The most frequently ruptured tendons in rheumatoid arthritis (RA) are the extensor digiti minimi (EDM), followed by the extensor digitorum communis (EDC) tendons to the small, ring, long, and index fingers, in that order; the extensor pollicis longus (EPL); the flexor pollicis longus (FPL); and, rarely, the flexor digitorum superficialis (FDS) and the flexor digitorum profundus (FDP).

Patients with isolated small finger extensor tendon (EDM) rupture may still be able to extend the small fingers through the EDC or through the juncturae connecting it to the ring finger (Fig. 31-1). However, these patients will not be able to perform independent extension of the small finger with the other fingers flexed.

Patients with rupture of the EDC to one finger may still be able to extend the finger owing to the juncturae connecting it to intact adjoining fingers. However, patients are usually unable to extend the finger when they have ruptured more than one EDC (Fig. 31-2). The inability to extend the finger in RA may also be caused by ulnar subluxation of the extensor tendons over the head of the metacarpal (Fig. 31-3) and rarely is due to posterior interosseous nerve palsy resulting from elbow synovitis. To differentiate between these causes, it is useful to passively extend the finger and ask the patient to hold it there. Patients with tendon rupture or nerve palsy will be unable to maintain the finger in extension, whereas patients with subluxation will be able to do so as the tendon relocates over the metacarpophalangeal (MCP) joint with finger extension. Patients with tendon rupture will also lose the tenodesis effect of finger extension with wrist flexion, whereas the tenodesis effect will be preserved in nerve palsy.

The function of the EPL is tested by asking the patient to lay the palm of the hand flat on the table and then asking the patient to lift the thumb away from the table (retropulsion).

One must also examine the integrity of the EIP by testing for independent extension of the index finger with the other fingers held in flexion. The function of the FDS and FDP is also checked. The EIP and FDS to the ring and long fingers are often used as motors for tendon transfers in patients with rupture of multiple extensor tendons. Figure 31-4 shows testing for FDS function of the long and ring fingers.

It is important to obtain radiographs of the wrist to evaluate the distal radioulnar (DRU), midcarpal, and radiocarpal joints. Pathology involving these joints will also need to be addressed at the time of tendon reconstruction to prevent progressive deformity and rerupture of the reconstructed tendons.