Three dimensional finite element analysis of the biomechanics influence of L4 inferior articular process and L5 superior articular process foraminoplasty under percutaneous endoscopy on the intervertebral disc

English Keywords:Lumbar percutaneous endoscopy  Foraminoplasty  Three-dimensional finite element

English Abstract:

  【Abstract】 Objectives: To evaluate the biomechanical effects of lumbar 4-facet arthroplasty and lumbar 5-facet arthroplasty under percutaneous endoscopy using three dimensional finite element analysis. Methods: a healthy young male volunteer was selected and scanned under the thin-layer spiral CT to establish a normal L3-L5 three-dimensional finite element model. The above normal finite element model and classical literature data were verified. The simulated lumbar percutaneous endoscopic technique was used to resect the L5 superior articular process and L4 inferior articular process through the lateral posterior approach. The normal model, L4 model (A model) and L5 model (B model) were obtained. The load of 400N was applied to the endplate on the upper surface of L3 vertebral body to simulate the load-bearing gravity of normal human lumbar spine. The pure torque of 7.5N·m was applied in the direction of forward bending, backward stretching, left and right side bending and left and right rotation respectively. The stress changes of L3/4 and L4/5 intervertebral discs of the three models were compared under the conditions of forward bending, backward stretching, left/right side bending and left/right rotation. Results: The maximum stress of L4/5 intervertebral disc was 0.390MPa, 0.520MPa, 0.450MPa, 0.430MPa, 0.510MPa and 0.498MPa respectively in flexion, extension, left flexion, right flexion, left rotation and right rotation after L5 superior articular process was formed; the maximum stress of L4/5 intervertebral disc was 0.375MPa, 0.490MPa, 0.440MPa, 0.420MPa, 0.482MPa and 0.478MPa respectively in flexion, extension, left flexion, right lateral flexion, left rotation and right rotation after L4 inferior articular process was formed. The maximum stress of L3/4 intervertebral disc was 0.368MPa, 0.478MPa, 0.436MPa, 0.430MPa, 0.465MPa and 0.444MPa after L5 superior articular process was formed under the condition of forward flexion, backward extension, left flexion, left rotation and right rotation, respectively. The maximum stress of L3/4 intervertebral disc was 0.369MPa, 0.480MPa, 0.442MPa, 0.432MPa, 0.468MPa and 0.452MPa under flexion, right flexion, left rotation and right rotation after L4 inferior articular process was formed, respectively. Conclusions: The biomechanics of L4/5 disc in the state of extension and rotation is more affected by the L5 superior articular process foraminoplasty through the lateral posterior approach than that through L4 inferior articular processforaminoplasty through the posterior approach. Both of them have little effect on the six kinds of stress changes of L3/4 disc.