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    Biomechanical Analysis of C5-C6 Spinal Unit with Prosthetic Disc by Finite Element Method
    (Polish Acad Sciences Inst Physics, 2019) Ozmen, R.; Gunay, M.; Demir, T.
    Spinal fusion and total disc arthroplasty are used in the surgical treatment of cervical disc degeneration. When mobility is desired in the functional spinal unit, total disc arthroplasty is preferred instead of fusion. In this research, the effects of artificial disc prosthesis on the biomechanical behaviour of the C5-C6 functional spinal unit were investigated via finite element method. Firstly, three-dimensional CAD models of C5 and C6 vertebrae were created by using a computerized tomography images of a healthy human neck via 3D Slicer computer software. The mobility of the healthy model consisting of intervertebral disc, joints, and soft tissues was validated by previously published experimental studies in the field. On the second step, a ball and socket type artificial disc was defined using connector elements between C5-6 functional spinal unit to simulate the total disc arthroplasty method. Finally, to investigate the effect of prosthesis core radius changes on the biomechanical properties of functional spinal unit, healthy and implanted models were analysed via finite element method.
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    Influence of posterior pedicle screw fixation at L4–L5 level on biomechanics of the lumbar spine with and without fusion: a finite element method
    (BioMed Central Ltd, 2021) Sengul, E.; Ozmen, R.; Yaman, M.E.; Demir, T.
    Background: Posterior pedicle screw (PS) fixation, a common treatment method for widespread low-back pain problems, has many uncertain aspects including stress concentration levels, effects on adjacent segments, and relationships with physiological motions. A better understanding of how posterior PS fixation affects the biomechanics of the lumbar spine is needed. For this purpose, a finite element (FE) model of a lumbar spine with posterior PS fixation at the L4–L5 segment level was developed by partially removing facet joints (FJs) to imitate an actual surgical procedure. This FE study aimed to investigate the influence of the posterior PS fixation system on the biomechanics of the lumbar spine before and after fusion by determining which physiological motions have the most increase in posterior instrumentation (PI) stresses and FJ loading. Results: It was determined that posterior PS fixation increased FJ loading by approximately 35% and 23% at the L3–L4 adjacent level with extension and lateral bending motion, respectively. This increase in FJ loading at the adjacent level could point to the possibility that adjacent segment disease has developed or progressed after posterior lumbar interbody fusion. Furthermore, analyses of peak von Mises stresses on PI showed that the maximum PI stresses of 272.1 MPa and 263.7 MPa occurred in lateral bending and flexion motion before fusion, respectively. Conclusions: The effects of a posterior PS fixation system on the biomechanics of the lumbar spine before and after fusion were investigated for all physiological motions. This model could be used as a fundamental tool for further studies, providing a better understanding of the effects of posterior PS fixation by clearing up uncertain aspects. © 2021, The Author(s).