A recently published study calls whole body magnetic resonance imaging (WBMRI) a “promising” new imaging modality for evaluating enthesitis in patients with psoriatic arthritis and axial spondyloarthritis.

The results of the prospective, cross-sectional study were published in the May 2015 issue of Annals of the Rheumatic Diseases. Enthesitis is inflammation of the entheses, the sites where tendons or ligaments insert into the bone.

The study, led by Dr. Rene Panduro Poggenborg of the Copenhagen Centre for Arthritis Research and Copenhagen Center for Rheumatology and Spine Diseases, in Denmark, included 18 patients with psoriatic arthritis and 18 with axial spondyloarthritis, with moderate to high disease activity. There were also 12 healthy control subjects. Enthesitis at 35 individual sites in the upper and lower limbs, chest and pelvis were evaluated in each patient by wbMRI and clinical examination and compared. Four other studies have looked at wbMRI to evaluate enthesitis, but have not compared the findings with clinical examination in patients with psoriatic arthritis and axial spondyloarthritis, or included a control group.
The study used the Philips Achieva, a 3-tesla MRI unit using the built-in Q-Body coil. wbMRI allowed evaluation of 53 percent of 1,680 sites investigated, and 54 percent of 35 entheses had a readability greater than 70 percent, according to the study. The percentage of agreement between wbMRI and a clinical examination was 49 to 100 percent, or what the study called “moderate agreement”.

With wbMRI, enthesitis — such as presence of bone marrow edema, soft tissue edema, change in tendon thickness, and erosions or enthesophytes in adjacent bones — was observed in 17 percent of the entheseal sites, according to the study, while clinical enteritis, which included tenderness when the enthesis was palpated, was present at 22 percent of the entheseal sites.

Enthesitis was more frequently found on the wbMRI than by clinical examination in the greater femoral trochanter, Achilles tendons and ischial tuberosity in both the patients and the healthy subjects. The researchers wrote that this could be related to other conditions, inducing mechanical stress, such as high body mass index or physical overuse. Many of the healthy subjects were runners, which they wrote could explain the general high frequency of enthesitis in the lower limbs and the difference in the frequency of clinical and MRI enthesitis. The researchers wrote that any future studies of enthesitis should take weight and physical activity into account.

The readability of the scans also varied greatly depending on the body part being examined, and researchers wrote that “optimizing patient positioning, adding sagittal slices to the knee scan, and use of external coils besides the build-in coil” will “increase readability substantially.”

The researchers concluded that though wbMRI seems promising for evaluating enthesitis, “introduction of wbMRI as a clinical tool should be preceded by more research including optimization of image acquisition, before clinical implementation is considered.”

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