To identify the anatomic features for clinical applications through a computational simulation of the fixation of three cannulated screws for a femoral neck fracture.

Thirty cadaveric femurs underwent computed tomography and the images were transferred to the Mimics® program, resulting in three-dimensional proximal femur models. A three-dimensional scan of the 7.0 mm cannulated screw was performed to enable computerized virtual fixation of multiple cannulated screws for femoral neck fractures. After positioning the screws definitively for cortical support, the intraosseous position of the cannulated screws was evaluated in the anteroposterior image and axial image direction.

Three cannulated screws located at the each ideal site showed an array of tilted triangles with anterior screw attachment and the shortest spacing between posterior and central screws. The central screw located at the lower side was placed in the mid-height of the lesser trochanter and slightly posterior, and directed toward the junction of femoral head and neck to achieve medial cortical support. All the posterior screws were limited in height by the trochanteric fossa and were located below the vastus ridge, but the anterior screws were located higher than the vastus ridge in 10 cases. To obtain the maximum spacing of the anterior and posterior screws on the axial plane, they should be positioned parallel to the cervical region nearest the cortical bone at a height not exceeding the vastus ridge.

The position of cannulated screws for cortical support were irregular triangular arrangements with the anterosuperior apex. The position of the ideal central screw in the anteroposterior view was at the mid-height of the lesser trochanter toward the junction of the femoral head and neck, and the anterior and posterior screws were parallel to the neck with a maximal spread just inferior to the vastus ridge.