膝后交叉韧带双束重建术中股骨隧道定位的计算机辅助设计研究

Femoral tunnel positioning in posterior cruciate ligament double-bundle reconstruction by computer aided design

目的 :采用现实虚拟互动技术及有限元分析法,探讨膝关节后交叉韧带双束重建术中股骨隧道合理定位及重建术后移植物固定膝关节力学响应。方法:取新鲜冰冻膝关节标本5具,用实验与计算机仿真相结合的方法,重建膝关节三维计算机模型,以实验获得的外部结构运动指标操纵此模型,真实再现人体膝关节屈伸运动。分析模型内部股骨与胫骨关节面在此运动过程中的空间位置变化情况,分别在后交叉韧带前外侧束(ALB)和后内侧束(PMB)股骨端附丽区选取前、后、中、近、远10个测试点,选取胫骨端止点中点,利用软件Geomagic计算连接两关节面各两点间的长度变化。将模型导入软件Ansys,采用四面体单元建立起股骨-胫骨复合体的有限元模型,模拟人体行走中单腿着地情况对模型施加自身体重冲击载荷,分析关节面的受力情况。结果:计算机还原出各运动角度下膝关节骨性结构的空间形态,软件Geomagic的几何计算功能能准确测量股骨各点与胫骨止点间在关节内的长度变化,ALB和PMB相同测试点在不同角度所得关节面两点间长度变化平均值间有显著性差异(P<0.05);且同一角度不同测试点所得数据间亦有显著性差异(P<0.05)。ALB各点中以A2变化最小(1.35±0.19)mm,A1变化最大(5.41±1.22)mm,A2和A3点比较,差异无统计学意义(P=0.913>0.05);PMB各点中以B3点变化最小(1.95±0.04)mm,B1变化最大(5.23±2.21)mm,只有A2、A3和B3点变化范围在2 mm以内。结论 :通过计算机技术能够建立可供分析测量的膝关节模型,能准确的对交叉韧带的长度进行测量。在后交叉韧带双束重建中,前外侧束应以其股骨附丽区上缘的中点(即近测试点)为中心钻孔;后内侧束应以其股骨附丽区上缘(即近测试点)为中心钻孔建立股骨骨隧道。模型为进一步评价重建等长点偏差对术后移植物固定力学环境影响的研究提供基础。

Objective：To study mechanical affect of knee joint of reasonable positioning of femoral tunnel during knee posterior cruciate ligament（PCL） double bundle reconstruction and graft fixation after reconstruction by virtual reality interactive technology and evaluate the biomechanical response of knee after reconstruction by finite element analysis. Methods：Knee specimens from five fresh frozen cadavers were used. Computer simulations and biomechanical experiments were used in this study. Experiments on flexion and extension movements of the knee joint were performed on specimens of fresh human knee joint. Laser three dimensional scanning was used to record and calculate the indexes of movements. Three dimensional models of knee joint bone structure were then reconstructed on computer with the experimental data. Simulations of flexion and extension movements were carried out on the models to show the spatial positions of femur and tibia and label the attachment sites of PCL. Ten test points in the anterior,posterior,proximal,distal at the femoral attachment area of anterior and lateral bundle（ALB） and postoperior medial bundle（PMB） were selected and the central points of tibial en attachment areat anchored. The distance btween each two points of two article surface was calculated and contacted by software of Geomagic. Model was import software Ansys,adopting the tetrahedron unit a finite element model of complex tibial and femoral was set up to simulat human walking in one leg,on this condition the the joint surface force of model under weight impact load were analyzed. Results：The three dimensional models could demonstrate the spatial positions of the bone structure of the knee in different flexions and extensions. The models could be used to measure the spatial distance between 2 points on the femoral and tibial planes by software Geomagic. There was significantly difference among the length changes of anterolateral bundle and posteromedial bundle at every fixed point with different flexion angles（P〈0.05）,so the fixed angle with different points. The length changes of anterior lateral bundle＇s A2,A1 and posterior medial bundle＇s B3,B1 points were（1.35±0.19） mm,（5.41±1.22） mm,（1.95±0.04） mm and（5.23±2.21） mm,respectively. The A2 and B3 points＇ length changes were the less,and that of the A1 and B1 points were the more. It had no significant difference between the length changes of anterior lanteral bundle＇s A2 and A3 point（P=0.913〉0.05）. All of the maximal length changes of anterior lateral bundle＇s A2,A3 and postterior medial bundle＇s B3 points were less than 2 mm. Conclusion：The models of knee joint were builded through computer technology and it can be measure the lenth of cruciate ligament with software Geomagic exactly. The femoral tunnel for the PCL double-bundle reconstruction should be located as follows： ALB at the middle point of upper edge of femoral attachment site（proximal point）,while PMB at the middle point of femoral attachment site（proximal point）. This model provides a satisfactory method for the evaluation of the biomechanical response of knee after cruciate ligament reconstruction.