Evaluation of a Novel Flexible Cage System for C5–C6 Fixation: A Finite Element Study Against Conventional ACDF Implants

Cervical spondylosis is a common cause of spinal cord dysfunction, and anterior cervical discectomy and fusion (ACDF) is widely employed when conservative treatment fails. Conventional implant systems such as the cervical cage with plate (CCP) and zero-profile stand-alone cage (ZPSC) are commonly used to enhance spinal stability and promote fusion, but they are associated with complications including dysphagia and adjacent segment degeneration. To address these limitations, a novel flexible plate cage system (FPCS) has been developed to optimize biomechanical performance while minimizing surgical risk. In this study, a finite element model of the C3–T1 cervical spine was constructed to simulate ACDF at the C5–C6 level using CCP, ZPSC, and FPCS implants. Under standardized loading conditions, von Mises stress was analyzed in the bone, intervertebral disc, endplates, cage, and screws, using the mean of the top 5% stress values to ensure accuracy. All surgical models showed increased stress compared to the intact reference spine. The ZPSC model exhibited the highest stress in the cage and screws, suggesting a more concentrated load path. The CCP model showed a more evenly distributed stress profile, particularly affecting the inferior adjacent segment. The FPCS model demonstrated moderate cage stress, reduced screw stress, and the highest plate stress, indicating a design that effectively redirects mechanical load from the screw-bone interface toward the anterior plate. This may be related to the unique structural configuration of the FPCS, which secures screws horizontally into the anterior vertebral body without penetrating the endplates. These findings suggest that the FPCS may offer a biomechanically favorable alternative to existing ACDF implants.