Cubital tunnel

Entrapment of the ulnar nerve at the elbow

The ulnar nerve classically supplies sensation to the little finger and the outer half of the ring finger. In addition it supplies many of the small muscles in the hand, which are particularly important in the fine movements of the fingers and the thumb. The nerve courses around the inner aspect of the elbow and it is quite close to the surface at this point. In fact when you hit your 'funny bone' it is the ulnar nerve itself that is bashed. The nerve is contained within a tunnel as it comes around the elbow, known as the cubital tunnel. It is vunerable at this point to becoming trapped or inflamed.

The presenting symptoms can be variable. It can start with just pins and needles affecting the little and ring fingers, with or without numbness or it can present with weakness and wasting of the muscles in the hand. Sometimes there are differing combinations of these symptoms. One of the tests doctors perform to assess the ulnar nerve's function is known as  Froment's sign and it shows specific weakness in one of the hand muscles (adductor pollicis).

The condition has to be distinguished from a trapped nerve in the lower part of the neck and usually investigations such as nerve conduction studies are performed. These will show clearly where the problem is arising from and can quantify the severity of the compressed nerve.

 

Treatment options

For mild sensory symptoms, physiotherapy and a careful look at posture is often sufficient. When muscle weakness and wasting has occurred surgery is usually needed. The surgical options include the following:

  1. Simple release of the ulnar nerve
  2. Medial epicondylectomy
  3. Transposition of the ulnar nerve

 

In many instances simple release of the nerve is sufficient but there are cases when this is inadequate and something else needs to be done. Many surgeons will transpose the nerve from behind the 'funny bone' (medial epicondyle) to in front. The alternative is simply to remove the prominence of the medial epicondyle, so the nerve does not lie behind it. There is controversy as to which is the best procedure but CP favours the epicondylectomy.