Predictors of Mechanical Failure Rate in Reduction of Intertrochanteric Fracture of the Femur Using Proximal Femoral Nail with Helical Blade

Background: The optimal implant for reducing intertrochanteric fracture is unknown. Several bone-related, implant-related and radiological variables seem to play a role in predicting the rate of intraoperative and postoperative mechanical failure. The objective of this study was to evaluate the rate and predictors of mechanical failure and its relationship with quality of reduction through assessing certain radiological parameters. Materials and methods: A retrospective study reviewed patients with stable (AO/OTA Type 3.1A1) and unstable (AO/OTA Type 3.1A2 and A3) intertrochanteric femur fracture who were treated with proximal femoral nail with helical blades (PFNA) between 2011 and 2017. Exclusion criteria were patients with pathologic fractures. Followup was undertaken at 1 day, 4-6 weeks, and 3 months postoperatively by reviewing radiographs and medical charts. The primary outcome was the rate of mechanical failure. Radiologic parameters of Tip apex distance (TAD), neck shaft angle and displacements were evaluated as indicators of reduction quality. All these were compared to each other and baseline patient characteristics to identify any association. Results: We found 69 patients who underwent PFNA procedure. There was no case of intraoperative or postoperative mechanical failure or non-orthopedic complication. The postoperative radiological outcomes revealed variable quality of reduction with: mean TAD of 26.07±3.69° (bimodal), mean neck shaft angle of 133±5.6° (range: 116-140°), 35% of patients having lesser trochanter displacement, 28% having displaced femoral shaft. There was no statistical significant relation between any of the radiological outcomes and patient characteristics except between neck shaft angle and osteoporosis (p=0.03). Conclusion: The radiological outcomes are independent of the patient's characteristics except for Neck Shaft Angle and Osteoporosis. Absence of mechanical failure despite the variability in reduction quality (optimal/suboptimal) might be explained by the decent implant design. Further studies are needed to confirm that PFNA implant design is the major preventer of mechanical failure.