Finite element modelling of hybrid stabilization systems for the bilevel disc degeneration of human lumbar spine

Fusion is a very common treatment for spinal disorders associated with Intervertebral Disc (IVD) degeneration. Dynamic implantation systems have become the preferable solution for Degenerative Disc Disease (DDD) to eliminate the negative effects of fusion prosedure. In this thesis, different commercial Hybrid Stabilization Systems (HSSs) and a new designed HSS named as Mobile-PEEK were analysed and compared to each other for the treatment of bilevel DDD. Finite Element (FE) model of L1-S1 lumbar spine was used in the analyses and Range of Motion (ROM), Intradiscal Pressure (IDP) and von Mises Stress (VMS) in case of intact and implanted spine were calculated as there is no comparison in the literature about the efficiency of these systems. Additionaly, some new combinations of Artifical Disc Replacement (ADR) systems and the dynamic portion of HSSs were analysed to suggest optional treatments of bilevel disc degenerations. Finite Element Analysis (FEA) of the HSSs showed that such systems could be effective for providing some of the natural lumbar spine motion, while reducing the probability for increasing adjacent segment degeneration. Results revealed that the hybrid combination of B-DYN, with a less flexible dynamic portion, and artificial disc showed more mobility than the conventional B-DYN hybrid structure. Additionally, B-DYN+ADR showed no indications for adjacent segment disease and no implant failure. Similarly, Mobile-PEEK may provide valuable indications for future device developments, as it was found to have desirable elastic movement and also low pressure at adjacent segment.