(A) Extensor indicis proprius
(B) Extensor pollicis longus
(C) Flexor carpi ulnaris
(D) Flexor digitorum profundus to the small finger
(E) Flexor pollicis longus

The correct response is Option B.

Tendon ruptures are a common complication of rheumatoid arthritis because the environment, structure, and vascularity of the tendon are affected abnormally by this condition. Tendon ruptures often occur as the tendon glides over a roughened area of bone, joint, retinaculum, or synovium. In addition, hypertrophic tenosynovium may displace a tendon from its normal position. Tendon ruptures typically manifest as sudden onset of sharp pain or a snapping sensation. However, associated findings may be more subtle in patients who have severe deformities resulting from rheumatoid arthritis.

The extensor tendons are ruptured most commonly, with the extensor pollicis longus (EPL) and extensor digiti quinti (EDQ) tendons being affected most frequently. While rupture of the EPL tendon may manifest as sudden inability
to extend the thumb, it also may be more subtle, because the intrinsic tendons of the thumb may act to extend the thumb. However, if this were to occur, thumb extension would be weak when compared with the contralateral extremity. Options for repair include direct surgical coaptation of the tendon (if the ends have not retracted) or transfer of the extensor pollicis or extensor carpi radialis longus tendon.

Other extensor tendon ruptures typically occur on the ulnar side of the wrist as the tendons glide over the damaged radioulnar joint. These ruptures generally occur in a pattern beginning at the ulnarmost digits and extending to the radial digits (ie, Vaughn-Jackson progression). In this pattern, the EDQ tendon ruptures first, followed by the extensor digitorum communis tendon to the small, the ring, and then the long fingers.

Flexor tendon ruptures are far less frequent and usually involve the radial digits. Rupture of the flexor pollicis longus tendon by a scaphoid spur is typically referred to as a Mannerfelt lesion.

References
1. Leslie BM. Rheumatoid extensor tendon ruptures. Hand Clin. 1989;5:191.
2. Mannerfelt L, Oetker R, Ostulund B, et al. Rupture of the extensor pollicis longus tendon after Colles’ fracture and by rheumatoid arthritis. J Hand Surg. 1990;15B:49.

Which of the following is the most likely cause of swan-neck deformities in patients with advanced rheumatoid arthritis?

(A) Hyperextension injuries of the proximal interphalangeal joints
(B) Ruptures of the extensor digitorum communis tendons
(C) Ruptures of the flexor digitorum superficialis tendons
(D) Tightness of the extrinsic tendons
(E) Tightness of the intrinsic tendons

The correct response is Option E.

Patients with advanced rheumatoid arthritis have profound tenosynovial hypertrophy of the metacarpophalangeal (MP) joints, resulting in subluxation of the joints. They also exhibit ulnar drift of all fingers and swan-neck deformities of the ulnarmost three fingers. The swan-neck deformity is characterized by flexion contractures of the MP joints and hyperextension deformities of the proximal interphalangeal (PIP) joints. This hand posture results from tightness of
the intrinsic tendons, which is caused by both intrinsic rheumatoid myositis and increased tension within the intrinsic system of the hand resulting from the aforementioned joint subluxation.

Recommended procedures for correction of swan-neck deformities include arthroplasties of the MP joints of the fingers, comprehensive soft-tissue and intrinsic releases, centralization of the extrinsic extensor tendons over the MP joints, and spiral oblique retinacular ligament or Zancolli-flexor digitorum superficialis lasso reconstruction of the ulnarmost three digits.

Hyperextension or volar plate injuries of the PIP joints can result in swan-neck deformities, but are unlikely to occur in patients with advanced rheumatoid arthritis.

Although ruptures of the extensor digitorum communis (EDC) tendons are common in patients with rheumatoid arthritis of the hand, they do not cause swan-neck deformities. Ruptures of the EDC tendons generally occur at the level of the distal ulna, impairing extension of the MP joints. These ruptures must be differentiated from subluxations of the EDC tendons at the level of the MP joints before surgery is performed. Rupture is characterized by a lack of continuity of the extensor tendons. In patients with subluxation, the tendons fall between the MP joints.

Ruptures of the flexor digitorum superficialis tendons can result in swan-neck deformities in patients with rheumatoid arthritis, but occur less frequently than ruptures of the EDC and profundus flexor tendons and thus are much less common than intrinsic tendon tightness.

Tightness of the extrinsic tendons may contribute to a swan-neck deformity but is not the sole cause in the absence of other deforming conditions. Extrinsic tendon tightness usually results from scarring and adhesions of the extensor tendons over the metacarpals. Neuromuscular and central hand disorders can also cause extrinsic tightness. Affected patients are unable to flex the PIP joints when the MP joints are flexed fully.

References
1. Feldon P, Terrono AL. Rheumatoid arthritis and other connective tissue diseases. In: Green DP, Hotchkiss RN, Pederson WC, eds. Operative Hand Surgery. 4th ed. New York, NY: Churchill Livingstone, Inc; 1999;2:1651-1717.
2. Rizio L, Belsky MR. Finger deformities in rheumatoid arthritis. Hand Clin. 1996;12:531-539.
3. Smith RJ. Intrinsic contracture. In: Green DP, Hotchkiss RN, Pederson WC, eds. Operative Hand Surgery. 4th ed. New York, NY: Churchill Livingstone, Inc; 1999;1:611.