title: Anterior internal fixator versus a femoral distractor and external fixation for sacroiliac joint compression and single stance gait testing: a mechanical study in synthetic bone.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the biomechanical stability and compressive forces across the sacroiliac (SI) joint of an anterior internal fixator compared to the femoral distractor and external fixator for vertically unstable pelvic fractures.
  
  
  METHODS
  Five composite pelvises with a simulated APC type III injury fixed with a femoral distractor, external fixator, or anterior internal fixator were tested. A pressure-sensitive film (Tekscan) was placed in the disrupted SI joint recording the magnitude of force. Then, in a single-leg stance model (Instron machine), a load was applied through the sacrum. We recorded displacement at the pubic symphysis and SI joint using high-speed video. Peak load and displacement were measured, and axial stiffness was calculated. Values were compared using a Student's t-test (p < 0.05).
  
  
  RESULTS
  The SI joint was compressed significantly (p < 0.001) more using the anterior internal fixator (18.9 N) and femoral distractor (18.6 N) than the two-pin external fixator (2.5 N). There was no significant difference between the anterior internal fixator and the femoral distractor in displacement at the SI joint. The pubic symphysis displaced less with the femoral distractor than the anterior internal fixator (5.5 mm vs. 4.1 mm; p < 0.05).
  
  
  CONCLUSIONS
  The anterior pedicle screw internal fixator allows for indirect compression across the sacroiliac joint that is superior to two-pin external fixation and comparable to the femoral distractor. The anterior internal fixator may be an option for temporary anterior pelvic fixation in situations where external fixation or the femoral distractor have otherwise been used.
authors: Orthopaedic Surgery, Detroit Medical Center, 4D4 University Health Center, Detroit Receiving Hospital, Wayne State University, 4201 St. Antoine Blvd., Detroit, MI 48201, USA. JVigdorchik@gmail.com
authors: Jonathan M
authors: JM
authors: Vigdorchik
authors: Amanda O
authors: AO
authors: Esquivel
authors: Xin
authors: X
authors: Jin
authors: King H
authors: KH
authors: Yang
authors: Rahul
authors: R
authors: Vaidya
mesh_terms: D001696:Biomechanical Phenomena; D001858:Bone Nails; D001863:Bone Screws; D016267:External Fixators; D005592:Fracture Fixation / Q000295:instrumentation* / Q000379:methods; D050723:Fractures, Bone / Q000000981:diagnostic imaging / Q000601:surgery*; D005684:Gait / Q000502:physiology*; D006801:Humans; D016268:Internal Fixators; D008422:Materials Testing; D010384:Pelvic Bones / Q000000981:diagnostic imaging / Q000293:injuries / Q000601:surgery; D011312:Pressure; D019736:Prostheses and Implants; D011859:Radiography; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging / Q000293:injuries / Q000601:surgery*; D016896:Treatment Outcome
references: Injury. 2004 Jul;35(7):671-7
references: 15203307
references: Acta Orthop. 2007 Oct;78(5):648-53
references: 17966024
references: J Orthop Trauma. 2004 Oct;18(9):589-95
references: 15448446
references: J Orthop Trauma. 2002 Feb;16(2):99-103
references: 11818804
references: J Biomech Eng. 2007 Aug;129(4):487-93
references: 17655469
references: J Orthop Trauma. 1994 Dec;8(6):476-82
references: 7869161
references: J Trauma. 1990 Jul;30(7):848-56
references: 2381002
references: J Orthop Trauma. 1993;7(2):107-17
references: 8459294
references: J Biomech. 2008 Nov 14;41(15):3282-4
references: 18829031
references: Proc Inst Mech Eng H. 2008 Nov;222(8):1175-83
references: 19143412
references: J Orthop Trauma. 2007 Apr;21(4):269-73
references: 17414555
references: Injury. 2005 May;36(5):599-604
references: 15826617
references: J Trauma. 1993 Nov;35(5):671-5; discussion 676-7
references: 8230327
references: J Orthop Trauma. 1996;10(8):517-22
references: 8915911
references: Injury. 1995 Mar;26(2):75-80
references: 7721471
references: J Trauma. 2005 May;58(5):1029-34
references: 15920420
references: J Orthop Trauma. 2004 Mar;18(3):138-43
references: 15091266
references: J Orthop Trauma. 1997 Nov;11(8):590-3
references: 9415866
references: J Orthop Trauma. 2007 Aug;21(7):435-41
references: 17762472
references: Clin Orthop Relat Res. 2012 Aug;470(8):2124-31
references: 22219004
references: J Orthop Trauma. 2012 Jan;26(1):1-8
references: 22048183
references: Orthopade. 1992 Nov;21(6):413-21
references: 1475127
references: Proc Inst Mech Eng H. 2008 Jul;222(5):611-6
references: 18756680