Pelvic fractures are divided into four anatomic types. Type IV fractures constitute approximately 20% of pelvic fractures and involve the acetabulum. The mechanism of injury is a force applied to the flexed hip. Type I fractures are stable pelvic fractures with no break in the pelvic ring, for example, a transverse sacral fracture. Type II fractures have a single break in the pelvic ring, such as a vertical fracture of the ileum parallel to the sacroiliac (SI) joint. Both type I and type II are stable fractures. Type III fractures (double break in the pelvic ring) are severe, unstable, and are associated with concomitant injuries. A Malgaigne fracture is a fracture of the ilium and a symphyseal dislocation.