RADIOLOGICAL ASPECTS OF DEFORMITIES ASSOCIATED WITH RHEUMATOID ARTHRITIS

Abstract

Rheumatoid arthritis (RA) is a chronic inflammatory disease that primarily affects synovial joints, leading to progressive structural changes whose radiological findings are fundamental for diagnosis, staging, and monitoring. Initial changes may include periarticular osteopenia, resulting from synovial hyperemia and bone demineralization associated with inflammation. As the disease progresses, bone erosions appear – a characteristic finding consisting of the loss of subchondral cortical bone, most frequently in areas of tendon and ligament insertion, such as the metacarpophalangeal and metatarsophalangeal heads. In addition to erosions, synovial thickening and joint effusion are observed, which can be detected by methods such as ultrasound and magnetic resonance imaging (MRI) even before the appearance of changes on conventional radiography. The progression of inflammation leads to changes in joint congruency, with subsequent instability and development of deformities. The most common deformities present recognizable radiological patterns: ulnar deviation of the fingers, with subluxation of the metacarpophalangeal joints; claw toes, resulting from flexion in the proximal phalanx and extension in the distal phalanx; buttonhole, caused by subluxation of the proximal phalanx over the distal phalanx; and hammer toes, resulting from flexion of the distal phalanx. In the foot joints, hallux valgus and claw toe deformities stand out. In advanced stages, there is synostotic fusion of joints, mainly on the backs of the hands and feet, in addition to alterations in large joints such as knees, hips, and shoulders, which may present narrowing of the joint space, subluxation, and avascular necrosis. Conventional radiography remains the initial method of evaluation, while MRI and ultrasound allow early detection of structural lesions. Radiological monitoring assists in evaluating the response to treatment and determining the patient's functional prognosis.