Type | Definition | Syndesmophyte characteristics | Synonymes |
---|---|---|---|
I | Dorsal ossification | Simple ossification of the dorsal spine bodies, no syndesmophytes | Spondylathritis type |
Iia | Incomplete anular ossification | Tender, the anulus fibrosus ventrally with or without lateral syndesmophytes, without overlapping of the vertebral bodies (incomplete) | Anulus-type |
Iib | Complete anular ossification | As type IIa, but with syndesmophytes overlapping the vertebral disc (complete) | Anulus-type |
IIIa | Partial ostotic ossification | Thick and wide syndesmophytes, often with cortical- and spongiosa structure, corresponding the bamboo-type, but not present in all segments (incomplete) | Ligament/sub-ligament type |
IIIb | Total ostotic ossification | As type IIIa, but several thoracic and lumbar segments are affected | Bamboo-spine |