Is it worth including subtalar joint in ultrasound ankle assessment of patients with juvenile idiopathic arthritis?

Abstract

None of the controls showed US STJ synovitis. US detected synovitis in 27 (54%) STJs of patients. Agreement between clinical and US assessment for presence and absence of STJ involvement was found in 17 (34%) and 16 (32%) ankles, respectively. In 10 (20%) STJs not considered to be clinically affected, synovitis was found on US. In 7 (14%) ankles labelled as having STJ involvement on clinical examination US was negative for STJ, but showed the involvement of different anatomical sites (midfoot, tibiotalar joint, tendons). Overall, the concordance between clinical and US evaluation was poor (k=0.32). The Cohen-kappa value for inter-observer reliability of STJ involvement on US was high (k= 0.92). All patients having US findings in the medial and/or posterior side of STJ presented also with US findings using the lateral scanning approach, but the reverse was not true. Conclusion US is more sensitive than clinical evaluation in the assessment of STJ in ankles with active disease. The high frequency of its involvement may suggest to include the assessment of STJ in US scanning protocols. In this perspective, the lateral approach to the joint seems to be more appropriate for US evaluation of STJ involvement.