Fig. 1.

Lateral flexion and extension lumbar X-ray showing radiological indices studied. Adjacent intervertebral mobility (L2–L3) = extension angle (a)–flexion angle (a’). Intervertebral mobility (L3–4) with Coflex insertion = extension angle (b)–flexion angle (b’). General adjacent segment mobility (GASM) at L2–4 = extension angle (c)–flexion angle (c’)