Explanation:
The correct option is a. The Young and Burgess classification system directs both acute resuscitation and definitive fixation of pelvic ring injuries based on the mechanism of injury. An Anteroposterior Compression (APC) injury progresses through sequential stages of ligamentous failure. An APC I involves only symphyseal diastasis (< 2.5 cm). An APC II involves symphyseal diastasis with rupture of the anterior sacroiliac, sacrotuberous, and sacrospinous ligaments, but crucially, the dense posterior sacroiliac ligaments remain intact, providing a 'hinge' that preserves vertical stability. An APC III represents the most severe manifestation: complete disruption of both the anterior and the robust posterior sacroiliac ligaments. This results in an entirely unstable hemipelvis (both rotationally and vertically) and carries an exceptionally high risk of catastrophic, life-threatening retroperitoneal hemorrhage from the presacral venous plexus and internal iliac arterial branches. Reference: Tile M et al. Fractures of the Pelvis and Acetabulum.