[3D printed personalized lumbar spinal fusion device design and biomechanical performance analysis]

The finite element analysis method was used to compare the biomechanical performance of the individualized interbody fusion cage, the clinically common double bullet type fusion cage and the healthy lumbar spine model under different working conditions.

According to the CT scan data of the lumbar spine of a real healthy human body, a finite element model of the lumbar spine of a healthy human body was designed using finite element software as a normal control group. On this basis, the individualized lumbar fusion cage model and the clinical standard bullet type fusion cage lumbar spine model were further established. These three finite element models were applied with different loads such as vertical compression, forward flexion, extension, and lateral bending to observethe changes in the stress distribution and stress magnitude of each component of the lumbar spine.

The maximum stress values of the vertebral body and the fusion cage under the extension condition in the clinical standard bullet type fusion cage lumbar spine model were 45.81 MPa and 97.07 MPa, respectively. The stress of the vertebral body and the fusion cage in the individualized lumbar fusion cage model was closer to the stress of the vertebral body and the intervertebral disc in the healthy lumbar spine model. From the perspective of displacement, the displacement of each component of the lumbar spine models of the two fusion cages was smaller than that of the healthy lumbar spine model, indicated that the internal fixation of the fusion cage limited the range of motion of the vertebral body. On the other hand, it also confirmed the validity of the finite element model established in the study. The displacement of the fusion cage and the vertebral body in the individualized model under different working conditions was generally smaller thanthat of the standard model fusion cage and the vertebral body.

The fusion cage can replace the diseased intervertebral disc to a certain extent, so as to reduce the patient's pain and restore the lumbar function. The personalized design of the fusion cage can better meet the needs of individual patients, which has the great significance to the recovery of the patient's lumbar spine function, the service life of the fusion cage and the protection of the contact vertebral body, and provides certain guidance for actual clinical treatment.