Determination of pelvic ring stability: a new technique using a composite hemi-pelvis.

Traumatic disruption of the pelvic ring caused by high-energy impact is associated with significant mortality and morbidity. A variety of fixation techniques have been developed for treating these injuries with the main aims of restoring the stability of the pelvic ring and promoting recovery of normal function. The stability of fixation of these techniques is often analysed by cadaveric studies, which can introduce high variability into the results and have small sample numbers. This study presents a new method that uses a composite hemi-pelvis to enable stabilization of the pelvic ring to be accurately determined. The pelvis was loaded cyclically to simulate walking conditions and to assess the stability of the fixation, which was measured using a displacement transducer that monitors the motion of the pelvis in six degrees of freedom. The motions measured showed comparable results with previously published cadaveric studies. This reproducible method of testing with a hemi-pelvis composite model and rig allows valid analysis of pubic symphysis implants, obviating the difficulties of performing a cadaveric study.