Objective To evaluate the biomechanical effects of nucleotomy with two procedures on the stability of lumbar spine and the highest von Mises stress in annulus.Method A three-dimensional finite element model of L4-5 motion segment was established by using CT scans.Nucleotomy through osseous lamina fenestration and through interlaminar fenestration was simulated on the model,respectively,and axial compressive load of 400N with moment of 6.0Nm in six directions,including flexion,extension,left and right lateral bending,left and right axial torsion,were employed on the models.Rotational degrees of inter-segment and the highest von Mises stress in annulus were examined. Result After nucleotomy through osseous lamina fenestration,the rotational degrees of inter-segment in flexion and extention conditions increased by 31% and 28%,respectively;the highest von Mises stress in annulus increased by 16% and 6%,respectively.After nucleotomy through interlaminar fenestration,the rotational degrees of inter-segment in flexion and extention conditions increased by 33% and 39%,respectively;the highest von Mises stress in annulus increased by 17% and 0.2%,respectively.After nucleotomy with the two procedures,the stress distribution in annulus keeps unchanged,but the stress values increased in all cases.Conclusion Contrast to nucleotomy through interlaminar fenestration,nucleotomy through osseous lamina fenestration can keep the lumbar spine more stable in extension condition,but the increase of stress in annulus is higher in the same condition.