Experimental study of the sacroiliac joint micromotion in pelvic disruption

Objective: To measure the sacroiliac (SI) joint micromotion when different ligamentous lesions are created to simulate various degrees of pelvic anteroposterior compression injury. Design: Cadaveric study. Materials and Method: Six SI joints were studied using a special device that made it possible to vary up to 310 N the loads applied on the ischial tuberosity and to measure simultaneously the SI micromotion. Results: SI micromotion increases when the sacrospinous and sacrotuberous ligaments, and even more when the interosseous ligaments, have been sectioned off. In these cases, the stability of the SI joint is not restored by an isolated pubic fixation. Conclusion: This microinstability of the SI joint could contribute to the pain and arthritic changes sometimes observed in patients after anteroposterior compression injury. These experimental results could justify a larger spectrum of indications of SI joint fixation, but this should be confirmed by clinical study.