Fig. 3A–D.

(A) Straight lateral film shows loss of normal forward curve, narrowing of intervertebral spaces between C4 and C5 and C5 and C6, and lipping posteriorly of C5 and C6. (B) Forward flexion view shows forward subluxation of C2 on C3 and C3 on C4. (C) Hyperextension view shows posterior subluxation of C2 on C3 and C3 on C4. Note fixation of C4, C5 and C6 in all positions. Motion occurs above and below these vertebrae. (D) Oblique view shows antero-posterior narrowing of intervertebral foramina between C4 and C5, and C5 and C6.