强直性脊柱炎胸腰椎后凸畸形患者不同体位下主动脉相对椎体位置变化的MRI观察

Positional changes on MRI of aorta relative to vertebra in different postures for ankylosing spondylitis patients with thoracolumbar kyphosis

目的:在MRI上探究强直性脊柱炎(ankylosing spondylitis,AS)胸腰椎后凸畸形患者不同体位下(仰卧位与侧卧位)主动脉相对椎体位置的解剖关系.方法:纳入2020年5月~2022年12月在我院行单节段经椎弓根椎体截骨术(pedicle subtraction osteotomy,PSO)治疗的AS胸腰椎后凸畸形患者33例.男29例,女4例;年龄38.3±8.8岁(22~54岁).收集性别、年龄及顶椎位置等基线资料.在术前站立位全脊柱侧位片上测量全脊柱整体后凸角(global kyphosis,GK).获取仰卧位与侧卧位MRI并测量以下参数:(1)主动脉-椎体角度(θ);(2)主动脉-椎体距离(d1);(3)主动脉外壁-椎体前缘间隙(d2).为探究左、右侧卧位对主动脉相对椎体位置的影响,根据侧卧位拍摄MRI的方向分为左侧卧位与右侧卧位两组以比较两组患者在仰卧位与(左或右)侧卧位时主动脉相对椎体位置的差异.根据AS患者的后凸畸形程度,将所有患者分为低后凸畸形组(GK≤70°)及高后凸畸形组(GK>70°)以探究AS患者后凸畸形程度对主动脉相对椎体位置的影响,并通过不同后凸畸形程度组患者探究低、高后凸畸形程度组患者主动脉在仰卧位与(左或右)侧卧位下相对椎体位置的差异.结果:33例患者中,左侧卧位组22例,右侧卧位组11例.两组患者性别、年龄、顶椎位置及术前GK无统计学差异.除右侧卧位组d2在T12存在差异(P=0.033),两组患者的仰卧位与侧卧位θ、d1、d2在T9~L3均无显著差异;低后凸畸形组与高后凸畸形组患者不同体位下(仰卧位与侧卧位)的θ、d1、d2在T9~L3亦无显著差异.在T9~T12,GK与θ均呈显著负相关(P<0.05);在T9、T10、T12,GK与d1存在显著正相关(P<0.05).在T9~T11,θ在高后凸畸形组更小(T9~T10,P<0.05;T11,P=0.057);在T9、T10、T12,高后凸畸形组d1更大(P<0.05);而在L1~L3,低后凸畸形组与高后凸畸形组间的θ、d1无显著差异.结论:对严重胸腰椎后凸畸形AS患者,术前可考虑行侧卧位MRI替代仰卧位MRI;在截骨及椎弓根螺钉置入过程中,腰椎节段发生主动脉损伤的风险可能较胸椎节段更大;后凸程度会影响主动脉活动度及胸主动脉相对椎体位置.

Objectives:To investigate the anatomical relationships of aorta relative to spine in different postures(supine and lateral positions)for ankylosing spondylitis(AS)patients with thoracolumbar kyphosis based on magnetic resonance images(MRI).Methods:33 AS patients with thoracolumbar kyphosis undergone single-level pedicle subtraction osteotomy(PSO)from May 2020 to December 2022 were included in the study.There were 29 males and 4 females,and the patients averaged 38.3±8.8 years old(22-54 years).Baseline information including age,gender,and apical vertebra was recorded.Global kyphosis(GK)was measured on lateral full-length spinal radiographs preoperatively.MRI examinations in supine and right or left lateral positions were performed in all patients preoperatively,and parameters including aorta-vertebra angle(θ),aorta-vertebra distance(d1),and the interval between posterior aorta wall to anterior vertebral cortex(d2)were measured.In order to analyze the influence of right and left lateral posture on the position of the aorta relative to the vertebra,patients were categorized into right and left lateral position groups according to the corresponding lateral positional MRI examinations performed preoperatively for comparing the aortic position relative to vertebra between supine posture and(left or right)lateral posture in both groups.All the patients were divided into mild(GK≤70°)and severe(GK>70°)kyphotic groups for analyzing the impact of the kyphotic degree on the aortic position;meanwhile,the difference of the position of aorta relative to vertebra between supine and(left or right)lateral postures were also explored according to varied degrees of kyphotic groups.Results:Of all the 33 patients,22 were divided into the left lateral position group and 11 were in the right lateral position group.There was no significant difference of baseline information and GK between both groups.Except for d2 in right lateral position group at T12(P=0.033),no significant difference ofθ,d1,and d2 between supine and lateral postures of both groups was observed at T9-L3;Moreover,no statistical difference was there inθ,d1,and d2 between supine and lateral postures of both mild kyphotic group and severe kyphotic group at T9-L3.At T9-T12,GK was significantly negatively correlated withθ(P<0.05);At T9,T10,and T12,GK was significantly positively correlated with d1(P<0.05).At T9-T11,smallerθwas noted in severe kyphotic group(T9-T10,P<0.05;T11,P=0.057);At T9,T10,and T12,larger d1 was observed in severe kyphotic group(P<0.05);And at L1-L3,no significant difference ofθand d1 was found between mild and severe kyphotic groups.Conclusions:MRI in lateral position can be considered as a replacement of supine positional MRI for AS patients with severe thoracolumbar kyphosis before operation;During the procedure of osteotomy or pedicle screw insertion,the risk of aortic damage in lumbar spine might be larger than that in thoracic spine;The mobility of aorta and the position of aorta relative to vertebra in thoracic region is going to be impacted by the severity of kyphosis.