椎弓根延长微创治疗骨质疏松腰椎椎管狭窄术的生物力学机制研究

Lumbar spinal stenosis (LSS) is a common spinal disease. Laminectomy and spinal canal decompression are primary surgical therapy, but epidural adhesion and changes of lumbar stability may lead to bad long-term results after operation. Pedicle-lengthening osteotomy is a new theory which had been proposed recently. After cutting off the pedicle, length adjustable pedicle screws were used to lengthen the pedicles. Then the volume of spinal canal and intervertebral foramen were enlarged, and the nerve compression was relieved. Pedicle-lengthening osteotomy is a new minimally invasive spine surgery with a prosperous application. It keeps lumbar posterior structure intact, which prevent the epidural scars hyperplasia and contraction. However, there are still a lot of questions unanswered. How to the quantized ratio relationship between the pedicle-lengthening length and the volume of spinal canal enlargement? How the pedicle-lengthening osteotomy would change the lumbar kinematics and motion stability? The impact of osteoporosis on this technique remains unrevealed. In order to answer these questions, we would establish 3-D models from collected MR images of normal and LSS cases first, then the ratio of pedicle-lengthening length and the volume of spinal canal enlargement were measured and calculated on the model; LSS finite element would be established to analysis the stress distribution and kinetic changes of lumbar anterior and posterior columns. We proposed a new technique for LSS patient with osteoporosis,which combine the vertebral plasty and pedicle-lengthening. The finite element model validation and the influence of the new technique on lumbar stability would be analyzed by biomechanical experiments with human lumbar specimens. The pedicle-lengthening osteotomy results would be assessed by animal experiments.

腰椎椎管狭窄是常见的脊柱疾病，传统手术治疗需切除椎板扩大椎管减压，术后硬膜外瘢痕粘连挛缩和腰椎失稳导致远期疗效不佳。椎弓根延长术是近年提出的新理论，该技术切断椎弓根后，利用长度可调节椎弓根螺钉延长椎弓根，扩大了椎管和椎间孔的容积，解除神经压迫，该术式维持了脊柱后路结构的完整，避免瘢痕增生挛缩，是具有应用前景的微创治疗新技术。然而，椎弓根延长与椎管容积增加的量化关系如何？椎弓根延长对腰椎应力分布和稳定性影响如何？骨质疏松对该技术影响如何等问题均未解决。本项目利用正常和椎管狭窄的 CT图像建立腰椎三维模型和有限元模型，利用数字化测量技术测量椎弓根延长与椎管容积和椎间孔面积增大的关系，分析椎弓根延长对腰椎前后柱应力分布和稳定性的影响；针对骨质疏松患者提出椎体强化加椎弓根延长的新技术，利用人体标本试验验证有限元模型并分析新技术对腰椎生物力学稳定性的影响。通过动物实验，在体评估椎弓根延长效果。

腰椎椎管狭窄（Lumbar Spinal Stenosis，LSS）是临床上常见的脊柱退行性病变之一。椎弓根延长术治疗LSS是近年提出的一项脊柱外科微创手术新技术。本课题组尝试自主研发椎弓根延长装置，探究新型椎弓根延长装置的性能以及椎弓根延长术对腰椎的生物力学影响。.本研究首先利用影像学分析、有限元分析、体外生物力学分析，探究了椎管延长术对腰椎的扩容作用响以及新型椎弓根延长器械的性能。.影像学研究发现：椎弓根后端离断要优于前端离断；椎弓根延长术对侧隐窝型椎管狭窄患者减压效果更好；对需要解除椎间孔部位神经压迫的患者，单独延长L4椎弓根作为首选；对中央型椎管狭窄患者，可利用方程L=0.06+9.06R得出理想椎弓根延长长度。.有限元分析发现：椎弓根后端离断力学稳定性优于前端离断，且对邻近节段影响相对较小；椎弓根延长螺钉能够保留腰椎的运动范围；椎弓根延长术对上位邻近节段的椎间盘应力稍有影响；椎弓根延长术会显著增大上位邻近节段小关节压力、减小下位邻近节段小关节压力，并且缩短上位邻近节段小关节压力出现时间，延长下位邻近节段小关节压力出现时间；椎弓根延长术后腰椎在前屈-后伸、左侧弯-右侧弯时的腰椎整体力学性能影响不大，但会使得左右旋转时腰椎椎间盘上的应力转移到小关节上，改变了腰椎整体应力分布；椎弓根延长术后后伸和左右侧弯时，螺钉不会受到损坏，但前屈和左右旋时需要保持在一定的运动范围内，才能够保证螺钉不受损坏，且椎弓根延长螺钉的应力大小主要与螺钉的直径有关。.体外生物力学实验发现：椎弓根延长螺钉需配合骨水泥使用，能够达到与传统螺钉一致的稳定性；佐证了有限元分析中小关节压力的结果，同时发现不同延长长度对腰椎小关节压力有影响：延长长度越长，上位邻近节段小关节压力越大，下位邻近节段小关节压力越小，但对远端节段的小关节压力影响甚小。.本课题的研究证实了椎弓根延长术在恢复椎管容积的同时，能够保持腰椎的稳定性。新型椎弓根延长螺钉联合骨水泥强化，是治疗椎管狭窄的有效手段。