A fatty corner lesion (FCL) is a well-demarcated fat infiltration in the corner of a vertebral body on T1 magnetic resonance imaging (MRI) sequence. It has been reported to be useful in the diagnosis of axial spondyloarthritis (axSpA). Our objective is to systematically evaluate the diagnostic accuracy of FCLs in tertiary centre patients with chronic back pain. Two hundred and thirty eight axSpA patients and 62 non-axSpA patients with back pain were recruited from five rheumatology centres. Clinical, biochemical, and radiological parameters were collected and all patients underwent a MRI of the spine and sacroiliac (SI) joints. FCLs in vertebral bodies from C4 to L5 were scored. The number and location of FCLs were clustered together to determine an optimal combination for diagnosis. Results were compared with expert diagnosis as the “gold standard”. FCLs of the anterior whole spine (AUC 0.62; p = 0.003) and anterior thoracic spine (AUC 0.64; p = 0.001) had diagnostic significance. Incorporating at least 5 whole spine FCLs into the imaging criteria of the Assessment of SpondyloArthritis international Society (ASAS) criteria for axSpA yielded a sensitivity of 91.6% and specificity of 91.9%. Similarly, applying at least 3 anterior thoracic FCLs to the imaging criteria of the ASAS axial SpA criteria yielded a sensitivity of 92.0% and specificity of 93.5%. FCLs could be used to diagnose axial SpA. The presence of at least 3 anterior thoracic FCLs in T1-weighted MRI spine suggests a diagnosis of axial SpA without additional MRI of the SI joints. The cohort has been registered in the clinical trial registry of the University of Hong Kong ( HKUCTR-2087 ).

中文翻译：

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T1加权磁共振成像中的脂肪角病变作为骶髂关节炎的替代诊断中轴型脊柱关节炎

脂肪角病变 (FCL) 是在 T1 磁共振成像 (MRI) 序列上在椎体角处界限清楚的脂肪浸润。据报道，它可用于诊断中轴型脊柱关节炎（axSpA）。我们的目标是系统地评估 FCL 在三级中心慢性背痛患者中的诊断准确性。从五个风湿病学中心招募了 238 名患有背痛的 axSpA 患者和 62 名非 axSpA 患者。收集临床、生化和放射学参数，并对所有患者进行脊柱和骶髂 (SI) 关节的 MRI 检查。对从 C4 到 L5 的椎体中的 FCL 进行评分。将 FCL 的数量和位置聚集在一起以确定诊断的最佳组合。结果与作为“金标准”的专家诊断进行比较。整个脊柱前部（AUC 0.62；p = 0.003）和胸椎前部（AUC 0.64；p = 0.001）的 FCL 具有诊断意义。将至少 5 个全脊柱 FCL 纳入国际脊柱关节炎评估协会 (ASAS) 的 axSpA 标准的成像标准中，产生了 91.6% 的敏感性和 91.9% 的特异性。同样，将至少 3 个前胸 FCL 应用于 ASAS 轴向 SpA 标准的成像标准产生了 92.0% 的敏感性和 93.5% 的特异性。FCL 可用于诊断轴向 SpA。在 T1 加权 MRI 脊柱中存在至少 3 个前胸 FCL，提示无需对 SI 关节进行额外 MRI 即可诊断为轴向 SpA。