title: Biomechanical comparison of two different periarticular plating systems for stabilization of complex distal humerus fractures.
abstract: BACKGROUND
  Complex intra-articular distal humerus fractures are relatively uncommon injuries but are fraught with poor outcomes such as malunion, elbow stiffness and deformity. Various types of internal fixation screw-plate constructs have been developed to improve fixation. Specifically, a 90 degrees offset periarticular system lowers the profile on the lateral epicondyle, yet it is unclear how this design compares to other plate constructs. This study compared the mechanical stiffness and plate surface strains between two types of constructs for stabilization of complex distal humerus fractures.
  
  
  METHODS
  Identical bi-columnar segmental intra-articular fractures were created in ten epoxy composite left humeri. Models were randomly assigned to two groups (n=5/group) with either parallel plates or perpendicular plates. Rosette strain gages were placed at the most distal possible space on the lateral plate for both constructs. Models were mechanically tested with estimates of physiologic loads in flexion, extension, varus, valgus axial compression and axial torsion. Data for mechanical stiffness, transverse plate strain and longitudinal plate strain were compared with a one-way ANOVA (P<0.05).
  
  
  RESULTS
  There was no statistical difference in stiffness in any direction. The longitudinal strain for the 90 degrees construct was significantly lower in axial compression. The 180 degrees system demonstrated significantly lower transverse strains during axial torsion.
  
  
  CONCLUSIONS
  Both systems demonstrated similar mechanical stiffness theoretically providing similar fracture stabilization. Plate strain differences may affect fragment position, but it is unclear how much plate loading occurs in vivo. Surgeon experience and preference may dictate the choice of a plate construct for this fracture configuration.
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Diego, San Diego, CA 92123-4282, United States.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Schwartz
authors.forename: Richard
authors.initials: R
authors.lastname: Oka
authors.forename: Tim
authors.initials: T
authors.lastname: Odell
authors.forename: Andrew
authors.initials: A
authors.lastname: Mahar
mesh_terms: D001696:Biomechanical Phenomena / Q000379:methods; D001860:Bone Plates; D019245:Compressive Strength; D004548:Elasticity; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D006810:Humeral Fractures / Q000503:physiopathology* / Q000601:surgery*; D007595:Joint Prosthesis; D013314:Stress, Mechanical; D016896:Treatment Outcome