Osteitis condensans ilii may demonstrate bone marrow edema on sacroiliac joint magnetic resonance imaging

Aim To reveal whether bone marrow edema (BME) may appear with osteitis condensans ilii (OCI) on sacroiliac joint (SIJ) magnetic resonance imaging (MRI) and to evaluate the characteristics of BME demonstrated with OCI. Method Altogether 27 symptomatic female OCI patients with both complete clinical records and SIJ-MRI examination data were enrolled for retrospective analysis. SIJ-MRI exams were retrospectively analyzed by two musculoskeletal radiologists. Patients were separated into BME group and non-BME group according to whether there was BME of SIJ demonstrated as high signal intensity on MR short tau inversion recovery sequences beneath the SIJ articular surface. For the BME group the characteristics of BME including distribution pattern and location, depth and signal intensity were assessed. Results BME could be seen in 48.1% (13/27) OCI patients. Ilium side BME demonstrated with OCI was centered at the ventral-cartilaginous joint part and had a trend of extending to bone marrow beneath the arcuate line in a continuous distribution pattern. There was a trend that OCI patients with BME demonstrated on MRI were younger (P = 0.054, Student's t-test) and with shorter pain duration (P = 0.091, Student's t-test) than OCI patients without BME, but the differences did not reaching statistical significance. More cases endured diagnosis delay in the BME group than the non-BME group (nine cases vs. two cases, P = 0.006, Fisher's exact test). Conclusion Some OCI may demonstrate BME on SIJ-MRI. Careful observation of the location and distribution pattern of BME may give some help in differentiating OCI from early spondyloarthritis.