (Tb.N) were significantly lower. There were significant correlations between VBQ and μCT parameters ranging from ρ=-.387 to ρ=0.314 as well as between vBMD and μCT parameters ranging from ρ=-.425 to ρ=.421, and vBMD and VBQ (ρ=-.300, p<.001). ROC analysis discriminated osteopenia/osteoporosis with a sensitivity of 84.7% and a specificity of 40.6% at a VBQ score threshold value of 2.18. Age, BV/TV and trabecular thickness (Tb.Th), but not VBQ, were significant independent predictors for vBMD (corrected R=0.434).
This study demonstrated for the first time that the VBQ score is associated with trabecular microstructure determined by μCT. The bone microstructure and VBQ score were significantly different in patients with impaired vBMD. However, the ability to predict osteopenia/osteoporosis with the VBQ score was moderate. The VBQ score appears to reflect additional bone quality characteristics and might have a complementary role to vBMD. This enhances our understanding of the biological background of the radiographic VBQ score and might be a take-off point to evaluate the clinical utility of it as non-invasive screening tool for bone quality.
骨质疏松症是脊柱手术中器械失败的一个风险因素。骨强度通常通过骨矿物质密度（BMD）作为替代标志物来评估。然而，BMD 仅代表骨强度的一部分，不能捕捉到骨的定性维度。最近，磁共振成像（MRI）为基础的椎体骨质量（VBQ）评分作为一种新的骨质量标志物被引入。然而，VBQ 评分是否与体内骨微观结构相关仍然不清楚。
本研究的目的是：（1）证明骨质疏松/骨质疏松症和正常骨之间基于 MRI 的（VBQ）和体内（微计算机断层扫描；μCT）骨质量之间的差异；（2）显示 VBQ 与骨微结构和体积 BMD（vBMD）之间的相关性；（3）确定 VBQ 评分对骨质疏松/骨质疏松症患病率的预测价值。
研究设计/设置：回顾性横断面研究。
2014 年至 2021 年期间在一家学术机构接受后路腰椎融合术的 267 名患者。118 名患者在术中采集了骨活检。
VBMD、VBQ 评分和来自 μCT 的骨微观结构参数。
对腰椎进行定量计算机断层扫描（QCT）测量，并将 L1/L2 的平均值用于将 vBMD≤120mg/cm 的患者分类为骨质疏松/骨质疏松症。VBQ 评分通过将 L1-L4 椎体的中位信号强度除以脑脊液的信号强度来确定，使用矢状 T1 加权 MRI 扫描。从后上髂嵴获得术中骨活检，并使用 μCT 进行评估。比较正常组和骨质疏松/骨质疏松组之间的 VBQ 评分和 μCT 参数。使用 Spearman 相关系数（ρ）评估 VBQ 评分、μCT 参数和 vBMD 之间的相关性。进行接收者操作特征（ROC）分析，以确定 VBQ 评分作为骨质疏松/骨质疏松症的预测因子。使用多元线性回归分析，以 vBMD L1/L2 为结果，从 VBQ、μCT 参数和人口统计学中识别独立预测因子。
分析了 267 名患者（55.8%为女性，年龄 63.3 岁，BMI 29.7kg/m；n=118 名有骨活检），骨质疏松/骨质疏松症的患病率为 65.2%。在骨质疏松/骨质疏松症组中，VBQ 评分、结构模型指数（SMI）和小梁分离（Tb.Sp）显著较高，而骨体积分数（BV/TV）、连通密度（Conn.D）和小梁数量（Tb.N）显著较低。VBQ 与 μCT 参数之间存在显著相关性，范围从 ρ=-.387 到 ρ=0.314，vBMD 与 μCT 参数之间也存在显著相关性，范围从 ρ=-.425 到 ρ=0.421，vBMD 与 VBQ 之间存在显著相关性（ρ=-.300，p<.001）。ROC 分析以 2.18 的 VBQ 评分阈值区分骨质疏松/骨质疏松症，灵敏度为 84.7%，特异性为 40.6%。年龄、BV/TV 和小梁厚度（Tb.Th），而不是 VBQ，是 vBMD 的显著独立预测因子（校正 R=0.434）。
本研究首次证明 VBQ 评分与 μCT 确定的小梁微观结构相关。骨微观结构和 VBQ 评分在 vBMD 受损的患者中存在显著差异。然而，VBQ 评分预测骨质疏松/骨质疏松症的能力中等。VBQ 评分似乎反映了额外的骨质量特征，并且可能对 vBMD 具有互补作用。这增强了我们对放射学 VBQ 评分的生物学背景的理解，并可能成为评估其作为骨质量非侵入性筛查工具的临床效用的起点。
