What is radial tunnel syndrome?
The radial nerve courses over the anterio-lateral aspect of the elbow between the brachialis and brachioradialis muscles. The nerve then dives beneath the supinator muscle and terminates into several branches at the mid-dorsal forearm. It gives off a sensory branch, the dorsal sensory branch of the radial nerve, prior to entering the supinator. As it enters the supinator it becomes the posterior interosseous nerve (PIN). The radial nerve gives sensation to the dorsal hand over the hand and digits with the exception of the little and part of the ring. It gives muscle function to the digit and wrist extensors, one of the thumb abductors, and the supinator (helps rotate the forearm into a palm up position). It is with this tight space where the nerve may become irritated or compressed.
What are the causes of radial tunnel syndrome?
The radial nerve can be compressed beneath the extensor carpi radialis brevis, the arcade of Frohse (mouth of supinator), or the radial recurrent artery most commonly. This can be compressed due to repetitive motion most commonly leading to swelling and inflammation of the muscle around the nerve or from direct trauma with damage to the soft tissue around the nerve or a bone fracture.
What are the symptoms of radial tunnel syndrome?
- Pain at lateral aspect of elbow
- Pain may radiate to dorsal forearm and wrist (occasionally will radiate proximally to arm)
- Pain increases with activity and decreases with rest
- Often feels like a “charley horse” within forearm muscles with deep aching pain
- Pain frequent after heavy manual work
- Nocturnal pain common
- Common history of unsuccessful treatment, conservative or surgical, for tennis elbow (lateral epicondylitis)
How to diagnose radial tunnel syndrome?
In addition to a careful history of the symptoms as described above the examination will reveal:
- Point tenderness at the point that PIN enters the supinator muscle; usually no sensory or motor disturbance; spot may be tender normally so it should be compared to opposite extremity; 3 important points are equidistant from one another in a line; lateral epicondyle, radial head, supinator entrance of PIN
- May also have tenderness at the distal edge of the supinator where the PIN exits.
- May have weakness when the entrapment is distal and involves predominantly the PIN
- Middle finger extension test: resisted middle finger extension with the elbow in extension; pain is reproduced at the point of tenderness.
- Resisted supination with elbow in extension.
Additional tests may be helpful:
X-rays of elbow:
Assess underlying bone and joint.
Usually negative unless muscle weakness is present; may show other problems such as cervical root compression.
MRI of cervical spine:
If neck problems as cervical radiculapathy may have similar symptoms
Non-surgical treatment of radial tunnel syndrome:
Rest, splinting, NSAID (i.e. Advil), therapy with modalities, work modification, ergonomic modification, injection if associated with lateral epicondylitis is present to resolve this problem.
Surgical treatment of radial tunnel syndrome:
Surgical decompression is necessary when after rest the symptoms return soon after returning to activity. An antero-lateral approach is made to allow adequate visualization of all possible pressure points.
A long arm splint (above the elbow) is applied at surgery. The patient returns ~8-10 days later for suture removal and removable splint is applied for an additional 2 weeks. At that time therapy begins and the removable splint is placed for 2 weeks to wear at night and when not exercising. Therapy lasts ~2 months.
How can Dr. Knight help you with radial tunnel syndrome?
Dr. Knight will look at all of the possible causes of pain in your forearm from the neck down. Once he confirms the diagnosis he will work with you to maximize conservative treatment to relieve your symptoms. He will only recommend surgery for this condition if exhaustive conservative care has failed. If radial tunnel surgery is needed, Dr. Knight will perform as minimally invasive procedure as necessary to minimize scarring and expedite a full recovery.
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