ARTHRITIS IN THE HAND
The term rheumatic disease refers to any illness characterized by pain and stiffness in or around the joints. These diseases are divided into two main groups: disorders that involve the joints primarily (the different forms of arthritis) and disorders that, although not directly affecting the joints, involve connective tissue structures around the joints (the periarticular disorders, or nonarticular rheumatism). The many types of arthritis and nonarticular disorders differ from one another in etiology, pathogenesis, pathology, and clinical features.
Rheumatoid arthritis and osteoarthritis (also called degenerative joint disease) are the most common forms of arthritis. Both of these chronic conditions are characterized by pain, stiffness, restricted joint motion, joint deformities, and disability, but their differences in pathogenesis, pathology, and clinical features must be distinguished because the prognosis and treatment of the two diseases differ. Other inflammatory arthritides that are of concern in the hand, especially gout, lupus, and psoriatic arthritis, are frequently seen.
Post-traumatic and postinfectious arthritis and treatment are typically specific to the joint affected by the insult, and the principles of treatment are often similar to those for the more common types of arthritis.
Some clinical manifestations are unique to particular joints. Heberden nodes, hallmarks of osteoarthritis, develop only at the terminal joints of the fingers. While the cartilage of the distal interphalangeal joint is degenerating, osteophytes grow from the dorsomedial and lateral aspects of the base of the distal phalanx to produce these nodular protuberances. Flexion or lateral deviation deformity usually results when the pathologic changes are severe. Early in their development, the nodes are tender and painful, especially when ganglion (mucoid) cysts coexist; when mature, they are asymptomatic and have only cosmetic significance. Heberden nodes are more common in women and are often familial. Bouchard nodes, similar to but less common than Heberden nodes, develop at the proximal interphalangeal finger joints.
At the base of the thumb, the carpometacarpal articulation is the most common joint to undergo the degenerative changes of osteoarthritis. This joint is affected much more often in women. Local tenderness and pain, usually severe, are exacerbated by firm grasping and pinching, and progressive stiffness ensues.
Early and Moderate Hand Involvement The joints of the hands and wrists are among the most frequent sites of involvement. In the fingers, some or all of the proximal interphalangeal joints are often bilaterally affected, whereas the distal interphalangeal joints are seldom involved. Because the inflammatory swelling occurs only at the middle joints, the affected fingers become fusiform in the early stages of disease. The metacarpophalangeal and wrist joints may also become inflamed. At first, there is little restriction of motion in the involved joints, but stiffness, swelling, and pain prevent the patient from making a tight fist, thus weakening grip strength. Except for soft tissue swelling, radiographs reveal no abnormalities.
Advanced Hand Involvement
As the disease progresses and the inflammation invades the joints, destroying articular cartilage and bone, joint motion becomes severely limited and joint deformities develop. Flexion deformities frequently occur at the proximal interphalangeal and metacarpophalangeal joints. The patient cannot fully extend or flex the fingers, and the grip becomes progressively weaker. Radiographs reveal cartilage thinning, bone erosions at the joint margins, and metaphyseal osteoporosis. After years of chronic inflammation, joint damage becomes severe; the joint capsule stretches; muscles atrophy and weaken; and tendons stretch, fray, and even rupture. All of these changes result in severe, incapacitating deformities.
A number of hand deformities are seen in the late stages of rheumatoid arthritis. For example, the muscles on the ulnar side of the fingers and wrist may over-power those of the radial group, causing ulnar deviation of the fingers at the metacarpophalangeal joints; the wrists may also be affected. The swan-neck deformity of the finger is common, as is the boutonniére deformity of the thumb, which is caused by hyperextension of the proximal interphalangeal joint and flexion at the metacarpophalangeal joint. The long extensor tendon may rupture near the distal interphalangeal joint, leaving the distal phalanx permanently flexed. Pro-longed disease may lead to permanent subluxation or dislocation of the finger joints, and severe cartilage and bone erosion at the wrist may literally destroy the carpus. In this late stage of the disease, radiographs help to define the severity of the structural damage and deformities.
About 10% of persons with psoriasis have some form of inflammatory joint disease. Onset of the skin disease may long precede the arthropathy, but occasionally the reverse is true. The distinguishing features of psoriatic arthritis are (1) a predilection for the distal joints of the fingers and toes, frequently accompanied by psoriatic involvement of only a few other joints of the limbs; (2) destructive and mutilating changes of the phalanges adjacent to the inflamed joints, which produce the radiographic appearance of a “whittling” or “pencil point in cup” of the proximal phalanx and a “cupping” of the central portion of the base of the apposing distal phalanx, with bony proliferation of the borders; (3) shortening, angulation, and telescoping of the fingers due to extensive bone resorption in the phalanges; and (4) frequent involvement of the sacroiliac joints and spine, which simulates ankylosing spondylitis.
GOUT AND GOUTY ARTHRITIS
Almost always, the first clinical evidence of gout is acute arthritis in one or a few peripheral joints. A fulminant synovitis begins abruptly, typically during the night, frequently involving the first metatarsophalangeal joint. After several years of recurrent acute arthritis and persistent hyperuricemia, deposits of monosodium urate, called tophi, form in joint structures (and other tissues). Tophi are the hallmark of chronic gout, occurring in 50% of patients. They cause structural damage to articular cartilage and adjacent bone, resulting in chronic arthritis. In this late stage of the disease, known as chronic tophaceous gout, the affected joints show irregular knobby swelling and signs of chronic inflammation. Joint motion is limited and painful, deformities develop, and sinuses tend to form at the swollen joint, from which a calcific exudate drains from the underlying urate deposits.
Radiographs show marked destruction of bone and cartilage and “punched out” areas in the bone caused by the urate deposits. Tophi often form in extra-articular structures as well, especially in the extensor tendons of the fingers and toes, the olecranon and infrapatellar bursae, the calcaneal tendon, the cartilage f the external ear, and the parenchyma of the kidney.
Reiter syndrome has been considered a clinical triad of urethritis, conjunctivitis, and arthritis. It is now accepted that a specific type of dermatitis is another characteristic of the disease, and diagnosis of complete Reiter syndrome requires the presence of at least three of these four signs: rarefaction of bone near the inflamed joints visible on radiographs (in chronic disease, articular cartilage destruction and joint deformities are also apparent); sacroiliac involvement (sometimes unilateral); vertebral syndesmophytes in skip distribution; and periosteal new bone formation at the insertion of the calcaneal tendon and calcaneal spurs.