The Research On Lumbar Spondylolysis Injury And Protective Strategy In+Gz Impact

The vertical acceleration from foot to head caused by a rapid ascent or landing during flight piloting is referred to as high G impact,or +Gz.According to the pilot medical examination statistics,the proportion of medical disorders resulting in disqualification and grounding owing to spondylolysis is increasing year after year.Long-term exposure of fighter pilots to high-G impact conditions may be a potential source of spondylolysis,hence investigating the influence of spondylolysis on the biomechanical response of the lumbar spine under high G impact and proposing appropriate lumbar protection methods is critical.To investigate the lumbar spondylolysis injury and protection strategy in +Gz impact,this research used lumbosacral CT scan data from volunteers without lumbar spine disease to build a lumbosacral finite element model with biomechanical properties,and destroyed the isthmus structure to obtain the spondylolysis finite element model.The two models were exposed to impact loads ranging from +1Gz to+7Gz in order to investigate the effect of spondylolysis on lumbar spine injury under high G impact.On this basis,the spondylolysis finite element model and the THUMS human finite element model were combined to create a human coupling finite element model with isthmic fracture.The position,direction and stiffness of the lumbar support were selected as the study factors,and simulation experiments of +Gz impact under single factor and cross factor were conducted on the human coupling model,respectively,to investigate the protection strategy for spondylolysis under +Gz impact.The simulation results on the effect of spondylolysis on lumbar spine injury show that:(1)spondylolysis significantly reduces the stability of the lumbar spine under high G impact and increases the amplitude of motion of the lumbar spine after compression;(2)spondylolysis increases the forces on the lumbar vertebrae,lumbar intervertebral discs,and ligaments in high G impact conditions,and increases the overall compression of the lumbar spine,The results of the single-factor analysis of lumbar support showed that:(1)Different lumbar support schemes were effective in reducing the injury of the lumbar spine with isthmic fracture;(2)an overly high support position and excessively small support stiffness are not conducive to lumbar spine protection;(3)a certain support angle can reduce disc stress.The results of the cross-factor analysis of lumbar support showed that(1)The orthogonal experimental design and extreme difference analysis of lumbar support factors revealed that support position and stiffness had a significant effect on lumbar spine injury,with support stiffness having the most effect;(2)The best lumbar support scheme under the three-factor analysis was the support angle of0°,the support position L5,and the Young’s modulus of the support material of 100 MPa,and when compared to no support,the maximum axial force,maximum axial moment,and maximum disc stress of the lumbar spine with spondylolysis were reduced by 30.9 percent,71.69 percent,and 22.56 percent,respectively.The corresponding data and conclusions derived from this paper can fill the gaps in existing studies on lumbar injury and protection of the spondylolysis under +Gz impact and serve as a reference for reducing lumbar and abdominal injuries and improving lumbar spine support protection strategies for high-speed carrier drivers.