BACKGROUND: How to determine the less invasive stabilization system-distal femur (LISS-DF) proximal cortical screw fixation of single and double cortex in a reasonable collocation way to reach a relative balance of fixation strength in screw at both ends of fractures, decrease shear stress between the screws and cortical bone, avoid stress concentration of the screws, receive a better clinical effect. All of those are the key to prevent internal fixation failure.
OBJECTIVE: To observe the LISS-DF treatment of distal femoral fractures proximal cortex of different combinations of single and double screw fixation by finite element analysis and mechanical evaluation.
METHODS: Solid model and finite element model of the LISS-DF plate for distal femoral fractures (AO/OTA33-A3 type) were builded in ANSYS9.0 software. Proximal screws in single and double cortex fixation of different combinations, axial compression torsion test were detected through the simulation of physiological stress, and stress changes the proximal screw was evaluate.
RESULTS AND CONCLUSION: In 16 different combinations, when the combination of proximal screw 1, 3 single and 2, 4 double fixed cortex, mean stress of the proximal 4 screws was minimum (24.219 75 N), and the mean shear stress was also the minimum, displacement was close to other fixation and all were tiny. Proximal screw near the end of femoral fractures, and the remaining cortical screws followed by alternating single and double fixed, the LISS-DF system stress is decentralized, effect of anti-pull and anti-reverse is well, thereby the early loosening of plate and screw off is reduced.