title: Multidirectional volar fixed-angle plating using cancellous locking screws for distal radius fractures--evaluation of three screw configurations in an extra-articular fracture model.
abstract: BACKGROUND
  Volar fixed-angle plating is a popular treatment for unstable distal radius fractures. Despite the availability of plating systems for treating distal radius fractures, little is known about the mechanical properties of multidirectional fixed-angle plates. The aim of this study was to compare the primary fixation stability of three possible screw configurations in a distal extra-articular fracture model using a multidirectional fixed-angle plate with metaphyseal cancellous screws distally.
  
  
  METHODS
  Eighteen Sawbones radii (Sawbones, Sweden, model# 1027) were used to simulate an extra-articular distal radius fracture according to AO/OTA 23 A3. Plates were fixed to the shaft with one non-locking screw in the oval hole and two locking screws as recommended by the manufacturer. Three groups (n = 6) were defined by screw configuration in the distal metaphyseal fragment: Group 1: distal row of screws only; Group 2: 2 rows of screws, parallel insertion; Group 3: 2 rows of screws, proximal screws inserted with 30° of inclination. Specimens underwent mechanical testing under axial compression within the elastic range and load controlled between 20 N and 200 N at a rate of 40 N/s. Axial stiffness and type of construct failure were recorded.
  
  
  RESULTS
  There was no difference regarding axial stiffness between the three groups. In every specimen, failure of the Sawbone-implant-construct occurred as plastic bending of the volar titanium plate when the dorsal wedge was closed.
  
  
  CONCLUSIONS
  Considering the limitations of the study, the recommendation to use two rows of screws or to place screws in the proximal metaphyseal row with inclination cannot be supported by our mechanical data.
authors.affiliation: Lorenz Boehler Trauma Hospital, Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Cluster for Tissue Regeneration, Vienna, Austria. patrick.weninger@gmx.net
authors.forename: Patrick
authors.initials: P
authors.lastname: Weninger
authors.forename: Enrico
authors.initials: E
authors.lastname: Dall'Ara
authors.forename: Herwig
authors.initials: H
authors.lastname: Drobetz
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Nemec
authors.forename: Markus
authors.initials: M
authors.lastname: Figl
authors.forename: Heinz
authors.initials: H
authors.lastname: Redl
authors.forename: Harald
authors.initials: H
authors.lastname: Hertz
authors.forename: Philippe
authors.initials: P
authors.lastname: Zysset
mesh_terms: D040761:Biomimetic Materials; D001860:Bone Plates; D001863:Bone Screws; D019544:Equipment Failure Analysis; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D011474:Prosthesis Design; D011885:Radius Fractures / Q000175:diagnosis / Q000601:surgery*; D016896:Treatment Outcome; D014954:Wrist Injuries / Q000175:diagnosis / Q000601:surgery*