What is Intersection Syndrome?
Intersection syndrome is a condition that impacts certain parts of the wrist known as the first and second compartments of the dorsal wrist extensors. These compartments are groups of muscles that help extend the wrist. This condition is believed to occur because of repeated rubbing where the tendons of the first group of muscles cross over the second, leading to inflammation of the tendon sheaths, a condition called tenosynovitis. Patients with this condition usually feel pain just on the top and slightly above the radial styloid, which is a prominent part of one of the bones in the forearm, or roughly 4 to 6 cm above the Lister tubercle, another small bony prominence found on the back of the forearm.
What Causes Intersection Syndrome?
The first section on the back of the wrist is made up of two tendons known as the abductor pollicis longus and the extensor pollicis brevis. These tendons follow a special pathway at the upper part of your wrist where they cross over the tendons of the second section on the back of the wrist just before they reach a band of tissue known as the extensor retinaculum and a part of your lower arm bone known as radial styloid.
Similarly, the second section on the back of your wrist consists of two tendons, named the extensor carpi radialis brevis and extensor carpi radialis longus.
Risk Factors and Frequency for Intersection Syndrome
Intersection syndrome is usually caused by repetitive exercises or activities that involve bending and straightening motions. It’s often seen in sports like rowing or canoeing, skiing, racquet sports, and horseback riding. Importantly, this syndrome affects both men and women, with no significant differences in how it occurs between the two.
Signs and Symptoms of Intersection Syndrome
Intersection syndrome is a condition first identified by Alfred-Armand-Louis-Marie Velpeau, a French anatomist and surgeon, in 1841. Velpeau is also known for his detailed definition of leukemia. The name ‘intersection syndrome’ was introduced by James H. Dobyns in 1978 at the Mayo Clinic. This condition has many other names in the medical field, including:
- Oarsmen’s wrist
- Crossover syndrome
- Squeaker’s wrist
- Abductor pollicis longus bursitis
- Abductor pollicis longus syndrome
- Subcutaneous polymyositis
- Peritendinitis crepitans
Testing for Intersection Syndrome
Intersection syndrome is a condition that’s diagnosed mainly through a physical check-up, though a specialized type of scan called a musculoskeletal ultrasound can make the diagnosis more confirmed. The first steps in diagnosing this condition involve a detailed examination of the elbow, wrist, and hand.
Your doctor follows a systematic approach during this examination that includes evaluating the appearance of the area, its motion range, feeling the area for any abnormality, conducting muscle-strength tests, and other specific tests. They will test each joint above and below the affected area in all possible movements. Particular attention will be paid to any swollen areas in the lower part of the forearm, as some patients can experience noticeable swelling 4 to 6 cm above the Lister tubercle, a small bony bump on the forearm. A common finding in patients with intersection syndrome is a creaking or grating sound, medically referred to as crepitus, over the site of irritation. This happens as the 2 dorsal compartments (in simpler terms, two groups of tendons at the back of your hand) rub against each other during certain hand movements.
One distinguishing characteristic between intersection syndrome and another similar condition called De Quarvain syndrome is the specific area that experiences discomfort and crepitus within the forearm. Additionally, a special test called the Finkelstein maneuver is used to diagnose De Quarvain Syndrome.
While some imaging methods like plain film imaging or CT scans are not recommended for diagnosing intersection syndrome, MRI scans can provide a detailed view of soft tissue and help confirm the diagnosis. Nevertheless, considering the efficient and cost-saving options, using an MRI to diagnose intersection syndrome may not be the best choice.
Ultrasound technology is a game-changer in diagnosing and treating musculoskeletal conditions like intersection syndrome. Some experts even compare its specificity to an MRI. It’s because most musculoskeletal conditions occur close to the skin’s surface, allowing a type of ultrasound probe known as the linear probe to pick up these conditions easily. For intersection syndrome, the ultrasound will typically show a hypoechoic (darker) area between the 2 dorsal compartments, indicating swelling due to friction. Thickening of the tendon sheaths may also be detected through ultrasound.
Treatment Options for Intersection Syndrome
If you’re suffering from this particular condition, the first recommendation is usually to rest and adjust your activities. You might also receive a corticosteroid injection, which is a type of medication that reduces inflammation and can considerably help improve your condition, especially if other basic treatments haven’t worked.
Over-the-counter anti-inflammatory drugs like ibuprofen, naproxen, meloxicam, or diclofenac, can also be used for quick relief from injury and pain. Acetaminophen may also be taken for pain relief. Generally, taking a break and modifying your activities has proven more effective than taking medicine. Applying an ice pack can work well, too. Sometimes, applying a temporary splint at night can provide comfort and protection. It is important to note that there isn’t yet a widely accepted rehabilitation protocol specifically for this condition. However, using progressive strength-building and stretching exercises as part of your rehabilitation plan can be beneficial.
If these simpler measures aren’t bringing results, your doctor may use ultrasound guidance to administer a precise corticosteroid injection. This approach involves injecting a mixture of corticosteroid and anesthetic directly into the affected area, in a technique similar to how the condition was initially diagnosed. Once the injection is complete, you’ll be asked to rotate your wrist while the doctor checks for any remaining discomfort or abnormal cracking sensation. Any relief from the pain can help further confirm the diagnosis. Keep in mind that it takes some time for the corticosteroid to achieve its full beneficial effect. Completing rehabilitation exercises alongside the injection, a few days following the procedure, can maximize its benefit.
Alternatively, prolotherapy is another injectable treatment option. This is carried out under ultrasound guidance like the corticosteroid injection. Prolotherapy uses an anesthetic, typically lidocaine, and a mixture of dextrose in sterile water. The idea behind prolotherapy is to produce an inflammation response that leads to the release of growth factors and eventually the creation of collagen, which strengthens tissues. This approach aims to minimize side effects and achieve similar improvements to corticosteroids in relieving pain and improving function.
In rare cases where all these measures have failed, a surgical procedure that involves clearing away the affected tissues may be necessary.
What else can Intersection Syndrome be?
When diagnosing intersection syndrome, a condition related to the wrist and forearm, doctors need to consider that the symptoms might indicate different conditions. Here are some potential diagnoses they might check for:
- Boutonniere defect
- Drummer’s wrist
- Dupuytren contracture
- Extensor digitorum tenosynovitis
- Jammed finger
- Jersey’s finger
- Mallet finger
- Metacarpophalangeal ligament rupture
- Ring avulsion injury
- Scaphoid fracture
Through comprehensive examination and tests, the doctor can establish the right diagnosis.