A Retrospective Cohort Study of the Variable Pitch Fully Threaded Headless Screws and Partially Threaded Screws in the Treatment of Femoral Neck Fractures

Abstract

(1) Introduction: The choices of the treatments for femoral neck fractures remain controversial. The purpose of this study is to evaluate the prognoses of the variable pitch fully threaded headless screws in the fixation of femoral neck fractures and to compare them with those of partially threaded cannulated screws. (2) Materials and Methods: Between 1st January 2012 and 31st December 2016, there were 89 patients with the main diagnose of femoral neck fracture who accepted the treatment of closed reduction cannulated screw fixation in Peking University People’s Hospital. 34 cases of partially threaded screws and 23 cases of fully threaded screws met the criterion. The characteristics, prognoses and the imaging changes of all cases were described and the differences between the two groups were compared. Statistical analyses were performed using SPSS version 23.0 (SPSS Inc., USA). Mann-Whitney U test, Analysis of Variance and Chi-square test were used. Statistical significance was defined as P value (two sided) less than 0.05. (3) Results: There was no significant difference in the general characteristics, fracture classifications and reduction quality between the two groups. The fully threaded group had a significant lower angle decrease rate (30.4% vs. 58.8%, P = 0.035), femoral neck shortening rate (26.1% vs. 52.9%, P = 0.044) and screw back-sliding rate (21.7% vs. 50.0%, P = 0.032), but a higher screw cut-out rate (21.7% vs. 0.0%, P = 0.008). No significant difference was found in the nonunion rate (8.7% vs. 0.0%, P = 0.159), avascular necrosis rate (17.4% vs. 23.5%, P = 0.744) and the good and excellent rate of Harris score (73.9% vs. 82.4%, P = 0.443). (4) Conclusion: Compared with the partially threaded screws, the variable pitch fully threaded headless screws had a lower screw back-sliding rate, femoral shortening rate, angle decrease rate and similar function score, but would result in more screw cut-outs and nonunions in Garden III-IV and Pauwels III fractures. As a conclusion, the variable pitch full threaded screws are recommended in stable undisplaced fractures rather than displaced unstable fractures. Further qualified investigations with a larger scale of patients and longer follow-up are needed in the future.