Biomechanical Analysis for Low Lumbar Spine Segment Fusion with Different Cage Locations

Aims: This paper aims to investigate the influence of cage location on the biomechanical behavior of lumbar spine with Transforaminal Lumbar Interbody Fusion (TLIF).
Methodology: Firstly, a three-dimensional finite element (FE) model for L4-L5 low lumbar spine segment is established based on computed tomography scan images of a 30-year-old healthy male volunteer. Flexion, extension, lateral bending and torsion motions are simulated and compared with in-vitro cadaveric test data in the literature to validate the lumbar spine FE model. The intact spine model is then modified to TLIF model with one cage insertion under three different implant angles (30°, 45° and 60°).
Results: Numerical results show that after fusion treatment the stress increases dramatically, and mainly distributes on cage and pedicle screw-rod system. Though 45° fusion does not have the lowest von Mises stress at the pedicle screw-rod system and the cage, it is still within an allowable strength limit. Besides, 45° fusion has the best balanced stability in four basic physiological motions. So if only one cage uses, the 45° posterior location may be more suitable for L4-L5 interbody fusion than 30° and 60° location.
Conclusion: If only one cage uses, the 45° posterior location may be more suitable for L4-L5 interbody fusion than 30° and 60° location.