Analytical and finite element analysis of shape memory polymer for use in lumbar total disc replacement

Prediction of the biomechanical behaviour of the lumbar spine under multi-axis whole-body vibration using a whole-body finite element model

Low back pain has been reported to have a high prevalence among occupational drivers. Whole-body vibration during the driving environment has been found to be a possible factor leading to low back pain. Vibration loads might lead to degeneration and herniation of the intervertebral disc, which would increase incidence of low back problems among drivers. Some previous studies have reported the effects of whole-body vibration on the human body, but studies on the internal dynamic responses of the lumbar spine under multi-axis vibration are limited. In this study, the internal biomechanical response of the intervertebral disc was extracted to investigate the biomechanical behaviour of the lumbar spine under a multi-axial vibration in a whole-body environment. A whole-body finite element model, including skin, soft tissues, the bone skeleton, internal organs and a detailed ligamentous lumbar spine, was used to provide a whole-body condition for analyses. The results showed that both vibrations close to vertical and fore-and-aft resonance frequencies would increase the transmission of vibrations in the intervertebral disc, and vertical vibration might have a greater effect on the lumbar spine than fore-and-aft vibration. The larger deformation of the posterior region of the intervertebral disc in a multi-axis vibration environment might contribute to the higher susceptibility of the posterior region of the intervertebral disc to injury. The findings of this study revealed the dynamic behaviours of the lumbar spine in multi-axis vehicle vibration conditions, and suggested that both vertical and fore-and-aft vibration should be considered for protecting the lumbar health of occupational drivers.

Intradiscal cement leakage (ICL) increases the stress on adjacent vertebrae after kyphoplasty for osteoporotic vertebra compression fracture (OVCF): a finite-element study

This study aimed to explore the biomechanical effects on adjacent vertebra of thoracolumbar Osteoporotic Vertebra Compression Fracture (OVCF) after Percutaneous Kyphoplasty (PKP) with intraoperative intradiscal cement leakage (ICL) by applying a Finite-Element Analysis. We collected pre- and post-operative computer tomography (CT) images of a 71-year-old female patient with single T12 OVCF, who underwent an intraoperative cement leakage into the T12-L1 disc. Three-dimensional finite element models of thoracolumbar spine (T10-L2) were built with the support of Materialise Interactive Medical Image Control System (MIMICS) and ABAQUS software. The stress on adjacent vertebrae and endplates under the uniform compressive pressure (0.3 MPa) and during different loading moments were analyzed. The three-dimensional finite element models reveal an asymmetrical distribution of von Mises stresses on the adjacent endplate unaffected by the surgical intervention. The maximum von Mises stress on adjacent vertebral bodies increased during different loading conditions, especially for lateral bending and rotation loading conditions, whereas the maximum von Mises stress on distal non-treated vertebrae decreased on anteflexion and backward extension loading conditions. Post-operative adjacent vertebra compression fractures after PKP with intraoperative intradiscal cement leakage (ICL) may be closely related to the biomechanical changes of adjacent vertebrae of thoracolumbar OVCF, and it may increase the risk of postoperative fracture.

Novel Composite Planks Made of Shape Memory Polyurethane Foaming Material with Two-Step Foaming Process

In this study, shape memory polyurethane (SMP) foaming material is used as the main material that is incorporated with carbon fiber woven fabrics via two-step foaming method, forming sandwich-structured composite planks. The process is simple and efficient and facilitates any composition as required. The emphasis of this study is protection performances, involving puncture resistance, buffer absorption, and electromagnetic wave shielding effectiveness. The proposed soft PU foam composite planks consist of the top and bottom PU foam layers and an interlayer of carbon fiber woven fabric. Meanwhile, PU foam is incorporated with carbon staple fibers and an aluminized PET film for reinforcement requirements and electromagnetic wave shielding effectiveness, respectively. Based on the test results, the two-step foaming process can provide the PU foam composite planks with excellent buffer absorption, puncture resistance, and electromagnetic wave shielding effectiveness; therefore, the proposed composite planks contribute a novel structure composition to SMP, enabling it to be used as a protective composite. In addition, the composites contain conductive material and thus exhibit a greater diversity of functions.