Tip–neck distance ratio as a novel predictor for failure in cephalomedullary nailing of unstable trochanteric fractures (UTF)

Objectives: Intertrochanteric femur fractures (ITFF) are frequently fixed with proximal femoral nailing (PFN), and a common cause of fixation failure is cut-out of the lag screws. In the literature, many factors have been defined to determine the failure risk, including the tip–apex distance (TAD), calcar-referenced tip–apex distance (CalTAD), the Cleveland zone and Parker's ratio. In this study, a novel technique is described which favors infero-posterior placement of the lag screw and predicts failure risk for PFN. The purpose of this study was to evaluate the tip–neck distance ratio as a factor for the prediction of cut-out after PFN of ITFF. Materials and methods: A retrospective evaluation was made of the data of 125 patients applied with PFN for ITFF between October 2016 and September 2019. The occurrence of mechanical complications was analyzed in relation to age, gender, fracture side, American Society of Anaesthesiologists classification, fracture classification, reduction quality, bone quality, Cleveland zone, Parker’s ratio, TAD, CalTAD and the TNDR. Results: A total of 125 patients, including 16 with mechanical complications, were suitable for full analysis. In the univariate analysis, reduction quality (p = 0.003), the TAD (p = 0.048) and the TNDR (p = 0.030) were statistically associated with mechanical complications (p < 0.05). In the multivariate analysis, good quality of reduction reduced risk of mechanical failure (p = 0.011) and the TNDR (p < 0.001) indicated that these were two independent factors affecting mechanical complications. Conclusion: The results of this study provide clinical evidence that the TNDR is a predictor for cut-out risk. Placement of the lag screw posterior and inferior reduces the risk of mechanical complications. Level of evidence: Level 3. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.