ULNAR NERVE DECOMPRESSION (Cubital tunnel syndrome)
What is cubital tunnel syndrome? Cubital tunnel syndrome is the second commonest cause of nerve entrapment in the body (the commonest cause is carpal tunnel syndrome with entrapment of the median nerve). In cubital tunnel syndrome the ulnar nerve which runs behind the inner side of the elbow becomes entrapped. In many cases the cause is unclear but it may be associated with a history of past injury or localised underlying arthritis. Some people have a tendency to multiple entrapments and may have entrapment in the opposite ulnar nerve although this is less common than in carpal tunnel syndrome. The symptoms are usually of numbness and tingling in the ring and little fingers of the hand. This may also be on the little finger side of the palm, it may be associated with weakening of the muscles, and sometimes wasting (thinning) of the small muscles in the hand. Typically the onset is gradual, starting with numbness and tingling, particularly at night, and it may then become continuous. Occasionally the onset may be very sudden. Some patients present only with weakness in the hand and others only with numbness but commonly there is a combination, particularly as the condition progresses. The diagnosis is normally reasonably obvious to an experienced Hand Surgeon, on the basis of the history the patient provides and the examination the surgeon undertakes.
Sometimes the surgeon will organise an X-ray of the elbow but that is not routine. It is, however, routine for an electrical test to be requested. This involves mild electrical shocks being sent up the arm and back down to assess the speed and strength of conductivity of electrical impulses in the nerve at the presumed site of injury (the elbow) and above and below that. This is done as a routine, as the results of surgery are less reliable than in carpal tunnel syndrome. In exception, however, the surgeon may elect not to do this if the clinical picture is especially clear-cut.
If the symptoms are mild and intermittent then they may resolve on their own. Wearing a splint at night can help this by tending to keep the elbow straight. Avoidance of prolonged bending of the elbow is also helpful. In more severe conditions, particularly if there is continuous numbness or weakness and wasting of the muscles, then surgery would be recommended.
What happens without the operation?
Particularly if there is established numbness and weakness and the patient is reporting that the symptoms are deteriorating then further deterioration will be expected with increasing dysfunction and disability. With the passing of time it becomes increasingly unlikely that full recovery will occur.
What does the operation involve?
The operation is now typically performed under local anaesthetic through a technique that we have pioneered. A tight tourniquet, which is a pressure cuff, is applied to the arm above the elbow and grips the arm during the operation. This is uncomfortable but does not become significantly painful for at least 20 minutes, by which time surgery should be completed. This allows the operation to be completed in a bloodless field, maximising the chances of safe surgery. The nerve is decompressed. An incision of 3-4cm is required, just behind the bony prominence on the inner side of the elbow. If, at the end of the release, the nerve is tending to ride forwards a lot, this, too, can cause further problems and part of the bony prominence on the inner side of the elbow (medial epicondyle) will be removed. This allows the nerve to sit in a more comfortable position, reducing the chances of recurrent compression or a poor result. If, however, the nerve sits nicely, then this further procedure would not be undertaken as it increases the discomfort in the initial post-operative period. Rarely the nerve will need to be formally removed in front of the medial epicondyle (prominent bone). If this is required it will have been identified pre-operatively and the operation will need to be performed under a general anaesthetic, as a substantially longer incision will be required. At the end of the operation the wound is stitched usually with absorbable sutures. This operation is performed on a day case basis with the patient in and out of hospital in a morning or an afternoon.
In the next few weeks (as per carpal tunnel syndrome).
What are the results of the operation?
The main aim of the operation is to prevent the symptoms becoming worse. This is reliable and successful in at least 85-90% of cases. A secondary aim, which we always hope for, is to improve the symptoms. This is a secondary aim as this is less reliable. In most patients, 70-80%, there will be some improvement in the symptoms but complete recovery is less frequent (less frequent than in carpal tunnel syndrome). It is not entirely clear why. It may be this is because the nerve is trapped further away from where the hand needs the supply or that patients typically come for surgery with more established continuous symptoms. It may take 2 years for the improvement in sensation, muscle bulk and strength to optimise.
Are there any risks?
- The risk of infection is less than 1%.
- The scar is likely to be a little tender for the first few weeks and particularly if a medial epicondylectomy (partial removal of the bony prominence on the inner side of the elbow) is performed, then this area is likely to be sore for a good 6-12 weeks. Long term scar tenderness is rare (less than 2%).
CRPS (as per IJL)
- Injury to the ulnar nerve can occur but this is rare and has not occurred in our Practice of over 10 years duration. Were this to occur there would be permanent numbness and weakness in the hand which may be worse than pre-operatively.
- Recurrence – Recurrent symptoms are recorded. They may occur due to further deterioration in the elbow if there is an underlying problem or for reasons that are not entirely clear. The risk of recurrence is of the order of 2-5% in the long term. Often this will settle or at least improve with surgery if this does not recover fully.