Factors Affecting Time to Bony Union of Femoral Subtrochanteric Fractures Treated with Intramedullary Devices

PURPOSE To evaluate the factors affecting the bone union time and the occurrence of nonunion after intramedullary nailing of subtrochanteric femoral fractures in adults. MATERIALS AND METHODS We retrospectively reviewed data from 31 patients (22 men and 9 women) who had undergone femoral intramedullary nailing at least 1 year post-operatively and analyzed the bone union time, nonunion rates, and factors that affected the bone union time according to the fracture classification (AO and Fielding classifications), comminution of the medial cortex, reduction method, and additional cerclage wiring. RESULTS The average union time was 26.4 weeks. There were no differences in the bone union time according to the fracture classification, reduction method, or additional cerclage wiring. Significant differences were found in the bone union time between the medial cortex comminution and non-comminution groups. A relatively strong positive correlation was detected between the degree of post-operative displacement and the bone union time. Nonunion occurred in three cases and there was no failure of implants. CONCLUSION The bone union time was not affected by the reduction method nor additional cerclage wiring in intramedullary nailing of subtrochanteric femur fractures. Comminution of the medial cortex and the degree of the postoperative displacement of fractures contributed to the delayed time of union.