Preclinical biomechanics of a new intramedullary nail for femoral diaphyseal fractures

This article presents new intramedullary (IM) nail design for femur diaphyseal fractures osteosynthesis. Biomechanical comparison of the two IM nails (standard locking and new developed) was conducted. Femur medullary canal architectonics was studied with the help of computer tomography (CT) data. Three-dimensional (3D) models of the femur, its transverse fracture, standard locking nail and new developed nail were constructed as well as the bone-implant system models. Stress-strain state of the bone-implant systems under three types of loads (axial, lateral and torsional) was studied using finite-element method in commercial software Ansys 14.0. Numerical results showed that new nail allows proximal fragment of the bone to move in an axial direction. New nail provides necessary compression at fragments junction. It was revealed that the highest values of effective stress (ES) for the standard nail were concentrated at contact area between locking screws and nail for all investigated loads. For the new nail the highest values of ES were concentrated on its body and blades at proximal region. Moreover, stresses occurred in the new nail were smaller than stresses appeared in the standard nail. This conclusion is valid for three investigated types of loads. So the new nail does not have serious disadvantages of standard nails. From the biomechanical point of view the new nail is more preferable for diaphyseal femur fractures osteosynthesis.