Biomechanical comparison of sacroiliac screw techniques for unstable pelvic ring fractures.

Abstract

To determine the stiffness and strength of various sacroiliac screw fixations to compare different sacroiliac screw techniques. Randomized comparative study on embalmed human pelvises. In 12 specimens, we created a symphysiolysis and sacral fractures on both sides. Each of these 24 sacral fractures was fixed with 1 of the following methods: 1 sacroiliac screw in the vertebral body of S1, 2 screws convergingly in S1, or 1 screw in S1 and 1 in S2. On the left and right side of a pelvis, different techniques were used. The pubic symphysis was not stabilized. We measured the translation and rotation stiffness of the fixations and the load to failure using a 3-dimensional video system. The stiffness of the intact posterior pelvic ring was superior to any screw technique. Significant differences were found for the load to failure and rotation stiffness between the techniques with 2 screws and a single screw in S1. The techniques utilizing 2 screws showed no differences. Based on the results of this study, we can conclude that a second sacroiliac screw in completely unstable pelvic fractures increases rotation stiffness and improves the load to failure.