Obtuse triangle screw configuration for optimal internal fixation of femoral neck fracture: an anatomical analysis

Abstract

Objectives: To identify the optimal screw configuration for internal fixation of femoral neck fractures based on anatomic analysis on radiologic imaging. Methods: 30 proximal femurs of 15 adults were constructed by CT. 3 femoral neck sections (FNS), the subcapital, medial, and the fundus, were projected on to the lateral femoral trochanteric wall. The simulated 3 screw configurations in the projection of FNS include: 2 inverted equilateral triangles symmetrised to the axis of the FNS (IET-FNS group) or the coronal axis of the proximal femur (IET-PR group) and an obtuse triangle (OT group). The distance between the screws, the distance between the centre of the FNS and the screws, and the area ratio of the triangle/FNS were calculated. Results: The projection of the FNS on to the lateral femoral trochanteric wall is displayed as a rotating forward ellipse. Measurements of distance between screws, distance between the centre of the FNS to the screws, and the area ratio of triangle/FNS were significantly larger in the OT group than in the IET-FNS and IET-PF groups ( p < 0.05). The values of the 3 parameters in the IET-FNS group were also larger than those in the IET-PF group ( p < 0.05). Conclusions: The obtuse triangle screw configuration displayed advantages with respect to the parameters of distance between screws, distance between the centre of FNS to screws, and the triangle area. Therefore, the obtuse triangle screw configuration may be the ideal pattern for internal fixation of femoral neck fractures (Pauwels I and II). This needs to be corroborated with biomechanics testing.