Biomechanical comparison of PFNA combined with the modified candy-package wiring technique versus PFNA alone in complex unstable intertrochanteric femoral fractures

Proximal femoral nail antirotation (PFNA) may not provide sufficient control of unstable fracture fragments in complex intertrochanteric fractures. The modified candy-package wiring technique may supplement PFNA by improving resistance to rotational and shear displacement. This biomechanical model study compared PFNA combined with modified candy-package wiring with PFNA alone in an Evans type III intertrochanteric fracture model. Ten standardized femoral fracture models were randomly allocated to a PFNA group (n = 5) or a PFNA plus modified candy-package wiring group (PFNA + MCW group; n = 5). Torsional and axial compression tests were performed. Three repeated loading cycles were conducted for each specimen as conditioning cycles; the prespecified third cycle was used for analysis. Torsional stiffness was calculated as the change in torque divided by the corresponding change in angular displacement (Kt = Δ T /Δ θ ). The mean torsional angle was significantly lower in the PFNA + MCW group than in the PFNA group (2.09 ± 0.24° vs 2.90 ± 0.18°; P = .0007). Torsional stiffness was also significantly lower in the PFNA + MCW group than in the PFNA group (0.48 ± 0.0529 vs 0.59 ± 0.0850 N·m/°; P = .045). The maximum failure load was numerically higher in the PFNA + MCW group than in the PFNA group (571.26 ± 92.75 N vs 510.34 ± 76.59 N), although the difference was not statistically significant ( P = .291). In this small biomechanical model study, PFNA combined with modified candy-package wiring reduced torsional displacement and showed favorable trends in axial load-bearing performance compared with PFNA alone. Because several outcomes were not statistically significant and only 5 models were included per group, these findings should be interpreted as preliminary biomechanical evidence rather than proof of superiority. Larger biomechanical studies and clinical validation are required.