Fatigue life analysis for butterfly-shaped cervical spine plates

The three-dimensional solid models of butterfly-shaped cervical spine plates were imported into ANSYS software for FEM analysis. According to the anti-fatigue test requirements, the mechanical model was simplified as a pair of compressive load or a bending moment load model for stress cloud calculation. Static FEM analysis was performed for four different types of butterfly-shaped cervical plates, subjected to compressive loads and bending moments respectively. The dangerous nodes with maximum stress were obtained after calculation. Based on the mathematical formula of the S-N curve and Goodman curve, the fatigue life (N) was obtained. It turned out that the stress and strain at the edge of center slot and screw holes are larger than those of the surroundings, and are vulnerable to fatigue fracture. Among four plate types, the fatigue life of three-orifice plate is the largest, and the six-orifice plate the minimum under the same loads.