title: Biomechanical analysis of anterior ring fixation of the ramus in type C pelvis fractures.
abstract: OBJECTIVE
  This biomechanical study compared the stability of four different ramus fracture fixation methods for Type C pelvic ring injuries in the absence of posterior fixation.
  
  
  METHODS
  A 5-mm vertical osteotomy of the mid-superior and inferior pubic ramus was created in 12 synthetic pelvic models. Four surgical constructs were compared: (1) two-pin AIIS external fixation, (2) 3.5-mm reconstruction plating, (3) bicortical, fully threaded 3.5-mm, and (4) 6.5-mm pubic ramus screws. Specimens were tested in a simulated one-legged stance on a hemiarthroplasty implant in three stages: (1) no applied load, (2) application of the loading fixture preload to the sacrum (6N), and (3) following six cycles of a 250N load. Stability was assessed based on resultant displacement of the fracture sites at the superior ramus and the anterior sacroiliac joint.
  
  
  RESULTS
  The bicortical, fully threaded 6.5-mm pubic ramus screw provided the most stable ramus fracture fixation (0.5 ± 0.4 mm) displacement under load and was the only construct to finish testing without gross posterior pelvic disruption. Plate constructs finished the final loading stage with only a small increase (3.1 ± 2.3 mm) in ramus fracture gap size, but had significant displacement at the SI joint (>20 mm). 3.5-mm screw constructs had 1.6 ± 0.7 mm of ramus displacement in the preload stage, but had complete posterior pelvic disruption (>20 mm) that prevented further testing. External fixation was unstable at the ramus and sacroiliac sites in the initial setup.
  
  
  CONCLUSIONS
  The bicortical, fully threaded 6.5-mm pubic ramus screw was the only anterior fixation construct tested that controlled motion at both the anterior and posterior pelvic rings in the absence of posterior fixation.
authors.affiliation: Orthopaedic Biomechanics Laboratory, Sunnybrook Research Institute, 2075 Bayview Ave., Room S611, Toronto, M4N 3M5, ON, Canada.
authors.forename: S
authors.identifier: http://orcid.org/0000-0002-8464-3032
authors.initials: S
authors.lastname: McLachlin
authors.affiliation: Division of Orthopaedic Surgery, University of Toronto, Toronto, ON, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Lesieur
authors.affiliation: Division of Orthopaedic Surgery, University of Toronto, Toronto, ON, Canada.
authors.forename: D
authors.initials: D
authors.lastname: Stephen
authors.affiliation: Division of Orthopaedic Surgery, University of Toronto, Toronto, ON, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Kreder
authors.affiliation: Orthopaedic Biomechanics Laboratory, Sunnybrook Research Institute, 2075 Bayview Ave., Room S611, Toronto, M4N 3M5, ON, Canada. cari.whyne@sunnybrook.ca.|Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada. cari.whyne@sunnybrook.ca.|Division of Orthopaedic Surgery, University of Toronto, Toronto, ON, Canada. cari.whyne@sunnybrook.ca.
authors.forename: C
authors.initials: C
authors.lastname: Whyne
mesh_terms: D001696:Biomechanical Phenomena; D001860:Bone Plates; D050723:Fractures, Bone / Q000601:surgery*; D006801:Humans; D008953:Models, Anatomic; D010384:Pelvic Bones / Q000293:injuries* / Q000601:surgery
keywords: Anterior ring fixation; Biomechanical stability; Pelvic fracture