Biomechanical Evaluation of Two Posterior Lumbar Intervertebral Fusion Surgical Scenarios Reinforced by a Rigid Posterior Fixation System in the Vertebral Column Analyzed by the Finite Element Method

Lumbar interbody fusion is a common procedure for treating lower back pain related to degenerative disc diseases, the following two scenarios of posterior lumbar interbody fusion cage (PLIF) were usually used, i.e., Model (I) posterior lumbar intersomatic fusion cage bilateral approach filled with bone graft (1) and (2), (Model II) PLIF with cage made of PEEK or titanium (Ti) materiel filled with bone graft. But the benefits or adverse effects among the two surgical scenarios were still not fully understood. In this regard, we installed these discs between the two vertebrae L5 and S1 of the spine, to ensure spinal stability and avoid slipping, we have used a posterior attachment system (6 screws plus 2 rods) at the pedicular levels of the lumbar vertebra (S1-L5, L5-L4). Finite element analysis (FEA), as an efficient tool for the analysis of lumbar diseases, was used to establish a three-dimensional nonlinear TH1-pelvic FE model (Intact Model) with the ligaments of solid elements. Then it was modified to simulate the two scenarios of PLIF. Two anterior bending moments (P2 and P3) with a P1 compression loading were applied to the 3D model of the spine (TH1-pelvic), respectively. Different mechanical parameters were calculated to evaluate the differences among the three surgical models. The results of numerical values show that these disks played a very important role in the absorption of the stresses and to minimize, On the other hand, the lumbar inter-somatic cage (Model II) filled with cancellous bone is too great a role in reducing the stress compared to another synthetic (Model I) disc. In general, the new model of the inter-somatic cage filled with cancellous bone and reinforced by a posterior fixation system has given a lower level of stress in the cortical bone and the spongy bone of the lumbar vertebra (L5) compared to the healthy disk (D1). The findings provide theoretical basis for the choice of a suitable surgical scenario for different.