Expandable intramedullary nail: review of biomechanical studies

This article reviews studies of Fixion expandable nail biomechanical properties in case of long bones fractures osteosynthesis. The purpose of this study was to systematize biomechanical researches dedicated to the expandable nail. There were found seven biomechanical studies published between 2005 and 2008. Among them, six studies are devoted to mechanical experiments, and one is a comment to the published study. In four papers, the authors compared biomechanical properties of expandable and locked nails. Expandable nail proved to be a highly effective device for fixation of long bone fractures. However, in case of mid-shaft fractures Fixion nail was significantly less stable than standard locked nails. This conclusion was obtained for humeri, tibia and femur. Stiffness of bone-implant system for expandable nail in case of torsional loads was significantly lower than the similar parameter of standard implant in case of transverse fracture models. Expandable Fixion nail rod should be used with great caution for osteosynthesis of long bones transverse shaft fractures. In contrast, in the case of oblique and spiral fractures, when contact area between fragments is sufficiently high and can share loads between nail and bone fragments, the expandable nail should be used.