Sonographic assessment of cartilage damage at metacarpal head in rheumatoid arthritis: qualitative versus quantitative methods

Objective: To test the validity of the Outcome Measure in Rheumatology (OMERACT) semiquantitative score by comparing with a quantitative method in the sonographic (US) assessment of hyaline cartilage at the metacarpal head (MH) in patients with rheumatoid arthritis (RA) and healthy subjects (HS).

Methods: The hyaline cartilage from second to fifth MHs of both hands was scanned. Hyaline cartilage was scored semiquantitatively and quantitatively (by measuring cartilage thickness and comparing with reference values). In RA patients, radiographic joint space narrowing (JSN) was scored on the same joints using the Simple Erosion Narrowing Score (SENS).

Results: Four-hundred and eight MHs in 51 RA patients and 320 MHs in 40 HS were evaluated. The OMERACT semiquantitative score was quicker to perform than the quantitative method (6.0 ± 0.5 vs 8.0 ± 1.5 min, p< 0.01). A significant correlation between the US scores (R = 0.68), and between the US scores and the JSN-SENS (R = 0.61 and R = 0.63, for semiquantitative and quantitative method, respectively) was found. The frequency of cartilage abnormalities was similar between the two US methods in RA patients (58.8% and 51.0% RA patients for semiquantitative and quantitative method, p= 0.46), while the former revealed more abnormalities in HS (27.5% and 7.5% of HS, p= 0.02).

Conclusion: The higher feasibility of the OMERACT semiquantitative score suggests its use as first-choice method in the evaluation of cartilage damage. However, despite its limits, the quantitative assessment of HC, providing patient-tailored information due to age- and sex-corrected cut-off values, may represent a valid supplement for optimizing the evaluation of cartilage damage in selected cases.

Keywords: Hyaline cartilage; Metacarpophalangeal joint; Rheumatoid arthritis; Structural Damage; Ultrasonography.