Annals of the Rheumatic Diseases
Source Reference: Poggenborg RP, et al “Enthesitis in patients with psoriatic arthritis, axial spondyloarthritis and healthy subjects assessed by ‘head-to-toe’ whole-body MRI and clinical examination” Ann Rheum Dis 2015; DOI: 10.1136/annrheumdis-2013-204239.
Whole body magnetic resonance imaging (WBMRI), which allows assessment of all peripheral and axial joints and entheses in one examination, is a promising new imaging approach to detect enthesitis in patients with psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA), a new prospective, cross-sectional pilot study has found.
The study showed that “it is possible to detect enthesitis by “head-to-toe” WBMRI with moderate percentage agreement between MRI and clinical findings at the entheseal level”, according to Rene Penduro Poggenborg, Copenhagen Centre for Arthritis Research and Copenhagen Center for Rheumatology and Spine Diseases, Denmark, and colleagues.
The study, published in the Annals of the Rheumatic Diseases, included 18 patients with PsA and 18 with axSpA, all with moderate to high disease activity. It also included 12 healthy controls (HS) without pain from peripheral joints or spine, family history of PsA, spondyloarthritis or rheumatoid arthritis, or personal history of psoriasis, anterior uveitis, inflammatory bowel disease, or heel pain.
Clinical enthesitis was defined as tenderness when the enthesis was palpitated with a pressure of the thumb until the tip of the nail bed blanched. Experienced clinicians examined study subjects at 18 peripheral and axial entheses at 35 different anatomical sites.
With MRI evaluations, enthesitis was defined as the presence of bone marrow edema, soft tissue edema, change in tendon thickness, erosions or enthesophytes in adjacent bones, and additional findings such as fluid around tendons or adjacent to bursa, alone or in combination.
WBMRI allowed evaluation of 53% of 1,680 sites investigated. More than half (54%) of 35 entheses had a readability of greater than 70%.
With “head to toe” WBMRI, the slices are usually thicker than on conventional MRI so readability of the scans varied greatly in the study. For example, all pelvic entheses, supraspinate tendon, greater femoral trochanter, and medial femoral condyle could be assessed in 94% or more of study subjects, and the Achilles tendon could be evaluated in 71%. In contrast, readability was low for the anterior chest wall and elbows and was compromised at the patellar ligament insertion into the patella and tibia. The plantar fascia and lateral femoral condyle could not be visualized by WBMRI.
WBMRI enthesitis was observed in 17% of individual entheseal sites, whereas clinical enthesitis was present at 22% of the corresponding entheseal sites. The sites most frequently observed with MRI enthesitis were the greater femoral trochanter (55% of readable entheses) and Achilles (43%) tendons.
According to the authors, this might be due to the presence of subclinical enthesitis, which may be related to other conditions inducing mechanical stress such as high body mass index or physical overuse.
This MRI observation was also found in controls. “Several HS were frequent runners, and this may explain the general high frequency of enthesitis in the lower limbs and the difference in the frequency of clinical and MRI enthesitis,” wrote the authors.
Future studies of enthesitis should take factors such as weight and physical activity into account, which may be associated with enthesitis, they said.
Patients had more enthesitis at clinical examination than on WBMRI (29% and 18% for PsA patients and 23% and 18% for axSpA patients) whereas it was the opposite for healthy subjects (8% and 14%).
The percent agreement between WBMRI and clinical enthesitis was 68%-100% for all entheseal sites except for the medial femoral condyle (64%), Achilles tendon (52%) and greater trochanter (49%).
After image assessments, researchers constructed three data-driven WBMRI enthesitis indices. Patients and healthy controls didn’t differ significantly in WBMRI scores when based on assessment of all 35 entheseal sites (median 3.5 versus 2.5; P=0.49), WBMRI Index 1 (2 versus 2; P=0.62), and Index 2 (2.5 versus 2; P=0.33). However, patients had higher scores when assessed by WBMRI Index 3 (1 versus 0; P=0.047).
This most discriminatory index, said Poggenborg and colleagues, “may be of clinical value for assessing disease activity and for differentiating patients from HS.” However, they added, “the discriminative capacity and responsiveness should be investigated in future studies.”
The authors stressed that although clinical examination is the ‘gold standard,’ previous studies have only documented a moderate reliability of clinical assessment among rheumatologists with expertise in spondyloarthritis, and this undoubtedly contributed to the lack of association with MRI findings. They also pointed out that although the radiologist in the study was blinded for all information, rheumatologists were not blinded for diagnosis and clinical data.
Poggenborg and colleagues also noted that image quality in the study was lower if the area scanned was in the periphery of the scanner, for example the elbows. Movement of the thorax through the respiratory cycle can lead to motion artifacts, which is a major problem for assessment of small joints at the anterior chest wall. And the supine position in the scanner facilitates external rotation of the legs and feet, resulting in an oblique sagittal scan plane that makes evaluation of the planter fascia difficult.
“All these technical issues can be improved in future studies by optimising patients’ positioning, adding sagittal slices to the knee scan, and use of external coils besides the build-in coil,” wrote the authors. “All together this will increase readability substantially.”
The authors have no competing interests.
Reviewed by Henry A. Solomon, MD, FACP, FACC Clinical Associate Professor, Weill Cornell Medical College and Dorothy Caputo, MA, BSN, RN, Nurse Planner
LAST UPDATED 04.17.2015