退变性脊柱侧凸不同方式长节段固定融合术后邻近节段生物力学变化的有限元分析

Finite element analysis of biomechanical changes of adjacent segments of degenerative scoliosis treated with different operative methods of long-segment internal fixation and fusion

中文关键词:  退变性脊柱侧凸  长节段固定  邻近节段  生物力学

英文关键词:Degenerative scoliosis  Long-segment fusion  Internal fixation  Adjacent segment  Biomechanics

中文摘要:

  【摘要】 目的：探讨退变性脊柱侧凸（degenerative scoliosis，DS）不同方式长节段固定融合术后脊柱活动度及固定邻近节段椎间盘和关节突软骨的应力变化。方法：基于DS患者T12～S1上段连续的CT扫描图像，导入E-feature Biomedical Modeler软件，从三维实体模型直接划分生成腰椎各节段的高质量体网格，根据DS的病理特点赋予模型特定的材料属性，将三维有限元模型导入ANSYS 12.0有限元分析软件，对其去除L4棘突、全椎板、部分关节突，行L4/5椎间融合后，分别采用L2~L4椎板融合＋L2～L5 8枚椎弓根螺钉固定（方案一）、L1～L4椎板融合＋L1～L5 10枚椎弓根螺钉固定（方案二）、L1～S1椎板融合＋L1～S1 12枚椎弓根螺钉固定（方案三），在前屈、后伸、左侧弯、右侧弯、左旋转、右旋转六种工况下对术后模型进行加载，计算和分析三种手术方案术后脊柱的活动度及固定邻近节段椎间盘和关节突软骨的应力变化，并与术前DS模型进行比较。结果：三种手术方案固定融合后脊柱活动范围均减小，方案三<方案二<方案一；三种手术方案对固定邻近节段椎间盘应力均有影响，前屈、旋转时三种方案均可使固定上位节段椎间盘的应力减少，侧弯时三种方案均可使上位节段椎间盘的应力增加，后伸时对上位椎间盘的应力减少明显；前屈、侧弯及左旋转时方案一、二均可使下位节段椎间盘应力增加，后伸、右旋转时方案一、二均可使下位节段椎间盘应力减少，但三种方案对固定邻近上、下位节段椎间盘应力的影响差异不明显。方案三的固定相邻节段关节突软骨最大应力达到532.98MPa，方案二为494.08MPa，方案一为63.27MPa，即方案二、三固定相邻节段的关节突软骨容易出现较大的应力集中情况，方案一影响较小。结论：治疗DS固定融合的节段越多，对术后脊柱活动度及固定相邻节段椎间盘和关节突软骨的应力影响越大，对于长节段固定融合术治疗DS时，在能够解除症状、达到脊柱稳定的前提下应尽可能减少固定节段。

英文摘要:

  【Abstract】 Objective：To investigate the effect of different types of long-segment internal fixation and fusion on spine range of motion（ROM） and stress in disc as well as cartilage of facet joint of adjacent segment in patients with spine degenerative scoliosis（DS） by finite element analysis.Method：Based on the DS patients′ CT images of the consecutive spine from T12 to superior segment of S1，the E-feature Biomedical Modeler was imported.The three dimensional solid model was divided into high quality body mesh，then the special material attributing to the model was assigned according to the pathological features of DS，and the three dimensional finite element model was introduced into ANSYS 12.0 analysis software.The spinous process and whole lamina of vertebra and partial facet process of L4 were removed，and interbody fusion at L4/5 was performed，after that，3 procedures termed as：1，L2-L4 laminar fusion plus L2-L4 instrumentation（8 pedicle screws）；2，L1-L4 laminar fusion plus L1-L5 instrumenation（10 pedicle screws）；3，L1-S1 laminar fusion plus L1-S1 instrumentation（12 pedicle screws）.The model was loaded on flexion-extension，lateral bending and rotation.The spine ROM and stress in disc as well as cartilage of facet joint of adjacent segment were measured，and all these data were compared with preoperative DS model.Result：The spine ROM of three procedures decreased in the order of 3<2<1.The stress in adjacent interverbral disc was affected significantly.All three procedures had the stress in adjacent upper disc decreased on flexion and rotation，while had it increased on lateral bending；on extension the stress in the upper disc decreased obviously.The first and second procedure had the stress in adjacent lower disc increased on flexion，lateral bending and left rotation，while had it decreased on extension and right rotation.But no difference with respect to their effects on upper and lower discs was noted.The highest stress of cartilage in adjacent facet joint was 532.98MPa for procedure 3，and that for procedure 2 and 1 was 494.08MPa and 63.27MPa respectively.Higher stress focusing in facet joint was more common in procedure 2 and 3 than in procedure 1.Conclusion：The more segments fusioned，the more effect has on adjacent ROM and stress in disc and facet joint.For degenerative scoliosis，on the criteria of complete decompression and stability reconstruction，long-segment fusion should be avoided.