Rheumatoid arthritis involves inflammation in the lining of the joints affecting several different joints, most commonly the MCP joint. It is typically chronic, which means it lasts a long time, and can be a disease of flare-ups. RA is a systemic disease that affects the entire body and is one of the most common forms of arthritis. It is characterized by the inflammation of the membrane lining the joint, which causes pain, stiffness, warmth, redness and swelling. The inflamed joint lining, the synovium, can invade and damage bone and cartilage. Inflammatory cells release enzymes that may digest bone and cartilage. The involved joint can lose its shape and alignment, resulting in pain and loss of movement. Symptoms include inflammation of joints, swelling, difficulty moving and pain. Other symptoms include loss of appetite, fever, loss of energy, anemia, and rheumatoid nodules.

Rheumatoid deformities in the hand

Rheumatoid hand deformities usually are usually bilateral and symmetric. Each deformity must be analyzed in detail before surgery is considered. Although combinations of deformities occur, involvement of the fingers, thumb, and wrist is typical. The metacarpophalangeal joints and the wrist are affected early in rheumatoid arthritis, whereas the distal two joints usually are affected later. The metacarpophalangeal is the most important joint affecting finger function in rheumatoid disease. Ulnar deviation with palmar subluxation or dislocation of the finger typifies the rheumatoid hand deformity. Osteochondral and ligamentous intraarticular damage, as well as the forces applied through the intrinsic and extrinsic muscles at the metacarpophalangeal joint, affect the deformities at the metacarpophalangeal joint and at the proximal and distal interphalangeal joints. The extent of disease and deformity at the wrist also has an effect on the finger joint deformities. In addition to the typical metacarpophalangeal deformities, the proximal interphalangeal joints may develop boutonniere or swan-neck deformities, and the distal interphalangeal joints, when affected, usually develop a mallet or hyperflexed deformity, depending on the extent of capsular disruption.

Thumb involvement can cause a variety of deformities, depending on the joint in which synovitis begins. Nalebuff et al. noted that synovitis beginning in the thumb MCP joint frequently leads to palmar subluxation and flexion of the proximal phalanx with hyperextension of the interphalangeal joint (boutonniere deformity). When synovitis begins in the thumb carpometacarpal joint, the deformity includes dorsal subluxation of the metacarpal base and hyperextension of the metacarpophalangeal joint (swan-neck deformity). Another thumb deformity caused by synovitic destruction of the capsuloligamentous supports on the ulnar side of the metacarpophalangeal joint is the gamekeeper thumb, which results from laxity of the ulnar collateral ligament of the thumb at the metacarpophalangeal joint. Involvement of the metacarpophalangeal joint also can result in laxity of the capsuloligamentous structures in the volar plate, leading to hyperextension of the metacarpophalangeal joint and interphalangeal hyperflexion but with a stable carpometacarpal joint. Other, more severe deformities of the fingers and thumb can be caused by an erosive rheumatoid disease, leading to the “main en lorgnette” (opera glass hand).

Early ulnar deviation of the metacarpophalangeal joints without subluxation can occur with a rheumatoid hand. Extensor tendons have slipped to the ulnar side. The fifth finger, in particular, is compromised with weak flexion, causing a loss of power grip. (Bottom, right): Complete subluxation with marked ulnar deviation at the metacarpophalangeal joints of a 90-year-old woman with RA. Arrows mark the heads of the metacarpals, now in direct contact with the joint capsule instead of the proximal phalanges.

Thumb Involvement

Three types of deformity have been described for the thumb:

Type I: MCP inflammation leads to stretching of the joint capsule and a boutonniere-like deformity.
Type II: Inflammation of the carpometacarpal (CMC) joint leads to volar subluxation during contracture of the adductor hallucis.
Type III: After prolonged disease of both MCP joints, exaggerated adduction of the first metacarpus, flexion of the MCP joint, and hyperextension of the DIP joint result from the patient’s need to provide a means to pinch.

One of the most common manifestations of RA in hands is tenosynovitis in flexor tendon sheaths, and this can be a major cause of hand weakness. This is manifested on the volar surfaces of the phalanges as diffuse swelling between joints or a palpable grating within flexor tendon sheaths in the palm and may occur in up to half of the patients.

Not infrequently, rheumatoid nodules or less well differentiated fibrin deposits develop within tendon sheaths and may “lock” the finger painfully into fixed flexion. When they are chronic and recurrent, it may be necessary to inject the tendon sheath, or if that fails, remove it surgically.

Significant tenosynovitis of the flexor and extensor tendons in the digits, palm, and over the flexor and extensor surfaces of the wrist can lead to erosive and attritional changes and rupture of the tendons.

Rheumatoid wrist deformities have a significant effect on hand function, especially the position of the fingers at the metacarpophalangeal joint. Rheumatoid synovitis can result in disruption of the intercarpal ligaments, especially the radioscaphocapitate ligament, leading to rotatory instability of the carpal scaphoid and subsequent destructive changes throughout the entire wrist. The distal radioulnar joint stabilizing ligaments are destroyed in a similar fashion, leading to dorsal dislocation of the ulnar head distally and subluxation of the extensor carpi ulnaris tendons with secondary ulnar translocation of the carpus.