Patient-specific anatomical alignment relative to the contralateral collodiaphyseal angle as an independent predictor of screw cut-out after proximal femoral nailing

Abstract

Background Screw cut-out remains a major mechanical complication after proximal femoral nailing (PFN) for intertrochanteric fractures. Traditional predictors such as tip-apex distance (TAD) and reduction quality do not account for individual femoral anatomy. This study aimed to determine whether deviation from the contralateral collodiaphyseal (CCD) angle (|Delta angle|) independently predicts screw cut-out after PFN. Methods A total of 354 patients (mean age 77.6 +/- 12.0 years; 58% female) treated with PFN between 2015 and 2020 were retrospectively analyzed. Radiographic parameters included TAD and the absolute difference between postoperative and contralateral collodiaphyseal (CCD) angles (|Delta angle|), representing patient-specific alignment. Functional outcomes were assessed using the Harris Hip Score, Barthel Index, and time to full weight bearing. Univariate and multivariable logistic regression analyses were performed to identify independent predictors of screw cut-out. Results Screw cut-out occurred in 56 patients (15.8%) and was associated with larger TAD, greater |Delta angle| deviation, and poorer reduction quality (all p < 0.01). In multivariable analysis, TAD, |Delta angle|, and reduction quality independently predicted cut-out. Patients with cut-out exhibited lower functional scores and delayed weight bearing, indicating substantial impairment in postoperative recovery. Conclusion Patient-specific anatomical alignment, along with TAD and reduction quality, independently predicts screw cut-out. Deviations >= 9 degrees from native CCD alignment increase mechanical failure risk and delay functional recovery.