Posterior fully threaded positioning screw prevents femoral neck collapse in Garden I or II femoral neck fractures

Introduction Osteosynthesis is recommended for Garden I and II femoral neck fracture treatment using parallel partially threaded cannulated screws. Postoperatively, excessive femoral neck shortening (FNS) and posterior tilt of the femoral neck (PTFN) are frequently encountered and are correlated with impaired quality of life and clinical outcomes. We hypothesized that stabilization by parallel partially threaded cannulated screws replacing a posterior partially threaded screw with a fully threaded positioning screw would improve fracture healing without further FNS and PTFN in femoral neck fractures. Methods We retrospectively reviewed Garden I and II femoral neck fractures treated by in situ fixation using parallel cannulated screws at our institution between January 2010 and November 2018. Patients with the applicable fractures were divided according to the utilization of posterior fully threaded screws: patients with partially threaded screws were included in Group C and those with posterior fully threaded screws were included in Group P. Intergroup comparisons were performed based on radiographic measurements that assessed the shortening in two vectors (the horizontal and vertical axes), FNS, and subsequent PTFN. Results No significant intergroup difference was found in demographics and fracture characteristics, except in the follow-up duration. The mean FNS and shortening in both vectors were significantly smaller in Group P than in Group C (FNS, 5.02 ± 1.31 vs. 8.84 ± 3.48 mm, p < 0.001; horizontal axis, 4.07 ± 1.06 vs. 6.18 ± 2.77 mm, p < 0.001; and vertical axis, 2.55 ± 1.68 vs. 5.74 ± 3.41 mm, p < 0.001). The mean subsequent PTFN was significantly smaller in Group P (2.21 ± 2.99 vs. 7.56 ± 6.20 mm, p < 0.001). A significantly smaller number of patients in Group P had moderate (5–10 mm) or severe (>10 mm) FNS and moderate (5–10°) or severe (>10°) subsequent PTFN. Conclusion Parallel cannulated screws replacing a posterior partially threaded screw with a fully threaded positioning screw as a length- and angle-stable construct for Garden I or II femoral neck fracture fixation can prevent femoral neck collapse in both the coronal and axial planes.