Rupture of long digital flexor and extensor tendons

Tendon rupture in RA occurs as a result of either synovitis or attrition over an eroded bone. The tendon may be directly invaded by the synovial pannus. This occurs in regions where the tendon is covered by tenosynovium (extensor retinaculum, carpal tunnel, and digital flexor sheath). Rupture may also result from ischemia caused by pressure from underlying proliferative synovitis. This occurs in regions where the tendon is in close relation to joints (DRU, radiocarpal, proximal interphalangeal [PIP] joints). Attritional rupture frequently involves the EDM at the ulnar head (Fig. 31-5), EPL at the Lister tubercle, and FPL in the carpal tunnel caused by a flexed scaphoid (see Fig. 31-5). Synovitis between the scaphoid and lunate leads to rupture of the scapholunate ligament and collapse of the scaphoid (scaphoid becomes horizontal with the distal pole protruding into the carpal tunnel).

Direct repair of ruptured tendons is usually not possible because the ruptured ends are of very poor quality. Additionally, these patients frequently present late, and a tendon graft is also not a reliable option owing to proximal myostatic contraction. A tendon transfer is the preferred option for reconstruction. Depending on the number of ruptured tendons, this may involve a simple end-to-side repair to an intact adjacent tendon or may require transfer of a new motor from the extensor or flexor side (Table 31-1; Fig. 31-6).

It is important to address the cause of the tendon rupture at the time of tendon reconstruction. This may require tendon and joint synovectomy and procedures to address any joint instability and bony erosions. For example, if the patient has small-finger extensor tendon rupture, it is highly likely that the ring finger extensor tendon will rupture subsequently, and this process will progress, resulting in ruptures of all the extensor tendons to the fingers. Therefore, when a patient has an extensor tendon rupture of the small finger, tendon reconstruction and either tenosynovectomy or distal ulna excision, or a combination of both, must be performed to prevent progressive ruptures of the other tendons.

A 6-cm longitudinal incision is made over the dorsum of the wrist in line with the long finger metacarpal (Fig. 31-7). Skin flaps are raised to expose the extensor retinaculum (Fig. 31-8). The extensor retinaculum is elevated using a stair-step design (Fig. 31-9). The stair-step incision is used to permit easier closure of the extensor retinaculum in a side-to-side fashion, rather than a straight line closure, which may be difficult because of the swelling under the retinaculum that puts pressure over the retinacular closure. Furthermore, if there is radiocarpal bone erosion, half of the retinaculum can be placed under the extensor tendons to shield the wrist from the extensor tendons, and the other half is used to close over the tendons. The septae are divided between the second and third; third and fourth; fourth and fifth; and fifth and sixth extensor compartments. This converts the multiple extensor compartments into a single compartment and reveals the exuberant amount of synovial tissue encasing the extensor tendons (Fig. 31-10).

If the distal ulna is excised, the patient should be placed in a supination splint for 4 weeks to allow healing of the dorsal capsular repair.

Fingers are kept in fully extended position for 4 weeks before initiating active range-of-motion exercises.

With extensor tendon ruptures, the outcome of tendon transfer is good, although an increase in extension lags is observed when more tendons are involved.

With flexor tendon ruptures, patients with isolated ruptures in the palm or at the wrist had the best functional results. Patients with multiple ruptures within the carpal canal had a worse prognosis.