1Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, Leeds, UK; 2Department of Rheumatology, MC Groep Hospitals, Lelystad, The Netherlands; 3Institute of Rheumatology, Charles University, Prague, Czech Republic; 4Hôpital Ambroise Paré, Boulogne-Billancourt, France; 5Universita degli Studi di Turino, Turin, Italy; 6Azienda Ospedaliero Universitaria Pisana, Pisa, Italy; 7Instituto Nacional de Rehabilatacion, Mexico City, Mexico; 8Diakljohemmet Hospital, Oslo, Norway; 9Virginia Mason Medical Center/University of Washington, Seattle, United States; 10Rehabilitation Clinical Hospital, Cluj Napoca, Romania; 11Instituto Poal de Reumatologia, Barcelona, Spain; 12Institute of Rheumatology and Orthopaedics, Royal Prince Alfred Hospital, Sydney, Australia; 13Cliniques Universitaires Saint-Luc Institut de Recherche Expérimentale et Clinique (IREC), Brussels, Belgium; 14Japanese Red Cross Medical Center, Tokyo, Japan; 15Center for Rheumatology and Spine Diseases, Rigshospitalet-Glostrup, Denmark; 16Clinical Hospital Sf. Maria, Clinical Hospital Sf Maria, Bucharest, Romania; 17Bergman Clinics, Naarden, The Netherlands
Background: Subtalar joint (STJ) disease in patients with rheumatoid arthritis (RA) is notoriously difficult to assess clinically [1, 2] and frequently overlooked in favour of assessing the tibiotalar joint. Pathology in the STJ greatly increases between five and ten years of disease duration and regularly precedes changes in the tibiotalar joint [1, 3, 4].
Ultrasound (US) is an accessible, non-invasive, and relatively inexpensive bedside imaging technique, that is repeatable as many times as required at the time of consultation and is characterised by high patient acceptability. Although US has been shown to have a higher sensitivity for detecting inflammation in patients with RA compared to clinical examination, reliability at the STJ has not been confirmed in patients with hindfoot problems [5, 6].
Objective: To evaluate the intraobserver and interobserver reliability of the US assessment of STJ synovitis in patients with RA using OMERACT consensual definitions.
Methods: Twelve sonographers (10 rheumatologists and two podiatrists) conducted an US reliability exercise on 10 RA patients with rearfoot pain. The anteromedial, posteromedial, and posterolateral STJ was assessed using B-mode and power Doppler (PD) techniques according to an agreed US protocol and using a 4-grade semiquantitative grading score for synovitis (synovial hypertrophy (SH) and power Doppler (PD) signal) and a dichotomous score for the presence of joint effusion (JE). Each patient was randomly assigned to a sonographer where they were assessed in two rounds, one in the morning and another in the afternoon. The STJs of both feet were included in the US assessment. Intraobserver and interobserver reliability were computed by Cohen and Light kappa. Weighted k coefficients with absolute weighting were computed for B-mode and PD signal. Kappa values of 0-0.20 were considered poor, 0.20-0.40 fair, 0.40-0.60 moderate, 0.60-0.80 good, and 0.80-1 excellent.
Results: Intraobserver reliability
Mean weighted Cohen’s kappa and 95% confidence intervals [CI] (range) for SH, PD, and JE, was 0.80 (0.62-0.98), 0.61 (0.48-0.73), and 0.52 (0.36-0.67), respectively. Weighted Cohen’s kappa for SH, PD, and JE in the anteromedial, posteromedial and posterolateral STJ was -0.04-0.79, 0.42-0.95, and 0.28-0.77; 0.31-1, -0.05-0.65, and -0.2-0.69; 0.66-1, 0.52-1, and 0.42-0.88, respectively.
Interobserver reliability
Weighted Light kappa (95%CI) for SH was 0.67 (0.58-0.74), 0.46 (0.35-0.59) for PD, and 0.16 (0.08-0.27) for JE. Weighted Light kappa for SH, PD, and JE was 0.63 (0.45-0.82), 0.33 (0.19-0.42) and 0.09 (-0.01-0.19) for the anteromedial; 0.49 (0.27-0.64), 0.35 (0.27-0.4), and 0.04 (-0.06-0.1) for posteromedial, and 0.82 (0.75-0.89), 0.66 (0.56-0.8), and 0.18 (0.04-0.34) for posterolateral STJ, respectively.
Conclusion: In this multi-observer study of the STJ in patients with RA, US is a reliable tool for assessing synovitis of the STJ in RA, using a consensus driven US protocol and agreed scoring system. The most reliable site is the posterolateral probe position. A reliable imaging scoring system would be of potential value in clinical practice and research to monitor the effects of drug therapy and mechanical interventions, such as footwear and orthoses, in patients with RA and hindfoot pain over time.
References:
1. Otter SJ, Lucas K, Springett K, et al. Comparison of foot pain and foot care among rheumatoid arthritis patients taking and not taking anti-TNF<alpha>: an epidemiological study. Rheumatol Int 2011; 31: 1515-9.
2. Wechalekar MD, Lester S, Hill CL, Lee A, Rischmueller M, Smith MD, Walker JG, Proudman SM. Active foot synovitis in patients with rheumatoid arthritis: Unstable remission status, radiographic progression, and worse functional outcomes in patients with foot synovitis in apparent remission. Arthritis Care Res (Hoboken) 2016; 68:1616-1623.
3. Vidigal E, Jacoby RK, Dixon AS, Ratliff AH, Kirkup J. The foot in chronic rheumatoid arthritis. Ann Rheum Dis. 1975 ; 34: 292-7.
4. Bouysset M, Tebib JG, Weil G, Lejeune E, Bouvier M. Deformation of the adult rheumatoid rearfoot. A radiographic study. Clin Rheumatol 1987; 6 :539-44.
5. Wakefield RJ, Kong KO, Conaghan PG et al. The role of ultrasonography and magnetic resonance imaging in early rheumatoid arthritis. Clin Exp Rheumatol 2003; 21:S42-S49.
6. Wakefield RJ, J E Freeston, P O’Connor, N Reay, A Budgen, E M A Hensor,P S Helliwell, P Emery, J Woodburn. The optimal assessment of the rheumatoid arthritis hindfoot: a comparative study of clinical examination, ultrasound and high field MRI. Ann Rheum Dis 2008; 67: 1678-82.