The rheumatoid finger : Treatment concepts and indications for surgery

Synovial proliferation in rheumatoid arthritis causes capsular distension, destruction of tendons and ligaments, and erosion of bone. The classic deformities in rheumatoid arthritis, like boutonnière or swan neck, are not consistent, and each patient may have his or her own pattern of deformities. The anatomic arrangement of the tendons enables motion of the proximal interphalangeal (PIP) joint isolated and separated from the distal interphalangeal (DIP) joint. The central band of the extensor mechanism and the flexor digitorum superficialis (FDS) both insert on the middle phalanx and both contribute to the control of the PIP joint. In contrast, the flexor digitorum profundus (FDP) tendon runs along the whole finger and acts on both the PIP and DIP joints. In a similar fashion, the conjoined lateral bands insert on the distal phalanx but influence the motion of the PIP joint as well. A change in length, by distention, rupture, or inability to glide one or several of these tendons, will provoke an imbalance, which may lead to a boutonnière or swan-neck deformity. A boutonnière deformity is often identified as a substantial problem to the patient, especially when the DIP joint has gone into hyperextension. Also the swan-neck deformity most often is identified by the patient as a source of severe subjective hand and finger functional impairment because of impaired grip. If a moderate lack of extension after treatment is accepted by the patient, surgical treatment offers an acceptable solution. Implants may be used in stiff joints to regain some mobility of the PIP joint but rebalancing of the extensor mechanism is difficult