The 'open book' pelvic injury involves symphysis pubis diastasis with external rotation of hemipelvis. Which ligamentous structure is the PRIMARY stabilizer of the posterior pelvic ring that must be intact for a stable ring injury?

• A Sacrospinous ligament
• B Sacrotuberous ligament
• C Iliolumbar ligament
• D Posterior sacroiliac ligament complex ✓

Explanation

The posterior sacroiliac ligament complex (posterior SI ligament and interosseous SI ligament) is the strongest ligamentous structure of the pelvis and the primary stabilizer of the posterior ring. In APC-I injury, only the symphysis is disrupted (stable). In APC-II, the anterior SI ligament and sacrospinous ligament also rupture (rotationally unstable), while in APC-III, the posterior SI ligament complex is disrupted making the injury completely unstable (rotationally and vertically). Preservation of the posterior SI complex distinguishes a rotationally unstable but vertically stable injury from a completely unstable injury.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.