Structure Design and Optimization of the C5-C6 Cervical Intervertebral Fusion Cage Using the Anterior Cervical Plate and Cage Fixation System

Background: The fifth and sixth cervical vertebra (C5-C6) is the most easily injured segment encountered in clinical practice. The anterior cervical plate and cage (ACPC) fixation system is always used to reconstruct the intervertebral height and maintain the segmental stability. The postoperative effect, such as subsidence, neck pain, and non-fusion, is greatly affected by the cervical cage structure design. This study determined reasonable structure size parameters that present optimized biomechanical properties related to the postoperative subsidence often accompanied with ACPC. Material/Methods: Twenty bionic cages with different structural sizes (distance between the center of the cage and groove, groove depth, and groove width) were designed and analyzed based on the regression optimization design and analysis method combined with FE analysis. Because a previous study showed that greater stresses on the endplate are associated with higher risk of subsidence, the optimization object was selected as the stresses on endplate to lower it. Results: The postoperative stresses on the endplate of all cages with bionic structure design were proved to be low- er than with the original one. The optimal structure size was the distance between the center of the cage and groove=0 mm, groove depth=3 mm, and groove width=4 mm. Regression analysis found the cage with optimized bionic structural parameters resulted in a 22.58% reduction of endplate stress response compared with the original one. Conclusions: The bionic cage with optimized structural sizes can reduce the subsidence risk, suggesting that the optimization method has great potential applications in the biomechanical engineering field.