Intersection Syndrome

Intersection syndrome is tenosynovitis of the radial wrist extensors, extensor carpi radialis longus (ECRL), and extensor carpi radialis brevis (ECRB). The condition also affects the extensor pollicis brevis (EPB) and the abductor pollicis longus (APL), causing pain and swelling of these muscle bellies. Intersection syndrome is characterized by pain and swelling in the distal dorsoradial forearm.[4, 5]

Frequency

Intersection syndrome is much less common than de Quervain tenosynovitis, the syndrome with which it is most easily confused. Draghi and Bortolotto reported that intersection syndrome was identified in 1.9% of 1,131 hand and wrist ultrasound examinations.[6]

Intersection syndrome can be caused by direct trauma to the second extensor compartment. It is more commonly brought on by activities that require repetitive wrist flexion and extension.[7] Weightlifters, rowers, and other athletes are particularly prone to this condition.[8, 9, 10]

While this condition occurs at the intersection of the first and second extensor compartments, many contend that the condition is a tenosynovitis of the extensor carpi radialis longus (ECRL) and extensor carpi radialis brevis (ECRB) tendons. However, the condition has long been held to be caused by friction from the overlying extensor pollicis brevis (EPB) and abductor pollicis longus (APL) tendons.[11] Tensile and shearing stresses in the tendons and peritendinous tissues may lead to thickening, adhesions, and cellular proliferation. Subsequent swelling and proliferation of tenosynovium may cause pain, as these tissues are compressed within the unyielding second extensor compartment.

Patients with intersection syndrome complain of radial wrist or forearm pain. Symptoms may be exacerbated by repetitive wrist flexion and extension.

On examination, discrete swelling at this area of intersection often is present. Active or passive wrist motion produces a characteristic "wet leather" crepitus. The examiner must exclude other causes of radial forearm pain, such as the following:

• de Quervain tenosynovitis
• Thumb CMC arthritis
• Radial sensory nerve irritation (Wartenberg syndrome)
• Extensor pollicis longus (EPL) tendinitis

Surgery is only rarely required, when symptoms persist despite an adequate course of conservative treatment (including activity modification).

The dorsal wrist and dorsal distal forearm are divided into six extensor compartments. Intersection syndrome involves the first two compartments. The tendons of the first compartment, the abductor pollicis longus (APL) and extensor pollicis brevis (EPB), pass obliquely over (dorsal to) the extensor carpi radialis longus (ECRL) and extensor carpi radialis brevis (ECRB) in the second compartment, approximately at their musculotendinous junction. This intersection occurs dorsoradially at the junction of the middle and distal thirds of the forearm, just proximal to the extensor retinaculum. Rarely, tenosynovitis may develop at the cross-section between the second and third compartments distal to the wrist joint.[12]

The radial wrist extensors continue distally through the second compartment, the boundaries of which are the distal radius, two vertical septal walls, and the overlying extensor retinaculum. The ECRL and ECRB pass over the dorsal wrist capsule before inserting into the base of the index and long finger metacarpals, respectively.[13]

Surgery is contraindicated in patients with vague nonspecific complaints or in those patients who have not received or been compliant with recommended nonoperative measures.

Anteroposterior (AP), lateral, and oblique radiographs of the wrist (including distal forearm) may be ordered.[15, 16] Ancillary studies do not help with the diagnosis of intersection syndrome but do allow the physician to exclude other causes of forearm pain. Radiographs can depict thumb carpometacarpal (CMC) arthritis and osteophytes around the distal radius.

Magnetic resonance imaging (MRI) is rarely indicated. However, an MRI scan could be ordered if the physician is suspicious of a soft tissue mass as the cause of swelling.[17, 18, 19, 20]

Ultrasound will demonstrate peritendinous inflammation and edema, and can differentiate this from other causes of swelling such as ganglia[6]

Nonspecific thickening, adhesions, and fibrocyte proliferation are seen in the tenosynovium. Histologic evidence of acute inflammation is rarely found.

If the physician suspects a radial sensory nerve neuropraxia rather than intersection syndrome as the cause of the patient's symptoms, nerve conduction studies may be helpful.[21] Slowing of radial nerve conduction cannot always be demonstrated in Wartenberg syndrome.

Conservative treatment of intersection syndrome includes immobilization, activity modification, and pharmacologic intervention. The radial wrist extensors can be immobilized with a cock-up wrist splint (20º of extension). Because of secondary irritation by the abductor pollicis longus (APL) and extensor pollicis brevis (EPB), a thumb spica splint (allowing thumb interphalangeal [IP] motion) is frequently required.

Three weeks of relatively constant immobilization, followed by gradual splint weaning, usually is recommended. Activity modification at home or work is also critical.[22]

Oral nonsteroidal anti-inflammatory drugs (NSAIDs) may decrease inflammation. A 2-mL injection of 1% lidocaine/betamethasone directly into the area of swelling may be effective in recalcitrant cases. A short course of oral steroids may be needed.

Once the most severe symptoms are under control, a program of supervised hand or occupational therapy leads to long-term recovery. This may include tendon stretching, ultrasound, and thermal modalities, followed by secondary strengthening and activities of daily living (ADL) modification or essential job task retraining.

Successful treatment of intersection syndrome using pulsed Nd:YAG laser theapy has been reported.[23]

Surgery can be effective in cases of intersection syndrome that do not respond to conservative measures.[24]

The second extensor compartment is approached through a dorsal longitudinal incision, beginning over the area of swelling and continuing distally 3-4 cm. Bluntly dissect down to the dorsal forearm fascia and divide longitudinally. Protect major veins and, particularly, branches of the radial sensory nerve that are located in this region. Completely mobilize the extensor carpi radialis longus (ECRL) and extensor carpi radialis brevis (ECRB) tendons by longitudinally incising the extensor retinaculum over the second compartment.

A bursa also may form between the overlying APL and EPB tendons. When present, this bursa should be resected.

Perform a thorough tenosynovectomy while elevating and protecting the tendons. This also may require mobilization of the EPB and APL, which then are retracted proximally and distally to provide complete access to the second compartment. The extensor retinaculum is not repaired. Skin is closed in routine fashion.

Immobilize the area in a compressive dressing and well-padded volar thumb spica splint, maintaining the wrist at 20º of extension for 7-10 days.

At the first postoperative visit, place the patient in a removable splint and encourage early wrist range-of-motion (ROM) exercises. Some patients require postoperative therapy similar to that used prior to surgery.

Occupational therapy generally is initiated early for patients with labor-intensive occupations. The goals of therapy are strengthening, full ROM, and modification of equipment. The rehabilitation period may last 4-6 weeks.

Cortisone injections near the skin may cause depigmentation in patients who are dark skinned. These injections also may lead to subcutaneous fat atrophy or necrosis, infection, and tendon rupture, although, fortunately, these complications are rare.

Theoretically, surgical release of the extensor retinaculum could lead to bowstringing of the tendons in extreme wrist extension. However, this potential problem has not been reported.

Most patients with intersection syndrome respond to a program of conservative management. They may need to maintain changes in work or avocational activities to prevent recurrence of symptoms. Individuals who require surgery rarely experience recurrence of symptoms.

No large series documenting treatment outcome exist in the literature. Eight patients in one study all responded to immobilization and corticosteroid injection. Grundberg and Reagan state that about 60% of patients in their practice with intersection syndrome respond to conservative management.[13] They report that 100% of their patients who require surgery obtain long-term symptomatic relief. In the author's experience, nonoperative treatment of intersection syndrome is successful in approximately 75% of cases; surgical decompression of the second extensor compartment is effective in the remainder of patients.

The major controversies surrounding intersection syndrome pertain to diagnosis and pathophysiology. The examining physician must be convinced that the patient's wrist or forearm pain is not due to inflammation or compression of other radial-sided structures, such as the flexor carpi radialis (FCR), tendons of the first extensor compartment, thumb CMC joint, or radial sensory nerve. Obviously, location of corticosteroid injection or surgical management would differ greatly for these other conditions.

In academic circles, some disagreement exists as to the exact location of tenosynovitis—whether it solely involves the second extensor compartment or represents an abnormal interaction between the tendons of the first and second compartments. While one's belief could affect choice of immobilization (cock-up wrist splint versus thumb spica splint), injection therapy and surgical release would not be altered.