Yang Ge, Battié Michele C, Boyd Steven K, Videman Tapio, Wang Yue
Spine lab, Department of Orthopedic Surgery, The First Affiliated Hospital of Zhejiang University, Hangzhou, China.
Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada.
Bone. 2017 Feb;95:102-107. doi: 10.1016/j.bone.2016.11.018. Epub 2016 Nov 19.
Clinically, vertebral fractures often occur in the upper lumbar spine and involve the superior endplate of a vertebra (which is immediately caudal to a disc). Knowledge that the cranial endplate of a disc is thicker and has greater bone mineral density (BMD) than the corresponding caudal endplate helps to explain this phenomenon. In this study, we investigated structural differences in vertebral trabeculae on either side of a lumbar disc to provide further insight into vertebral fracture risk. As the focus is trabecular difference within a spinal motion segment, we define cranial and caudal vertebral trabeculae relative to the disc. Ninety-two spinal motion segments from 46 cadaveric lumbar spines (males, mean age 50years, range 21-63years) were studied. Disc narrowing on radiography and spread of barium sulfate (BaSO) on discography were measured to indicate disc degeneration. Micro-computed tomography (μCT) images were obtained at a resolution of 82μm for each vertebra and processed to include only vertebral trabeculae. Using image processing, the vertebral trabeculae were divided into superior and inferior halves, and then into central and peripheral regions which were approximately opposite to the disc pulposus and annulus, and further into anterior and posterior sub-regions. Microarchitecture measurements for each vertebral region were obtained to determine the differences between the cranial and caudal trabeculae (relative to disc) and their associations with age and disc degeneration within each spinal motion segment. Data from the upper (L1/2-L3/4) and lower (L4/5) lumbar segments were analyzed separately. In the upper lumbar region, the trabeculae cranial to a disc on average had 5.3% greater BMD and trabecular bone volume, 3.6% greater trabecular number, 9.7% greater connectivity density, and 3.7% less trabecular separation than the corresponding caudal trabeculae (P<0.05 for all). Similar trends were observed in peripheral, anterior and posterior regions, but not in central region. No structural difference was observed in the trabeculae of L4/5 segment. Structural asymmetries of vertebral trabeculae were not associated with age, disc degeneration, or disc narrowing. Vertebral trabecular parameters cranial to the disc were greater than caudally in the upper but not in the lower lumbar region. Findings further explain why vertebral fractures are more common in the upper lumbar region and more frequently involve the endplate caudal to a disc.
临床上，椎体骨折常发生于上腰椎，累及椎体的上终板（紧邻椎间盘尾侧）。椎间盘头侧终板比相应尾侧终板更厚且骨密度（BMD）更高，这一认识有助于解释这一现象。在本研究中，我们调查了腰椎间盘两侧椎体小梁的结构差异，以进一步了解椎体骨折风险。由于重点是脊柱运动节段内的小梁差异，我们相对于椎间盘定义头侧和尾侧椎体小梁。对46具尸体腰椎（男性，平均年龄50岁，范围21 - 63岁）的92个脊柱运动节段进行了研究。测量X线片上的椎间盘狭窄和椎间盘造影时硫酸钡（BaSO）的扩散情况以指示椎间盘退变。对每个椎体以82μm的分辨率获取微计算机断层扫描（μCT）图像，并进行处理以仅包括椎体小梁。通过图像处理，将椎体小梁分为上半部分和下半部分，然后分为大致与椎间盘髓核和纤维环相对的中央和周边区域，再进一步分为前侧和后侧子区域。获取每个椎体区域的微观结构测量值，以确定头侧和尾侧小梁（相对于椎间盘）之间的差异及其与每个脊柱运动节段内年龄和椎间盘退变的关联。分别分析上腰椎节段（L1/2 - L3/4）和下腰椎节段（L4/5）的数据。在上腰椎区域，相对于椎间盘，头侧小梁的骨密度、骨小梁体积平均比相应尾侧小梁大5.3%，骨小梁数量大3.6%，连接密度大9.7%，骨小梁间距小3.7%（所有P<0.05）。在周边、前侧和后侧区域观察到类似趋势，但在中央区域未观察到。在L4/5节段的小梁中未观察到结构差异。椎体小梁的结构不对称与年龄、椎间盘退变或椎间盘狭窄无关。相对于椎间盘，上腰椎区域头侧的椎体小梁参数大于尾侧，但下腰椎区域并非如此。这些发现进一步解释了为什么椎体骨折在上腰椎区域更常见，且更常累及椎间盘尾侧的终板。
