The Rheumatoid Finger: Treatment Concepts and Indications for Surgery

Abstract

Synovial proliferation in rheumatoid arthritis causes capsular distension, destruction of tendons and ligaments, and erosion of bone. The classic deformities in rheumatoid arthritis, like boutonniere 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 boutonniere or swan-neck deformity.