AB1203 Use of magnetic resonance imaging of the pelvis to describe inflammatory changes at different anatomic sites in the pelvis which are potentially specific findings in patients with polymyalgia rheumatica
Authors: M. Fruth, M. Franklin, B. Buehring, X. Baraliakos, J. Braun
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Pelvic girdle pain is a common clinical symptom of patients with polymyalgia rheumatica (PMR). It also occurs in patients with rheumatoid arthritis (RA). The origin of this characteristic pain is not really clear, even though some imaging findings have been reported. However, this has neither changed pathophysiologic thinking nor clinical practice related to diagnosis. <h3>Objectives</h3> To describe pelvic structures in PMR patients in detail which show signs of inflammation by magnetic resonance imaging (MRI) in order to find a disease specific pattern. <h3>Methods</h3> In a retrospective study we used MRIs of patients who had presented with clinical symptoms suggestive of PMR in our centre between 2015 and 2017. Only patients with complete MRI examinations, including contrast enhanced scans in coronal and transversal planes were included to be carefully examined by an experienced musculoskeletal radiologist (MF). After having first described all findings in much detail we developed a preliminary semiquantitative scoring system that assesses a total of 12 sites which appeared to be frequently involved. A total of 40 patients with pelvic girdle pain and complete data were identified from the hospital records. The median (25th/75th percentiles) age of the patients was 67 (55/73) years, the median symptom duration was 13 (6/22) weeks, 55% were female, the median C-reactive protein measured close to the day of the MRI examination was 1.9 (0.7/4) mg/dl, and the median erythrocyte sedimentation rate was 30 (17/43) after the 1st hour. Only 3 patients were rheumatoid factor positive, and 2 patients had anti-CCP antibodies. Ten patients had a diagnosis of RA (25%) in addition to the leading PMR like symptom. <h3>Results</h3> The MRI signal of interest for PMR is a post-gadolinium signal in T1 weighted pelvic images. The most frequently involved anatomic sites were: the hamstring tendon and the M.gluteus medius and minimus tendon near the greater trochanter in all cases, which were found to be bilaterally involved as was the proximal M.rectus femoris in all cases, and the insertion of the adductor muscles, especially the M.adductor longus at the inferomedial pubic symphysis in 90% of cases. Other sites were also, but less frequently, involved. We think that the involvement of 4 sites including either the M.rectus femoris or the M.adductor longus is rather specific for PMR, see examplary images below. There was no major difference between patients with and without RA. <h3>Conclusions</h3> This study suggests that there may be a MRI pattern specific for PMR. The target structure of the characteristically inflamed anatomic site seems to be the paratenon which implies that the pattern observed in PMR differs from the enthesitis seen in patients with spondyloarthritis. Prospective randomised trials are needed to further test and prove the clinical usefulness of this approach. <h3>Disclosure of Interest</h3> None declared