Biomechanical Analysis of a Modified Triangular Osteosynthesis Technique for Treatment of Spinopelvic Dissociation.

Objectives: The purpose of this study was to evaluate the biomechanical stability of a modified triangular osteosynthesis construct with S1 pedicle screws compared with other described lumbopelvic fixation constructs in a U-type sacral fracture model.

Methods: U-type sacral fractures were created in validated fourth-generation spinopelvic models. Four different constructs were cyclically loaded with displacement measured in all planes: (1) bilateral L5 pedicle screws with rods attached to iliac bolts, (2) bilateral L5 and S1 pedicle screws with rods attached to iliac bolts, (3) bilateral L5 pedicle screws with rods attached to iliac bolts with a transsacral-transiliac screw, and (4) bilateral L5 and S1 pedicle screws with rods attached to iliac bolts with a transsacral-transiliac screw.

Results: The bilateral L5 and S1 pedicle screws with rods attached to iliac bolts with a transsacral-transiliac screw construct had significantly decreased horizontal, vertical, and angular displacement compared with all other constructs.

Conclusions: From a biomechanical perspective, a modified triangular osteosynthesis construct with S1 pedicle screws improves stability in fixation of U-type sacral fractures.