The relationship between synovitis and bone changes in early untreated rheumatoid arthritis - A controlled magnetic resonance imaging study

Objective. The interrelationship between synovitis and bone damage in rheum atoid arthritis (RA) is a subject of controversy. Using magnetic resonance imaging (MRI), this study followed the bone changes in early RA and determi ned their relationship to synovitis. Methods. Thirty-one patients with early RA who had swelling of the metacarp ophalangeal (MCP) joints and 31 healthy control subjects with no clinical e vidence of arthritis underwent MRI of the second through fifth MCP joints o f the dominant hand by use of a 1.5T scanner. Coronal T1-weighted and T2-fa t suppressed (FS) sequences were performed to evaluate bone edema, and gado linium-diethylenetriaminepentaacetic acid (Gd-DTPA) pulse sequences were ob tained to evaluate synovitis, Bony abnormalities were described as bone ede ma (low signal on T1-weighted sequences and intermediate/high signal on T2 FS sequences adjacent to the bone cortex) or as bone cysts (circular juxtac ortical abnormalities with low signal on T1-weighted images and with very h igh signal on T2 FS sequences). Contrast and noncontrast MRI films were sco red in a blinded manner, and Fisher's exact probability test was used to de termine differences between groups. Results. Twenty-one of the 31 RA patients (68%) had bone edema, which was s een in 43 of 124 joints (35% of joints) and 3 of the 31 control subjects ha d bone edema seen in 3 of 124 joints (2% of joints) (P < 0.0001), Thirty RA patients (97%) had Gd-DTPA-confirmed MCP joint synovitis, and bone edema w as seen in 10 of the 75 joints with Gd-DTPA-proven synovitis (53%), but in only 3 of 49 without (6%) (P < 0.0001). Conclusion. MCP joint bone edema is present in the majority of patients wit h RA at presentation, but is seen only occasionally in normal control subje cts. The fact that bone edema occurred rarely in the absence of synovitis i n patients with RA suggests that bony changes in RA are secondary to synovi tis.