Evaluation of the involvement of axial entheses and sacroiliac joints in relation to diagnosis: comparison among diffuse idiopathic skeletal hyperostostis (DISH), osteoarthrosis and ankylosing spondylitis.

Since diffuse idiopathic skeletal hyperostosis (DISH) is frequently difficult to differentiate radiologically from the axial involvement of ankylosing spondylitis and osteoarthrosis, some features of these 3 different diseases were compared. The predominantly horizontal nature of the enthesiophyte in DISH and its right preponderance in the thoracic region were demonstrated. This right preponderance was due to the presence of the thoracic aorta located in the left thoracic side. A midthoracic notch was described in DISH which seemed to be confined to noninflammatory conditions, but was not found in ankylosing spondylitis. The importance of sacroiliac computerized tomography to differentiate sacroiliac joint abnormalities associated with DISH from the sacroiliitis of spondylarthropathies was stressed.