Background From our experience, a small cohort of patients with juvenile idiopathic arthritis (JIA) develop irreversible damage to ankle and subtalar joints despite immunosuppression with methotrexate and multiple biologic agents. In this case series, we describe 4 patients with JIA and erosive damage to ankle or subtalar joints who underwent arthrodesis by a single surgeon between 2011-2017 due to longstanding pain and impaired function despite medical and orthotic interventions. We assessed patient satisfaction regarding the procedure in terms of pain and function. There are no previous case series describing arthrodesis of ankle and subtalar joints in JIA. A case series of 8 patients with severe tibiotalar JIA who had arthrodiastasis (joint distraction) reported an improvement in pain and functional scores. Methods In this retrospective case series we reviewed the records of 4 paediatric patients with JIA in Scotland who underwent ankle arthrodesis performed by a single orthopaedic surgeon between 2011 and 2017. Questionnaires were posted out to each patient. These included Manchester-Oxford Foot scores (MOxFQ) and EQ5D scores. Results Time from diagnosis to commencing methotrexate (MTX) was 22 (6-30) months, time from diagnosis to biologic therapy was 5 (2-8) years and time to arthrodesis was 10 (6-14) years (Table 1). Age at surgery was 16 (13-20) years. Prior to surgery all patients reported significant ankle pain and 2 patients needed to wear an ankle-foot orthosis (AFO). Radiological features before surgery in these patients included marked degenerative changes and loss of articular cartilage in the ankle joints on MRI. All patients reported favourable scores in terms of function and pain following ankle or subtalar arthrodesis. Two patients expressed that they wished they had undergone surgery sooner. P12 Table 1: Patient Characteristics Patient JIA Subtype Comorbidity Age at diagnosis of JIA (years) Systemic Therapy No of joint injection episodes Visual Analogue Pain Score Post-Surgery 1 RF –ve Polyarticular Nil 8 MTX 3 Etanercept Adalimumab Abatacept 2 Extended oligoarticular Uveitis 3 MTX 4 1/10 Adalimumab 3 RF –ve Polyarticular Nil 6 MTX 4 0/10 Etanercept 4 RF –ve Polyarticular Trisomy 21, VSD closure, obstructive sleep apnoea 11 MTX 7 Etanercept Tocilizumab Patient JIA Subtype Comorbidity Age at diagnosis of JIA (years) Systemic Therapy No of joint injection episodes Visual Analogue Pain Score Post-Surgery 1 RF –ve Polyarticular Nil 8 MTX 3 Etanercept Adalimumab Abatacept 2 Extended oligoarticular Uveitis 3 MTX 4 1/10 Adalimumab 3 RF –ve Polyarticular Nil 6 MTX 4 0/10 Etanercept 4 RF –ve Polyarticular Trisomy 21, VSD closure, obstructive sleep apnoea 11 MTX 7 Etanercept Tocilizumab P12 Table 1: Patient Characteristics Patient JIA Subtype Comorbidity Age at diagnosis of JIA (years) Systemic Therapy No of joint injection episodes Visual Analogue Pain Score Post-Surgery 1 RF –ve Polyarticular Nil 8 MTX 3 Etanercept Adalimumab Abatacept 2 Extended oligoarticular Uveitis 3 MTX 4 1/10 Adalimumab 3 RF –ve Polyarticular Nil 6 MTX 4 0/10 Etanercept 4 RF –ve Polyarticular Trisomy 21, VSD closure, obstructive sleep apnoea 11 MTX 7 Etanercept Tocilizumab Patient JIA Subtype Comorbidity Age at diagnosis of JIA (years) Systemic Therapy No of joint injection episodes Visual Analogue Pain Score Post-Surgery 1 RF –ve Polyarticular Nil 8 MTX 3 Etanercept Adalimumab Abatacept 2 Extended oligoarticular Uveitis 3 MTX 4 1/10 Adalimumab 3 RF –ve Polyarticular Nil 6 MTX 4 0/10 Etanercept 4 RF –ve Polyarticular Trisomy 21, VSD closure, obstructive sleep apnoea 11 MTX 7 Etanercept Tocilizumab Conclusion This case series helps demonstrate patient satisfaction in the small group of patients in our service where irreversible erosive disease caused pain and dysfunction not responsive to medical therapy. Conflicts of Interest The authors declare no conflicts of interest. [ABSTRACT FROM AUTHOR]