title: Mechanical testing of a device for subcutaneous internal anterior pelvic ring fixation versus external pelvic ring fixation.
abstract: BACKGROUND
  Although useful in the emergency treatment of pelvic ring injuries, external fixation is associated with pin tract infections, the patient's limited mobility and a restricted surgical accessibility to the lower abdomen. In this study, the mechanical stability of a subcutaneous internal anterior fixation (SIAF) system is investigated.
  
  
  METHODS
  A standard external fixation and a SIAF system were tested on pairs of Polyoxymethylene testing cylinders using a universal testing machine. Each specimen was subjected to a total of 2000 consecutive cyclic loadings at 1 Hz with sinusoidal lateral compression/distraction (+/-50 N) and torque (+/- 0.5 Nm) loading alternating every 200 cycles. Translational and rotational stiffness were determined at 100, 300, 500, 700 and 900 cycles.
  
  
  RESULTS
  There was no significant difference in translational stiffness between the SIAF and the standard external fixation when compared at 500 (p = .089), 700 (p = .081), and 900 (p = .266) cycles. Rotational stiffness observed for the SIAF was about 50 percent higher than the standard external fixation at 300 (p = .005), 500 (p = .020), and 900 (p = .005) cycles. No loosening or failure of the rod-pin/rod-screw interfaces was seen.
  
  
  CONCLUSIONS
  In comparison with the standard external fixation system, the tested device for subcutaneous internal anterior fixation (SIAF) in vitro has similar translational and superior rotational stiffness.
authors.affiliation: Division of Trauma Surgery, University of Zurich, Raemistrasse 100, Zurich 8091, Switzerland. georg.osterhoff@usz.ch.
authors.forename: Georg
authors.initials: G
authors.lastname: Osterhoff
authors.forename: Simon
authors.initials: S
authors.lastname: Tiziani
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Ferguson
authors.forename: Gregor
authors.initials: G
authors.lastname: Spreiter
authors.forename: Max J
authors.initials: MJ
authors.lastname: Scheyerer
authors.forename: Gian-Leza
authors.initials: GL
authors.lastname: Spinas
authors.forename: Guido A
authors.initials: GA
authors.lastname: Wanner
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Simmen
authors.forename: Clément M L
authors.initials: CM
authors.lastname: Werner
mesh_terms: D001858:Bone Nails; D001863:Bone Screws; D019245:Compressive Strength; D006801:Humans; D066298:In Vitro Techniques; D016268:Internal Fixators; D008422:Materials Testing; D008953:Models, Anatomic; D056888:Patient Positioning / Q000009:adverse effects; D010384:Pelvic Bones / Q000293:injuries / Q000601:surgery; D018583:Pliability; D013314:Stress, Mechanical; D054159:Torsion, Mechanical; D016474:Weight-Bearing