Biomechanical effects of fusion levels on the risk of proximal junctional failure and kyphosis in lumbar spinal fusion surgery.

Background: Spinal fusion surgery is a widely used surgical procedure for sagittal realignment. Clinical studies have reported that spinal fusion may cause proximal junctional kyphosis and failure with disc failure, vertebral fracture, and/or failure at the implant-bone interface. However, the biomechanical injury mechanisms of proximal junctional kyphosis and failure remain unclear.

Investigation of the compressive stiffness of spinal cages in various experimental conditions based on finite element analysis.

Recently, novel polymers, including polyetheretherketone and carbon fibre reinforced polymer, have been used for spinal implants. Because the in vitro experimental test uses metal blocks with different material properties from those of polymer cages in standard test protocols for prediction of the mechanical performance, it is necessary to analyse the influence of various experimental conditions, such as the material of the blocks. In this study, the compressive stiffness of spinal cages was investigated for different materials (polyetheretherketone, carbon fibre reinforced polymer, and titanium) under simulations of the mechanical experimental tests and the in vivo situation based on finite element analysis.