Fig. 4

Configuration of cervical facet joint ankylosis and bridging syndesmophytes as assessed during the entire or stratified follow-up periods based on (A) total spinal radiographs and (B) spinal radiographs in the presence of either cervical facet joint ankylosis or bridging syndesmophytes. Each bar shows the frequency of the presence and/or absence of at least one ankylosis in facet joints or vertebral bodies at a given time period for the C2–C3 to C6–C7 vertebral level

Y, follow-up year