To investigate the association between magnetic resonance imaging (MRI) findings at the sacroiliac (SI) joints and vertebral endplates and pain characteristics assumed to be indicative of axial inflammation.
Patients ages 18-40 years with persistent low back pain referred to an outpatient spine clinic participated, including an unknown proportion of axial spondyloarthritis patients. Data included MRI of the spine and SI joints and self-reported responses to questions covering the Calin, Berlin, Assessment of Spondyloarthritis International Society, and Bailly inflammatory back pain (IBP) definitions.
In the 1,020 included patients, 53% were women, and the median age was 33 years. Positive associations were found between the SI joint MRI findings and pain characteristics, odds ratios ranging from 1.4 to 2.7. SI joint bone marrow edema (BME) was associated with morning stiffness >60 minutes, and SI joint erosions with the Calin, Berlin, and Bailly IBP definitions, alternating buttock pain, and good response to nonsteroidal antiinflammatory drugs. SI joint fatty marrow deposition (FMD) was associated with insidious onset, and SI joint sclerosis with pain at night. In addition, the spinal MRI changes were associated with IBP, odds ratios ranging from 1.4 to 2.0; vertebral endplate BME was associated with morning stiffness, and vertebral endplate FMD with the Calin and Bailly IBP definitions, improvement with exercise, morning stiffness >30 minutes, and pain worst in the morning.
The identified associations between inflammatory MRI findings and pain characteristics indicate that axial inflammation to some degree induces a specific pain pattern. Thus, the results add to knowledge of axial inflammatory processes. However, all identified associations were weak, which compromises the use of IBP as a marker of axial inflammation.