Intramedullary Nailing for Atypical Femoral Fracture with Excessive Anterolateral Bowing

Background: Intramedullary nailing is the treatment of choice for atypical femoral fractures. However, several problems, such as iatrogenic fracture and medial gap opening, can occur during intramedullary nailing when atypical femoral fractures are associated with excessive anterolateral bowing. To overcome these problems, we have developed a new grading system for anterolateral femoral bowing and a new technique for intramedullary nailing. The core of this new technique is matching the anterior curvature of the femoral nail with the anterolateral bowing of the femur when the nail passes the apex of the curvature, by rotating the nail externally. Methods: From January 2005 through March 2016, 24 female patients (30 cases) who underwent a surgical procedure for atypical femoral fracture with anterolateral bowing at 2 institutes were evaluated. The postoperative outcomes (anterolateral bowing grade, anterior and lateral bowing angles, medial gap and posterior gap of the fracture site, iatrogenic fracture, and time to initial medial callus formation and osseous union) were compared between the new technique (18 cases) and the conventional technique (12 cases). Results: With regard to the reliability of the new grading system, the interobserver and intraobserver reliability of the new grading system demonstrated an almost perfect agreement (kappa(inter) = 0.893, kappa(intra) = 0.883). For patients with complete fractures, the differences between the preoperative and postoperative anterior and lateral bowing angles were significantly less (p = 0.013 for both) in the new technique group. The medial and posterior gaps at the fracture site were also significantly less in the new technique group (p = 0.013 for the medial gaps and p = 0.022 for the posterior gaps). Iatrogenic fracture occurred only in the conventional technique group, affecting 2 cases. The time to initial medial callus formation was significantly shorter (p = 0.033) in the new technique group compared with the conventional technique group. Conclusions: Our new grading system for anterolateral femoral bowing is convenient and reliable. Furthermore, the new intramedullary nailing technique with the current intramedullary nail system is appropriate for the repair of atypical femoral fractures with excessive anterolateral bowing.