Numerical analysis of stress shielding of platedhuman femur using 3-dimensional finite element method

Conventional compression bone fracture plates sometimes cause osteoporosis under the plate due to their high rigidity. In order to prevent the osteopenia, many researchers have attempted various types of bone plates. To meet the same purpose, a new concept bone plate which have a vicoelastic washer between plate and screw head is introduced. The washer is made of a biocompatible polymer (ultra high molecular weight polyethylene, UHMWPE). This research was performed first to establish a more realistic and detailed plated-bone system using finite element method and second to investigate the effect of the UHMWPE washer on the stress shielding comparing with the conventional plate model. Three-dinensional finite element meshes of the human femur with the conventional and new concept bone plate were generated and the comparative stress analysis of the stress shielding was performed with static half-stance loading condition. The results of analysis showed that the new and conventional bone plate transfer the stress through the bone average 15% and 10% that of the intact bone respecively. However, the local stress in the bone under the new bone plate have increased about 13-150% that of the conventional bone plate depending on the region. Earlier preliminary animal studies showed some promising results. It is suggested that the in vivo and FEM results support the feasibility of the new concept bone plate.