Ability of Oblique Foot Radiographs to Detect Erosions in Early Arthritis: Results in the ESPOIR Cohort

Objective. To assess the usefulness of using oblique foot radiographs in addition to posteroanterior radiographs of the hands and feet for detecting erosions in patients with recent-onset arthritis. Methods. We included 813 patients from the prospective French ESPOIR cohort with arthritis of <6 months' duration and >= 2 swollen joints. Baseline standardized posteroanterior radiographs of the hands and feet and oblique radiographs of the feet were assessed by 2 blinded readers for erosions typical for rheumatoid arthritis (ETRA) and the Sharp score as modified by van der Heijde. Results. A total of 715 complete sets were available. Mean +/- SD total Sharp scores were 3.6 +/- 6.6, 2.5 +/- 6.3, and 1.8 +/- 5 for the band and wrist, foot, and oblique foot, respectively. ETRA were visible in 160 (22.4%) of 715 patients (95% confidence interval [95% CI] 19.4-25.6). They were seen on hand radiographs in 86 (53.7%) of 160 patients (95% CI 45.7-61.6), on posteroanterior foot radiographs in 91 (56.9%) of 160 patients (95% CI 48.8-64.6), and on oblique foot radiographs in 84 (52.5%) of 160 patients (95% CI 44.5-60.4). ETRA were visible at the feet, but not at the hands, in 74 (46%) of 160 patients (95% CI 38.4-54.3), among whom 22 (30%) had erosions only on the posteroanterior view, 16 (21%) only on the oblique view, and 36 (48.6%) on both. Conclusion. ETRA were found in 22.4% of patients. Adding an oblique foot radiograph identified 16 (10%) of 160 additional patients (95% CI 6-16), compared with 27.5% and 13.8% identified by adding posteroanterior radiographs of the hands and feet, respectively.