2023 Volume 35 Issue 1 Pages 4-12
We should consider the condition when we judge the X-rays images of the joint. In RA, bone erosion starts from bare area, just beside articular surface. Sometime we may see ankylosis under well-controlled RA. When disease control is insufficient, we may find instability to cervical spine. In PsA, osteogenesis is occurred out of joint, whereas bone resorption is occurred in joint. It leads to form pencil in cup deformity.
Ankylosis of the sacroiliac joint is characteristic in AS, and we should focus on articular surface located in lower half of sacroiliac joint. In AS, straight syndesmophytes start from enthesis of disk and spinal body. On the other hand, in PsA, chunky syndesmophytes start from a bit distant part of the enthesis. We should distinguish AS or PsA form PAO, DISH, or OCI.
It is important to ascertain existence of inflammation and a structural change in MRI. The inflammation, so called bone edema, is recognized as low intensity in T1WI and high intensity in STIR or T2fs. The structural change is judged with T1WI.
