Usefulness of US to show subclinical joint abnormalities in asymptomatic feet of RA patients compared to healthy controls.

Objectives: The aim of the present study was to demonstrate the utility of ultrasound to show subclinical feet disease in RA.

Methods: The foot joints (talocrural, talocalcaneal, talonavicular, naviculocuneiform, calcaneocuboid, 5th tarsometatarsal and 1st to 5th metatarsophalangeal [MTP] joints) of 50 healthy subjects and 50 RA patients, with asymptomatic feet, were compared bilaterally. Statistical significance was set at 5%.

Results: Twenty-two joints were examined per individual (2200 in the entire sample). Significantly higher values were found in the RA group regarding quantitative synovitis in all joints recesses (p<0.003), the presence of synovitis (p<0.035) (except the 5thtarsometatarsal and 3rdMTP joint), power Doppler (PD) signals (p<0.029) (talocalcaneal, talonavicular, 1st, 2nd, 3rd and 4thMTP joints) and bone erosion (p<0.003) (except for the talocrural and talocalcaneal joints). Synovitis, PD signals and erosion were observed in 18.3% and 3.05% (p<0.001), 5.77% and 0.22% (p<0.001) and 34.45% and 2.85% (p<0.001) of the RA group and control group, respectively. Greater DAS-28, HAQ and FFI values were associated with ultrasound findings in only some joints (p<0.046). Interobserver agreement was ≤0.686 for semi-quantitative synovitis, ≤0.641 for quantitative synovitis, ≤0.474 for PD signals and ≤1.000 for erosion. Low Cohen Kappa values were found in the correlation between radiography and ultrasound (0.084-0.400). CONCLUSIONS. Ultrasound on RA asymptomatic feet demonstrated a significantly greater number of inflammatory changes in current activity (synovitis, PD signals) and sequelae (erosion) in comparison to control subjects. In the midfoot, the talonavicular joint has the greatest number of ultrasound findings.