The nail-shaft-axis of the of proximal femoral nail antirotation (PFNA) is an important prognostic factor in the operative treatment of intertrochanteric fractures

Due to the world's aging population, intertrochanteric fractures are frequent. Considering age and comorbidities of most of these patients, it is indispensable to enable early postoperative mobilization of these patients. Intramedullary osteosynthesis with PFN-A is widely used and, in general, considered safe and reliable for the operative treatment of intertrochanteric fractures. However, implant -related complications are reported in 6-21% of all cases. In this study, we are analyzing complication rates and risk factors for implant-related complications. All intertrochanteric fractures admitted to our hospital and treated with PFN-A between January 2012 and January 2016 were analysed retrospectively. Radiological analyses of the CCD and the lateral offset on the uninjured side was compared to the CCD initially postoperatively and during follow-up on the operated side. Furthermore, we analysed the tip-apex distance (TAD), blade position in the femoral head and introduced the nail-shaft axis as a new parameter. Within 101 intertrochanteric fractures included, 16 implant-related complications were encountered (15.84%). Analyses of risk factors for secondary varus displacement of greater than 10A degrees within the follow-up and thus risk for cut-out in the osteosynthesis revealed that etasblished risk factors such as a TAD > 25 mm, reduction in varus and an improper position of the blade were also significant risk factors in our cohort for failure of the osteosynthesis. Moreover, we introduced the nail-shaft axis a new potential risk factor and could show that a too medial or too lateral nail-shaft axis is also significantly associated with secondary varus displacement. When treating introchanteric fractures with PFNA reduction in neutral or even slight valgus, aiming for a TAD < 25 mm and a correct position of the blade within the femoral head reduced the risk for secondary varus displacement significantly. Furthermore, we suggest to aim for a central nail-shaft axis.