Clinical Implication of Subgrouping in Valgus Femoral Neck Fractures: Comparison of 31-B1.1 With 31-B1.2 Fractures Using the OTA/AO Classification

Abstract

OBJECTIVES: This study aimed to identify the clinical implications of valgus-impacted femoral neck fractures and compare fractures with >15-degree angle of impaction (31-B1.1) against fractures with <15-degree angle of impaction (31-B1.2). DESIGN: Retrospective study. PATIENTS/PARTICIPANTS: We enrolled 78 patients with 31-B1 femoral neck fractures who were treated by screw osteosynthesis. MAIN OUTCOME MEASUREMENTS: We evaluated the clinical and radiographic outcomes. RESULTS: Thirty-six patients sustained 31-B1.1 fractures, and 42 patients sustained 31-B1.2 fractures. The average follow-up period was 15 months, and bony union occurred in all cases. The mean femur neck shortening was 8.88 mm for B1.1 and 3.70 mm for B1.2 fractures (P < 0.001). The mean sliding distance of the screw was 3.36 mm for B1.1 fractures and 1.38 mm for B1.2 fractures (P < 0.001). The mean Harris hip score was 82.0 for B1.1 and 88.8 for B1.2 fractures (P = 0.029). Avascular necrosis (AVN) of the femoral head occurred in 4 patients with B1.1 fractures, and none with B1.2 fractures (P = 0.041). Eighteen of the 78 patients required a second operation, and 15 of them were included in 31-B1.1 fracture (P = 0.003). Three patients underwent arthroplasty due to AVN, and 15 patients required hardware removal due to pain after bony union. CONCLUSIONS: More femoral neck shortening and less functional recovery should be expected in valgus-impacted femoral neck fracture patients based on the severity of the initial deformity. Even though we obtained bony union in all of the cases, the risk of AVN and second operation after bony union was higher with greater initial deformity.