title: Interfragmentary lag screw fixation in locking plate constructs increases stiffness in simple fracture patterns.
abstract: BACKGROUND
  The aim of the current biomechanical cadaver study was to quantify the influence of an additional lag screw on construct stiffness in simple fracture models at the distal femur stabilised with a locking plate.
  
  
  METHODS
  For biomechanical testing paired fresh frozen human femora of 5 donors (mean age: 71 (SD 9) years) were chosen. Different locking plate configurations either with or without interfragmentary lag screw were tested under torsional load (2/4Nm/deg) or axial compression forces (500/1000N).
  
  
  RESULTS
  Data show that plate constructs with interfragmentary lag screw reveal similar axial and torsional stiffness values compared to intact bone as opposed to bridging plate constructs that showed significantly lower stiffness for both loading conditions.
  
  
  CONCLUSIONS
  The current biomechanical testing unveils that the insertion of a lag screw combined with a locking plate dominates over a bridging plate construct at the distal femur in terms of axial and torsional stiffness.
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: Department of Trauma Surgery, Medical University Innsbruck, Anichstraße 35, 6020 Innsbruck, Austria. Electronic address: werner.schmoelz@uki.at.
authors.forename: Werner
authors.initials: W
authors.lastname: Schmölz
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: D000368:Aged; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D005260:Female; D005269:Femur / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D016268:Internal Fixators; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D013314:Stress, Mechanical
keywords: Absolute stability; Lag screw; Locking plate; Osteosynthesis philosophy; Relative stability