Three-dimensional finite element analysis study of 3D printing occipitocervical fusion system

Objective To evaluate the biomechanics of 3D printing occipital cervical fusion system (3D-OCF) using three-dimensional finite element analysis.

Methods A 3D-OCF was designed and developed, and compared with the traditional Summit internal fixation system.Two sets of three-dimensional finite element models of occipitocervical fusion internal fixation were established to simulate the postoperative movement of the upper cervical spine.A 40 N vertical load and a preload of 5 N·m torque were applied under flexion and extension, lateral flexion and rotation, respectively, to observe the vertebral activity, peak occipital displacement, and stress distribution of the internal fixation device under the fixation of the two internal fixation systems.

Results Under the six working conditions of flexion, extension, lateral flexion, and rotation, compared with the traditional Summit internal fixation system, the range of motion of each segment of the upper cervical spine fixed with 3D-OCF significantly decreased, and the overall range of motion of each segment decreased by 73.02 % to 100.00%.Compared with the traditional Summit internal fixation system, the maximum displacement of the cervical spine after 3D-OCF fixation was significantly reduced, with a decrease of 78.09 % to 95.73% under various working conditions.Stress analysis of the internal fixation system showed that the maximum stress values of the two sets of internal fixation systems under six working conditions of flexion, extension, lateral flexion, and rotation were both in the forward flexion state.The maximum stress value of 3D-OCF was 37.43 MPa, and the maximum stress value of Summit internal fixation system was 533.32 MPa.Compared with the traditional Summit internal fixation system, the maximum stress value of 3D-OCF under various working conditions was significantly reduced, and the stress difference under various working conditions was balanced, without significant stress concentration points.

Conclusions 3D-OCF can provide sufficient strength and stability for occipitocervical fusion and internal fixation, and the stress of 3D-OCF device is relatively dispersed, with a small possibility of fracture and failure of the system device.