Stresses analysis of the facet joints of a lumbar motion segment after discectomy / 中国矫形外科杂志

ABSTRACT

[Objective]To study the stresses value and distribution of the facet joint of the normal L4、5 segment model and that of the denucleated lumbar segment model. [Method]A finite element model of the intact L4、5 segment was developed through Ansys software.The property of nucleus pulposus was changed to be negligible to model lumbar discectomy through anterior approach.Then the finite element model of the denucleated lumbar spine segment was created.The inferior end plate of L5 was fixed.Models were subjected to 6 Nm flexion,extension or right rotation moment in combination with 400 N axial compression preload.Forces were applied to the superior L4 end plate.Stresses value and distribution of the lumbar facet joint were analyzed under different loading conditions.[Result]Finite element models of the intact L4、5 segment and the denucleated lumbar spine segment were created.The facet joint was treated as a three dimensional contact,linear frictionless problem.The facet joint was composed of the inferior and superior facet surface and ligamentous structure.Both facet joints,especially the left of the intact model produced larger stresses in right rotation.Comparing with that of the intact model,stresses of the facet joint of the denucleated model increased in flexion,extension and right rotation.[Conclusion]The region of contact of each facet joint varies according to different loading conditions.So does the stresses value and distribution.The facet stresses of the lumbar segment increase in flexion,extension and rotation after discectomy.