Risk Factors for Nonunion in Patients with Intracapsular Femoral Neck Fractures Treated with Three Cannulated Screws Placed in Either a Triangle or an Inverted Triangle Configuration

Background: Intracapsular femoral neck fractures are associated with high rates of nonunion. We aimed to identify risk factors for nonunion in patients with both displaced and nondisplaced intracapsular femoral neck fractures treated with three 7-mm parallel cannulated screws, placed in either a triangle or an inverted triangle configuration, using failure of fixation as the primary outcome. Methods: Clinical and radiographic data for patients with intracapsular femoral neck fractures treated with either triangle fixation (one proximal screw and two distal screws) or inverted triangle fixation (two proximal screws and one distal screw), between January 1, 2000, and July 30, 2009, were analyzed. Results: A total of 202 patients, seventy-six men and 126 women with an average age (and standard deviation) of 64.53 +/- 15.81 years (range, nineteen to ninety-three years), were included in the analysis. Union occurred in 158 patients, and nonunion occurred in forty-four. There were no differences between the union and nonunion groups with respect to age, sex, fracture side, fracture angle, fracture level, or estimated bone density. There were significant differences in fracture type, fixation configuration, reduction quality, and screw-tip subchondral purchase between patients with and without union. The estimated odds ratio for fracture nonunion was 2.93 (95% confidence interval [Cl], 1.08, 7.96) in subjects with displaced fractures compared with those without displaced fractures (p = 0.035), 18.92 (95% CI, 1.91, 187.09) in subjects with borderline and unacceptable reduction compared with those with anatomic reduction (p = 0.012), and 2.92 (95% Cl, 1.27, 6.69) for internal fixation with a triangle configuration compared with fixation with an inverted triangle configuration (p = 0.010). Conclusions: Screw fixation with a triangle configuration, a displaced fracture, and poor reduction are risk factors for nonunion in intracapsular femoral neck fractures treated with fixation with multiple screws.