Fractures of long bones are commonly treated with intramedullary (IM) nails and they have been shown to have a very high success rate. Recently we have concerns with the use of the newer IM nailing systems, that uses longer cross screws, which have been developed with variation in implant designs. We believe that the newer implants provide less fracture stability, due to decreased stiffness of the IM nailing system. The aim of this study was to biomechanically determine the influence of the length of cross screw on the stiffness of the IM nailing system, using a composite model. Our test results confirmed our suspicion that the newer IM nailing system using longer cross screw-length is less stiff than traditional nailing systems using shorter cross screw length, during axial loading.
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