Whole-body magnetic resonance imaging vs. clinical evaluation of enthesitis in patients with spondyloarthritis
If you or someone you know lives with spondyloarthritis (SpA), you’re probably familiar with enthesitis—the inflammation of tendon or ligament attachments to bone that causes deep, aching pain. Enthesitis is one of the first and most unique signs of SpA, but many cases go undetected by standard clinical exams. A 2021 study from Chinese researchers explored whether whole-body MRI (WB-MRI)—a tool that images the entire body in one scan—could fill this gap by detecting enthesitis more comprehensively than physical exams.
Enthesitis is a hallmark of SpA, often preceding joint pain and linked to more severe, erosive disease. But with over 100 entheses in the human body, standard methods like tenderness checks, X-rays, or local ultrasound only assess a handful of sites. WB-MRI, by contrast, can visualize every major enthesis in a single session—though it has lower resolution than targeted MRI.
To test WB-MRI’s value, Zi-Kang Guo (First Central Clinical College, Tianjin Medical University) and colleagues from Tianjin First Central Hospital enrolled 30 adults with axial SpA (ax-SpA), the form that primarily affects the spine. All patients underwent WB-MRI on a 3T scanner, which evaluated 18 entheseal sites across five regions: shoulders, anterior chest wall, pelvis, knees, and feet. Two musculoskeletal radiologists independently reviewed scans for signs of inflammation—like bone marrow edema (BME) or soft tissue swelling—using STIR (short-tau inversion recovery) and T1-weighted images.
For comparison, the team used two clinical scoring systems: the modified Maastricht Ankylosing Spondylitis Enthesitis Score (MASES) and the Leeds Enthesitis Index (LEI), which rely on physical exams to check for tenderness at specific entheses.
The results revealed a clear gap: WB-MRI detected enthesitis in 76% of patients (22 out of 30), while clinical exams only found it in 57% (17 out of 30). The biggest difference was in the pelvis—WB-MRI identified inflammation in 50% of patients (e.g., ischial tuberosity, greater femoral trochanter), but clinical exams only caught it in 20% (a statistically significant difference, P < 0.05). The anterior chest wall (including sternoclavicular joints) was the most common site for clinical enthesitis (40% of patients), but WB-MRI showed the pelvis was the true “hot spot” for inflammation.
Why the discrepancy? The study points to two key factors: subclinical inflammation (swelling that’s too early or too deep to cause pain) and deep entheses (like pelvic sites) that are hard to assess via tenderness. For example, previous research found 54% of psoriatic arthritis (PsA) patients had inflammation in sternoclavicular joints on scans—yet only 13% had clinical symptoms. WB-MRI can spot these “hidden” cases, while physical exams miss them.
The team also found a modest correlation between WB-MRI and clinical enthesitis scores (Spearman’s rho = 0.45, P < 0.05), meaning the two methods agree to some extent. But there was no link between WB-MRI findings and the Ankylosing Spondylitis Disease Activity Score (ASDAS)—a common tool for measuring SpA severity. This suggests ASDAS may not fully capture the burden of enthesitis, a finding supported by earlier work from researchers like R.P. Poggenborg.
WB-MRI isn’t perfect. Its lower resolution can make small entheses hard to see, and high signals on T2-weighted images (used to spot edema) can stem from non-inflammatory causes. The team also noted that training radiologists on standard scoring systems—like the OMERACT MRI Whole-Body Inflammation in Peripheral Joints and Entheses (MRI-WIPE) score—improved reliability, with an intrareader correlation coefficient (ICC) of 0.91 for WB-MRI assessments.
For patients with ax-SpA, the takeaway is hopeful: WB-MRI offers a “one-stop shop” to map enthesitis across the entire body, potentially catching early or hidden inflammation that clinical exams miss. This could help doctors tailor treatment—like biologic drugs or physical therapy—to address the full scope of disease.
The study was published in the Chinese Medical Journal in 2021 by researchers from Tianjin Medical University’s First Central Clinical College and Tianjin First Central Hospital’s Departments of Rheumatology and Immunology and Radiology.
doi:10.1097/CM9.0000000000001813
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