THU0412 LONGITUDINAL ASSOCIATIONS BETWEEN MRI-DEFINED INFLAMMATION AND PAIN IN THUMB BASE OSTEOARTHRITIS

Background:  Hand osteoarthritis (OA) typically affects the interphalangeal (IP) joints and the thumb base (TB), including the first carpometacarpal (CMC-1) and scaphotrapeziotrapezoid (STT) joints. Based on previous studies, TB OA can be considered a distinct hand OA subset with a high burden of disease. In a cross-sectional study it was shown that TB pain is more strongly associated with radiographic damage than with MRI-defined inflammation, yet it is unknown if and how TB pain changes over time, and whether this is related to changes seen on imaging. Objectives Our aim was to investigate the course of TB OA pain and its association with changes in MRI-defined inflammation and structural damage. Methods Longitudinal data of the Hand OSTeoArthritis in Secondary care (HOSTAS) study, which included patients diagnosed with primary hand OA by their treating rheumatologist, were used. Patients who underwent hand radiography, MR imaging and clinical examination of the right TB at baseline and two-year follow-up were studied. Pain on palpation of the TB was assessed by trained research nurses (0-3). Baseline and follow-up MR images were scored paired in known time-order by two readers following the OMERACT TB OA MRI scoring system (TOMS). The CMC-1 and STT joints were assessed for synovitis (0-3) and bone marrow lesions (BMLs; 0-6 and 0-9, respectively). Radiographs were assessed for the presence of osteophytes in CMC-1 and STT joints following the OARSI atlas by two readers. Since pain was assessed for the TB as a whole, imaging scores of CMC-1 and STT joints were combined, comparing no change in both joints (i.e. ‘stable’) versus change in at least one joint. In TBs without maximum baseline pain, associations between increase in MRI features and increase in TB pain were investigated using logistic regression, presented as odds ratios (ORs) with 95% confidence intervals (CIs). Similarly, in TBs with pain and MRI features present at baseline, associations between decrease in imaging features and decrease in TB pain were investigated. Results Out of 161 patients (82.6% women, mean age 60.8 years, 91.3% fulfilling ACR hand OA criteria) 64 had TB pain at baseline (of whom 11 with maximal score). At the two-year follow-up visit, pain had decreased in 31 patients and increased in 33 patients. The majority had stable synovitis (n=106) and BML (n=96) scores over two years, although decreased (n=22, n=26, resp.) and increased (n=29, n=36, resp.) scores were common. Increase in radiographic osteophytes was rarely (n=10) observed. Increase in synovitis or BML was associated with increased pain, also after adjusting for baseline osteophyte status (Table). A decrease in BML was associated with a decrease in pain, although it did not reach statistical significance. Presence of osteophytes on baseline radiographs was weakly associated with change in pain in univariate analyses and attenuated when adjusting for the change in MRI features. Decrease of synovitis in patients with baseline pain was scarce (n=7), therefore ORs were not computed. Conclusion In this cohort of hand OA patients, thumb base pain levels varied over the course of two years in approximately forty percent of patients. Changes in MRI-defined synovitis and BMLs of the TB joints were positively associated with change in pain on palpation. Baseline osteophytes were not significantly associated with change in pain. While cross-sectionally MRI-defined inflammation may be a less important determinant of pain than radiographic damage, this study shows that a change in inflammatory features may indeed be relevant.  Disclosure of Interests:  Sjoerd van Beest: None declared, H.M. Kroon: None declared, Monique Reijnierse Grant/research support from: Funding from the Dutch Arthritis Foundation. The funding source had no role in the design and conduct of the study., Frits Rosendaal: None declared, Margreet Kloppenburg Grant/research support from: Pfizer, IMI-APPROACH (Grant Agreement n° 115770), Consultant for: GlaxoSmithKline, Merck-Serono, Abbvie, Levicept, Pfizer, Feline P.B. Kroon: None declared