RESUMO
PURPOSE: A compression plate fixation was generally used in the fracture of a femoral diaphysis but it produced the stress shielding problem which resulted in a decrease of bone mass and impaired mechanical properties. This study was designed to compare with the stiffnesses of three different internal fixation types ; fixation with only plate, with only cross-pins, and with both a plate and cross-pins. MATERIALS AND METHODS: To compare the stress distribution and stiffness of three types of fixation devices, the device-bone system are analyzed under axial compression(70Kg) and 3-point bending(500Nmm) in planes using the 2-D finite element method(ABAQUS 5.8). Also the stiffness of each device was evaluated at seven different time points during fracture healing by increasing Young's modulus of callus. RESULTS: The plate fixation model had the highest stress distribution and occurred the stress concentration in the cortex beneath the plate. During the healing of bone fracture, the fixation with cross-pins relatively had a higher compression and bending stiffness. The fixation with only cross-pins was as stiff as that with an only plate in bending but less stiff than in compression. CONCLUSION: The internal fixation added to cross-pins may decrease the stress shielding problems due to dispersing the stress concentration and also improve the stiffness of a device-bone system.