Craniocervical traumatic ligamentous injuries - AO spine type B injuries - Anatomy, biomechanics and clinical perspectives.

The craniocervical junction (CCJ) relies on strong ligamentous structures to maintain stability, which can be compromised by traumatic injuries. Defining stability is critical for selecting operative or non-operative management. This review summarizes the anatomy, imaging, and biomechanical relevance of the main CCJ ligaments, with emphasis on type B injuries in the AO Spine Upper Cervical Classification. Current evidence suggests that neurologically intact patients with normal CT scans (occipitoatlantal joints) and mild MRI abnormalities may be treated conservatively, with fluoroscopic traction testing serving as a supportive tool. Considering C1-2 ligamentous injuries, transverse ligament injury (TL), however, often requires an MRI for accurate diagnosis, particularly in association with atlas lateral mass fractures. While surgical treatment may provide advantages in pain and function, non-operative strategies remain appropriate in selected cases. When surgery is indicated, C1 ORIF is a feasible alternative to C1-2 fusion in patients with TL rupture, also considering an intraoperative test for abnormal motion at C1-2.