POS1367 MICROWAVE ABLATION OF SYNOVIAL HYPERTROPHY IN THE TREATMENT OF MEDICAL TREATMENT RESISTANT RECURRENT MONOARTHRITIS
Authors: R. Deniz, T. Güzelbey, İ. N. Mutlu, Ç. Erdim, B. Karaalioglu, D. Ozgur, G. Akkuzu, F. Yildirim, K. Kalkan, Ö. Kiliçkesmez, C. Bes
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Recurrent monoarthritis (RM) causes serious disability in many rheumatic diseases. Local interventions, namely intra-articular synovial fluid aspiration (IAA) and intra-articular corticosteroid injection (IAS) are frequently used to control single-joint involvement. Although medical (chemical or radiation) or surgical (arthroscopic or open) synovectomy are options in cases that cannot be controlled with local and systemic medical treatments, it is gradually abandoned due to both unfavorable long-term results and complications. Ablation is a well-known minimally invasive technique in the treatment of benign or malign lesions of different etiologies and has been recently started to be used in muskuloskeletal disorders. Until now, most experience is on osteoarthritis used to relieve pain resistant to conventional treatment. Also, in a small case series pigmented villonodular synovitis (PVNS) was treated successfully with radiofrequency ablation (RFA). <h3>Objectives:</h3> We aimed to to investigate the use and safety of microwave ablation (MWA) as an adjunctive therapy in medical treatment resistant RM. <h3>Methods:</h3> Rheumatoid arthritis, spondyloartropathy, Behçet's disease, juvenile idiopathic arthritis, and undifferrentiated inflammatory monoarthritis patients with RM attacks were included. MWA was performed after measuring size of synovial hypertrophy with proper power and duration until microbubbles were shown indicating necrosis. Patients' demographics, treatments, IAA, complications, functional disability and pain scores, routine laboratory parameters, ultrasonography and magnetic resonance images were recorded. <h3>Results:</h3> We applied MWA in totally 17 knee joints of 6 female and 10 male patients aged between 22-71 years. Pre-procedure IAA need in last 6 months was median 5 (3-11). In one patient MWA was applied only to reduce synovial hypertrophy volume without a need for frequent IAA need. Second MWA session was needed in 3 patients and third session in 1 patient. The median follow-up was 9 (4-13) months. Six post-procedure IAA were performed in overall follow-up; in two patient in second MWA session, in one patient at 10 th month, and 3 in first 3 months of follow-up. Overall IAA count in last 6 months before MWA in total 102 months was 93 and it decreased to 6 in post-MWA follow-up in total 148 months (p&lt;0.001). In 8 patients, short time low-dose additional corticosteroid were given for different reasons, especially in first 3 months. Functional disability and pain scores were improved significantly (median score from 9 to 1, p&lt;0.00001, in both, Figure 1). In MRI follow-up significant regression in synovial hypertrophy volume was shown especially after 6 th months (figure 2). No complication was observed during procedure or follow-up. <h3>Conclusion:</h3> As a less invasive technique, MWA technique did not lead to any important adverse effects and seems as a promising adjunctive treatment in RM resistant to medical treatment and synovial hypertrophy in rheumatic diseases in whom synovectomy was not suitable. The number of monoarthritis attacks, size of synovial hypertrophy, the need of intraarticular corticosteroid injection, and IAA were decreased, and both functional disability and pain scores were dramatically improved. Long-term results and replication of these findings in different centers and larger patient cohorts are expected to verify these favorable outcomes and the applicability of the MWA technique. <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>