Straight nail insertion through a laterally shifted entry for diaphyseal atypical femoral fractures with bowing: good indications and limitations of this technique.

Purpose: Inserting a straight (piriformis fossa entry) nail through the tip of the greater trochanter has been used for treating atypical femoral fractures (AFFs) with bowing. This study aimed to determine what degree of bowing can be successfully treated using a laterally shifted entry technique.

Methods: Twenty-three complete and six incomplete diaphyseal AFFs treated using the shifted entry technique were retrospectively analysed. Radiologic parameters and complications were evaluated. The complete AFFs were divided into two groups based on the severity of preoperative bowing: grade 0-II bowing and < 20° lateral bowing (minimal/moderate) and grade III bowing or ≥ 20° lateral bowing (severe). Comparison according to postoperative malalignment, a change of lateral or anterior bowing ≥ 5° was also performed.

Results: Three complete AFFs in the minimal/moderate group showed malalignment, as did all in the severe group (p < 0.001). The change of bowing was greater for the severe group in lateral and anterior bowing (p = 0.004 and 0.001, respectively). A greater fracture gap was found on AP and lateral radiographs in the severe group (p = 0.044 and 0.026, respectively). In the comparison according to postoperative malalignment, a significant difference was found for the percentage of severe deformity (p < 0.001). All incomplete AFFs were united without complication.

Conclusion: Diaphyseal AFFs with grade 0-II bowing and < 20° anterior bowing were treated successfully by the shifted entry technique. However, postoperative malalignment was found in all cases of AFFs with severe bowing. Therefore, other techniques should be considered for AFFs with grade III bowing or ≥ 20° anterior bowing.