Biomechanical comparison and operation on cadaver of a novel atlantoaxial lateral mass cage

Abstract

Abstract Background To improve clinical efficacy of atlantoaxial instability. We design a novel lateral mass cage and compare the biomechanical differences between Pedicle Screw model and Cage + Pedicle Screw model to demonstrate the practicability of the cage. Methods From computed tomography (CT) images, a nonlinear intact three-dimensional C0-3 finite element model was developed. Then a finite element analysis (FEM) of an unstable model treated with Pedicle Screw model, was compared to that with Cage + Pedical Screw model. All models were subjected to vertical load in flexion, extension, lateral bending, rotation, vertical compression and forward shear. Range of motion (ROM) of C1-C2 segment and maximum von Mises Stress of the rod and screws were quantified in two models. Then, we do a simulation operation on cadaver specimen to evaluate the practicability of the mass cage trough photos and CT scan. Results Both two models significantly reduced ROM compared with the unstable model. In comparison with the Pedicle Screw model, the Cage + Pedicle Screw model reduced the ROM by 24.47%, -7.05%, 3.17% and 4.79% in flexion, extension, lateral bending and rotation. The Cage + Pedicle Screw model showed a significant increase stresses on rod and screw than the Pedicle Screw model in flexion, lateral bending, rotation, vertical compression and forward shear. Through the photos and CT scan, the lateral mass cage can be plated into a accurate place. Conclusion Our study indicated that either pedicle screw or cage + pedicle screw can reduce the ROM of C1-C2, while the cage will enhance the stability of C1-C2 in flexion significantly, meanwhile, decrease the stress on the rod and screws.