基于椎体CT扫描的骨密度HU值分析退变性腰椎侧弯患者骨质疏松的发生率和分布规律

目的 探讨椎体退变性腰椎侧弯(DLS)患者骨质疏松的发生率和分布规律,为骨水泥螺钉的选择性使用提供参考。方法 回顾性分析2015年1月—2019年9月北京大学第三医院骨科接受手术治疗的95例DLS患者的临床和影像学资料,其中男20例、女75例,年龄(63.3±6.5)岁。于脊柱X线全长片上测量患者Cobb角、冠状平衡距离(CBD)值,统计患者冠状位失衡分型例数。选择患者主弯和代偿弯内椎体前缘皮质后方2 mm、椎体中部和椎骨后缘皮质前方2 mm三个层面的CT冠状面重建图像,于椎体松质骨部分选择最大可能的椭圆形区域作为骨密度Hounsfield units(HU)值测量兴趣区,取三个层面测量的平均值作为相应椎体的骨密度HU值,同样方法分别测量椎体凸、凹侧的HU值;以L₁≤110 HU作为骨质疏松的诊断标准,观察患者骨质疏松发生率,并按观察结果将患者分为正常骨密度组和骨质疏松组两组,进而对比两组患者临床基线资料。观察全组患者主弯与代偿弯内椎体HU值,以及主弯和代偿弯内各椎体及其凸凹两侧骨质疏松的发生情况。结果 全组95例患者Cobb角为25.5°±11.1°,CBD为(22.8±18.7)mm,冠状位失衡为A型者74例、B型12例、C型9例。骨密度正常58例(61.1%),骨质疏松37例(38.9%);女性骨质疏松的发生率45.3%(34/75),高于男性的15.0%(3/20),差异有统计学意义(χ²=6.110, P＜0.05)。正常骨密度组和骨质疏松组患者的年龄、体质量指数、Cobb角、CBD、侧弯方向、冠状位失衡分型比较,差异均无统计学意义(P值均＞0.05)。主弯与代偿弯内椎体HU值:L₁为(122.2±45.0)HU、稳定椎为(124.7±44.8)HU、中立椎为(120.9±42.9)HU、上端椎为(124.3±46.1)HU、顶椎(134.4±49.4)HU、下端椎(153.3±63.8)HU、L₅椎(169.8±75.8)HU。主弯内各椎体的骨质疏松发生率分别与L₁椎体比较,差异均无统计学意义(P值均>0.05);而代偿弯内L₅椎体的骨质疏松发生率则低于主弯的L₁椎体,分别为17.9%(17/95)和38.9%(37/95),差异有统计学意义(χ²=10.349,P＜0.05)。L₅椎体、下端椎、顶椎的凸侧骨质疏松发生率高于凹侧,差异均有统计学意义(P值均＜0.01);而上端椎、中立椎、稳定椎凸凹两侧骨质疏松的发生率比较,差异均无统计学意义(P值均＞0.05)。结论 DLS患者中骨质疏松发生率为38.9%,女性患者的发生率更高。代偿弯内椎体骨质疏松发生率低于主弯内椎体,L₅椎、下端椎和顶椎凸侧是骨质疏松的好发部位。

Prevalence and distribution of osteoporosis in degenerative lumbar scoliosis based on Hounsfield units measurement from CT examination

Objective To demonstrate the prevalence and distribution of osteoporosis in degenerative lumbar scoliosis (DLS) patients based on Hounsfield units (HU) measurement and to provide a reference for the selective use of cement-augmented pedicle screws.Methods Ninety-five DLS patients surgically treated in Peking University Third Hospital from January 2015 to September 2019 were retrospectively reviewed. Patients comprised 20 males and 75 females with a mean age of (63.3±6.5) years old. Cobb's angle and coronal balance distance (CBD) were measured by using the full-spine X-ray. Regions of interest were measured on coronal images of the vertebrae at three separate locations, namely, immediately posterior to the anterior vertebrae margin, in the middle of the vertebral body, and anterior to the posterior vertebrae margin. For each measurement, the largest possible elliptical region of interest was drawn. The cortical margins were excluded to prevent volume averaging. The average of the HU values from the three coronal slices was obtained to provide a mean HU value for each vertebral body. Then, HU measurements for the concavity and convexity of the vertebrae were obtained separately. For HU-based criterion, a cut-off of ≤110 HU was used for osteoporosis diagnosis. Patients were divided into two groups according to their diagnosis. General data and HU value of scoliosis related vertebrae were compared between the two groups.Results The mean Cobb angle was 25.5°±11.1° degrees, and the mean CBD was (22.8±18.7) mm. Coronal imbalance type A was detected in 74 patients, type B was detected in 12 patients, and type C was detected in 9 patients. Fifty-eight patients (61.1%) presented with normal bone density, whereas 37 patients (38.9%) presented with osteoporosis. Female patients (34/75,45.3%)were more likely to present with osteoporosis than males(3/20, 15.0%)(χ²=6.110, P＜0.05). No significant difference was found in age, body mass index, Cobb's angle, CBD, apex orientation of the major curve, and coronal imbalance types between patients with normal bone density and those with osteoporosis (P＞0.05 for all). The HU values were (122.2±45.0) Hu of L₁, (124.7±44.8) Hu of stable vertebrae, (120.9±42.9) Hu of neural vertebrae, (124.3±46.1) Hu of upper end vertebrae, (134.4±49.4) Hu of apex vertebrae, (153.3±63.8) Hu of lower end vertebrae, and (169.8±75.8) Hu of L₅. All scoliosis-related vertebrae within the major curve presented similar incidence of osteoporosis to L₁ vertebrae (all P values＞0.05). L₅ vertebrae (17/95, 17.9%) presented lower incidence of osteoporosis when compared with the L₁ vertebrae(37/95, 38.9%) (χ²=10.349, P＜0.05). The incidence of osteoporosis within the convex side was significantly higher than that within the concave side at L₅, lower end, and apex vertebrae (all P values＜0.01). No significant difference was found between convex and concave side HU values in the upper end, neural, and stable vertebrae (all P values＞0.05).Conclusions The prevalence of osteoporosis is 38.9% in DLS patients based on HU measurements. Females were more likely to present with osteoporosis. The vertebrae within compensatory curve presents lower incidence of osteoporosis. The convex side of apical, lower end, and L₅ vertebrae are the most common sites of osteoporosis and which needs to be strengthened by cement-augmented pedicle screws.