Threaded compression rods were placed between the posterior-superior spines as a 
means of posterior stabilization of pelvic fractures. To document the increase 
in sacroiliac stability afforded by this technique, biomechanical testing was 
performed. Malgaigne-type fractures with sacroiliac disruptions were created in 
four cadaver pelvises. The fractures were stabilized with anterior frames of the 
Slatis or Pittsburgh type and subjected to longitudinal and torsional loading 
patterns on an Instron machine. The anterior fixation was then augmented with 
threaded compression rods placed between the posterior-superior spines to 
compress the disrupted sacroiliac joints, and repeat testing was conducted. 
Anterior frames alone were found to provide little stabilization of the 
disrupted sacroiliac joints with either longitudinal or torsional loading. 
Markedly improved stabilization in both loading modes was achieved with 
posterior augmentation. Two typical cases are presented to demonstrate that 
posterior stabilization is as efficacious in clinical practice as in the 
biomechanics laboratory.