The interosseous sacroiliac ligament is the strongest ligament in the human body and the primary stabiliser of the sacroiliac joint, filling the posterior sacroiliac joint space deep to the posterior long dorsal sacroiliac ligament. Its massive, irregular bundles resist the enormous shear forces across the sacroiliac joint during walking and lifting. Its failure in high-energy pelvic ring disruptions allows sacroiliac joint diastasis that requires surgical fixation.
| Origin | Sacral tuberosity |
|---|---|
| Insertion | Iliac tuberosity |
| Actions | The strongest ligament in the body per unit area, resisting all motion at the sacroiliac joint, particularly nutation (anterior sacral rotation) and shear |
|---|
The interosseous SI ligament is the key structure in posterior pelvic ring stability. Its disruption is classified in the Young-Burgess classification of pelvic ring fractures as a laterally compressed, anteroposteriorly compressed, or vertical shear injury. Percutaneous sacroiliac joint screw fixation is the most common surgical method for posterior ring stabilisation, with screws passing through the sacral body near the interosseous ligament attachment.
Interosseous SI ligament failure in high-energy pelvic trauma producing posterior pelvic ring instability requiring percutaneous screw fixation through the sacroiliac joint.
