Three-dimensional CT diagnosis of myositis ossificans of the sacrospinous ligament.

We present the case of a 4-year-old female with a complex fracture of the left hemipelvis who, on follow-up CT imaging, developed new ossific densities within the peripelvic soft tissues of the contralateral side. Three-dimensional surface reformations of the pelvis demonstrated myositis ossificans along the course of the right sacrospinous ligament, thus elucidating unsuspected ligamentous injury and implying prior instability.