Intersection syndrome is a painful inflammatory condition affecting the thumb-side of the wrist and forearm on the back of the arm. The wrist and forearm contain several compartments of extensor muscles that help move the wrist, hand, and fingers. Intersection syndrome occurs where the compartment containing the muscles that help move the thumb crosses over the compartment containing the muscles that help extend the wrist.
The first dorsal extensor compartment contains the abductor pollicis longus and extensor pollicis brevis muscles and their tendons, which contribute to thumb motion. The second extensor compartment contains the extensor carpi radialis longus and the extensor carpi radialis brevis muscle bellies and tendons, which contribute to wrist extension. Intersection syndrome involves these two compartments and is a type of tenosynovitis that develops gradually. The mechanism of injury is usually repetitive resisted extension, as with rowing, weight lifting, or pulling.
Diagnosis of intersection syndrome is clinical, based on patient symptoms. Imaging is not required for a diagnosis, but ultrasound and MRI can be used to confirm the diagnosis if the presentation is unclear.
Intersection syndrome is often confused with another condition called DeQuervain's syndrome, which is a similar inflammatory condition of the first dorsal extensor compartment of the wrist. Pain is often felt in a similar area, but closer to the thumb.
Signs and symptoms
Symptoms of intersection syndrome include pain, tenderness, and edema on the thumb-side of the dorsal forearm and wrist. These findings are reported to be most severe about 4 to 8 cm proximal to the radial styloid. Notably, this discomfort is more proximal on the wrist than seen in De Quervain syndrome. In severe cases, crepitus may be heard or palpated in this region.
Provocative tests, such as resisted wrist extension, thumb extension, or ulnar deviation can be used to elicit symptoms in the area. :
- Abductor pollicis longus (APL) and extensor pollicis brevis (EPB)
- Extensor carpi radialis longus (EPRL) and extensor carpi radialis brevis (EPRB)
- Extensor pollicis longus (EPL)
- Extensor digitorum communis (EDC) and extensor indicis proprius (EIP)
- Extensor digiti minimi (EDM)
- Extensor carpi ulnaris (ECU)
While intersection syndrome primarily involves the second compartment (ECRL and ECRB), many of the symptoms come from irritation along the first compartment as well. Notably, the fourth dorsal extensor compartment also contains the posterior interosseous nerve (PIN) which supplies nearly all of the wrist extensor muscles.
- De Quervain syndrome
- Intersection syndrome
- Drummer's wrist
- Extensor tenosynovitis
- Vaughan-Jackson syndrome
- Snapping ECU
Pathophysiology
The pathophysiology of intersection syndrome is unclear with two main prevailing theories. Early data suggests the etiology of symptoms arising from friction between the first two extensor compartments. Repetitive friction at this site, especially from wrist extension and pronation, aggravates the tendon sheaths.
In the mid 1980s, a landmark study by Grundberg et al., 1985 suggested that the etiology of intersection syndrome came primarily from stenosis of the second dorsal extensor compartment, also known as stenosing tenosynovitis. This narrowed compartment develops an accumulation of reactive tissue beneath the APL and EPB.
Differential diagnoses
Differential diagnoses
Rehabilitation should follow after conservative measures, with progressive stretching and mobilization of the wrist and surrounding joints. Later on, gradual strength training should be incorporated.
In refractory cases or in patients who do not desire conservative treatment, surgical intervention with decompression of the second dorsal compartment may be considered. This surgery has demonstrated promising results in symptom elimination 10 months after completion.