Finite element analysis on a modified cannulated screw for fixation of femoral neck fracture / 医用生物力学

ABSTRACT

Objective To establish the three-dimensional finite element model of the cannulated screws for fixing the femoral neck fracture, and investigate stress distributions on three cannulated screws as well as determine whether internal fixation by a modified cannulated screw can provide sufficient stiffness and strength for the fixation. Methods The 3D finite element model was internal-fixed at the angle of 127°with femoral shaft under the inverted triangle mode to simulate loading on single legged standing condition. Stresses on three screws (No 1 the underneath screw, No 2 the anterosuperior screw, No 3 the posterosuperior screw) were calculated at different Pauwels angle (50°, 60°, 70°, 80°), respectively. A bore was drilled in the screw with the largest stress to study the effect of bore size and bore direction on the femoral neck fracture model with screw fixation. Results The stresses of three screws increased with the Pauwels angle increasing and reached the maximum value at 80°. The maximum stresses on No.1, No.2 and No.3 screw were 304, 515 and 154 MPa, respectively. When the No 2 screw had an opening bore with 1 mm in diameter, and the direction of the bore was not between 150°and 195°, the stresses on three screws were all within the safe limits. Conclusions From the mechanical point of view, three screws are subject to different stresses. The cannulated screws with side bore have good biomechanical properties for fixing the femoral neck fracture with safety and reliability, which can provide advantages for accelerating fracture healing by injecting drugs through the central and side bore into the fracture side.