Impact of Wedge Effect on Outcomes of Intertrochanteric Fractures Treated with Intramedullary Proximal Femoral Nail.

The purpose of this study is to investigate the risk factors for wedge effect and its relevance between blade cut-out in patients with intertrochanteric fractures (ITF) treated with proximal femoral nail antirotation II (PFNA-II). A total of 113 patients with ITF treated with PFNA-II between 2012 and 2016 were retrospectively analyzed. Radiographic variables including preoperative fracture pattern, fracture classification, lateral wall fracture, and postoperative neck-shaft angle (NSA), femoral offset (FO), blade cut-out, and Parker's ratio were measured for analysis. An average of 4.16° of varus malalignment in NSA and 5.5 mm of femoral shaft lateralization in FO was found post-operatively. The presence of lateral wall fracture was significantly related to post-operative varus change of NSA ( p < 0.05). After at least one year of follow up, the blade cut-out rate was 2.65% (3/113), and Parker's ratio was significantly higher in patients with blade cut-out ( p = 0.0118). This study concluded that patients with ITF-present preoperative lateral wall fracture and postoperative higher Parker's ratio in AP radiography showed higher incidence of wedge effect that might increase risk of blade cut out.