title: Effects of muscle-equivalent forces on the biomechanical behavior of proximal femur fracture models: a pilot study on artificial bones.
abstract: BACKGROUND
  There has been extensive analysis of the influence of muscle forces and their effects on the biomechanical behavior of the proximal femur. Nevertheless, these forces have only been taken into account in a handful of biomechanical studies in the field of traumatology. The aim of this study was to analyze the biomechanical behavior of two typical fracture models of the proximal femur based on muscle-equivalent forces.
  
  
  METHODS
  Plate osteosynthesis was performed on two groups of artificial femora to stabilize either a trochanteric osteotomy (n= 5) or a femur shaft osteotomy (n = 5). After fixation axial loading was applied to the constructs first without muscle-equivalent forces and then with the addition of these forces (abductor groups and vastus lateralis). Displacement at the osteotomy site and the stiffness of the whole construct were measured during loading.
  
  
  RESULTS
  Comparison of the two loading modes revealed no significant differences for displacement or stiffness for the trochanteric fractures. For the femur shaft fractures, a significant difference was found for displacement (p = 0.023) and stiffness (p = 0.003) with or without muscle-equivalent forces.
  
  
  CONCLUSIONS
  The loading protocol for implant testing on femur shaft fractures should include muscle-equivalent forces. For trochanteric fractures, consideration of muscle forces is not entirely necessary since they will have little effect on the results, for example, when comparing implants.
authors.affiliation: Department of Orthopaedics and Traumatology, Albert-Ludwigs-University Freiburg, Germany. lukas.konstantinidis@uniklinik-freiburg.de
authors.forename: Lukas
authors.initials: L
authors.lastname: Konstantinidis
authors.forename: Christoforos
authors.initials: C
authors.lastname: Papaioannou
authors.forename: Anja
authors.initials: A
authors.lastname: Hirschmüller
authors.forename: Theodoros
authors.initials: T
authors.lastname: Pavlidis
authors.forename: Steffen
authors.initials: S
authors.lastname: Schröter
authors.forename: Norbert P
authors.initials: NP
authors.lastname: Südkamp
authors.forename: Peter
authors.initials: P
authors.lastname: Helwig
mesh_terms: D040761:Biomimetic Materials; D003198:Computer Simulation; D005264:Femoral Fractures / Q000503:physiopathology*; D025981:Hip Injuries / Q000503:physiopathology*; D006621:Hip Joint / Q000503:physiopathology*; D006801:Humans; D008954:Models, Biological; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010865:Pilot Projects