Ulnar nerve


The ulnar nerve is one of the major nerves to supply impulses to the muscles of the hand and also sensation (feeling) for the little and ring finger.

At the elbow the ulnar nerve is found behind the medial epicondyle (bony prominence on the inside of the elbow).  It passes through a triangular tunnel (cubital tunnel) with two walls formed by the ulna bone and the third by the cubital retinaculum.
Immediately after passing through the cubital tunnel the nerve passes beneath the deep fascia (muscle lining) of the flexor carpi ulnaris (Osborne’s Fascia). This is the most common site of entrapment of the nerve at the elbow.

Cubital Tunnel Syndrome (CuTS)

This is an entrapment neuropathy of the ulnar nerve.  This means that the nerve becomes trapped and cannot function properly.

What are the symptoms of Cubital Tunnel Syndrome?

People with cubital tunnel syndrome may experience tingling or numbness in the little finger.  This tingling may come and go or may be permanent.  As the condition gets worse people may experience weakness or wasting of the muscles in the hand.  People with cubital tunnel syndrome often complain that they are “dropping things” more often.

Other symptoms may be present.  Pain on the inside of the elbow is not uncommon and must be differentiated from Golfers Elbow.

Who gets Cubital Tunnel Syndrome?

Most cases of CuTS are idiopathic, which means that no obvious predisposition can be found.  Factors that may increase the risk of developing CuTS are diabetes, arthritis and previous trauma to the elbow (Tardy Ulnar Nerve Palsy).

What are the clinical signs of Cubital Tunnel Syndrome?

In the early stages of the syndrome the patient may not have any clear signs on examination.  Later as the muscles weaken the hand may show signs of muscle wasting with scalloping of the web space between the thumb and index finger on the back of the hand.  “Guttering” between the metacarpal bones on the back of the hand may be seen.  “Clawing” (fingers held in a bent posture with extension at MCPJ, and flexion at PIPJ and DIPJ) of the little and ring finger may be seen.  A positive tinel’s sign may be elicited by gently tapping over the ulnar nerve at the elbow and producing tingling down to the little finger.  Care must be taken not to attach too much importance to this as it may be positive in normal subjects.  Some specific signs are given below:

Froment’s Sign – flexion at the interphalangeal joint of the thumb when gripping a piece of paper due to recruitment of flexor pollicis longus because of weakness of adductor pollicis.

Appley’s Sign – ask the patient to spread the fingers wide and then push the two little fingers against each other.  This is a sensitive test for mild weakness.

Wartenberg’s Sign – the little finger may be held in abduction due to the weakness of the finger adductors and the eccentric pull of extensor digiti minimi.

What is Ulnar Paradox?

This refers to the different manifestation of a high ulnar nerve lesion (at the elbow) and a low ulnar nerve lesion (at the wrist).  In a high lesion the clawing is paradoxically more mild than in a low lesion.  This is because in the low lesion the hand muscles are weak but the long flexors which are supplied by the ulnar nerve just below the elbow are not affected.  In the high lesion both are weak and the clawing is more mild.

How is the severity graded?

McGowan has developed a useful clinical grading system of cubital tunnel syndrome.

Grade 1 – Isolated numbness of the little finger.
Grade 2 – Numbness of the little finger and weakness of the muscles of the hand.
Grade 3 – Numbness of the little finger with wasting and paresis of the muscles of the hand.

What special tests can be used?

Nerve conduction studies can be used to help make the diagnosis of cubital tunnel syndrome.  Sometimes an X-ray of the elbow may help to identify a cause.

How is Cubital Tunnel Syndrome Treated?

The first line of treatment is observation, activity modification and splinting if sensory symptoms only are present.
It is thought that holding the elbow in a bent position for prolonged periods at night may contribute to CuTS so wearing an elbow extension splint at night may help.

If the symptoms are more severe then surgery may be indicated.  The surgery may be performed as an open or endoscopic operation.  The results of both techniques are very similar.  A number of different operations have been described to treat CuTS.  The evidence suggests that for most people a simple (in-situ) decompression of the nerve will produce good results.  In some circumstances the nerve may be unstable or in tension and it may be necessary to move the nerve to the front of the elbow (transposition).  Here the nerve can be placed between the subcutaneous fat and fascia (subcutaneous transposition), beneath the fascia (subfascial transposition) or beneath the muscle (submuscular transposition).  Evidence suggests that the outcomes of these procedures are the same but that the risk of complications may be lower after subcutaneous transposition.  Some surgeons prefer to remove some of the bone at the elbow when treating CuTS (medial epicondylectomy).

The outcome of surgery is normally very good but depends on the grade of disease at the time of surgery.

What is the recovery period after this surgery?

Must people will be able to return to driving and work at approximately two weeks after surgery.  Splints may be used but are not a necessity.  It is important to note that 3/4 of patients will still experience some symptoms even after a successful procedure.  The aim of surgery is to stop the symptoms from getting worse but total recovery cannot be guaranteed.

What are the risks of surgery?

The risks are low but include infection, bleeding, nerve injury, scar tenderness, new pain at the elbow and worsening of symptoms.

for a summary of Tendon Transfers for Nerve Injury Click Here