Intersection syndrome, a painful condition of the wrist, is common but underdiagnosed. With careful evaluation of the mechanism of injury to the wrist and identification of specific landmarks for location of pain, the health care provider may consider intersection syndrome in the differential diagnosis of wrist pain.
Anatomy and Pathophysiology
The intersection area of the forearm is located at the musculotendinous junctures of the abductor pollicis longus (APL) and the extensor pollicis brevis (EPB) as they cross over the underlying tendons of the extensor carpi radialis longus and brevis (ECRL and ECRB).1 The first dorsal compartment contains the tendons of the APL and the EPB, while the second houses the ECRL and the ECRB (see Figure 1).
The pathophysiology of intersection syndrome remains unclear. Some authors attribute it to friction between the muscle bellies of the APL and the EPB with the tendon sheath that contains the ECRL and the ECRB, possibly causing a tenosynovitis2,3; others prefer to describe the condition as a pure form of tendinitis.4 Stenosis of the second dorsal compartment has also been proposed as the causative factor.5
Clinical terms for the disorder include peritendinitis crepitans, APL bursitis, crossover tendinitis, adventitial bursitis, and subcutaneous perimyositis.3,6-9 In addition, several nonclinical monikers exist, including oarsman’s wrist and bugaboo forearm10,11; yet most authors, believing that these names misstate the pathologic abnormality, prefer intersection syndrome. This term makes a clear statement about the location of the physical findings without being misleading about the pathologic anatomy.5
Symptoms
Intersection syndrome presents as pain and swelling over the dorsal radial aspect of the forearm about 4.0 cm (range, 3.5 to 4.8 cm12) proximal to the wrist (see Figure 2). Severe cases may also manifest with redness and a leathery crepitus that has been likened to the crunch produced by footsteps on freshly fallen snow.5,6,10 The pain associated with wrist motion is reported to be greater than that triggered by thumb motion.
A subtle but important distinction must be made between intersection syndrome and de Quervain’s stenosing tenosynovitis, a painful wrist condition that involves thickening of the extensor retinaculum of the first dorsal compartment with stenosis of the canal that contains the APL and the EPB.13 While the pain associated with de Quervain’s stenosing tenosynovitis manifests over the radial styloid, the pain of intersection syndrome is located in the second dorsal compartment, several centimeters proximal to the radial styloid.5 Pain, edema, and crepitus that are found 4.0 to 8.0 cm proximal to the radial styloid are considered pathopneumonic for intersection syndrome.9,14
Risk Factors
Intersection syndrome is most commonly seen in occupational health and sports medicine clinics. Workers or athletes whose activities involve repetitive forceful flexion and extension of the wrist are predisposed to the condition. Symptoms tend to develop with the initiation of a new activity (as with the patient featured in Figure 2) rather than as a result of prolonged repetitive wrist motion.2 Environmental factors, such as vibration or prolonged constrained postures, may increase a person’s risk of developing intersection syndrome. Symptoms usually occur in the dominant hand and are exacerbated by exposure to cold temperatures.4,10
Occupations that require forceful, repetitive radial deviation of the wrists (eg, spraying, cementing, threshing and planting, hammering) are associated with an increased incidence of symptoms; working in refrigerated or cold areas may exacerbate the condition.10 One group of researchers who examined the incidence of intersection syndrome in Alpine powder skiers attributed their injuries to repetitive dorsiflexion and radial deviation of the wrist as skiers withdraw their planted ski poles against the resistance of deep snow.11 Advanced skiers may be at greater risk because of their more aggressive style of pole planting.
Treatment and Prognosis
Management of intersection syndrome is similar to that of most overuse syndromes. Two to three weeks of conservative treatment with NSAIDs and immobilization of the forearm with a splint that keeps the wrist in 15° continual extension is usually effective in decreasing symptoms. Once the pain and swelling begin to subside, a gradual resumption of normal wrist motion may be initiated. Physical therapy that focuses on range-of-motion exercises and wrist extensor strengthening may prove beneficial.15 Patients who do not respond to conservative treatment may be candidates for injection therapy using an anesthetic steroid combination.4,5,9
For recalcitrant cases, MRI is considered a helpful noninvasive method for further evaluation of the wrist or forearm.16 However, the area of intersection between the first and second dorsal compartments is not usually included in standard protocols for MRI evaluation of the wrist; thus, imaging must be ordered to include a view of the forearm.12