title: Biomechanical stability of a supra-acetabular pedicle screw internal fixation device (INFIX) vs external fixation and plates for vertically unstable pelvic fractures.
abstract: BACKGROUND
  We have recently developed a subcutaneous anterior pelvic fixation technique (INFIX). This internal fixator permits patients to sit, roll over in bed and lie on their sides without the cumbersome external appliances or their complications. The purpose of this study was to evaluate the biomechanical stability of this novel supraacetabular pedicle screw internal fixation construct (INFIX) and compare it to standard internal fixation and external fixation techniques in a single stance pelvic fracture model.
  
  
  METHODS
  Nine synthetic pelves with a simulated anterior posterior compression type III injury were placed into three groups (External Fixator, INFIX and Internal Fixation). Displacement, total axial stiffness, and the stiffness at the pubic symphysis and SI joint were calculated. Displacement and stiffness were compared by ANOVA with a Bonferroni adjustment for multiple comparisons
  
  
  RESULTS
  The mean displacement at the pubic symphysis was 20, 9 and 0.8 mm for external fixation, INFIX and internal fixation, respectively. Plate fixation was significantly stiffer than the INFIX and external Fixator (P = 0.01) at the symphysis pubis. The INFIX device was significantly stiffer than external fixation (P = 0.017) at the symphysis pubis. There was no significant difference in SI joint displacement between any of the groups.
  
  
  CONCLUSIONS
  Anterior plate fixation is stiffer than both the INFIX and external fixation in single stance pelvic fracture model. The INFIX was stiffer than external fixation for both overall axial stiffness, and stiffness at the pubic symphysis. Combined with the presumed benefit of minimizing the complications associated with external fixation, the INFIX may be a more preferable option for temporary anterior pelvic fixation in situations where external fixation may have otherwise been used.
authors.affiliation: Detroit Receiving Hospital, 4201 St Antoine St, Detroit, MI 48201, USA.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Vigdorchik
authors.forename: Amanda O
authors.initials: AO
authors.lastname: Esquivel
authors.forename: Xin
authors.initials: X
authors.lastname: Jin
authors.forename: King H
authors.initials: KH
authors.lastname: Yang
authors.forename: Ndidi A
authors.initials: NA
authors.lastname: Onwudiwe
authors.forename: Rahul
authors.initials: R
authors.lastname: Vaidya
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D001860:Bone Plates / Q000592:standards*; D001863:Bone Screws / Q000592:standards*; D016267:External Fixators / Q000592:standards*; D005593:Fracture Fixation, Internal / Q000295:instrumentation / Q000592:standards; D050723:Fractures, Bone / Q000601:surgery*; D006801:Humans; D016268:Internal Fixators / Q000592:standards*; D010384:Pelvic Bones / Q000293:injuries / Q000601:surgery*; D016474:Weight-Bearing / Q000502:physiology