Biomechanical comparison of fracture site stabilities of femur nails after fracture site resorption

Instability increases after fracture site resorption. This study aimed to compare the fracture site stabilities of different femoral nails after fracture site resorption. Thirty composite femurs were divided into three groups of 10 interlocking nails. Using axial compression-distraction machines and a custom-made torsion device, the fracture site rotational and axial stabilities after 1 mm fracture site resorption were determined. Between 6 Nm external and 6 Nm internal rotation torques, the means of the maximum fracture site rotation arc of motion were 5.94 mm for compression nails, 5.9 mm for interlocking nails and 3.5 mm for CAROT nails. Between 2300 N compression and 150 N distraction forces, the means of the fracture site axial motion were 3.15 mm for interlocking nails, 1.26 mm for compression nails and 1.26 mm for CAROT nails. CAROT nails are superior to compression and interlocking nails in fracture site rotational and axial stabilities after 1 mm fracture site resorption.