Proximal intersection syndrome

Intersection syndrome is an overuse tenosynovitis that occurs around the intersection of the first extensor compartment (abductor pollicis longus and extensor pollicis brevis) and second extensor compartment (extensor carpi radialis longus and extensor carpi radialis brevis) within the forearm. It occurs proximal to the location of the more common condition De Quervain tenosynovitis and is distinct from distal intersection syndrome, which occurs at the intersection of the second and third dorsal compartments distal to Lister's tubercle.

Terminology

The condition goes by an excessive array other names including peritendinitis crepitans, oarsmen's wrist, crossover syndrome, subcutaneous perimyositis, squeaker's wrist, bugaboo forearm, adventitial bursitis and APL syndrome ¹.

Clinical presentation

There is usually a history of overuse through repetitive wrist flexion and extension, or less commonly direct trauma. Weightlifters, rowers, racket sport players, horseback riders and skiers are particularly prone ^1,2. Patients complain of radial wrist or forearm pain exacerbated by flexion and extension. Swelling and tenderness at the area of intersection may be present ².

Pathology

The musculotendinous junctions of the first extensor compartment tendons (abductor pollicis longus and extensor pollicis brevis tendons) intersect the second extensor compartment tendons (extensor carpi radialis longus and extensor carpi radialis brevis tendons) at an angle of approximately 60° at a location approximately 4 cm proximal to Lister's tubercle. In intersection syndrome there is tenosynovitis particularly of the second extensor compartment possibly caused by friction from the overlying first compartment tendons ².

Radiographic features

The diagnosis is often made clinically but may be found when wrist and forearm pain is investigated with ultrasound and MRI.

Ultrasound

Ultrasound often reveals fluid within the tendon sheaths and peritendinous oedema. There is interruption of the hyperechoic plane that divides two tendon groups. Subcutaneous oedema can be present.

MRI

The main finding is peritendinous oedema concentrically surrounding the second and first extensor compartments centred around the point of crossover ~4 cm proximal to the Lister tubercle. Sometimes the oedema may extend as far distally as the radiocarpal joint. There may or may not be tendon sheath fluid or fluid found in the interval between the tendon sheaths at the intersection point. Increased intrasubstance tendon signal may be seen indicating tendinosis ^1,3.

Treatment and prognosis

Conservative management with immobilisation, activity modification and anti-inflammatory medications is usually sufficient to control the symptoms. Local injection of corticosteroid can also be effective. Surgical treatment exists for recalcitrant cases ².

History and etymology

The term "intersection syndrome" was proposed by Dobyns et al. in 1978. It refers to the intersection (at an angle of around 60°) of the musculotendinous junctions of the first and second extensor compartment tendons.

Differential diagnosis

On imaging consider:

• De Quervain tenosynovitis (first extensor compartment involvement only, located more distal at the radial styloid)
• Wartenburg syndrome
• distal intersection syndrome