Abstract
Background In recent years, pedicle screw (PS) fixation has often been used to stabilize the spine and correct deformities, yielding good clinical results. On the other hand, PS fixation is known to show problems such as instrumentation failure. However, few biomechanical studies have described causes of instrumentation failure. In this study, causes of instrumentation failure in lumbar PS fixation were investigated from the perspective of load sharing by measuring both strains generated in the rod and intradiscal pressure.Methods Four human cadaveric multi-segmental lumbar vertebrae (L2-L5) were used to prepare a control model and a PS fixation model. Next, axial compression tests were performed on each model using a universal material testing machine, and the strains generated in the rods and the intradiscal pressures were measured from strain gauges attached to the rods and a pressure sensor installed between L3-L4.Results Combined compressive and bending stresses were found to be generated in the rod, with bending stress around 10 times higher than compressive stress, and with vast differences in the levels of stress generated between right and left rods. Moreover, the stress shielding by PS fixation was small, and intervertebral discs were still subjected to a large load. Conclusion Preventing instrumentation failure in lumbar spine PS fixation, it seems necessary to strengthen the durability of the rod against bending stress and to ensure the stability of the anterior stabilizing element of the spine.
The use of electrical stimulation to enhance spinal fusion