title: Internal fixation of dorsally comminuted fractures of the distal part of the radius: a biomechanical analysis of volar plate and intramedullary nail fracture stability.
abstract: BACKGROUND
  The purpose of the present study was to carry out biomechanical testing of "new generation" volar plates and an intramedullary nail.
  
  
  METHODS
  Four volar locking plates (Column Plate, VariAx distal radius, 2.4 mm-LCP and 3.5 mm-LCP) and the intramedullary nail, Targon-DR, were implanted in biomechanically validated artificial bones after simulation of a wedge osteotomy with total transection of the volar cortex to mimic a type 23 A3-fracture according to the AO-classification. Axial load (250 Newton [N]) and volar and dorsal bending loads (both 50 N) were applied. Axial load was increased to fixation failure. Gap motion was measured three-dimensionally directly at the fracture gap. The 3.5 mm-LCP was used for comparison as it currently represents an established locking implant that has been well tested biomechanically.
  
  
  RESULTS
  In this experimental setting, the 2.4 mm-LCP showed the lowest resistance under all three loading modi and, consequently, the highest level of motion at the osteotomy gap in comparison to all other implants (p < 0.05). Under axial loading, there were no significant differences between the other four implants. Under dorsal bending, the Targon-DR-nail and the VariAx-plate showed less gap displacement in comparison to the 3.5 mm-LCP (p < 0.05). Under volar bending, only the Targon-nail showed greater resistance than the 3.5 mm-LCP (p < 0.05) with no other significant differences between the Column Plate, the VariAx and the 3.5 mm-LCP.
  
  
  CONCLUSIONS
  In this experimental setting, all "new generation" implants for distal radius fractures with the exception of the 2.4 mm-LCP showed identical or higher stability compared to the 3.5 mm-LCP. The 2.4 mm-LCP showed the lowest resistance and this must be taken into consideration when planning postoperative functional therapy.
authors: Department of Orthopaedic and Trauma Surgery, Albert-Ludwigs-University Freiburg, Hugstetter Str. 55, 79106 Freiburg, Germany. lukas.konstantinidis@uniklinik-freiburg.de
authors: Lukas
authors: L
authors: Konstantinidis
authors: Peter
authors: P
authors: Helwig
authors: Judith
authors: J
authors: Seifert
authors: Anja
authors: A
authors: Hirschmüller
authors: Emmanouil
authors: E
authors: Liodakis
authors: Norbert Paul
authors: NP
authors: Südkamp
authors: Michael
authors: M
authors: Oberst
mesh_terms: D001696:Biomechanical Phenomena; D001858:Bone Nails; D001860:Bone Plates; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation; D018460:Fractures, Comminuted / Q000601:surgery*; D006801:Humans; D011474:Prosthesis Design; D011885:Radius Fractures / Q000503:physiopathology* / Q000601:surgery*