Finite Element Analysis Of ACL Reconstruction Of The Knee Based On Dual Fluoroscopic Imaging Technique

BackgroundAnterior cruciate ligament(ACL)injuries are common and are closely related to flexion-extension activity of the knee joint.The influence of this factor cannot be ignored when studying the mechanism of injury and evaluating the effect of surgical ACL reconstruction.Because of the complicated anatomical structure and motion mechanism,it is very difficult to study the mechanics of soft tissue around the knee joint.Traditional in vitro biomechanics experiments cannot replicate the flexion motion under physiological condition.Finite element analysis makes up for this deficiency to some extent.But there are still some problems such as complexity of modeling process,low accuracy and inability to realize personalization.The mechanical evaluation of grafts after ACL reconstruction is mainly based on the results of in vitro experiments and the in vivo mechanical performance of grafts is not completely clear.ObjectiveA displacement controlled finite element analysis was performed based on the kinematic data of the knee joint to study the biomechanics of ligaments at different flexion angles.Dual fluoroscopic imaging technique was further combined to explore a finite element simulation method of knee flexion under physiological load and to evaluate the grafts tensions and stresses at different femoral locations during anatomical single-bundle ACL reconstruction.Methods1.Finite element simulation of knee flexion and biomechanical study of ligaments based on the fluoroscopic kinematic data of geometric central axisThe kinematic equations of multiple degrees of freedom of femur relative to tibia were established according to the kinematic data of geometric central axis reported in literature.Translation and rotation were applied to the femur and tibia to analysis the biomechanics of knee ligaments at different flexion angles.2.Personalized knee flexion kinematics study combined with dual fluoroscopic imaging techniqueThe right knee of a healthy volunteer was studied during lunge motion by using a validated dual fluoroscopic imaging technique.The kinematics data of the femur related to the tibia at six degrees of freedom were calculated.3.Finite element analysis of in vivo forces and stresses of grafts in anatomical single-bundle ACL reconstruction at different femoral locationsTibial footprint and femoral footprint of the ACL were located according to bony landmarks.Twenty-one ACL reconstruction models were established in SolidWorks.Six degrees of freedom kinematic data were applied to the femur in Abaqus to realize personalized knee lunge simulation and calculate the reaction forces of the femur and the maximum principal stresses of the grafts.Results1.There are significant differences in the length and stress state of knee ligaments during lunge motion.The displacement controlled finite element analysis of the knee joint can be realized to simulate the flexion motion based on fluoroscopic kinematics data of the geometric center axis.2.Personalized knee lunge analysis was realized and the six degrees of freedom kinematic data of femur related to the tibia under physiological condition was obtained which provided a basis for subsequent studies.3.Increased and decreased graft forces were observed when the grafts were located higher and lower on the femoral footprint,respectively;anterior and posterior graft placement did not significantly affect the graft force.Lower and posterior graft placement resulted in less stress on the graft at higher degrees of flexion;there were no significant differences in stress when the grafts were placed from 0° to 30° of flexion on the femoral footprint.ConclusionFinite element analysis combined with dual fluoroscopic imaging technology can and simulate knee flexion motion under physiological condition and can be used to study the biomechanics of soft tissue reconstruction of the knee joint such as anterior cruciate ligament.It can also guide the related surgery.