title: Mechanical comparison between lengthened and short sacroiliac screws in sacral fracture fixation: a finite element analysis.
abstract: OBJECTIVE
  To compare the stability of lengthened sacroiliac screw and standard sacroiliac screw for the treatment of unilateral vertical sacral fractures; to provide reference for clinical applications.
  
  
  METHODS
  A finite element model of Tile type C pelvic ring injury (unilateral Denis type II fracture of the sacrum) was produced. The unilateral sacral fractures were fixed with lengthened sacroiliac screw and sacroiliac screw in six different types of models respectively. The translation and angle displacement of the superior surface of the sacrum (in standing position on both feet) were measured and compared.
  
  
  RESULTS
  The stability of one lengthened sacroiliac screw fixation in S1 or S2 segment is superior to that of one sacroiliac screw fixation in the same sacral segment. The stability of one lengthened sacroiliac screw fixation in S1 and S2 segments respectively is superior to that of one sacroiliac screw fixation in S1 and S2 segments respectively. The stability of one lengthened sacroiliac screw fixation in S1 and S2 segments respectively is superior to that of one lengthened sacroiliac screw fixation in S1 or S2 segment. The stability of one sacroiliac screw fixation in S1 and S2 segments respectively is markedly superior to that of one sacroiliac screw fixation in S1 or S2 segment. The vertical and rotational stability of lengthened sacroiliac screw fixation and sacroiliac screw fixation in S2 is superior to that of S1.
  
  
  CONCLUSIONS
  In a finite element model of type C pelvic ring disruption, S1 and S2 lengthened sacroiliac screws should be utilized for the fixation as regularly as possible and the most stable fixation is the combination of the lengthened sacroiliac screws of S1 and S2 segments. Even if lengthened sacroiliac screws cannot be systematically used due to specific conditions, one sacroiliac screw fixation in S1 and S2 segments respectively is recommended. No matter which kind of sacroiliac screw is used, if only one screw can be implanted, the fixation in S2 segment is more recommended than that in S1.
  
  
  METHODS
  Experimental study Level III.
authors.affiliation: Orthopaedics Department, Yantai Shan Hospital, 91#, Jiefang Road, Yantai 264008, PR China. nihaoedde@126.com
authors.forename: Y
authors.initials: Y
authors.lastname: Zhao
authors.forename: S
authors.initials: S
authors.lastname: Zhang
authors.forename: T
authors.initials: T
authors.lastname: Sun
authors.forename: D
authors.initials: D
authors.lastname: Wang
authors.forename: W
authors.initials: W
authors.lastname: Lian
authors.forename: J
authors.initials: J
authors.lastname: Tan
authors.forename: D
authors.initials: D
authors.lastname: Zou
authors.forename: Y
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D001863:Bone Screws; D005260:Female; D020342:Finite Element Analysis; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D017102:Fracture Healing / Q000502:physiology*; D006801:Humans; D008297:Male; D011379:Prognosis; D011474:Prosthesis Design; D012447:Sacrum / Q000293:injuries*; D016103:Spinal Fractures / Q000601:surgery*; D013314:Stress, Mechanical; D013718:Tensile Strength; D016896:Treatment Outcome
keywords: 3-Dimensional finite element; Pelvic ring disruption; Pelvis; Sacral fracture; Sacroiliac screw; Stability