What is a late radiographic finding of Ankylosing Spondylitis?

• A. Bamboo spine
• B. Syndesmophytes
• C. Sclerosis on the SI joints
• D. Bone edema

Answer: (A)

In ankylosing spondylitis, radiographic changes evolve from inflammation in the sacroiliac joints to the formation of marginal syndesmophytes along the spine, and finally to fusion across the vertebral bodies. When this fusion becomes extensive, the spine takes on a rigid, bamboo-like appearance called bamboo spine. That complete bridging and fusion across multiple levels is what makes bamboo spine a late radiographic finding.

Syndesmophytes can appear earlier in the disease process, but the characteristic bamboo spine reflects advanced bridging and fusion. Sclerosis of the SI joints and bone edema are not the defining late radiographic pattern on plain X-rays—the former can be present but isn’t the late hallmark, and the latter is typically detected on MRI rather than plain radiographs.