Mechanical loading effects on isthmic spondylolytic lumbar segment: Finite element modelling using a personalised geometry

Abstract

Biomechanics of the isthmic spondylolysis was investigated by using a nonlinear 3D-finite element model (FEM). A personalised in vivo pediatric geometry of L5–S1 low-grade spondylolisthesis patient was used to develop a L5–pelvis motion segment model that took into consideration vertebrae, disc and ligaments. The stress distribution in the affected motion segment under axial force only, and for a combination of flexion and extension was evaluated. Predicted results showed that, under all loading conditions, stresses were much higher on the pedicle and in the dorsal wall of the pars interarticularis due to the abnormal geometry which is consistent with clinical observations.

Keywords:

• isthmic spondylolysis
• finite element model
• biomechanics
• personalised geometry
• stress concentration

Acknowledgements

This project was supported by the Natural Sciences and Engineering Research Council of Canada, the Canada Research Chair Programme and an unrestricted educational/research grant from Medtronic Sofamor Danek. The authors would like also to thank the members of the Spinal Deformity Study Group (Spondylolisthesis Section) and Hicham Gharbi for his contribution.