Radial tunnel syndrome, also known as radial nerve entrapment and entrapment of the posterior interosseous nerve, occurs when the radial nerve gets compressed or restricted causing pain on the outside of the elbow, similar to that of tennis elbow.
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- Causes & anatomy
Radial nerve entrapment symptoms
The symptoms of radial nerve entrapment are very similar to those of tennis elbow, with pain on the outside of the elbow. Symptoms also include pins and needles or tingling in the hand and outer forearm. Tenderness may be felt in the muscles of the upper forearm with the maximum tenderness at a point about 4-6 cm down from the lateral epicondyle (a bony bit on the outside of the elbow) in the supinator muscle. Lateral epicondylitis (Tennis elbow) pain is likely to be most tender at the attachment of the tendon at the lateral epicondyle. The patient may also experience aching in the wrist and pain may also radiate upwards into the upper arm.
Specific tests to help diagnose radial nerve entrapment will reproduce pain on resisted supination (turning the palm of the hand up against resistance) and pain on extending (straightening) the middle finger against resistance. One aid to diagnosing radial nerve entrapment is to inject a local anaesthetic into the muscle, then see if the pain is reduced when ‘palpating’ (pressing in) at the tender spot on the muscle.
Causes & anatomy
The radial nerve divides into two branches at the elbow. These are the superficial radial nerve and the posterior interosseous nerve (PI nerve). It is the posterior interosseous nerve that may become entrapped or compressed. This may occur at several locations in the elbow and upper forearm.
Radial nerve entrapment is more common in those who pronate and supinate the arm repetitively or turn the hand over, whereas tennis elbow is usually caused more by repetitive wrist extension or bending the wrist back.
Radial nerve entrapment treatment
Treatment involves applying the PRICE principles of protection, rest, ice/cold therapy to the elbow and forearm to reduce pain and inflammation, in particular avoiding any repetitive wrist movements.
A doctor may prescribe anti-inflammatory medication such as Ibuprofen to reduce pain and inflammation and relax the muscles (check with your doctor before taking any medication and do not take Ibuprofen if you have asthma). In severe or persistent cases a surgeon may operate to decompress the nerve which is generally successful.
A professional therapist may use soft tissue massage techniques to relax and release the supinator muscle in the forearm which is often the cause of entrapment. Massage will pump blood into the muscle, reducing muscle spasm and helping to relax any tension in the muscle.
Exercises to stretch the forearm muscles and in particular, the supinator muscles can be done as soon as pain allows. Neural stretches will also be given as part of physical therapy. Stretching should be maintained throughout the rehabilitation program and continued even when the injury has healed.
Wrist extensor stretch
The arm is placed in front with the hand pointing down. Pull the hand towards the body to feel a stretch in the back of the wrist, forearm, and elbow. The forearm can be rotated inwards to increase the stretch which will be felt more on the outside of the elbow. The stretch can be held for 20 seconds and repeated up to 5 times.
Partner elbow stretches
The arm should be out to the side and rotated inwards (downwards). The wrist is then flexed (bent) to increase the stretch. This stretch is more easily done with a partner to help. Hold the position for 30 seconds and repeat 5 times. Aim to stretch at least 3 times a day.
Pain in the elbow may be contributed to by tension in the neck. This neural stretch may be beneficial in helping to release tension, especially in conjunction with sports massage. Hold neural stretches initially for a maximum of 5 seconds and only do so if this is comfortable. If there is any pain or tingling in the arm or hand then stop immediately. Gradually progress the duration of the stretch up to 10 seconds.
Strengthening exercises to target the forearm muscles should be performed but only if they can be done pain-free. If it hurts don’t do it! If any adverse effects or pain is felt either during, after or the next day then rest and take a step back. Applying ice or cold therapy after exercises may help keep inflammation under control.
Wrist extension exercise
Wrist extension targets the muscles on top of the forearm and can be performed using a resistance band or a dumbbell. Rest your forearm on your knee, or the end of a table, pinning one end of the band under your foot. Wrap the other end around your hand. Start with the wrist in a flexed position (pointing down to the floor) and the band pulled taught. Extend your wrist, keeping the forearm still. Slowly return back to the start position and repeat 10-15 times. Gradually increase the number of repetitions you perform.