MRI Assessment of Extra-axial Findings at Pelvic Sites in a Group of Axial-SpA Patients

Introduction MRI allows a better evaluation of inflammatory and structural lesions of the sacroiliac joints and spine in patients with axial spondyloarthritis (axial SpA), so MRI plays an important role in the classification and diagnosis of axial SpA. The aim of our study was to assess extra-axial MRI findings at pelvic sites and their possible associations with clinical indices in patients with axial SpA. Methods Axial-SpA patients who were classified according to the ASAS criteria and consecutively attended our clinic were assessed with pelvic MRI. The main clinical and demographic characteristics of all patients, including age, sex, BMI, presence of HLA-B27 and type of axial SpA (radiographic or nonradiographic), were evaluated. The main indices of disease activity and joint function were assessed, including BASDAI, ASDAS-PCR, BASMI and BASFI. Finally, the presence/absence of inflammatory/structural lesions at extra-axial structures (the hip joints, pubic symphysis, greater and lesser trochanters, ischial tuberosity, iliac spines and iliac crest) was evaluated. Results 35 patients (21 males and 14 females) with a mean age (SD) of 47 (12.7) years and a mean duration of symptoms of 5 (2.1) years were enrolled. Hip abnormalities were found in 14 (40%) patients. Trochanteric enthesopathy/bursitis and pubic osteitis were found in 2 patients (5.7%) and 1 patient (2.8%), respectively. No other abnormalities were found at other sites. We found significant associations between the presence of extra-axial alterations, disease activity and joint function. Conclusions Our study demonstrated the presence of extra-axial abnormalities in more than one-third of patients with axial SpA, suggesting that MRI evaluation should be extended to the entire pelvis.