title: Distal Ulna Fractures: A Biomechanical Comparison of Locking Versus Nonlocking Plating Constructs.
abstract: OBJECTIVE
  To determine the biomechanical properties of plating options for distal ulna fractures.
  
  
  METHODS
  Fourth-generation ulna artificial bones were osteotomized and fixed with 4 different constructs: 2 locking compression plates (a straight 2.7-mm plate and a 2.4-mm T-plate) with both nonlocking and locking screws. The artificial bones underwent nondestructive tests to determine construct stiffness in flexion/extension and lateral bending. The final testing consisted of cyclical loading in axial torsion until implant failure.
  
  
  RESULTS
  The straight plate fixation construct was significantly stiffer than the T-plate construct for both flexion/extension bending (P < 0.001) and radial/ulnar bending (P < 0.05). Nonlocking screws provided significantly stiffer fixation in flexion bending than locking screws (P < 0.05); however, no difference was found in extension bending. Conversely, locking screws were significantly stiffer in radial/ulnar bending than the nonlocking screws (P < 0.05). Failure under torsional cyclical loading was significantly different among constructs. The straight plate with nonlocking construct withstood the most half-cycles. The mechanisms of failure were unique to each type of fixation.
  
  
  CONCLUSIONS
  These results do not show any clear biomechanical advantage of locked plating for fractures of the distal ulna. The increased stiffness associated with locked plating likely contributes to earlier and more pronounced failure mechanisms under repetitive axial torsion.
authors.affiliation: McGill University, Division of Orthopedic Surgery, Montreal, Quebec, Canada.
authors.forename: Melissa
authors.initials: M
authors.lastname: Collins
authors.forename: Adam
authors.initials: A
authors.lastname: Hart
authors.forename: Jerod
authors.initials: J
authors.lastname: Hines
authors.forename: Thomas
authors.initials: T
authors.lastname: Steffen
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Harvey
authors.forename: Paul A
authors.initials: PA
authors.lastname: Martineau
mesh_terms: D001696:Biomechanical Phenomena; D001860:Bone Plates; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D008953:Models, Anatomic; D014458:Ulna Fractures / Q000503:physiopathology / Q000601:surgery*