Background Approximately 90% of Rheumatoid Arthritis (RA) patients report foot-related complaints within 10 years of disease onset. More than one-third of patients have significant disease in the feet. Athritis of the foot affects the forefoot, midtarsal, subtalar and ankle in order of decreasing frequency. In recent decade, ultrasonography has been shown to be more specific than clinical examination for detecting synovitis and tenosynovitis in forefoot/hindfoot of RA patients. However, disease of subtalar and midfoot joint is often overlooked and data in this aspect is limited.
Objectives This study described and compared both clinical and ultrasound detected subtalar and/or midfoot joint disease in Chinese RA patients in a tertiary hospital in Hong Kong, China.
Methods A prospective, cross-sectional clinical and ultrasound study where Chinese RA patients with symptomatic ankle, subtalar and/or midfoot joint problems were collected and compared, characteristics and frequency of various pathologies were evaluated. Grey-scale ultrasound (GSUS) and power Doppler ultrasound (PDUS) was used for sonographic assessment according to scanning guidelines published by Outcome Measures in Rheumatology Clinical Trails (OMERACT) ultrasound group.
Results Fifty RA patients with mean disease duration 8.6±6.1 years (ranges from 0-18.5 years) were recruited. Total 55 symptomatic feet scanned. The mean Disease Activity Score (DAS28-CRP) was 3.89±1.02. Clinically 31 patients (56%) had pes planus. The commonest presenting complaint was ankle/midfoot swelling. Clinical versus (vs) sonographic detected synovitis was as follow: ankle (40% vs 33%), subtalar (22% vs 53%), midfoot (29% vs 55%) and tarsometatarsal (2% vs 20%) joints. More clinical synovitis was documented in ankle and midfoot, compared to subtalar and tarsometatarsal joints; whereas synovitis by ultrasound was more evident in subtalar, talonavicular, followed by ankle joints. Sonographically there was more tendon pathologies reported than clinical examination: Peroneal (29% vs 16%) and Tibialis Posterior (25% vs 9%) tendons. Only 10 joints had effusion (4 tibiotalar, 2 talofibular, 2 subtalar, 2 midtarsal joints) and bone erosion was most frequently seen at naviculars and cuneiforms by ultrasound.
Conclusions Subtalar and midfoot joint disease is not uncommon in our cohort of Chinese RA patients. Subtalar synovitis is often mistaken for ankle synovitis. Deformities will set in if the synovitis is not aggressively control. Ultrasonography allows more accurate evaluation of foot pathologies in these patients which aids appropriate treatment adjustment. It is a patient-friendly imaging tool for diagnosis and disease monitoring and shall be done for evaluation of all RA patients.
Acknowledgements Special thanks to Department of Rheumatology, Allergy and Immunology, Tan Tock Seng Hospital, Singapore.
Disclosure of Interest None declared
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