Comparative Study of Biomechanical Model of the L4-L5 Lumbar Section with Mechanical Fixation

Abstract

The risk of fixation loosening by the pedicle failure during or after the screw insertion surgery is high, causing fracture of the bone tissue due to the high stress concentration. The purpose of this paper is study the influence of osteoporosis on the bone-screw interface, based on a 3D biomechanical model of the lumbar section. The Finite Element (FE) method was used. Mechanical properties in health vertebra (HV) and osteoporotic vertebra (OV) were defined. A compression load of 500 N and a moment of 7.5 Nm were assumed in four load scenarios: compression, flexion, flexion-extension and axial rotation. The bone-screw interaction zone and the posterior of vertebra and pedicles were susceptible to bone tissue failure, because the higher equivalent stress were close to bone failure stress. The HV stresses were higher than OV stresses. The higher stress was 8.83 MPa. Opposite to stresses results, the strains were higher in OV than in HV, being the OV strain more than 2 times higher than HV strain.