Abstract
INTRODUCTION: This retrospective matched case-control study aimed to identify predictors of cut-out following intramedullary nailing of intertrochanteric fractures with the 200-mm Synthes proximal femoral nail antirotation (PFNA). METHODS: 609 patients underwent intramedullary nailing for intertrochanteric fractures at our institution between January 2011 and December 2014. 370 patients satisfied the inclusion criteria. There were 20 cases of implant cut-out. Cases and controls were matched using a propensity score-matching method with an m:n ratio, matching the criteria of gender, age and side of operation. Radiographs were assessed to determine fracture classification, fracture reduction quality, tip-apex distance, calcar referenced tip-apex distance (CalTAD), anteroposterior (AP) Parker's ratio index, lateral Parker's ratio index and cervical angle difference. Conditional logistic regression analysis was performed to determine any association between potential predictors and cut-outs. RESULTS: The cut-out incidence was 5.4%. Of the 20 cut-outs, 16 were superior and four were cut-throughs. Univariate analysis only showed a significant association between unsatisfactory fracture reduction quality and cut-outs (odds ratio [OR] 10.1, 95% confidence interval [CI] 1.31-77.6, p = 0.027). This association remained significant with multivariate logistic regression analysis (OR 16.4, 95% CI 1.9-140.4, p = 0.011). Cut-throughs had significantly lower CalTAD (16.2 vs. 27.5, p = 0.016) and AP Parker's ratio index values (38.7 vs. 50.7, p = 0.007) than superior cut-outs. CONCLUSION: Unsatisfactory fracture reduction quality was a significant predictor of cut-out in intertrochanteric fractures treated with the 200-mm PFNA. Cut-outs had two distinct modes, with cut-throughs having a deeper and more inferior helical blade position in the femoral head compared to superior cut-outs.