SAT0270 Backfill is a Specific Sign of Axial Spondyloarthritis Seen on MRI. (9th June 2015) - Hu, Z.
Abstract : Background: Backfill (BF) is a specific sign seen on magnetic resonance imaging (MRI) in patients with ankylosing spondylitis (AS). BF is considered to be a key intermediary in the development of ankylosis in patients with AS. But the research on BF is rare. Objectives: To summarize the characteristics of BF in axial Spondyloarthritis (SpA) patients and patients with non-specific back pain (NSBP) and healthy controls, and to assess the value of BF in diagnose axial SpA. Methods: Three readers blinded recorded BF seen on T1SE MRI scans from 647 subjects: 297 patients with AS, 126 patients with non-radiographic axial SpA (nr-axSpA), 147 patients with NSBP, and 77 healthy controls. The SPARCC SIJ Structural Score (SSS) method was used to assess BF. The changes of BF were evaluated by the follow-up MRI scans from 157 patients. We summarized the characteristics of BF and calculated its sensitivity and specificity for diagnosing axial SpA. Results: BF was recorded in 78.8% AS patients, 11.1%nr-axSpA patients, 1.8% patients with NSBP, and no healthy control. BF affected more frequently at ilium bone, lower half of sacroiliac joints in axial SpA (both p<0.05), but not in patients with NSBP. The SSS score of BF was much higher in axial SpA than in patients with NSBP (both p<0.01) and it did not correlate with demographics and BASDAI, BASFI, and CRP (all p>0.05). BF score only positively correlated with symptom duration in AS (r=0.251, p<0.01) and in nr-axSpA (r=0.743, p<0.01) patients. Only 8.9% patients had the change of BF in an average follow-up time of 1.09 years. BF had high specificity (0.98) and moderate sensitivity (0.59) for diagnosing axial SpA. Conclusions: We summarized the characteristics of BF and found that BF is a specific sign of axial SpA seen on MRI. References: Chiowchanwisawakit P, Lambert RGW, Conner-Spady B, et al. Focal fat lesions at vertebral corners on magnetic resonance imaging predict the development of new syndesmophytes in ankylosing spondylitis. Arthritis Rheum 2011;63:2215-25. Maksymowych WP, Wichuk S, Chiowchanwisawakit P, et al. Fat Metaplasia and Backfill are Key Intermediaries in the Development of Sacroiliac Joint Ankylosis in Patients with Ankylosing Spondylitis. Arthritis Rheumatol 2014;66(11):2958-67. Disclosure of Interest: None declared