A biomechanical comparison of locked plate fixation with percutaneous insertion capability versus the angled blade plate in a subtrochanteric fracture gap model.

OBJECTIVES The angled blade plate has been the historical standard in fixed-angle extramedullary subtrochanteric femur fracture fixation, but it requires an extensile lateral approach to the femur. Little formal evaluation exists for specifically designed percutaneous extramedullary implants. The purpose of this study was to compare 3 locked plating constructs, all with percutaneous insertion capability, with the standard 95-degree angled blade plate to determine whether specifically designed fixed-angle extramedullary implants for subtrochanteric femur fractures were biomechanically comparable to the angled blade plate. METHODS Forty composite adult femurs were divided into 4 equal groups. The constructs evaluated included a 95-degree angled blade plate, a broad 4.5-mm combination locking plate, and a precontoured proximal femoral locking plate (PFLP) with and without an oblique, angled strut or "kickstand" screw. A 30-degree wedge osteotomy was used to create a subtrochanteric fracture gap model. Each specimen underwent axial and torsional stiffness testing along with cyclic axial loading to failure. RESULTS Axial stiffness testing revealed that the PFLP with the "kickstand" screw was the stiffest construct (92.2 +/- 17.4 Nm/m), which was 211% stiffer than the blade plate, 309% stiffer than the broad plate, and 194% stiffer than the PFLP without the kickstand screw. The blade plate had the highest torsional stiffness (2.42 +/- 0.08 Nm/degree), which was 151% stiffer than the broad plate, 128% stiffer than the PFLP with the kickstand, and 138% stiffer than the PFLP without the kickstand screw. The PFLP with the kickstand screw had the least irreversible deformation (6.3 mm), which was 52% less than the broad plate and 61% less than the PFLP without the kickstand screw. CONCLUSIONS Our data reveal that the PFLP with the "kickstand" screw provides more axial stiffness, less torsional stiffness, and equivalent irreversible deformation to cyclic axial loading when compared with the blade plate.