The value of quantitative radioisotope scanning in the differential diagnosis of low back pain and sacroiliac disease.

The specificity of scintigraphic scanning in detecting inflammatory sacroiliitis has been investigated. The sacroiliac band profile (R[Band]) was used and a new index (R[SIJ/F]) comparing the sacroiliac joint with the ipsilateral femur is described. Using the R (Band) index the mean value (1.34) for patients with definite sacroiliac disease was no different from that found for control subjects (1.35). There were significant differences using the R(SIJ/F) (7.8 versus 6.4): this ratio alone correlated with age. We conclude that neither technique is sufficiently specific to be of diagnostic value in most instances of low back pain.