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What is Syndesmophytes are seen in - and explain in detail?
Syndesmophytes 

Syndesmophytes are thin, slender vertical radiodense spicules bridging the vertebral bodies, giving the spine `bamboo' appearance. They are actually ossification of outer fibres of annulus fibrosus.

Syndesmophytes are seen in :

Ankylosing spondylitis
Psoriatic arthritis
Reiter's disease
Arthritis associated with Inflammatory bowel disease