[Finite element analysis of screw in percutaneous axial lumbosacral interbody fusion].

Objective: To establish a 3D finite element model of L5/S1 motion segment with percutaneous axial lumbosacral interbody fusion (AxiaLIF) screw and conduct a preliminary analysis of biomechanical stress.

Methods: The titanium screw was implanted in L5 and S1 vertebral body. Solid model was established by CAD software according to the actual dimensions of screw. Then computer graphics were obtained from iges format and imported into the finite element analysis software to establish the finite element model. With the aid of Mechanical Virtual Human of China, a 3D finite element model of L5/S1 motion segment with AxiaLIF screw was established. Vertical compression, torque moment and bending moment were loaded respectively on the upper surface of L5 vertebrae to simulate the load stress in human body. Stress distribution of screw was obtained.

Results: Generally stress values were relatively low. Peak stresses of screw under three loading conditions were 175.334 Mpa, 183.765 Mpa and 146.237 Mpa respectively. Stress value was relatively high at the central part of interbody fusion. And all the highest values were localized at the first thread below the central part. Result of comparison between three conditions: torque load was the highest, followed by vertical load and lateral bending.

Conclusion: Percutaneous axial lumbosacral screw can meet the normal loading conditions. Further clinical applications are recommended.