title: Biomechanical comparison of a transiliac internal fixator and two iliosacral screws in transforaminal sacral fractures: a finite element analysis.
abstract: OBJECTIVE
  Vertically unstable sacral transforaminal fractures can be stabilized with a transiliac internal fixator (TIFI) or two iliosacral screws (IS). This study was designed to compare stiffness between TIFI and IS.
  
  
  METHODS
  Using CT images finite element model of the pelvis was developed. Denis II type fracture was simulated and fixed either with TIFI or two IS. The sacral base was loaded vertically (250-500 N), displacement magnitudes on medial and lateral fracture surface and the maximum bone stress were calculated. The intact pelvis was used as a reference. Stiffness was determined by linear regression of load and displacement, computed stiffness ratio %. The von Mises stress was expressed as % ratio, evaluation of colour mapping was made.
  
  
  RESULTS
  The mean stiffness ratio medially in TIFI was 75.22%, in IS 46.54% (p = 0.00005), laterally in TIFI 57.88%, in IS 44.74% ( p = 0.03996). The von Mises stress ratio of TIFI was 139.27%, of IS 565.35% ( p < 0.00001).
  
  
  CONCLUSIONS
  Significantly higher stiffness and lower stress were found in TIFI model. TIFI provides a lower risk of over-compression of the fracture line in comparison with IS. TIFI thus exhibits superiority for fixation of trans- foraminal fractures, particularly with comminutive zone.
authors.affiliation: Department of Orthopaedics and Traumatology, Faculty of Medicine of Charles University and Faculty Hospital in Plzeň, Czech Republic.|Department of Mechanics, Faculty of Applied Sciences and New Technologies for Information Society of West Bohemian University in Plzeň, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Salášek
authors.affiliation: Department of Mechanics, Faculty of Applied Sciences and New Technologies for Information Society of West Bohemian University in Plzeň, Czech Republic.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Jansová
authors.affiliation: Department of Mechanics, Faculty of Applied Sciences and New Technologies for Information Society of West Bohemian University in Plzeň, Czech Republic.
authors.forename: Jiří
authors.initials: J
authors.lastname: Křen
authors.affiliation: Department of Orthopaedics and Traumatology, Faculty of Medicine of Charles University and Faculty Hospital in Plzeň, Czech Republic.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Pavelka
authors.affiliation: Department of Orthopaedics and Traumatology, Faculty of Medicine of Charles University and Faculty Hospital in Plzeň, Czech Republic.|Department of Mechanics, Faculty of Applied Sciences and New Technologies for Information Society of West Bohemian University in Plzeň, Czech Republic.
authors.forename: Drahomíra
authors.initials: D
authors.lastname: Weisová
mesh_terms: D000063:Accidents, Traffic; D001696:Biomechanical Phenomena; D001863:Bone Screws; D019245:Compressive Strength; D005260:Female; D020342:Finite Element Analysis; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D050723:Fractures, Bone / Q000601:surgery*; D006801:Humans; D007085:Ilium / Q000601:surgery; D021621:Imaging, Three-Dimensional; D016268:Internal Fixators; D016014:Linear Models; D008422:Materials Testing; D015233:Models, Statistical; D012044:Regression Analysis; D012447:Sacrum / Q000601:surgery; D016103:Spinal Fractures / Q000601:surgery*; D014057:Tomography, X-Ray Computed