Influence of anteversion angles on stress distributions of the proximal femur after femoral neck fracture fixation: A finite element analysis / 医用生物力学

ABSTRACT

Objective To investigate the effects of different anteversion angles on stress distributions of the proximal femur after femoral neck fracture fixation by cannulated screw, and to provide biomechanical evidences for the importance of anatomical reduction in internal fixation in clinic. Methods Femoral neck fracture with Pauwells angle 70°was treated with cannulated screw internal fixation, and its three-dimensional finite element models with five different anteversion angles set at 0°，5°，10°，15°and 20°, respectively, were constructed based on normal human anatomical data from multi slice spiral CT as well as reverse engineering and CAD software. Loads were applied on each model to simulate normal walking status. Changes in stress distributions of the proximal femur in each model were observed. Results When the anteversion angle was 10°, the stress, displacement and equivalent strain of the femur was were the minimum, as the maximum stress of the proximal femur was 1.7 MPa, and the displacement was 1.1 mm. With the anteversion angle increasing or decreasing, the effective stress and displacement of the proximal femur was gradually increasing. When the anteversion angle was 20°, the stress of on the proximal femur and on the cannulated screw was became the maximum. When the anteversion angle was 0°, the displacement and equivalent strain of the femur also became the maximum. The stress concentration site of the femoral neck was gradually transferred from the inside rear to the outer top of the head and neck junction. The three cannulated screws there stood the higher stress than the surrounding bone tissues, and with the bottom screw stood the higher stress than the other top two screws. Conclusions Anatomic reduction is essential for femoral neck fracture fixation treated by cannulated screw. Changes in biomechanical factors after femoral neck fracture may play an important role in postoperative femoral head necrosis.