Cut-Off values for PFNA nail and blade protrusion predicting postoperative pain in intertrochanteric fractures

Proximal femoral nail antirotation (PFNA) fixation for intertrochanteric fractures often results in nail or blade protrusion, particularly in Asian populations, and is associated with postoperative lateral hip pain. However, not all patients with protrusion experience pain. The specific lengths and locations causing clinically significant pain remain unclear. This study aims to determine the cut-off values and locations of PFNA nail and blade protrusions that predict lateral hip pain and to evaluate their relationship with functional outcomes.

Protrusion of the PFNA-II nail and blade beyond specific radiographic cut-off values is associated with increased lateral hip pain after intertrochanteric fracture fixation.

In this comparative observational study, 226 patients with intertrochanteric fractures treated with PFNA-II fixation were recruited from August 2021 to December 2023. Inclusion criteria included age ≥60 years, ≥6 months post-fixation, and radiographic fracture union. Lateral hip pain was evaluated using the Visual Analog Scale (VAS, 0-10) at two sites: the nail tip (greater trochanter) and the end of the blade. The patients were divided into four groups according to VAS scores: Group A (nail tip pain, VAS < 4), Group B (nail tip pain, VAS ≥ 4), Group C (blade end pain, VAS < 4), and Group D (blade end pain, VAS ≥ 4). Protrusion lengths (medial/lateral nail, superior/inferior blade) were measured radiographically. The Receiver Operating Characteristics (ROC) analysis determined the cut-off values, and multivariate logistic regression evaluated the risk factors. The Harris Hip Score (HHS) was used to evaluate functional outcomes.

Medial nail protrusion ≥3.775 mm (sensitivity 91%, specificity 61%) and lateral nail protrusion ≥8.015 mm (sensitivity 85%, specificity 65%) predicted nail tip pain. The superior blade protrusion ≥10.95 mm (sensitivity 56%, specificity 70%) and the inferior blade protrusion ≥3.265 mm (sensitivity 60%, specificity 66%) predicted blade end pain. Medial nail protrusion increased pain risk (odds ratio 17.17, 95% CI 7.68-38.39). HHS did not show a significant correlation with protrusion, except for a weak negative correlation with inferior blade protrusion (r = -0.39, p = 0.032).

Distinct radiographic cut-off values of PFNA-II protrusion predict postoperative lateral hip pain. While pain is mainly associated with medial nail and superior blade protrusion, excessive inferior blade protrusion may slightly impair hip function. The refinement of the PFNA II design and surgical technique to minimize protrusion could further improve postoperative outcomes in Asian patients.

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