Small joint involvement: a systematic roentgenographic study in rheumatoid arthritis.

Standard hand and foot roentgenograms from 200 consecutively hospitalised patients with definite or classical rheumatoid arthritis (RA) were read for marginal erosions by three independent observers. For each joint or group of joints analysed the degree of symmetry (S = absolute symmetry, U = unilateral, PS = partial symmetry) was determined. The total number of joints affected significantly correlated only with disease duration; symmetry of erosions and number of affected patients were not influenced by seropositivity. Metatarsophalangeal erosions (in 70%) were the most common and were classified as S in 16%, U in 21%, and PS in 63%. Metacarpophalangeal erosions (in 68%) were also common, with a symmetry pattern of S in 19%, U in 21%, and PS in 60%. Proximal finger interphalangeal erosions (in 42%) were unilateral in 42% (S in 8% and PS in 50%). The only site where symmetry was usual (90%) was the wrist, but radiocarpal and intercarpal joints were considered together. Erosions also occurred in about 16% of the finger distal interphalangeal and 28% of the great toe interphalangeal joints. In RA roentgenographic asymmetry is usual and unilateral involvement common.