99mTc-MDP scintigraphy in ankylosing spondylitis.

99mTechnetium-MDP bone scintigrams in 11 patients with ankylosing spondylitis were reviewed. Increased activity in sacroiliac joints was present in five of 11 cases, all of whom had symptoms of less than 5 years duration. Patients with longstanding disease had normal or low sacroiliac joint activity. In the spine, appearances included diffuse symmetrical, unifocal or multifocal asymmetrical increased uptake involving the costovertebral, costotransverse and facet joints as well as the spinous processes. In advanced disease with extensive ankylosis, the lumbar spine was featureless on scintigraphy, except for focal increased activity at the site of previous fracture in one patient. Of six available views of the sternum, increased uptake was present in five at the manubriosternal joint and five at the sternoclavicular joints. Increased peripheral uptake was mainly in the hips and knees in advanced cases. Plain radiographic changes correlated poorly with scintigraphic changes, scintigraphy detecting considerably more lesions than radiography. Awareness of the scintigraphic appearances of ankylosing spondylitis may lead to diagnosis before the development of radiographic changes and avoid confusion with other pathology. Clinical indications for bone scintigraphy in ankylosing spondylitis are suggested.