Background MRI of the wrist can be used to measure cartilage damage in rheumatoid arthritis (RA) (1) and this is usually diffuse in distribution, involving multiple joints. We have recently developed a score for quantifying cartilage damage in gout (2) and now explore the pattern of involvement and associations with joint inflammation.
Objectives To compare MRI cartilage damage in gout with RA, focussing on distribution and severity. To investigate associations between cartilage damage and joint inflammation indicated by MRI synovitis and bone marrow edema (BME) in gout vs RA.
Methods Two cohorts were studied using 3T high field MRI with wrist coil and cartilage-sensitive sequences (1). 40 gout and 38 RA patients were scanned (mean disease duration 18 and 7.6 yrs respectively). Cartilage damage was scored using validated criteria: AMRICS  for RA and the gout MRI cartilage scoring system . Comparisons used the 6 carpal sites common to both systems. The total cartilage damage score was expressed as % possible maximum. Synovitis and BME were scored using RAMRIS. Ordinal logistic regression was used to compare the number of cartilage sites involved between gout and RA patients, and also to compare total cartilage scores, both adjusted for disease duration and synovitis.
Results Many fewer sites were affected by cartilage damage in gout compared with RA despite the much longer disease duration (p=0.001). 42.5% of gout patients had 0 sites involved and 15% had 3-6 sites involved vs 10.5% and 60.5% respectively for RA patients (Figure 1). Ordinal logistic regression revealed that the association (fewer abnormal cartilage sites in gout compared with RA) was significant (p=0.001). % Max total cartilage scores were significantly lower in gout compared with RA (p=0.0009), adjusting for synovitis and duration. In gout, increasing total synovitis scores were associated with increasing number of cartilage sites (p=0.02) but there was no association between % Max total cartilage score and synovitis in gout. The Spearman's correlation between cartilage damage and synovitis in gout did not reach significance (R =0.31, p=0.10) compared with a strong correlation in RA (R =0.60, p<0.0001). Examining the differences in BME between the 2 conditions: the median (min,max) RAMRIS BME score for gout was low at 0 (0, 6) compared with RA at 10 (0, 29) and there was no correlation between BME and cartilage scores in gout (R =0.10, p=0.55) as opposed to a highly significant correlation in RA (R =0.70, p<0.0001).
Conclusions Patterns of cartilage damage at the wrist differ for these 2 conditions. In gout, cartilage damage is focal and mild compared with RA where it is diffuse and more severe. Cartilage damage is associated with synovitis and osteitis in RA but not in gout. Pathways leading to cartilage damage are likely to differ in these 2 diseases.
McQueen F, Clarke A, McHaffie A, et al. ARD 2010;69:1971-75. 2) Popovich I, Dalbeth N, Doyle A, et al. Skeletal Radiol. Revision submitted
Disclosure of Interest None declared