Coflex和X-STOP在治疗腰椎管狭窄中生物力学性能研究

目的 分析棘突间撑开器Coflex和X-STOP在治疗腰椎管狭窄中的不同生物力学特性，为棘突间植入物的设计改进提供参考。方法依据1名正常志愿者中立位下螺旋CT扫描资料构建L2~5健康腰椎有限元模型、L4/5椎间盘轻度退变有限元模型、棘突撑开器X-STOP和Coflex的动态固定模型，并对4组模型分别模拟前屈、后伸、侧弯和轴向旋转，验证和对比分析活动度（range of motion, ROM）的变化和应力在棘突和撑开器上的分布。结果与退变模型相比，Coflex和X-STOP有效限制退变节段后伸ROM-48.12%和-75.35%，Coflex还能限制前屈ROM-59.58%，侧弯和扭转ROM不受限制。Coflex和X-STOP减少椎间盘后伸时应力达-58.03%和-80.75%，Coflex在前屈时应力减少-52.84%。侧弯和扭转的ROM基本不受影响。Coflex最大应力发生在前屈时U型弯处，X-STOP最大应力出现在扭转时左翼螺钉连接处。Coflex与腰椎接触最大应力发生在扭转时，为31.38 MPa。X-STOP与腰椎接触最大应力发生在侧弯时，为46.86 MPa。结论Coflex和X-STOP是治疗腰椎管狭窄的有效方法，均可以显著降低后伸ROM和椎间盘压力，对相邻节段无明显影响。

Biomechanical properties of Coflex and X-STOP in treatment of lumbar spinal stenosis

Objective To analyze different biomechanical properties between Coflex and X-STOP device in the treatment of lumbar spinal stenosis (LSS), and provide references for design improvement of interspinous process spacer. MethodsFour finite element models, i.e., the L2-5 healthy segment model, the mild degenerated L4/5 segment model, the X-STOP-fixed L4/5 segment model, the Coflex-fixed L4/5 segment model, were constructed based on the normal lumbar CT images of a volunteer, and the models under flexion, extension, lateral bending and axial rotation were simulated to compare range of motion (ROM) changes and stress distributions on the spinous process and interspinous process spacer. ResultsX-STOP and Coflex decreased extension ROM by -48.12% and -75.35%, respectively, and released disc pressure by -58.03% and -80.75%, respectively. Coflex even restricted flexion ROM by -59.58% and reduced flexion disc pressure by -52.84%. No distinct changes appeared in lateral bending and axial rotation ROMs and disc pressure. The largest Von Mises stress appeared at the U-shape place during flexion in Coflex and at connection between left wing and screw during torsion in X-STOP, respectively. The largest contact pressure between Coflex and spinous process was 31.38 MPa during bending, and that between X-STOP and spinous process was 46.86 MPa during torsion. Conclusions Both X-STOP and Coflex are an effective treatment for LSS, and can effectively restrict the ROM of extension and reduce the disc pressure, without affecting the adjacent segments.