title: The mechanical stability of extra-articular distal radius fractures with respect to the number of screws securing the distal fragment.
abstract: OBJECTIVE
  The treatment of distal radius fractures with volar locked plating (VLP) has gained popularity. Many different designs and sizes of plates afford a wide variety of configurations of locking screws that can be placed into the distal fracture fragment. The purpose of this study was to determine whether using half of the distal locking screws decreased stability when compared with using all possible distal locking screws with 4 different VLP systems.
  
  
  METHODS
  Twenty-four identical synthetic distal radius sawbone models were instrumented with 1 of 4 designs of VLP devices over a standardized dorsal wedge osteotomy to simulate a dorsally comminuted, extra-articular distal radius fracture. Distal locking screws were placed in varying configurations. Six radii per plate model with different screw configurations then underwent axial loading, volar bending, and dorsal bending using a servohydraulic machine. Distal fragment displacement was recorded using a differential variable reluctance transducer.
  
  
  RESULTS
  There was no significant difference in fracture fragment displacement when using half of the distal locking screw set compared with using the full screw set. Mean differences in displacement between half and full screws were less than 0.1 mm. All configurations had the greatest magnitude of displacement during axial loading. Mean displacement was less in plates containing 2 rows of distal locking screws (-0.4 mm) compared with plates containing 1 row (-0.6 mm).
  
  
  CONCLUSIONS
  Using half of the distal locking screws in VLP in an extra-articular, nonosteoporotic distal radial fracture model with noncyclical, nondestructive loading does not decrease construct stability compared with using all of the screws. Not filling all holes in VLP is more cost effective and does not sacrifice plate stiffness or construct stability. Plates with 2 rows of distal locking screws create more stable fixation than plates with 1 row of distal locking screws.
authors.affiliation: Vanderbilt Orthopaedic Institute and the Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN 37232-8774, USA. samuel.n.crosby@vanderbilt.edu
authors.forename: Samuel N
authors.initials: SN
authors.lastname: Crosby
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Fletcher
authors.forename: Erwin R
authors.initials: ER
authors.lastname: Yap
authors.forename: Donald H
authors.initials: DH
authors.lastname: Lee
mesh_terms: D001860:Bone Plates; D001863:Bone Screws; D004867:Equipment Design; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D018460:Fractures, Comminuted / Q000601:surgery; D006801:Humans; D008422:Materials Testing; D011885:Radius Fractures / Q000503:physiopathology* / Q000601:surgery*