The relationship between soft tissue swelling, joint space narrowing and erosive damage in hand X-rays of patients with rheumatoid arthritis

Objectives. To test the hypotheses that the progression of joint space narr owing behaves differently from the progression of erosions and that clinica lly and radiologically assessed soft tissue swelling relates more to diffus e cartilage loss than to erosive damage. Methods. Radiographs and clinical data were obtained from 28 patients in a prospective, multicentre, randomized, placebo-controlled trial of prednisol one 7.5 mg daily over 2 yr. Radiographic scoring included the Larsen score, joint space narrowing and soft tissue swelling. Clinical joint inflammatio n in the hands was assessed every 3 months and cumulative synovitis score o ver the period of study was then calculated for each joint. The placebo-tre ated patients and the prednisolone-treated patients were analysed separatel y. The Larsen scores were compared after log transformation [transformed sc ore = log(10) (original score + 1)1. Changes in Larsen scores and joint spa ce narrowing scores were compared with the cumulative presence of clinical synovitis and radiological soft tissue swelling using the correlation coeff icient. Results. There was a difference in the rate of progression in the Larsen sc ore between placebo- and prednisolone-treated patients. but there was no si gnificant difference in the rate of joint space loss. In placebo-treated pa tients, measures of synovitis correlated more strongly with progression of joint space narrowing than with changes in the Larsen score. In prednisolon e-treated patients there was no correlation between clinical synovitis and change in Larsen score (r = 0.029) and only a slight and non-significant co rrelation with joint space narrowing (r = 0.127). Radiographic evidence of soft tissue swelling remained correlated with joint space narrowing (I = 0. 279. P < 0.001) but was not correlated with change in Larsen score (r = - 0 .113, P < 0.001 for difference between correlations). The correlation betwe en Larsen score progression and joint space narrowing seen in the non-treat ed patients was completely abolished in the glucocorticoid-treated group (r = - 0.003). Conclusions. The progression of joint space narrowing behaves differently f rom the progression of erosions. Prednisolone slows (or even slops) the pro gression of erosions las assessed by the Larsen score) while making no diff erence to the progression of cartilage loss (as assessed by joint space nar rowing). The results also suggest that synovitis, whether measured clinical ly or radiologically, is more closely related to diffuse cartilage loss tha n to erosion progression. Any link between synovitis acid erosions is aboli shed by glucocorticoid therapy while the link between synovitis and cartila ge loss is not, pointing to at least two different mechanisms for these obs erved radiological features.