Anterior versus posterior provisional fixation in the unstable pelvis. A biomechanical comparison.

Pelvic ring injuries with associated hemorrhage often require provisional fixation to achieve tamponade. Biomechanics information regarding these provisional fixators is unknown. Six fresh-frozen cadaveric pelvic specimens were physiologically loaded, first intact and then after each of the following modifications: disrupted--unilateral superior and inferior rami osteotomies, ipsilateral anterior and posterior sacroiliac joint, and sacrospinous and sacrotuberous ligament disruption; disrupted and with placement of a Ganz pelvic resuscitation clamp; and disrupted and with placement of a simple anterior 2-bar external fixator. This injury resulted in significant motion at the disrupted rami and the injured sacroiliac joint, compared with the intact pelvic specimen. Motions at the superior ramus and injured sacroiliac joints were significantly (p < 0.05) greater than the intact specimen, with both the external fixator and the Ganz clamp. Motions at the superior ramus and injured sacroiliac joints were not significantly (p < 0.05) different when comparing the Ganz clamp to the external fixator. However, the anterior external fixator decreased motion to a greater degree at the disrupted rami, whereas the Ganz clamp decreased motion to a greater degree at the disrupted sacroiliac joint.