Abstract
BackgroundSegment fusion using interbody cages supplemented with pedicle screw fixation is the most common surgery for the treatment of low back pain. However, there is still much controversy regarding the use of cages in a stand-alone fashion. The goal of this work is to numerically compare the influence that each surgery has on lumbar biomechanics.MethodsA non-linear FE model of the whole lumbar spine was developed to compare between two types of cages (OLYS and NEOLIF) with and without supplementary fixation. The motion of the whole spine was analysed and the biomechanical environment of the adjacent segments to the operated one was studied. Moreover, the risk of subsidence of the cages was qualitatively evaluated.ResultsA great ROM reduction occurred when supplementary fixation was used. This stiffening increased the stresses at the adjacent levels. It might be hypothesised that the overloading of these segments could be related with the clinically observed adjacent disc degeneration. Meanwhile, the stand-alone cages allowed for a wider movement, and therefore, the influence of the surgery on adjacent discs was much lower. Regarding the risk of subsidence, the contact pressure magnitude was similar for both intervertebral cage designs and near the value of the maximum tolerable pressure of the endplates.ConclusionsA minimally invasive posterior insertion of an intervertebral cage (OLYS or NEOLIF) was compared using a stand-alone design or adding supplementary fixation. The outcomes of these two techniques were compared, and although stand-alone cage may diminish the risk of disease progression to the adjacent discs, the spinal movement in this case could compromise the vertebral fusion and might present a higher risk of cage subsidence.
Highlights
Segment fusion with intradiscal cage and pedicle screw fixation (PSF) is the “gold standard” treatment for lumbar hernia and degenerative intervertebral disc (IVD) diseases
The results for extension, lateral bending and axial rotation perfectly fitted within Campbell et al results
The main goal of this work was to compare between two different intervertebral lumbar cages with and without supplemental PSF and argue if stand-alone cage is a feasible solution for lumbar disc degeneration and hernia
Summary
Segment fusion with intradiscal cage and pedicle screw fixation (PSF) is the “gold standard” treatment for lumbar hernia and degenerative intervertebral disc (IVD) diseases. Few clinical prospective randomised studies have been comparing stand-alone construct versus fusion with supplemental PSF [10, 11] These studies did not show significant differences in clinical outcomes whilst several advantages were reported for the use of stand-alone cages in degenerated lumbar segments without previous instability: the surgical technique is less demanding, it takes less time, the implant cost is lower and pedicle screw-related complications are avoided. Conclusions: A minimally invasive posterior insertion of an intervertebral cage (OLYS or NEOLIF) was compared using a stand-alone design or adding supplementary fixa‐ tion The outcomes of these two techniques were compared, and standalone cage may diminish the risk of disease progression to the adjacent discs, the spi‐ nal movement in this case could compromise the vertebral fusion and might present a higher risk of cage subsidence
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