title: Biomechanical comparison of parallel versus 90-90 plating of bicolumn distal humerus fractures with intra-articular comminution.
abstract: OBJECTIVE
  To compare the biomechanical properties of 90-90 versus mediolateral parallel plating of C-3 bicolumn distal humerus fractures.
  
  
  METHODS
  We created intra-articular AO/Orthopaedic Trauma Association C-3 bicolumn fractures in 10 fresh-frozen matched pairs of cadaveric elbows. We determined bone mineral density of the metaphyseal region with dual-energy x-ray absorptiometry. The matched pairs of elbows were randomly assigned to either 90-90 or parallel plate fixation. We tested anteroposterior displacement at a rate of 0.5 mm/s to a maximum load of ± 100 N for both the articular and entire distal humerus segments. We tested torsional stability at a displacement rate of 0.1 Hz to a maximum torque of ± 2.5 Nm. After cyclical testing, we loaded the specimens in torsion to failure.
  
  
  RESULTS
  There was no significant difference in the bone density of the paired specimens. Compared with parallel fixation, 90-90 plate fixation had significantly greater torque to failure load. Both plating constructs were equally sensitive to bone density. Both techniques had the same mode of failure in torsion, a spiral fracture extending from the medial plate at the metaphyseal-diaphyseal junction. There was no significant difference in the stiffness of fixation of the articular fragment or the entire distal segment in anteroposterior loading.
  
  
  CONCLUSIONS
  This study demonstrated that 90-90 and parallel plating had comparable biomechanical properties for fixation of comminuted intra-articular distal humerus fractures, and that 90-90 plating had greater resistance to torsional loading.
authors.affiliation: Department of Orthopaedic Surgery, Warren Alpert Medical School, Brown University, Providence, RI 02903, USA. cgotmd@gmail.com
authors.forename: Christopher
authors.initials: C
authors.lastname: Got
authors.forename: John
authors.initials: J
authors.lastname: Shuck
authors.forename: Alison
authors.initials: A
authors.lastname: Biercevicz
authors.forename: Dave
authors.initials: D
authors.lastname: Paller
authors.forename: Mary
authors.initials: M
authors.lastname: Mulcahey
authors.forename: Matthew
authors.initials: M
authors.lastname: Zimmermann
authors.forename: Theodore
authors.initials: T
authors.lastname: Blaine
authors.forename: Andrew
authors.initials: A
authors.lastname: Green
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D001696:Biomechanical Phenomena; D015519:Bone Density; D001860:Bone Plates; D002102:Cadaver; D005260:Female; D005593:Fracture Fixation, Internal / Q000379:methods*; D018460:Fractures, Comminuted / Q000601:surgery*; D006801:Humans; D006810:Humeral Fractures / Q000601:surgery*; D057072:Intra-Articular Fractures / Q000601:surgery*; D008297:Male; D008875:Middle Aged