Definition of ideal configuration for femoral neck screw fixation in older people

Femoral neck fractures are the most common injuries encountered by older individuals, and they are associated with high mortality and morbidity. Internal fixation to femoral neck fracture with cannulated screws placed with a configuration of an inverted triangle remain a feasible and effective treatment for femoral neck fractures. The objection of this research was to evaluate the femoral neck morphology, especially the shape of the femoral neck in Chinese people to find the optimal screw position and interval between the screws. 96 consecutive normal subjects without any previous proximal femur operation were reviewed. The patients’ information were collected from our database. The minimum of neck canal height (NCHM), neck canal width (NCWM) and inclination angle (AIA and PIA) were measured in different level. There was a significant difference between the AIA and PIA, neck canal height at inferior and superior 1/3 on posterior wall (NCHIP and NCHSP). Although there was a significant difference between the neck canal height at inferior and superior 1/3 on anterior wall (NCHIA and NCHSA, p < 0.001), but the changes were small. The shape of the anterior wall was perpendicular to the horizon and almost parallel with the FNA. In contrast, the shape of the posterior wall resembled a reverse question mark. The inverse triangular fixation was in accordance with the morphology of the femoral neck, and triangular fixation had a high risk of perforation, which may lead to nonunion and avascular necrosis. The anterior screw can be inserted easily with the help of a C-ARM, and the posterior screw positioned mildly posterior to the femoral shaft axis is recommended.