The fatty Romanus lesion: a non-inflammatory spinal MRI lesion specific for axial spondyloarthropathy

Background Fatty changes at vertebral corners have been reported on MRI in ankylosing spondylitis but the distribution or specificity of these lesions to early axial spondyloarthropathy (axial-SpA) has not been determined. Objective To assess the diagnostic utility of fatty Romanus lesions (FRLs) for axial-SpA in a population with chronic back pain. Methods Axial-skeleton TI SE and fat-suppressed MRI were performed on 174 patients with back pain and 11 controls. MRI lesions including FRLs were scored blind. An imaging diagnosis was given on MRI findings alone and compared with the 'gold standard' treating doctor's diagnosis. Results Twenty-nine patients had FRLs: 31% (20/64) of patients with spondyloarthropathy, 13% (6/45) with degenerative arthritis, 4% (2/45) with spinal malignancy, 5% (1/20) with 'other' diagnoses; none of 11 normal subjects had FRLs. The majority of the FRLs in SpA 60% (135/226) were present in the thoracic spine. The diagnostic utility of FRLs for SpA (likelihood ratio (LR) = 4.7) was significantly (p<0.05) greater than for other diagnoses and increased further (LR = 12.6, p<0.05) when more than five FRLs were present. Of note 5/20 (25%) patients with SpA with FRLs had no diagnostic bone-oedema lesions on fat-suppressed MRI, suggesting that FRLs may be useful diagnostically in axial-SpA. Conclusion This study defines the FRL as a diagnostic imaging feature of axial-SpA, which may be useful where inflammatory changes are absent on fat-suppression MRI and where radiography is normal.