Comparison of femoral neck shortening and outcomes between in situ fixation and fixation after reduction for severe valgus-impacted femoral neck fractures.

INTRODUCTION: Severe valgus-impacted femoral neck fractures are associated with femoral neck shortening (FNS). However, no study has focused on the effect of reduction for severe valgus impaction in terms of healing and restoration of the femoral neck length. This study aimed to compare FNS and treatment outcomes of in situ fixation and fixation after reduction for severe valgus-impacted femoral neck fractures in patients aged 65 years or younger. METHODS: This retrospective study included 55 patients who underwent internal fixation with three parallel screws for femoral neck fractures with valgus impaction >15° (AO/OTA classification 31-B1.1) between January 2006 and December 2018. Twenty-eight and 27 patients underwent in situ fixation (in situ group) and fixation after reduction (reduction group), respectively. In the reduction group, reduction using lateral traction with a Schanz pin was performed before internal fixation. Complications such as fixation failure, non-union, and avascular necrosis (AVN), caput-collum-diaphysis (CCD) angle, posterior tilt angle, amount of FNS, and Harris Hip Score (HHS) were compared between the groups. RESULTS: Bone union was achieved in all patients; AVN occurred in two patients in each group. No significant difference was seen in the preoperative characteristics between the groups. The CCD angle at 1 year postoperatively was significantly different between the groups, whereas the posterior tilt angle at 1 year postoperatively was not different. FNS at 1 year postoperatively was significantly lower in the reduction group than in the in situ group. FNS by >5 mm was significantly less frequent in the reduction group than in the in situ group (11% versus 75%). The mean HHS at 1 year and 2 years postoperatively was significantly higher in the reduction group than in the in situ group. FNS and HHS were negatively correlated; the mean HHS was significantly higher in patients with none/mild shortening (<5 mm) than in those with moderate/severe shortening (≥5 mm). CONCLUSION: In patients aged 65 years or younger, internal fixation after reduction for severe valgus-impacted femoral neck fractures is safe and effective for achieving successful bone union and restoring the femoral neck length.