Biomechanical Study Of Lumbar Spine After TKA Based On Finite Element Model

Objective:Total knee arthroplasty（TKA）is the gold standard for the treatment of end-stage knee osteoarthritis（KOA）,however many patients experience symptoms of low back pain after a period of TKA,a phenomenon that is relatively common in clinical practice,but the mechanism has not yet been elucidated.In order to investigate the biomechanical changes of the lumbar spine after TKA correction of KOA flexion deformity,a digital model of the lumbar spine-pelvis-lower limb of the human body was constructed by finite element analysis,and the steps of TKA correction of flexion deformity were simplified to change the knee flexion angle of the finite element model,and TKA correction of knee flexion deformity was simulated by changing the knee flexion angle of the model to observe the biomechanical changes of the lumbar spine after TKA correction of knee flexion deformity,providing a reference for the biomechanical study of low back pain after TKA.Methods:A healthy adult volunteer was selected and scanned with CT and MRI respectively to obtain medical image data.Using image processing software such as Mimics,Geomagic,Solid Works and Workbench,a three-dimensional finite element model of the human lumbo-pelvis-lower limb was constructed and its effectiveness was verified.A 30°knee flexion deformity model was constructed,on which the knee flexion angle was gradually reduced,and a 15°and 10°flexion deformity model and a 0°neutral position model after surgery were established,respectively,to simulate TKA to correct knee flexion deformity.The same load was applied to the upper endplate of L₁ in the above model,and the stress distribution and maximum equivalent stress of the lumbar vertebral body and intervertebral disc were observed and calculated,respectively,to study the stress changes of the lumbar vertebral body and intervertebral disc.Results:A three-dimensional finite element model of the human lumbar spinal-pelvis-lower limb was successfully established,with a total of 3,643,895 elements and 819,920 nodes.Vertebral stress clouds showed that the S₁ vertebral body carried the greatest stress in each vertebral body.In the same level of vertebral body,with the decrease of knee flexion angle,the stress on the vertebral body gradually increases,and the distribution of stress gradually moves forward from the posterior edge of the vertebral body.The stress clouds of the intervertebral discs showed that the L₅/S₁ disc carried the greatest stress in each disc,and the stress was mainly concentrated at the anterior edge of the disc.In the same segment of the disc,the stress on the disc gradually increases as the knee flexion angle decreases,and the distribution of stress gradually moves forward from the posterior edge of the vertebral body.Conclusions:A three-dimensional finite element model of lumbar vertebra,pelvis and lower limb was established to simulate TKA to correct flexion deformity.The results of lumbar vertebral body and intervertebral disc stress at different knee flexion angles were compared.In the same model,S₁ vertebral body carried the greatest stress in each vertebral body,and L₅/S₁ intervertebral disc carried the greatest stress in each intervertebral disc.In the same vertebral body and intervertebral disc,with the decrease of knee flexion angle,the stress of lumbar vertebral body and intervertebral disc gradually increased,and the stress distribution of lumbar vertebral body and intervertebral disc gradually moved anteriorly from the posterior edge.In this experiment,finite element models were used to observe changes in stress in the lumbar vertebral body and intervertebral disc after TKA in KOA patients with flexion deformity.