*2.3. Loading and Boundary Conditions*

The preload was set to 150 N and applied evenly using the follower load technique on the T10 superior endplate to simulate the weight of the upper body. For the simulation of the upper body weight, a preload ranging from 100–200 N was used in the literature, and a 150 N preload was chosen in the present study [29]. A 10 Nm moment was applied in the sagittal, coronal, and transverse plane to create motions in flexion–extension, lateral bending, and axial rotation, respectively. The boundary condition of the simulations was set with the nodes on the inferior endplate of L3 constrained in all directions. The interfaces between the bone, pedicle screws, PMMA, and titanium cage were assigned with tie constraints.
