Novel Design of Expandable Spinal Cage for Efficient Lumbar Spine Fusion Operation

This study proposes a novel expandable spinal cage to maximize the effectiveness of spinal fusion surgery in the treatment of lumbar disk disorders and aims to verify its mechanical stability through finite element method (FEM) analysis and mechanical testing. To address the limitations of existing cages, which do not provide sufficient height and angle expansion and have constraints in independently adjusting height and angle with continuous fine-tuning, this study introduces a new linkage mechanism. This design enables precise spinal alignment restoration tailored to the individual anatomical characteristics of patients, even in minimally invasive surgical environments, distinguishing itself from traditional rack-and-pinion or wedge-based designs. The results of FEM analysis and static load testing demonstrated a high correlation between the predicted yield locations in FEM analysis and actual test results. Furthermore, the compression and compression–shear load tests confirmed that the proposed cage achieved an ultimate load exceeding the lowest fifth percentile of FDA-approved products, meeting clinical requirements. The proposed expandable spinal cage offers significant improvements over existing products and has the potential to evolve into a safer and more effective spinal fusion device through further dynamic fatigue testing and clinical studies to assess long-term durability and practical applicability.