Radial tunnel syndrome
Posterior interosseous syndrome (PIN)

Radial tunnel syndrome is the name given to describe a trapped nerve in the forearm. The condition is also referred to as PIN (posterior interosseous syndrome).

Radial tunnel syndrome is less common than the more frequently diagnosed tennis elbow. Both conditions have similar symptoms and are therefore difficult to distinguish from one another.

Description of condition

In radial tunnel syndrome, the radial nerve is constricted. This is the nerve on the back of the forearm. The constriction is located between a number of muscles and/or tendons in the forearm. These form a tunnel near the outside of the elbow. We call this space, through which the nerve runs, the radial tunnel.

Cause and history

The symptoms usually arise in people who frequently turn the forearm (pronation and supination). For example, when turning screws or unscrewing the lid of a jar. Due to this strain, the muscles swell and become hard and painful. This may cause the local nerve to become irritated. In the tunnel, the nerve may become constricted in several places.

Signs & symptoms

• Pain on the upper outer side of the forearm.
  
• Loss of strength in forearm and hand.
  
• The symptoms increase with activities that require outward rotation of the forearm against resistance. For example, using a screwdriver or twisting the lid off a jar.
  
• Increased muscle tension can be observed in the muscles that are located just beneath the elbow.
  
• Usually this is not accompanied by pins and needles. Only when the impingement is located higher up will this be associated with pins and needles on the upper side of the hand.

Diagnosis

During a physical examination, the most painful location is assessed. With radial tunnel syndrome, the pain is felt lower on the forearm than with a tennis elbow. In addition, the symptoms can be provoked by turning the palm of the hand up with resistance from a bent elbow position. Stretching the middle finger and radial nerve tension tests are also likely to trigger the symptoms.

If necessary, electromyography (EMG) may be performed to measure the nerve conduction velocity. If this is clearly slower than in the other arm, the conclusion is clear: the nerve is not transmitting its signals properly and is therefore constricted or damaged somewhere

Treatment

The most important thing is to give the arm some rest and to relax the muscles of the forearm in order to take the pressure off the nerve. This can be done, for example, through massage, dry needling and stretching. When these instructions and therapy do not have the desired result, the nerve can be released surgically.

Exercises

You can check your symptoms using the online physiotherapy check or make an appointment with a physiotherapy practice in your locality.

References
Bayramoglu, M. (2004). Entrapment neuropathies of the upper extremity. Neuroanatomy. 2004;3:18-24.
Brukner, P. & Khan, K. (2010). Clinical sports medicine. McGraw-Hill: Australia. 3e druk.
Cleland, J.A. & Koppenhaver, S. (2011). Netter's orthopaedic clinical examination: an evidence-based approach. 2nd ed. Philadelphia: Saunders Elsevier.
Conneely, A. & Wilcox, R. (2007). Standard of care: radial tunnel syndrome. The Brigham and Women`s Hospital, Inc. Department of Rehabilitation Services.
Nugteren, K. van & Winkel, D. (2011). Onderzoek en behandeling van elleboog en onderarm. Houten: Bohn Stafleu van Loghum.
Thatte, M.R. & Mansukhani, K.A. (2011). Compressive neuropathy in the upper limb. Indian J Plast Surg. 2011 May-Aug; 44(2):283-297.