Does the PFNA™ nail limit impaction in unstable intertrochanteric femoral fracture? A 115 case-control series

AbstractIntroductionFemoral neck shortening after dynamic fixation of extra-capsular fracture may impair functional results, but is rarely assessed. The present study measured impaction in stable and unstable fractures (on the Ender classification) treated by PFNA™ nail. The objectives were: 1) to validate the Ender classification to assess fracture stability; 2) to determine whether neck shortening and head purchase quality varied with stability; and 3) to determine the functional impact of femoral neck shortening.HypothesisThe study hypothesis was that the PFNA™ nail stabilizes unstable as well as stable fractures.Materials and MethodsOne hundred and fifteen consecutive patients, aged over 70 years, operated on for intertrochanteric fracture using the PFNA™ nail were followed up prospectively for 6 months. Multivariate analysis, including age, gender, assembly quality and body-mass index, was applied to assess the predictive power of the Ender classification with respect to femoral neck shortening. Secondly, patients were grouped according to stable versus unstable fracture (n=70 and 45, respectively), and impaction and femoral head purchase were assessed on a dedicated radiographic protocol. Functional results were assessed on Parker score.ResultsIn the unstable fracture group, 3 assembly failures required revision by total hip replacement. Ender grade>2 was significantly predictive of>5mm neck shortening. Neck shortening was greater in unstable fracture: 8.1±8.4mm (range, 4–32mm), versus 2.5±3.7mm (range, 3–14mm) (P=0.0004). Mean blade cut-through was 1.2±2.9mm (range, 1–12mm) in unstable fracture, versus 0.3±1.3mm (range, 1–6mm) (P=0.02). Mean cut-out was 2.3±6mm (range, 2–21mm) in unstable fracture, versus 0.5±2.6mm (range, 1–8mm) (P=0.03). Parker scores diminished comparably in the two groups, without significant difference at follow-up: 3.9±2.6 (range, 0–9) in stable and 3.1±1.9 (range, 0–8) in unstable fracture; reduction in Parker score showed no correlation with femoral neck shortening (r=0.013, P=0.88).DiscussionThe PFNA™ nail provides poorer stabilization of unstable compared to stable fracture. Femoral neck shortening should be taken into account in assessing internal fixation hardware perfomances.Level of evidenceLevel III. Prospective case-control study