title: Working length of locking plates determines interfragmentary movement in distal femur fractures under physiological loading.
abstract: BACKGROUND
  This study aimed to investigate the influence of the screw location and plate working length of a locking plate construct at the distal femur on interfragmentary movement under physiological loading.
  
  
  METHODS
  To quantitatively analyse the influence of plate working length on interfragmentary movements in a locking plate construct bridging a distal femur fracture, a finite element model based on CT (computed tomography) data was physiologically loaded and fracture gap conditions were calculated. Four working lengths with eight screw variations each were systemically analysed.
  
  
  RESULTS
  Interfragmentary movements for axial (12-19%, p<0.001) and shear movements (-7.4-545%, p<0.001) at all tested nodes increased significantly with longer plate working length, whereas screw variations within the groups revealed no significant influence. The working length (defined by screw location) dominates the biomechanical fracture gap conditions.
  
  
  CONCLUSIONS
  The current finite element analysis demonstrates that plate working length significantly influences interfragmentary movements, thereby affecting the biomechanical consequences of fracture healing.
authors.affiliation: Centre for musculoskeletal surgery, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany. Electronic address: sven.maerdian@charite.de.
authors.forename: Sven
authors.initials: S
authors.lastname: Märdian
authors.affiliation: Centre for musculoskeletal surgery, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany. Electronic address: klaus-dieter.schaser@charite.de.
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Schaser
authors.affiliation: Julius Wolff Institute for Biomechanics and Musculoskeletal Regeneration, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany. Electronic address: georg.duda@charite.de.
authors.forename: Georg N
authors.initials: GN
authors.lastname: Duda
authors.affiliation: Julius Wolff Institute for Biomechanics and Musculoskeletal Regeneration, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany. Electronic address: mark.heyland@charite.de.
authors.forename: Mark
authors.initials: M
authors.lastname: Heyland
mesh_terms: D001860:Bone Plates; D001863:Bone Screws; D004867:Equipment Design; D005264:Femoral Fractures / Q000503:physiopathology* / Q000601:surgery*; D020342:Finite Element Analysis; D005593:Fracture Fixation, Internal / Q000379:methods*; D017102:Fracture Healing / Q000502:physiology*; D018460:Fractures, Comminuted / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D009068:Movement; D013312:Stress, Physiological / Q000502:physiology
keywords: Distal femur fracture; Finite element model; Interfragmentary movement; Locking plate