title: Influence of screw diameter and number on reduction loss after plating of distal radius fractures.
abstract: BACKGROUND
  The current options for plate-screw combinations in volar locking distal radius plates used for the treatment of distal radius fractures are either plates with a single distal screw row or plates with multiple distal screw rows. Additionally, the screws themselves may have either fixed angle locking or polyaxial locking mechanisms. To date, there is no evidence or consensus regarding the optimal plate-screw combination. The aim of this study was to assess the biomechanical behaviour of different plate-screw combinations with respect to total distal screw number, number of distal screw rows and screw projection surface area of the most distal row.
  
  
  METHODS
  Biomechanical study to assess six different plating configurations in five different volar locking plate models in a Sawbone distal radius fracture model. The specimens were loaded with 800 Newton loads for 2.000 cycles at 1 Hz. After cyclic loading, load-to-failure testing was performed.
  
  
  RESULTS
  With cyclical testing, there was a significant and positive correlation between rigidity and a greater projection area of the most distal screws. Dorsal tilting was significantly more pronounced in plate models with a lesser projection area of the most distal screws and a smaller number of distal screws. With load-to-failure testing, there was a significant increase in rigidity with increasing screw projection area of the most distal row and total number of distal screws.
  
  
  CONCLUSIONS
  Additional distal screw rows in volar locking distal radius plates might not add substantially to resistance against loss of reduction in the post-operative period.
authors.affiliation: Department of Orthopaedic Surgery, Mackay Base Hospital, Mackay, Queensland, Australia. drobo@aon.at
authors.forename: Herwig
authors.initials: H
authors.lastname: Drobetz
authors.forename: Michael
authors.initials: M
authors.lastname: Schueller
authors.forename: Elmar Karl
authors.initials: EK
authors.lastname: Tschegg
authors.forename: Clare
authors.initials: C
authors.lastname: Heal
authors.forename: Heinz
authors.initials: H
authors.lastname: Redl
authors.forename: Reinhold
authors.initials: R
authors.lastname: Muller
mesh_terms: D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D008422:Materials Testing; D015999:Multivariate Analysis; D011885:Radius Fractures / Q000601:surgery*; D012044:Regression Analysis