后路寰枕斜坡螺钉枕颈固定的生物力学有限元分析

A biomechanical finite element analysis of posterior atlantoccipital-clivus screws in occipitocervical fixation

中文关键词:  枕颈固定  寰枕斜坡螺钉  内固定  有限元分析

英文关键词:Occipitocervical fixation  Atlantoccipital transarticular-clivus screw  Internal fixation  Finite element

中文摘要:

  【摘要】 目的：利用有限元分析研究后路寰枕斜坡螺钉（atlantoccipital transarticular-clivus screw，TACL）枕颈固定的稳定性及其应力影响。方法：应用志愿者枕颈CT数据建立正常枕颈模型，验证模型有效性后建立枕颈失稳模型和6种枕颈固定的有限元模型：枕骨螺钉（occipital screw，OS）+寰椎侧块螺钉（C1 lateral mass screw，C1LMS）+枢椎椎弓根螺钉（C2 pedicle screw，C2PS）、OS+寰枕关节螺钉（atlantoccipital transarticular screw，TA）+C2PS、OS+TACL+C2PS、枕骨髁螺钉（occipital condyles screw，OcC）+C1LMS+C2PS、TA+C2PS、TACL+C2PS，对模型赋值材料参数，在枕骨上表面施加40N的垂直向下压力模拟头部重力，施加1.5N·m扭矩，使模型产生屈伸、侧弯和旋转运动，比较各枕颈固定模型在不同工况下的稳定性、置入物应力分布情况以及骨骼应力分布情况。结果：建立的正常枕颈模型生理状态下的活动度与文献报道的结果相近，在屈、伸、侧弯、旋转工况下的活动度分别为19.53°、17.37°、10.44°、38.74°；失稳模型在屈、伸、侧弯、旋转工况下的活动度分别为26.17°、18.90°、10.99°、42.30°，较正常模型分别增加 34.00%、8.82%、5.34%、9.20%。6种内固定模型在相同工况下的活动度均减小。相较于失稳模型，TACL+C2PS在前屈、后伸、侧弯、旋转工况下削减了97.43%、94.06%、96.68%、99.01%的活动度。在相同工况下TACL+C2PS的内固定应力峰值为241.00MPa、241.2MPa、166.94MPa、168.8MPa，OS+TACL+C2PS的内固定应力峰值为295.00MPa、295.00MPa、73.54MPa、81.40MPa；内固定应力集中于连接棒中部和TACL尾部，且两种应用TACL固定技术的模型对骨骼的切割应力均较小，较其他枕骨固定技术具有更合理的应力分布。结论：后路TACL作为枕骨侧固定的技术可以满足枕颈固定的力学强度要求，相较于其他单独应用的枕骨固定技术，具有更优异的稳定性和应力分布，其与后路OS联合应用具有更强的力学稳定性。

英文摘要:

  【Abstract】 Objectives: To study the influence on stability and stress of posterior atlantoccipital transarticular-clivus screw(TACL) in occipitocervical fixation using the finite element analysis method. Methods: Finite element models were established using the occipitocervical CT data of a volunteer, including an intact model, an unstable model, and six models of occipitocervical fixations: occipital screw(OS)+C1 lateral mass screw(C1LMS)+C2 pedicle screw(C2PS), OS+atlantoccipital transarticular screw(TA)+C2PS, OS+atlantoccipital transarticular-clivus screw(TACL)+C2PS, Occipital condyles screw(OcC)+C1LMS+C2PS, TA+C2PS, and TACL+C2PS. Material parameters were assigned to the models, and a vertical downward force of 40 N was applied to the upper surface of the occipital bone to simulate the weight of head. A torque of 1.5N·m was applied to induce flexion, lateral bending, and rotational movements. The stability, implant stress distribution, and bone stress distribution of each occipitocervical fixation model under different conditions were compared. Results: The range of motion(ROM) of the intact model under physiological conditions was similar to those reported in the literatures, and the ROMs under flexion, extension, lateral bending and rotation conditions was 19.53°, 17.37°, 10.44° and 38.74°, respectively. The ROMs of the unstable model under flexion, extension, lateral bending and rotation conditions were 26.17°, 18.90°, 10.99° and 42.30°, respectively, which were 34.00%, 8.82%, 5.34% and 9.20% higher than those of the intact model, respectively. The ROMs of the six fixation models were reduced under the same working conditions. Compared to the unstable model, TACL +C2PS cut 97.43%, 94.06%, 96.68%, and 99.01% of the ROM under the four working conditions. The peak internal fixation stresses were 241.00MPa, 241.20MPa, 166.94MPa, and 168.80MPa for TACL+C2PS, and 295.00MPa, 295.00MPa, 73.54MPa, and 81.40MPa for OS+TACL+C2PS in the same working conditions; The internal fixation stresses were concentrated in the middle of the connecting rod and the tail of the TACL, and both models applying the TACL fixation technique had less cutting stress on the bone, which had a more reasonable stress distribution than other occipital fixation techniques. Conclusions: Posterior TACL as a technique for occipital fixation can meet the mechanical strength requirements for occipitocervical fixation and has superior stability and stress distribution compared with other occipital fixation techniques applied alone, and its combined application with posterior occipital screws provides greater mechanical stability.