Objective:

Lumbar spinal canal stenosis (LSS) with diffuse idiopathic skeletal hyperostosis (DISH) can require revision surgery due to the intervertebral instability after decompression. However, there is a lack of mechanical analyses for decompression procedures for LSS with DISH.

Methods:

This study employed a validated, three-dimensional finite element model of a L1-L5 lumbar spine, L1-L4 DISH, pelvis, and femurs to compare the biomechanical parameters (range of motion (ROM), intervertebral disc, hip joint, and instrumentation stresses) with a L5-sacrum (L5-S) and L4-S posterior lumbar interbody fusion (PLIF). A pure moment with a compressive follower load was applied to these models.

Results:

L5-S and L4-S PLIF models’ ROM decreased by more than 50% at L4-L5 respectively and decreased by more than 15% at L1-S compared to the DISH model in all motions. The L4-L5 nucleus stress of the L5-S PLIF increased by more than 14% compared to the DISH model. In all motions, the hip stress of DISH, L5-S and L4-S PLIF had very small differences. The SIJ stress of L5-S and L4-S PLIF model decreased by more than 15% compared to the DISH model. The stress values of the screws and rods in L4-S PLIF model was higher than in L5-S PLIF model.

Conclusion:

The concentration of stress due to DISH may influence ASD on the non-united segment of PLIF. A shorter-level lumbar interbody fixation is recommended to preserve ROM; however, it should be used with caution as it could provoke adjacent segment disease.