Surgical outcomes of intramedullary nailing for diaphyseal atypical femur fractures: is it safe to modify a nail entry in bowed femur?

Introduction: The purpose of the study was to determine the surgical outcomes of intramedullary nailing in diaphyseal atypical femoral fractures (AFFs) and to evaluate the clinical outcomes of nail entry modification technique. Materials and methods: We retrospectively reviewed diaphyseal AFFs treated with IMN at nine institutions. In total, 82 patients were included. Surgical outcomes such as complication, union time, and femoral bowing were evaluated. We modified the nail entry of the straight nail from piriformis fossa to the tip of the greater trochanter in the bowed femur and compared the surgical outcomes between the original group and the modification group. Results: The average union time was 20.1 weeks, and the union rate was 89.0%. The average union time was 13.1 weeks and 21 weeks in incomplete and complete AFFs, respectively. There was no nonunion in incomplete AFFs, but 13.8% in complete AFFs. Complete AFFs had 86.2% of union rate. There were 46 cases of group 1 with original entry point and 19 cases of group 2 with modified entry. In group 2, the union rate was similar to group 1 and union time was shorter. Conclusion: Changing the entry point laterally allowed the nail to be accommodated in bowed femurs, decreasing the risk of deformity and improving healing time. In severely varus femur, the lateral entry of the straight nail can be a useful technique.