轴向负荷对腰椎硬膜囊的影响

Impact of axial load to lumbar dural sac

背景:常规CT、MRI检查是在仰卧位进行,这时人体在直立位时腰椎所承受的生理轴向负荷消失,腰椎间盘、硬膜囊等结构在生理负荷状态下的生理或病理改变不能真实反映出来。目的:实验拟探讨轴向负荷对腰椎硬膜囊的影响。设计、时间及地点:对照观察试验,于2006-03/2007-02在中山大学附属第二医院完成。参试者:选择本科收治的腰椎退行性变患者45例,男29例,女16例。所有患者均有腰腿疼痛症状。年龄22～79岁,病程为1个月至10年。方法:对45例慢性腰腿痛患者进行常规CT检查(扫描范围为L1～S1)和轴向负荷CT检查。主要观察指标:在椎间盘中央水平的横断面图像上分别测量负荷前后硬膜囊横截面积、椎间盘的面积、椎管内背侧脂肪垫面积及黄韧带厚度。结果:纳入腰椎退变患者45例,扫描L5/S1时有3例患者由于腰椎骶化排除。与常规CT检查比较,轴向负荷检查可见硬膜囊横截面积不同程度的缩小,平均缩小8.2～19.7mm2。与常规CT检查比较,轴向负荷检查对椎间盘的形态分类不产生影响,只引起椎间盘面积不同程度的增加(P<0.05);椎间盘膨出、突出或脱出的程度有所加重。轴向负荷时L1/2、L2/3、L3/4、L4/5各水平黄韧带增厚(P<0.05),但对L5/S1水平黄韧带及椎管内背侧脂肪垫面积无显著影响(P>0.05)。结论:轴向负荷时椎间盘向后膨出、突出或脱出程度加重、黄韧带增厚,是引起硬膜囊横截面积缩小的主要原因。

BACKGROUND： Physiological load on lumbar spine at upright position disappears when a patient is examined at supine position during routine CT or MRI examination. Consequently, the physiological or pathological condition of disc or dural sac cannot be correcdy reflected at supine posture. OBJECTIVE： To investigate the impact of axial load on lumbar dural sac. DESIGN, TIME AND SETTING： A comparative observation was performed at Second Hospital of Sun Yat-sen University from March 2006 to February 2007. PARTICIPANTS： Forty-five patients with lumbar degenerative changes aged 22-79 years were included in the study. There were 29 male and 16 female. All patients complained of low back pain. The duration of symptoms ranged from one month to ten years. METHODS： Conventional CT scanning and axially loaded CT examination were performed in 45 patients with low back pain （SCan range L1-S1）. MAIN OUTCOME MEASURES： The cross-sectional area of dural sac （D-CSA）, intervertebral disc, dorsal fat pad within spinal canal and the thickness of ligamentum flavum were measured on the transverse plane at central part of the disc. RESULTS： Of 45 included patients with lumbar degenerative changes were included, 3 were excluded with L5 sacralization during L5/S1 level scanning. Compared with conventional CT, D-CSA decreased by 8.2 mm^2-19.7 mm^2 averagely during axially loaded examination. While disc appearance did not change during axially loaded examination （P 〈 0.05）, only the severity of disc bulging, protrusion or extrusion aggravated. The thickness of ligamentum flavum increased significantly at L1/2, L2/3, L3/4 and L4/5 levels （P 〈 0.05）, but no significant changes in thickness were found at L5/S1 level or the area of dorsal fat pad during axially loaded examination （P 〉 0.05）. CONCLUSION： The degree of disc bulging, protrusion or extrusion is aggravated and the thickness of ligamentum flavum increased during axially loaded examination, which are main factors for reduction of D-CSA in lumbar spine.