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The commonest sites for compression of the ulnar nerve are at the elbow (cubital tunnel syndrome) or in Guyon’s canal at the wrist (ulnar tunnel syndrome).

Anatomy

The ulnar nerve passes from the flexor to the extensor compartment in the upper arm through an opening in the intermuscular septum. It then passes through the cubital tunnel at the elbow, posterior to the medial epicondyle of the humerus (where it can be palpated with ease) and into the forearm between the heads of the flexor carpi ulnaris muscle.

It enters the hand by passing over the flexor retinaculum, lateral to the pisiform bone and medial to the hook of hamate. In the palm, it divides into superficial and deep terminal branches.

Patient presentation

The patient usually presents with paraesthesia or numbness in the little finger and the ulnar half of the ring finger. While there is rarely wasting of the intrinsic hand musculature in the early stages of compression, the sensory symptoms are often accompanied by a weak grip.

Clinical assessment

1. Percussion test at the cubital tunnel A positive Tinel’s test when the nerve is percussed over the medial epicondyle can indicate entrap-ment at this level. This test on its own is not diagnostic as almost a quarter of asymptomatic people have a positive response to this test.

2. Elbow flexion test (Wadsworth, 1977) This test is analogous to Phalen’s wrist flexion test for carpal tunnel syndrome. It involves holding the elbow in maximum flexion with the forearm in supination and the wrist in neutral to avoid confusion with Phalen’s wrist flexion test for carpal tunnel syndrome. The position is held for two minutes and the test is considered positive if symptoms of numbness and paraesthesia in the ulnar nerve distribution are elicited during this timeframe. False positives can occur in 25 per cent of the population (Fig. 7.12).

Figure 7.12. The elbow flexion test is used in the assessment of cubital tunnel syndrome.

3. Semmes–Weinstein monofilament test Decreased sensibility over the dorsal ulnar aspect of the hand would indicate that the lesion is proximal to the wrist as the dorsal cutaneous branch of the ulnar nerve branches proximal to Guyon’s canal.

4. Muscle assessment

Flexor carpi ulnaris, flexor digitorum profundus to the ring and little fingers and the intrinsics should be assessed. It must be remembered that the median nerve can contribute to innervation of the intrinsics via a Martin–Gruber anastomosis and that FCU and FDP are spared if their innervation is proximal to the cubital tunnel.

5. X-ray of the elbow

This is useful for patients with arthritis or a history of trauma to the elbow.

6. Electrodiagnostic studies

These will help establish the diagnosis and will help determine the level of the lesion.

Cubital tunnel syndrome

Cubital tunnel syndrome is the second most common nerve compression after carpal tunnel syndrome. At this level, the ulnar nerve is predis-posed to compression because of anatomical peculiarities in the region of the elbow (Feindel and Stratford, 1958). Cubital tunnel syndrome may be caused by: bony abnormalities, e.g. spurs or cubitus valgus, constricting fascial bands, soft tissue structures, e.g. tumour or ganglion, or subluxation of the nerve over the medial epi-condyle during elbow flexion.

In patients under 40 years of age, the most common cause of cubital tunnel syndrome (with the exclusion of trauma), is a shallow canal with partial anterior subluxation of the ulnar nerve during elbow flexion.

Activities involving repeated elbow flexion and extension can aggravate cubital tunnel syndrome, although there are no data pointing to work as a risk factor.

Conservative management

Approximately half of all patients with cubital tunnel syndrome will improve spontaneously.

Mild, intermittent sensory symptoms (i.e. in the absence of motor changes) can be managed with night splinting that holds the elbow joint in 30 to 45 degrees of flexion. This will prevent acute elbow flexion when the cubital tunnel is at its narrowest. Prolonged elbow flexion during the day should also be avoided (Fig. 7.13).

Oral anti-inflammatory medication is sometimes used in conjunction with splinting. Patients are instructed in ulnar nerve gliding exercises (Totten and Hunter, 1991). These exercises are performed every 1 to 2 hours with 5 to 10 repetitions. Some relief of symptoms should be apparent within 3 weeks if conservative management is having any effect. Where this is not the case, surgical options are considered (Fig. 7.14).

Surgical procedures for cubital tunnel syndrome

There are a number of surgical options for the management of this syndrome. Choice of proce-dure will depend upon the patient’s age (in the older patient, the nerve is vulnerable to iatrogenic injury during transposition), pathology, and pres-ence or abspres-ence of nerve subluxation.

Procedures include:

1. Simple decompression

This procedure involves releasing the arch of the FCU origin so that unrestricted movement of the Figure 7.13. Mild, intermittent sensory symptoms of cubital tunnel syndrome can be managed with night splinting that prevents acute elbow flexion during sleep.

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nerve can occur during elbow flexion. In this procedure the ulnar nerve is not disturbed in its bed and does not undergo neurolysis. The ulnar nerve may sublux following this procedure.

The elbow is protected in flexion with a bulky dressing with plaster reinforcement for the first 10 postoperative days. Early gentle active elbow movement is commenced following this procedure.

2. Medial epicondylectomy

The medial epicondyle is removed and the bone is smoothed. This allows the nerve to migrate anteriorly and lie free. To maintain the integrity of the anterior medial collateral ligament, removal of the epicondyle should be restricted to 1–4 mm, i.e.

about one fifth of the width of the epicondyle. A soft compressive dressing is applied and early active elbow motion is encouraged following this procedure.

3. Anterior subcutaneous transposition This procedure is indicated for anatomic lesions that interfere with or compress the ulnar nerve

along its course, e.g. tumour, ganglion or osteophyte.

The ulnar nerve is decompressed as for simple decompression. The medial intermuscular septum is then resected and the nerve is placed in the subcutaneous tissue, anterior to the medial epi-condyle. Sometimes a flap of antebrachial fascia is used to create a fasciodermal sling around the transposed nerve. The elbow is protected with a bulky dressing and light plaster for about 1 week.

Early gentle elbow movements can then be commenced.

4. Anterior submuscular transposition This procedure is indicated for more severe neuropathy and is the best salvage procedure for previous procedures that have failed, as it places the nerve in an unscarred bed. The procedure involves unroofing of the cubital tunnel and elevation of the flexor-pronator muscle mass at its origin. The nerve is moved anterior to the medial epicondyle and the muscle mass is returned to its origin and now overlies the ulnar nerve.

To protect the reattachment of the muscle mass for 2 to 3 weeks, the elbow is protected in a sugar tong splint which immobilizes the forearm Figure 7.14. Ulnar nerve gliding exercises used in conservative management of cubital tunnel syndrome. The sequence is performed only to the point where slight tension is produced. When this point is reached, the patient is asked to back off slightly. The first three positions emphasize the distal ulnar nerve and begin with a position of minimal stress. Position 1: the head is in the midline and the shoulder is forward flexed and adducted. The elbow is extended and the wrist and fingers are flexed. Position 2: the wrist and fingers are extended. Position 3: the elbow is flexed. The final three positions in the sequence focus on the proximal ulnar nerve with the distal segment in a more neutral position. Position 4: the shoulder is abducted, the elbow extended and the wrist brought to neutral. Position 5: external rotation of the shoulder is added to the previous posture. Position 6: this position incorporates lateral cervical flexion to maximize tension. (Redrawn with permission from Philadelphia Hand Centre, PC, 901 Walnut St., Philadelphia, Pennsylvania.)

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and wrist but permits a short arc of elbow movement.

5. Anterior intramuscular transposition This procedure resembles the above procedure;

however, the ulnar nerve is placed within the flexor-pronator muscle mass rather than beneath it.

Following surgery, the elbow is maintained in 90 degrees of flexion, the forearm in 30 to 45 degrees of pronation and the wrist in 30 degrees of flexion for a period of 3 weeks. Gentle active elbow, forearm and wrist movements are commenced after 3 weeks; however, intermittent use of the long arm splint is maintained for another week or two.

If passive range of motion exercises are required, they are commenced after 6 weeks together with strengthening exercises.

Regaining movement

When active and passive movements are com-menced, they are done so gently and carefully so as not to exacerbate neurological symptoms. These

symptoms will be present if axonal regeneration is occurring and will subside with time. End range of elbow movement is not a priority in the first few weeks following surgery.

Nerve gliding exercises

Postoperative ulnar nerve gliding exercises are instituted as soon as active motion is allowed (Fig. 7.15).

Scar and oedema management

Scar is treated with gentle oil massage which will also serve to desensitize the area. Raised scar is managed with silicone gel. This is held in place with Tubigrip stockinette and will control oedema around the elbow.

Pain or tenderness over the medial elbow following epicondylectomy can be addressed with a soft elbow pad if silicone gel does not provide sufficient relief. Patients should avoid leaning on the elbow until tenderness has subsided.

Figure 7.15. Postoperative ulnar nerve gliding exercises. Position 1: the shoulder is adducted and flexed to 90 degrees, the elbow is flexed to 90 degrees and the wrist and fingers are in gentle flexion. Position 2: the wrist and fingers are extended. Position 3: the elbow is extended. Position 4: the shoulder is abducted, the elbow is flexed to 90 degrees and the wrist and fingers are flexed. Position 5: the arm is externally rotated. Position 6: lateral cervical flexion is added to the previous position. (Used with permission from the Philadelphia Hand Centre, PC, 901 Walnut St., Philadelphia, Pennsylvania).

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Hypersensitivity

Hypersensitivity resulting from scar or axonal regeneration is addressed with a layer of Opsite Flexifix. Silicone gel can be used over the Opsite.

Ulnar tunnel syndrome

The ulnar nerve courses through Guyon’s canal between the volar carpal ligament and the trans-verse carpal ligament. Depending on the precise location of the compression, entrapment at this level may manifest as purely sensory, motor or mixed.

Causes

The commonest non-traumatic cause of ulnar carpal syndrome is a ganglion arising from the triquetrohamate joint. Other causes include bony lesions, e.g. fractures of the hook of hamate, or muscle anomalies.

Patient presentation

The patient may present with wrist pain and associated numbness, tingling or burning that radiates into the ring and little fingers. Weakness of the intrinsic musculature can occur and can progress to atrophy if the compression is not relieved.

Clinical assessment

This includes palpation of tender areas (e.g. over hook of hamate) and checking for the presence of swelling or a soft tissue mass. The nerve is percussed for presence of Tinel’s sign and sensi-bility is assessed with Semmes–Weinstein mono-filaments. Symptoms of ulnar carpal syndrome can sometimes be provoked by sustained wrist hyper-flexion or hyperextension. Muscle testing of the intrinsic hand musculature is carried out.

Conservative management

Where an obvious cause of compression cannot be found, conservative management is trialled.

This involves wrist splinting in neutral or slight extension, modification of work activities where indicated, and non-steroidal anti-inflammatory medication. If conservative measures fail to provide relief of symptoms, the ulnar nerve is

released within Guyon’s canal and is explored from the distal forearm into the palm.

Aftercare

The wrist is supported for the first 10 postoperative days. Where there has been excision of the hook of hamate, palmar tenderness may persist and should be managed with silicone gel compression.