Lateral extension radiograph (A) and T2-weighted magnetic resonance image (B). A line based on the C3 upper endplate is drawn on a lateral extension radiograph of the cervical spine. Candidates for the subaxial anterior approach should have a mandibular angle higher than the line. Lateral extension radiograph (C) and T2-weighted magnetic resonance image (D). A large chin with a mandibular angle that extends over the line may make it difficult to reach C2 with the subaxial anterior approach.