Predictive indicators of proximal femur nail antirotation device cut-out in intertrochanteric fractures: introduction of a novel radiographic parameter

Introduction

Cut-out remains the predominant complication after proximal femoral nail antirotation (PFNA) fixation in intertrochanteric fractures, significantly affecting clinical outcomes. Established predictive parameters, such as tip-apex distance (TAD) and calcar-referenced TAD (CalTAD), offer valuable insights but have limitations. This study introduces a novel radiographic parameter—the discrepancy between preoperatively estimated and intraoperatively selected lag screw length—and assesses its predictive value in implant cut-out.

Materials and methods

In this retrospective cohort study, 276 patients undergoing PFNA fixation for intertrochanteric fractures from January 2019 to June 2023 were analyzed. Patients were classified into cut-out (n = 20, 7.2%) and uneventful healing (n = 256, 92.8%) groups. Demographics, AO/OTA fracture classification, TAD, CalTAD, shaft-neck angle, reduction quality, and the discrepancy between preoperative radiographic estimates of lag screw length (based on contralateral hip measurements) and actual intraoperative lengths were evaluated. Statistical methods included ROC analysis and multivariate logistic regression modeling.

Results

TAD (median 31.5 vs. 23.0 mm, p < 0.001) and CalTAD (median 40.9 vs. 31.4 mm, p < 0.001) were significantly greater in the cut-out group. The novel screw length discrepancy parameter demonstrated significant predictive accuracy (AUC = 0.818), with a difference exceeding 3 mm (shorter screw) strongly associated with cut-out risk (OR = 63.0, p < 0.001). Multivariate analysis identified CalTAD > 38.55 mm (OR = 14.2, p = 0.004) and screw length discrepancy > 3 mm (shorter than estimated) as independent predictors for cut-out.

Conclusions

This study introduces a novel predictor of cut-out in PFNA-treated intertrochanteric fractures: discrepancy exceeding 3 mm between preoperatively estimated and intraoperatively selected lag screw length. Incorporating contralateral hip measurements into preoperative planning protocols may improve surgical precision and decrease the risk of implant failure. Prospective validation studies are recommended to further confirm clinical applicability.