新型颈前路高贴附性弹性内固定合金板的设计与有限元分析

Design and finite element analysis of a new type of high adhesion elastic internal fixation alloy plate for anterior cervical spine

背景:颈椎前路椎间盘切除减压内固定通常于颈前辅助接骨板进行内固定,由于传统接骨板体积较大、突出于椎体前缘及接骨板材质导致弹性模量较高等原因,术后患者常存在吞咽不适、相邻节段退行性变等并发症。目的:运用三维有限元研究方法比较并分析3种自主研发的新型颈前路高贴附性弹性内固定合金板在术后的应力分布特点,为内植物的改进及临床应用提供参考。方法:利用镍钛合金设计3种内植物:合金板A为阶梯型,合金板B为弧面阶梯型,合金板C为弧面型。随机采集1名21岁健康成年女性志愿者C5、C6节段的CT薄层扫描图像,应用Mimics 21.0、Geomagic Studio 2013、Abaqus 2020等软件处理,构建3种新型颈前路合金板装配完成的颈椎有限元模型,在C5上加载50 N垂直力及1.5 N·m纯扭矩载荷,模拟颈椎中立、前屈、后伸、左右侧屈及左右旋转7种运动状态,采集3种合金板6个应力集中区域的应力值。结果与结论:①中立位时,3种合金板上各个应力集中区域处分布的应力相对其余工况为最小;前屈及后伸工况下,合金板A加压件上部的平均应力大于合金板B(P<0.05),合金板C下部的平均应力大于合金板B(P<0.05);侧屈工况下,屈侧的平均应力大于伸侧(P<0.05);旋转工况下,旋转对侧上部及同侧下部的平均应力相对较大(P<0.05);侧屈及旋转动作时,合金板A大多区域的平均应力远小于合金板B、C(P<0.05);②3种合金板的平均应力均在中立位时较小、在做旋转动作时较大,应力最大部位几乎均集中于螺纹孔周围;③合金板A较适合于术后需做各种类似侧屈旋转动作的患者;合金板B对椎体影响较小,适合于椎体存在基础疾病等的患者;合金板C可在考虑相关并发症的前提下适当增加下部厚度。该新型合金板仍需进一步实验及临床研究。

BACKGROUND:Anterior cervical discectomy and fusion is performed with anterior cervical auxiliary plate.However,due to the large volume of traditional plate,protruding at the anterior edge of vertebral body,and high elastic modulus caused by steel plate material,postoperative patients often have complications,such as swallowing discomfort and adjacent segment degeneration.OBJECTIVE:Three-dimensional finite element method was used to compare and analyze the stress distribution characteristics of three new types of selfdeveloped anterior cervical discectomy and elastic internal fixation alloy plates after operation,so as to provide the reference for the improvement and clinical application of implants.METHODS:Three kinds of inner plants were designed by using Ni-Ti alloy:alloy plate A was ladder type;alloy plate B was arc surface ladder type;and alloy plate C was arc surface type.The thin slice CT images of C5 and C6 segments of a 21-year-old healthy female volunteer were randomly collected and processed by Mimics 21.0,Geomagic Studio 2013,and Abaqus 2020 to construct the finite element models of three new types of anterior cervical alloy plates.The C5 was loaded with 50 N vertical force and 1.5 N·m pure torque load to simulate seven motion states of cervical vertebra:neutrality,flexion,extension,left and right flexion,and left and right rotation.The stress values of six stress concentration areas of three kinds of alloy plates were collected.RESULTS AND CONCLUSION:(1)In the neutral position,the stress distributed in each stress concentration area of the three kinds of alloy plates was the smallest relative to the other working conditions.Under the flexion and extension conditions,the average stress of the upper part of the alloy plate A was higher than that of the alloy plate B(P<0.05).The average stress of the lower part of the alloy plate C was higher than that of the alloy plate B(P<0.05).Under the lateral flexion condition,the average stress of the flexion side was larger than that of the extension side(P<0.05).Under the rotating condition,the average stress of the upper part of the rotating opposite side and the lower part of the same side was relatively larger(P<0.05).During lateral flexion and rotation,the average stress in most areas of alloy plate A was much lower than that of alloy plates B and C(P<0.05).(2)The average stress of the three kinds of alloy plates was smaller in the neutral position and larger in the rotation,and the maximum stress was almost concentrated around the threaded hole.(3)Alloy plate A was more suitable for patients who need to do a variety of similar lateral flexion and rotation movements.Alloy plate B had little effects on the vertebral body and was suitable for patients with underlying diseases of the vertebral body.Alloy plate C could appropriately increase the lower thickness under the premise of considering related complications.The new alloy plate still needs further experimental and clinical research.