Pyogenic sacroiliitis in i.v. drug abusers.

We evaluated the sensitivity of imaging studies in six IV drug abusers who had back pain from pyogenic sacroiliitis. Initial radiographs of the sacroiliac joints showed bone destruction in two. A third had slight joint narrowing and sclerosis resembling degenerative disease. Radiographs were considered normal in three. Two of the patients with initially normal radiographs subsequently showed loss of cortices on follow-up studies within 2 weeks. All of the patients had increased activity on scintigrams (five were obtained with technetium-99m methylene diphosphonate; one was with gallium). The findings suggest that scintigraphy is useful in the detection of pyogenic sacroiliitis in IV drug abusers when plain films are normal.