Is there any advantage of using stand-alone cages? A numerical approach

• Published in: Biomedical engineering online 2019-05, Vol.18 (1), p.63-63, Article 63
• Main Authors: Calvo-Echenique, Andrea, Cegoñino, José, Perez Del Palomar, Amaya
• Format: Article
• Language: English
• Subjects: Biomechanics; Bone implants; Cages; Care and treatment; Clinical outcomes; Computer simulation; Contact pressure; Degeneration; Finite element analysis; Finite element method; Health aspects; Human behavior; Intervertebral disc; Ligaments; Low back pain; Lumbar spine; Mathematical analysis; Mathematical models; Methods; Observations; Orthopedic fixation devices; Patient outcomes; Posterior lumbar interbody fusion; Posterior screw fixation; Risk analysis; Shear strain; Spinal fusion; Spine; Spine (lumbar); Stand-alone cages; Studies; Surgery; Surgical techniques
• ISSN: 1475-925X; 1475-925X
• DOI: 10.1186/s12938-019-0684-8

Segment 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. A 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. A 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. A 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.