A
Symphysis pubis and anterior sacroiliac ligaments
B
Sacrotuberous and sacrospinous ligaments
C
Posterior sacroiliac ligaments and iliolumbar ligaments
D
Symphysis pubis and posterior sacroiliac ligaments
Explanation:The correct option is 'a'. In the Young-Burgess classification, an APC II pelvic fracture involves widening of the pubic symphysis (or longitudinal rami fractures) combined with widening of the anterior sacroiliac (SI) joint. This indicates disruption of the symphyseal ligaments, sacrotuberous, sacrospinous, and the anterior SI ligaments. Crucially, the strong posterior SI ligaments remain intact, preventing vertical instability but allowing rotational "open book" instability.
Reference: Young JW, Burgess AR, Brumback RJ, Poka A. Pelvic fractures: value of plain radiography in early assessment and management. Radiology. 1986;160(2):445-451.