To assess the role of diagnostic imaging techniques in the identification and follow-up of the anatomical damage induced by the chronic inflammatory process of rheumatoid arthritis (RA) not only to study the natural history of the disease but also and especially to assess the long-term response to disease-modifying anti-rheumatic drugs (DMARD).
The relative literature data were reviewed and compared with our personal experience with different imaging modalities such as conventional radiography (CR), ultrasound (US) and magnetic resonance imaging (MRI).
Several radiologic techniques have been used over the years to study articular damage in RA: they describe and quantify the articular damage (semi-quantitative analysis) based on a series of parameters and elementary anatomical lesions which are given a rising score. For its sensitivity in detecting early disease signs and the possibility to express anatomical damage progression quantitatively, Sharp's index is considered the best tool for evaluating RA patients. The close correlation between clinical parameters and the radiologic scores obtained regardless of the method applied led to a new concept of anatomical damage related to the 'radiologic progression of the disease' which is a more precise measure of RA severity than the single isolated radiograph. The progression of radiologic damage in rheumatoid arthritis is expressed as the number or proportion of new eroded joints/year: independent of the index adopted and the terms used to express progression, severe radiologic damage occurs in the early disease stage, involving approximately 2% of the joints within about 1 year, and 13% within 2 years, with an estimated average annual progression of 1.3%. Radiologic techniques evaluate the anatomical damage in the course of RA only with reference to the osseous component of the joint and therefore apply to a disease stage that is largely irreversible. MRI and US detect the soft-tissue damage occurring in the earlier phases and are more likely to respond to early treatment. The former technique appears to be useful to detect soft-tissue damage like synovial pannus, intra- and periarticular and peritendinous effusion, capsuloligamentous articular and tendon changes. Its high sensitivity for minimal bone erosions and chondromalacia has been demonstrated. US allows to demonstrate a wide range of soft-tissue changes of the hand and wrist. Joint-cavity widening, loss of cartilage definition, bone erosions, widening of flexor tendon sheath and tendon structure are also well depicted on ultrasound images.
CR is the central tool in the diagnosis, staging and follow-up of RA patients and in general in the assessment of treatment efficacy; MRI and US are complementary tools.