颈椎椎板成形术后脊髓后移的相关因素分析

Analysis of related factors of posterior shifting of the spinal cord after cervical laminoplasty

目的探讨颈后路单开门椎板成形术后脊髓后移的影响因素及其规律。方法2008年2月至2010年10月收治的压迫性颈脊髓病患者经筛选后43例纳入本研究，均接受C3-C7后路单开门椎板成形术，男32例，女11例；年龄33-78岁，平均57．9岁。脊髓型颈椎病伴发育性颈椎管狭窄30例，颈椎后纵韧带骨化症13例。门轴侧关节突螺钉锚定法2l例，保留门轴侧肌肉韧带复合体的钛缆悬吊法22例。术前、术后3个月颈椎中立位MRI正中矢状面测量各节段代表脊髓及硬膜囊后移的参数：脊髓前缘后移，脊髓后缘后移，硬膜囊前缘后移，硬膜囊后缘后移；将齿突与T1椎体后下角的连线定义为E线，其长度为E值，从每个基准点向E线作垂线，每个垂线段的长度为Px（x=l-6），得到代表每个节段局部曲度的参数下100×Px/E）；以颈椎曲度指数（curvature index，CI）表示颈椎整体曲度。对以上参数进行线性相关分析。结果硬膜囊前缘后移在不同水平无明显变化，脊髓前缘后移、脊髓后缘后移与硬膜囊后缘后移则随所处节段小同而相应发生变化，且三者的变化具有一致性。脊髓后缘后移最大值位于C5，6水平，但G5，6水平脊髓后缘后移与CI无相关性。相关分析表明脊髓后缘后移与硬膜囊后缘后移呈高度线性相关，与（100×Px/D）具有较低的相关性。结论颈椎单开门椎管扩大成形术后脊髓的后移程度与同水平硬膜囊的后移程度高度相关，与局部曲度相关性较弱，与颈椎整体曲度无相天性。

Objectives To investigate influencing factors and pattern of posterior shifting of thespinal cord after cervical lmninoplasty. Methods Forty three patients with compressive cervical myelopathy, including 32 males and 11 females, aged from 33 to 78 years （average, 57.9 years）, treated with open-door laminoplasty from C3 to C7 between February 2008 and October 2010, were enrolled in this study. There were 30 cases of cervical spondylotic myelopathy with developmental cervical stenosis and 13 cases of ossification of the posterior longitudinal ligament. Twenty one cases underwent modified open-door laminoplasty using anchor method, and the other 22 cases underwent laminoplasty with preservation of the unilateral muscular ligament complex. According to midsagittal T2-weighted MRI in the neutral position, several parameters indicating shift distance of the spinal cord and dural sac were measured at each level before operation and at 3 months after operation： shift of anterior margin of the spinal cord （SAMSC）, shift of posterior margin of the spinal cord （SPMSC）, shift of anterior margin of the dural sac （SAMDS） and shift of posterior margin of the dural sac （SPMDS）. The line connecting the top of dens and posterior inferior angle of T1 was defined as E line and the length was E. The length of perpendicular line from each base point to E line was Px （x = 1-6）. The parameter （100×Px/E） was used to represent local curvature at each level, and the curvature index （CI） was used to represent the global curvature of the cervical spine. Then correlation analyses of the parameters above were performed. Results There was no significant change in SAMDS at different level after surgery, however SAMSC, SPMSC and SPMDS changed significantly and synchronously. At the level of C5 and C6, SPMSC was maximum, but not correlated to CI. Actually, SPMSC was correlated to the local curvature and highly correlated to SPMDS at the same level. Conclusion After cervical laminoplasty, posterior shifting of the spinal cord was highly correlated to posterior shifting of the dural sac at the same level, weakly correlated to local curvature and not correlated to the global curvature of the cervical spine.