title: Locked versus standard unlocked plating of the symphysis pubis in a Type-C pelvic injury: a cadaver biomechanical study.
abstract: BACKGROUND
  The benefits of locked plating for pubic symphyseal disruption have not been established. The purpose of this biomechanical study was to determine whether locked plating offers any advantage over conventional unlocked plating of the pubic symphysis in the vertically unstable, Type-C pelvic injury.
  
  
  METHODS
  In each of eight embalmed cadaver pelvis specimens, sectioning of the pubic symphysis in conjunction with a unilateral release of the sacroiliac, sacrospinous, and sacrotuberous ligaments and pelvic floor was performed to simulate a vertically unstable Type-C (Orthopaedic Trauma Association 61-C1.2) pelvic injury. The disrupted SI joint was then reduced and fixed using two 6.5mm cannulated screws inserted into the S1 body. Using a six-hole 3.5mm plate specifically designed for the symphysis pubis having both locked and unlocked capability, four pelvises were fixed with locked screws and four pelvises were fixed with standard unlocked bicortical screws. Both groups were similar based on a dual-emission X-ray absorptiometry evaluation (P=0.69). Each pelvis was then mounted on a servohydraulic materials-testing apparatus using a bilateral stance model to mainly stress the symphyseal fixation and was cycled up to 1 million cycles or failure, whichever occurred first.
  
  
  RESULTS
  Five specimens experienced failure at the jig mounting/S1 vertebral body interface, occurring between 360,000 and 715,000 cycles. Frank failure of the anterior or posterior instrumentation did not occur. However, end-trialing diastasis of the initial pubic symphysis reduction was found in all pelvises. There were no differences between the groups with respect to this loss of symphyseal reduction (P=0.69) or average cycles to failure (P=1.0).
  
  
  CONCLUSIONS
  Pubic symphyseal locked plating does not appear to offer any advantage over standard unlocked plating for a Type-C (OTA 61-C1.2) pelvic ring injury.
authors: Department of Orthopaedic Surgery, Saint Louis University School of Medicine, 3635 Vista Avenue, 7th Floor Desloge Towers, St. Louis 63110, Missouri, United States; Department of Biomedical Engineering, Parks College of Engineering, Aviation and Technology, Saint Louis University, 3450 Lindell Boulevard, St. Louis 63103, Missouri, United States. Electronic address: moedbr@slu.edu.
authors: Berton R
authors: BR
authors: Moed
authors: Department of Orthopaedic Surgery, Saint Louis University School of Medicine, 3635 Vista Avenue, 7th Floor Desloge Towers, St. Louis 63110, Missouri, United States.
authors: Christopher P
authors: CP
authors: O'Boynick
authors: Department of Orthopaedic Surgery, Saint Louis University School of Medicine, 3635 Vista Avenue, 7th Floor Desloge Towers, St. Louis 63110, Missouri, United States; Department of Biomedical Engineering, Parks College of Engineering, Aviation and Technology, Saint Louis University, 3450 Lindell Boulevard, St. Louis 63103, Missouri, United States.
authors: J Gary
authors: JG
authors: Bledsoe
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D001860:Bone Plates; D002102:Cadaver; D019544:Equipment Failure Analysis; D005260:Female; D005593:Fracture Fixation, Internal; D050723:Fractures, Bone / Q000601:surgery*; D006801:Humans; D008297:Male; D010388:Pelvis / Q000293:injuries / Q000473:pathology* / Q000601:surgery*; D011631:Pubic Symphysis / Q000293:injuries / Q000601:surgery*
keywords: Fixation failure; Locked plating; Symphyseal locked plating