Intersection Syndrome: An Overview

What Is Intersection Syndrome?

Intersection syndrome is inflammatory tenosynovitis affecting the tendons of the first and second compartments of the dorsal surface of the forearm and wrist. The main cause of the syndrome is repetitive rubbing or continuous friction between muscles and tendons of the extensor carpi radialis longus and extensor carpi radialis brevis. This repetitive friction between the tendons initiates the pathogenesis of tenosynovitis. This condition is presented as pain that gradually intensifies and swelling of the involved tendons of the wrist.

What Is the Pathophysiology of Intersection Syndrome?

Frequent wrist movements often result in friction between the tendinous compartments of the wrist and forearm at the junction where the first and second extensor compartments intersect. Hence the name, intersection syndrome. An inflammatory reaction is initiated in response to the friction created, leading to pain and swelling of the affected tendons, subsequently causing tenosynovitis.

What Is the Anatomy of Dorsal Wrist?

To understand the pathology of Intersection syndrome, it is crucial to understand the anatomy of the dorsal wrist.

• The wrist's first extensor musculotendinous compartment comprises the abductor pollicis longus and the extensor pollicis brevis. The posterior interosseous nerve is responsible for supplying the nerve innervations to both tendons. These two tendinous muscles are responsible for the movements of abduction and extension in the thumb.

• The extensor carpi radialis longus and the extensor carpi radialis brevis tendons form the second extensor musculotendinous compartment of the dorsal surface of the wrist. The radial nerve supplies both the tendons of the second compartment. These tendons are responsible for the hand movements of extension and abduction.

The abductor pollicis longus and the extensor pollicis brevis intersect the extensor carpi radialis longus and extensor carpi radialis brevis while performing their respective movements. This classic intersection of the two compartments occurs proximally to the tubercle of Lister at about four to eight centimeters of distance at an approximate angle of 60 degrees (Lister’s tubercle is a bony prominence present on the dorsal surface of the radius that functions as a pulley).

Intersection syndrome is characterized by the inflammation of the muscles and tendons of the second compartment of the dorsum of the wrist that occurs due to repetitive rubbing and friction done by the affected tendons. This results in severe pain, numbness, and tenderness in the wrist with restricted movements. It is of great clinical significance that both the above-mentioned two compartments are also responsible for causing De Quervain’s tenosynovitis (a painful disorder affecting the muscular tendons on the side of the thumb of the wrist). Therefore it becomes critical to differentiate between Intersection syndrome and De Quervain’s syndrome.

How Common Is Intersection Syndrome?

The syndrome is most commonly seen in people active in sports such as horseback riding, competitive rowing in a boat using oars or canoe, or even skiing over snow, sports activities involving racquets, weight lifting, gardening activity, and horseback riding. Females are more commonly affected than males, with an increased risk after pregnancy. It is a rare syndrome with an incidence rate of less than one in 100000 people yearly.

What Are the Signs and Symptoms of Intersection Syndrome?

The signs and symptoms of the syndrome include:

• Pain in the tendons of the wrist or forearm gradually intensifies.

• Both muscle extension and muscle flexion aggravate the tenderness.

• There is swelling at the point of intersection where the tendons of the first compartment crossover the tendons of the second compartment.

• There is no overlying redness but only warmth on the affected part.

• Patients with the movement of the fingers and wrist at the intersection point of repetitive friction commonly report a creaking sound known as crepitus.

• Uneasy wrist movements with pronation were found more difficult than supination.

How to Differentiate Between De Quervain Tenosynovitis and Intersection Syndrome?

Intersection syndrome is often confused with De Quervain’s tenosynovitis, but it is critical to differentiate between the two conditions as the therapeutic approach and prognosis of both conditions vary considerably.

In de Quervain syndrome, there is the involvement of the first extensor compartment of the dorsum of the wrist. There is stenosis tenosynovitis of the tendons of the first compartment. This condition is observed more distally to the radial bone.

Intersection syndrome is characterized by crossover tenosynovitis of the tendons of the second compartment of the dorsal surface of the wrist. The pain is more proximal and dorsal than De Quervain’s syndrome.

Crepitus is a classic squeaking sound called crepitus characteristic of Intersection syndrome.

The healthcare practitioner usually carries out the Finkelstein test to differentiate between the two syndromes. It is a stretch test where the doctor can ask the patient to flex the thumb towards the palm of the hand and then bend the fingers over the thumb along with ulnar abduction or extension. If sharp severe pain is encountered on the thumb side of the wrist, it is suggestive of De Quervain’s syndrome.

How Is Intersection Syndrome Diagnosed?

A thorough and extensive clinical examination is crucial to establish the diagnosis of Intersection syndrome. However, to confirm the diagnosis, ultrasound and magnetic resonance imaging of the affected tendons can be done. The characteristic imaging findings of the syndrome include fluid deposition at the periphery of the tendons of the first and second compartments.

What Is the Treatment of Intersection Syndrome?

The management of Intersection syndrome is mainly conservative.

• Stop Physical Activities- Cessation of the sporting activities or other activities that provocate the syndrome, followed by proper rest, helps resolve the disease's symptoms.

• Drug Therapy- Nonsteroidal anti-inflammatory drug therapy or corticosteroid therapy may be considered useful to improve the condition and relieve the pain.

• Ice Packs- The application of ice packs can also be considered effective.

• Splints- Splints can be temporarily placed to protect the affected tendons of the wrist.

• Surgery- Surgical intervention is required in rare cases.

Conclusion

Intersection syndrome is a rare syndrome affecting the tendons of the second compartment of the wrist. Diagnosis is established based on clinical and other imaging techniques. The pain is managed by a conservative technique, which includes discontinuing the provocative activities that exacerbate the symptoms. It is important to differentiate De Quervain’s syndrome from Intersection syndrome to treat the affected individual properly.