A Modified Benchtop Test Method to Measure the Movements of Intervertebral Body Fusion Devices

This study developed and evaluated a new benchtop test method to measure the movements of different designs of intervertebral body fusion devices (IBFDs) under cyclic loads. The experimental method simulates and evaluates the movement resistance of intervertebral cages under flexion-extension cyclic loads experienced by the lumbar spine. The present method modifies a method developed previously and offers a possibility to be more clinically relevant and robust. This is because it allowed for closer achievement of levels of IBFD rotation reported in the literature and introduced the ability to control the flexion-extension movement and, consequently, the rotation of the cage more precisely. Polyurethane foam blocks were used as the bone substitute material. Optical and contactless displacement measurements were performed using a robust six degrees of freedom measuring system (OptiTrack) to evaluate the movements of the IBFD during testing. The results obtained by applying the new benchtop method showed greater sensitivity in capturing the implant movements in all directions measured, with magnitude significantly superior from Ribeiro et al. (2022). A test method to measure the movements of different IBFD designs was modified to better simulate and control the lumbar spine flexion-extension movements. The proposed benchtop methodology can evaluate the IBFD movements in all directions to more efficiently discriminate in a potentially standardized test the efficacy of different IBFD designs.