Which is the better posterior lumbar dynamic device: Dynesys or BioFlex?

Abstract

Objective: The purpose of this study was to analyze the biomechanical characteristics of the lumbar posterior dynamic devices: the Dynesys system and the BioFlex system. Methods: We validated the FE model of an lumbar spine (L3-S1) established by transferring the data, collected by 3D CT scan, to the FE software ABAQUS and comparing these data with the data from published studies. Then, were reconstructed by the lumbar posterior dynamic devices to analyze the range of motion (ROM) and stress distribution on the lumbar posterior dynamic devices. Results: The current lumbar FE model was able to measure the biomechanical changes in a follow-up surgery simulation. The total ROM of the surgery simulation models was substantially decreased compared with the total ROM of the intact group, and the Dynesys system group had the closest total ROM to the intact group. The maximal von Mises stress concentrate at the middle part of the screws in Dynesys system, but at the Nitinol memory loop in BioFlex system. The maximal stress level was only 49 MPa in Dynesys system, but 164 MPa in BioFlex system. Conclusion: Through the comparison of ROM and the stress distribution of the prosthesis, we find that the Dynesys system maybe has a better theoretical outcome.