Knowledge of spinal loads in neighboring discs after interbody fusion plays an important role in the clinical decision of this treatment as well as in the elucidation of its effect. However, controversial findings are still noted in the literature. Moreover, there are no existing models for efficient prediction of intervertebral disc stresses within annulus fibrosus (AF) and nucleus pulposus (NP) regions. In this present study, a new hybrid rigid-deformable modeling workflow was established to quantify the mechanical stress behavior within AF and NP regions of the L4-5, L2-3, and L1-2 discs after interbody fusion at L3-4 level. The changes in spinal loads were compared with results of the model without interbody fusion. The fusion outcomes revealed maximal stress changes (10%) are noted in AF region of L1-2 disc and in NP region of L2-3 disc. The minimal stress change (1%) is noted at the NP region of the L1-2 disc. The validation of simulation outcomes of fused and intact lumbar spine models against those of other computational models and in vivo measurements showed good agreements. Thus, our present study may be used as a novel design guideline for a specific implant and surgical scenario of the lumbar spine disorders.