MATERIAL and METHODS: A normal healthy finite element model, two degeneration models and corresponding nucleotomy models of the L4-5 segment were created. Combined with 800 N preloading, 10 Nm moment was applied on the L4 superior endplate to simulate extension, flexion, left axial rotation and lateral bending, respectively. The shear stress of annulus fibrosus, posterior annulus bulge along with the contact force of facet joint at L4-5 were investigated.

RESULTS: In all loading directions, the shear stress and contact force of the facet joint in two nucleotomy models were higher than those in mildly or moderately degenerative models, while the posterior annulus bulge was lower than those in mildly or moderately degenerative models.

CONCLUSION: Nucleotomy may adversely aggravate lumbar degeneration at the operated level Keywords : Nucleotomy, Posterior annulus bulge, Contact force of facet joint, Shear stress, Finite element analysis