title: A numerical comparative analysis of ChM and Fixion nails for diaphyseal femur fractures.
abstract: OBJECTIVE
  Today intramedullary locked nails are widespread in treatment of diaphyseal long bone fractures of the lower limb. However, such nails have a number of drawbacks: complexity and duration of the installation, high axial stiffness, as well as the failure of locking screws and nail body. Expandable nails such as Fixion have several advantages over lockable ones. They can be quickly installed without the need of reaming and provide sufficient stabilization of the fracture. However, many studies show their low stability under torsional loads.
  
  
  METHODS
  In this paper, geometric characteristics of Fixion nail were investigated. Bone-nail systems (with Fixion and locked nail) under the influence of three types of loads were numerically studied. Two types of diaphyseal femoral fractures (type A and B in accordance with AO/ASIF classification) were examined.
  
  
  RESULTS
  It was revealed that Fixion nail provides axial stiffness of 489 N/mm for the fractures studied. Expandable nail showed higher compression at fragments junction than locked nail. Torsional stability of Fixion nail was also high. Corrosion was found on inner surface of Fixion nail.
  
  
  CONCLUSIONS
  Fixion nail showed high stability under influence of the three loads studied. Corrosion on the internal wall of the nail may indicate its relatively low resistance to saline.
authors.affiliation: Saratov State University, Saratov, Russia.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Ivanov
authors.affiliation: Saratov Scientific Research Institute of Traumatology and Orthopedics, Saratov, Russia.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Barabash
authors.affiliation: Saratov Scientific Research Institute of Traumatology and Orthopedics, Saratov, Russia.
authors.forename: Anatoly
authors.initials: A
authors.lastname: Barabash
mesh_terms: D001696:Biomechanical Phenomena; D001858:Bone Nails; D001863:Bone Screws; D018483:Diaphyses / Q000601:surgery*; D005264:Femoral Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D005594:Fracture Fixation, Intramedullary; D006801:Humans; D021621:Imaging, Three-Dimensional; D008962:Models, Theoretical; D011312:Pressure; D019736:Prostheses and Implants; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed; D016474:Weight-Bearing