An Avulsion (Arrow) of the Transverse Ligament from the Ring of C1 Indicates Instability and May Require Arthrodesis of C1–c2.

(From KalantarSB, KimY, BawaM, et al. Occipitocervical and C1–2 fusion with instrumentation. In: RheeJM, BodenSD, eds. Operative Techniques in Spine Surgery. 2nd ed. Philadelphia: Wolters Kluwer; 2016:46–59.)