AUTHOR AND EDITOR INFORMATION

Section 1 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Further Reading
• References

INTRODUCTION

Section 2 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Further Reading
• References

Because of the anatomic positioning of the ulnar nerve, it is subject to entrapment and injury by a wide variety of causes.¹ It is the second most common entrapment neuropathy in the upper extremity (the first being the median nerve and its branches). Because of its superficial position at the elbow, it is often injured by excessive pressure in this area (leaning on the elbow during work or while driving a car). This article discusses the most common type of entrapments of the ulnar nerve, which occur most frequently at the elbow and wrist.^{2, 3}

Related eMedicine topics:
Nerve Entrapment Syndromes
Hand, Nerve Compression Syndromes: Upper Extremity
Ulnar Neuropathy

Related Medscape topics:
Resource Center Exercise and Sports Medicine
Specialty Site Orthopaedics
Geriatric Physical Diagnosis: The Upper Extremities
Assessing the Hands and Wrists in Elderly People
Diabetic Polyneuropathy

Problem

Pressure or injury to the ulnar nerve along its anatomic course may cause denervation and paralysis of the muscles supplied by that nerve. One of the most severe consequences is loss of intrinsic muscle function in the hand. When the ulnar nerve is divided at the wrist, only the opponens pollicis, superficial head of the flexor pollicis brevis, and lateral 2 lumbricals are functioning.

Frequency

Ulnar nerve entrapment is the second most frequent entrapment neuropathy in the upper extremity. Because of the anatomic arrangement of structures, the area around the elbow is the most common area for entrapment. The wrist at the Guyon canal is the second most common area of entrapment.

Etiology

In a 1998 article, Posner⁴ defined 5 areas of potential compression around the elbow as follows:

• Under the heading intermuscular septum, Posner lists the arcade of Struthers (a musculofascial band about 8 cm proximal to the medial epicondyle), the medial intermuscular septum (which the nerve pierces to reach the olecranon groove), and the medial head of the triceps muscle (which can be hypertrophied or can chronically snap over the medial epicondyle, causing a neuritis).
• The area of the medial epicondyle is a valgus deformity caused by malunion of a condylar fracture, nonunion of a condylar fracture, or an epiphyseal injury to the lateral side of the elbow. These may cause tardy ulnar palsy secondary to chronic stretching of the ulnar nerve.
• The olecranon or epicondylar groove is a fibroosseous tunnel holding the ulnar nerve and its vascular accompaniment. A congenitally shallow groove or a torn fibrous roof can allow the nerve to chronically subluxate or dislocate, causing neuritis and palsy. Fracture fragments and arthritic spurs in or around the groove impinging on the nerve can also cause entrapment and subsequent neuritis. Traumatic hemorrhage, soft tissue tumors, ganglia, infections, osteochondromas, synovitis secondary to rheumatoid diseases, and malposition during work or sleep all may cause entrapment and nerve dysfunction.
• The cubital tunnel is the passage between the 2 heads of the flexor carpi ulnaris, which are connected by a continuation of the fibroaponeurotic covering of the epicondylar groove (Osborne ligament). During elbow flexion, the tunnel flattens as the ligament stretches, causing pressure on the ulnar nerve.^{5, 6, 7}
• Flexor-pronator aponeurosis is the fifth topic. As the nerve exits the flexor carpi ulnaris, it perforates a fascial layer between the flexor digitorum superficialis and the flexor digitorum profundus. Entrapment can occur here also. The most common sites of entrapment around the elbow are the olecranon groove and the cubital tunnel.

Guyon canal

The Guyon canal is the second most common site of entrapment and is located at the wrist. Entrapment may cause purely motor, purely sensory, or a mixed lesion, depending on the site of compression.

Anatomically, the canal is divided into 3 zones. Zone 1 is the area proximal to the bifurcation of the ulnar nerve. Compression in zone 1 causes combined motor and sensory loss. It is most commonly caused by a fracture of the hook of the hamate or a ganglion. Zone 2 encompasses the motor branch of the nerve after it has bifurcated. Compression causes pure loss of motor function to all of the ulnar-innervated muscles in the hand. Ganglion and fracture of the hook of the hamate are the most common etiological factors. Zone 3 encompasses the superficial or sensory branch of the bifurcated nerve. Compression here causes sensory loss to the hypothenar eminence, the small finger, and part of the ring finger, but it does not cause motor deficits. Common causes are an aneurysm of the ulnar artery, thrombosis, and synovial inflammation.

Pathophysiology

Seddon⁸ in 1972 and Sunderland⁹ in 1978 classified nerve injuries similarly.

Seddon classified 3 levels of injury as follows:

1. Neuropraxia is a transient episode of complete motor paralysis with little sensory or autonomic involvement. This usually is secondary to a transitory mechanical pressure. Once this is relieved, return of function is complete.
2. Axonotmesis is a more severe injury involving loss of continuity of the axon with maintenance of continuity of the Schwann sheath. Motor, sensory, and autonomic paralysis is complete, and denervated muscle atrophy can be progressive. Recovery depends on a number of factors, including timely removal of the compression and axon regeneration. The time necessary to recover function depends on the distance between the denervated muscle and the proximal regenerating axon. Recovery can be complete.
3. Neurotmesis is the most serious level of injury. It entails complete loss of continuity of the axon and of the Schwann sheath. Recovery rarely is complete, and the amount of loss can only be determined over time; regenerating axons without intact neural tubes reinnervate muscle fibers that were not part of their original network.

Sunderland's classification has 5 degrees of nerve damage. The first degree corresponds to neuropraxia; the second degree corresponds to axonotmesis; and the third, fourth, and fifth correspond to increasingly severe levels of neurotmesis. Axons and Schwann sheaths are disrupted within intact nerve fascicles in a third degree injury. In a fourth degree injury, the perineurium surrounding the fascicles is damaged, as is the endoneurium. In a fifth degree injury, the nerve trunk is severed.

Clinical

Presenting symptoms of ulnar nerve entrapment can vary from mild transient paraesthesias in the ring and small fingers to clawing of these digits and severe intrinsic muscle atrophy. The patient may report severe pain at the elbow or wrist with radiation into the hand or up into the shoulder and neck. Patients may report difficulty in opening jars or turning doorknobs. Early fatigue or weakness may be noticed if work requires repetitive hand motions. If the patient rests on the elbows at work, increasing numbness and paraesthesias may be noticed throughout the day.¹⁰

A careful clinical history is imperative, noting the time of occurrence of symptoms. Determine whether symptoms are transient or continuous. Determine whether symptoms are related to work, sleep, or recreation. Elicit duration of symptoms and possible relation to trauma.

Begin the clinical examination at the neck and shoulder and move down the affected extremity to the elbow. Pain on neck movement mimicking the patient's symptoms could indicate cervical disc disease; pain on palpation or with shoulder motion could indicate a pathological condition in the brachial plexus or lung. Provocative maneuvers for thoracic outlet syndrome should be assessed. Masses on the medial side of the arm could indicate a soft tissue tumor or hemorrhage compressing the nerve. At the elbow, any deformity is noted, the nerve is palpated, and any abnormal mobility is noted. Masses are discerned, and if any question remains, use the opposite elbow as a standard. The course of the nerve is palpated in the forearm to the wrist.

Flexor capri ulnaris and flexor digitorum profundus strength should be assessed. Intrinsic muscle function is tested by asking the patient to cross the long finger over the index finger (ie, crossed finger test). Only 2 muscles can be tested accurately in the hand, the abductor digiti quinti and the first dorsal interosseous. The tendons or bellies of these muscles can be palpated or visualized. Weakness of thumb pinch may be elicited by the Froment sign. A Martin-Gruber anastomosis in the forearm or a Riche-Cannieu anastomosis in the palm may deceive the examiner by apparent functioning of ulnar-innervated muscles.

Numbness usually precedes motor loss. Muscle wasting and clawing of the ring and small digits are indicative of a chronic compressive syndrome.

Differential diagnosis usually includes the following:

• Cervical disc disease
• Brachial plexus abnormalities, thoracic outlet syndrome, Pancoast tumor
• Elbow abnormalities, epicondylitis
• Infections, tumors, diabetes mellitus, hypothyroidism, rheumatoid diseases, and alcoholism
• Wrist fractures
• Ulnar artery aneurysms or thrombosis at the wrist

INDICATIONS

Section 3 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Further Reading
• References

Indications for surgery for ulnar nerve entrapment are the following:

• No improvement in presenting symptoms after 6-12 weeks of conservative treatment
• Progressive palsy or paralysis
• Clinical evidence of a long-standing lesion (eg, muscle wasting, clawing of the fourth and fifth digits)

RELEVANT ANATOMY

Section 4 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Further Reading
• References

The ulnar nerve is the terminal portion of the medial cord of the brachial plexus, after the medial head of the median nerve has separated from it, with fibers from C8-T1. Initially, it lies medial to the axillary artery and then to the brachial artery to the middle of the arm. It pierces the intermuscular septum at this point and follows the medial head of the triceps muscle to the groove between the olecranon process and the medial epicondyle. It gives off no branches in the arm. It then crosses the elbow, giving off articular branches and branches to the flexor carpi ulnaris and the medial half of the flexor digitorum profundus. It slips between the 2 heads of the flexor carpi ulnaris and continues into the forearm between this muscle and the flexor digitorum profundus.

In the distal half of the forearm, it is joined on its lateral side by the ulnar artery. Proximal to the wrist, the nerve gives off a large dorsal branch, sensory in nature. The ulnar nerve continues into the hand via the Guyon canal. It then splits into a superficial or sensory portion and a deep or motor portion. The dorsal branch supplies sensation to the dorsum of the wrist and the ulnar side of the hand.

The superficial branch in the Guyon canal supplies the palmaris brevis and the skin of the hypothenar eminence and digital nerves to the small and ulnar side of the ring finger. The deep branch passing between the abductor digiti quinti and the flexor digiti quintus brevis, with the deep branch of the ulnar artery, perforates the opponens digiti quinti and follows the deep volar arch across the interossei. It supplies the 3 small muscles of the small finger, the third and fourth lumbricales, the volar and dorsal interossei, the adductoris pollicis, and the deep head of the flexor pollicis brevis.

Two nerve anomalies must be noted because, in ulnar neuropathy, these anomalies may confuse the diagnosis. The first is the Martin-Gruber anastomosis in the forearm. In this anomaly, fibers that supply the intrinsic muscles are carried in the median nerve to the middle of the forearm where they leave the median nerve to join the ulnar nerve. Functioning intrinsic muscles could be observed with injury above this anastomosis, although the ulnar nerve dysfunction is proximal. The second is the Riche-Cannieu anastomosis, in which the median and ulnar nerves are connected in the palm. Even with an injury at the wrist, some intrinsic function occurs.

CONTRAINDICATIONS

Section 5 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Further Reading
• References

Progressive palsy with increasing muscle weakness is an indication that conservative treatment for ulnar nerve entrapment should be terminated and surgery carried out.

If a fracture of the hook of the hamate is noted in the wrist, cast immobilization or splinting is required for 4-6 weeks. Surgery is indicated if symptoms progress during this time. On the other hand, as swelling subsides, pressure on the nerve may abate and symptoms may disappear. Nonsteroidal anti-inflammatory medications are also valuable to reduce swelling in the tunnel.

Contraindications to each of the operative procedures used to decompress the nerve are the following:

• Decompression in situ should not be used in cases of severe posttraumatic neuropathy with scarring, chronic subluxation, or dislocation of the ulnar nerve from the epicondylar groove and soft tissue masses in the epicondylar groove.
• Medial epicondylectomy is not used when double crush syndrome with entrapment at the distal end of the cubital tunnel or soft tissue masses in the epicondylar groove are suspected.
• Subcutaneous transposition does not release the ulnar nerve completely, leaving the distal course from the cubital tunnel as a possible site of compression. It may not be the best choice for transposition in a thin person who lacks significant adipose tissue at the site of transposition because of the possibility of repeated trauma to the nerve at the elbow.
• Intramuscular transposition is the most controversial of the procedures because of the claim of severe postoperative scarring.
• Submuscular transposition is contraindicated when scarring of the joint capsule or irregularity of the elbow joint due to malunited fracture or severe arthritis is present.

WORKUP

Section 6 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Further Reading
• References

Lab Studies

• Routine studies for ulnar nerve entrapment are used to rule out anemia, diabetes mellitus, and hypothyroidism and include the following:
• • CBC
  • Urinalysis
  • Fasting blood sugar
• If rheumatoid diseases are suspected, order the appropriate tests.

Imaging Studies

• Obtain radiographs of the neck if cervical disc disease is suspected and to rule out cervical ribs.
• Obtain radiographs of the chest if Pancoast tumor or tuberculosis is suspected.
• Radiographs of the elbow and wrist are mandatory in ulnar nerve compression because double crush syndrome may be present. Entrapment of the ulnar nerve may occur at more than one level.
• • Radiographs of the elbow reveal abnormal anatomy, such as a valgus deformity, bone spurs or bone fragments, a shallow olecranon groove, osteochondromas, and destructive lesions (eg, tumors, infections, abnormal calcifications).
  • Radiographs of the wrist reveal fractures of the hook of the hamate, dislocations of the wrist bones, and to a lesser extent, soft tissue masses and calcifications.
• MRI is not usually necessary unless delineation of soft tissue masses or visualization of swelling or other abnormalities in the nerve is desired.

Diagnostic Procedures

• Electromyography tests and nerve conduction studies are indicated to confirm the area of entrapment, document the extent of the pathology, and detect or rule out the possibility of double crush syndrome.^{11, 12, 13}
• Motor and sensory conduction velocities are more useful in a recent entrapment of the ulnar nerve, whereas conduction velocities and EMG are useful in chronic neuropathies because EMG shows axonal degeneration.

TREATMENT

Section 7 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Further Reading
• References

Medical therapy

Conservative treatment of ulnar nerve compression is most successful when paresthesias are transient and caused by malposition of the elbow or blunt trauma. Patient education and insight are important. Resting on elbows at work, using elbows to lift the body from bed, and resting elbows on car windows while driving all are causes of paraesthesia that can be corrected without surgical treatment. Patient education, anterior elbow extension splinting (if necessary), and correction of ergonomics at work should correct these transient palsies.

Nonsteroidal anti-inflammatory medications also are useful adjuncts to relieve nerve irritation. Oral vitamin B-6 supplements may be helpful for mild symptoms. This treatment should be carried out for 6-12 weeks, depending on patient response. Surgical intervention is indicated if increasing paresthesias occur despite adequate conservative treatment and at the first sign of motor changes.

Surgical therapy

Surgical treatment of ulnar nerve entrapment depends on the site of compression. The 2 most common sites are the elbow and the wrist. Surgical treatment at the elbow falls into 2 categories, decompression in situ and decompression with anterior transposition.

Decompression in situ

Decompression in situ essentially is a localized decompression of the nerve, accomplished by incising the Osborne ligament and opening the tunnel beneath the 2 heads of the flexor carpi ulnaris by incising the fascia holding them together. It is carried out through a small incision, beginning at a midpoint between the olecranon and the medial epicondyle and extending 6-8 cm distally over the flexor carpi ulnaris. It is carried out under tourniquet control for better visualization of the nerve. Postoperatively, no immobilization is needed, and active use of the extremity is encouraged. Continued release proximally into the epicondylar groove is discouraged because of the possibility of nerve subluxation occurrence.

Medial epicondylectomy, although not a true decompression in situ, is another procedure to release pressure on the ulnar nerve at the elbow. Removal of the epicondyle removes a compressive area. Excision of the proper amount of bone is critical to the success of this procedure. If too much bone is excised, damage to the medial collateral ligament of the elbow with valgus instability may occur. If too little is removed, the procedure is unsuccessful because the compressive area remains.

Decompression with anterior transposition

Decompression with anterior transposition usually is the operation of choice for ulnar nerve compression at the elbow because it removes the nerve from its compressive bed and puts it in one that is more suitable. By transferring the nerve anteriorly, it effectively lengthens the nerve, decreasing tension on it in flexion. Three types of transposition are possible, each with its own set of advocates.

Initial surgical approach essentially is the same with each type of transposition. Under sterile tourniquet control, an incision begins 8 cm above the medial epicondyle and continues downward to a point midway between the medial epicondyle and the olecranon groove. It then continues for about 6 cm distally over the flexor carpi ulnaris. As skin flaps are developed, the posterior branches of the medial antebrachial cutaneous nerve must be protected. If they are injured, numbness and neuroma over the olecranon and medial epicondyle develops.

Once the nerve has been visualized from about 8 cm proximal to the medial epicondyle to 6 cm distal to the epicondyle, the distal portion of the medial intermuscular septum, the fibroaponeurotic roof of the epicondylar groove, the Osborne ligament, and the fascia of flexor carpi ulnaris are incised, freeing the ulnar nerve. When surgically removing the distal medial intermuscular septum, beware of large collateral vessels in this area. Also, in mobilizing the ulnar nerve from the epicondylar groove, small motor branches to the flexor carpi ulnaris must be preserved. The articular branch may be sacrificed.

The main indications for subcutaneous transposition are necessity of transposition following fracture reduction during elbow arthroplasty and when length is needed following nerve injury. It is the most commonly used method of transposition because it is easy to perform and results are good. The nerve is positioned beneath the subcutaneous tissue and held to the muscle fascia with a few sutures through the epineurium. However, the preferred method is to construct a fasciodermal sling based laterally, passing it under the nerve and then suturing it to the subcutaneous tissue. Postoperatively, immobilize the elbow in a cast or splint at 45 degrees of flexion for 2 weeks.

In submuscular transposition, the origin of the flexor-pronator muscle group must be released. This can be accomplished in a number of ways, and the most important part of any of these releases is to be able to reattach the muscle origin securely. Once the nerve has been transposed to its new bed deep to the flexor pronator muscle group and on the brachialis muscle, the flexor carpi ulnaris fascia is closed, as is the roof of the epicondylar groove. Postoperatively, the elbow is immobilized in 45 degrees of flexion in a post mold or cast for 3-4 weeks.

In intramuscular transposition, once the ulnar nerve has been freed proximally and distally, it is laid across the flexor pronator muscle group to ensure that no kinks are present in the new path of the nerves. Then, a gutter is cut in the muscle, and the nerve is gently placed in this gutter. The fascia is sutured over the nerve to hold it in place.

Preoperative details

Appropriate blood work, chest radiography (if indicated), and a careful clinical examination are required for ulnar nerve entrapment. The usual surgical preparation of the affected extremity from fingers to neck is indicated. This is followed by the application of a tourniquet, if necessary.

Intraoperative details

See Surgical therapy.

Postoperative details

Release and removal of the sterile tourniquet is useful. Subcuticular skin closure is preferred. With decompression in situ, no postoperative immobilization is necessary, and active motion is started immediately according to patient tolerance. Within 1-2 months, full activity should be resumed.

With medial epicondylectomy, no postoperative immobilization is necessary, and active motion is started immediately according to patient tolerance. Within 1-2 months, normal activities should be resumed.

With subcutaneous transposition, postoperative immobilization of the elbow in 45º of flexion for 2 weeks is necessary. Then, active mobilization with muscle stretching and strengthening is carried out for 2-3 months.

Submuscular transposition requires immobilization for 3-4 weeks in a sugartong splint with slight pronation and the wrist in neutral position. Active range of motion, stretching, and strengthening are then carried out for 3-4 months.

Intramuscular transposition requires 3 weeks of immobilization at 90º of elbow flexion with the forearm in full pronation. This is followed by gradual active range-of-motion exercises, stretching, and muscle strengthening.

Follow-up

Follow-up after surgery for ulnar nerve entrapment is at 1 month, 3 months, 6 months, and 1 year.

COMPLICATIONS

Section 8 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Further Reading
• References

The most serious complications of any of the surgical procedures are the following¹⁴:

• Injury to the nerve while decompressing it or transposing it
• Neuromata of the medial antebrachial cutaneous
• Failing to decompress it adequately, causing a new area of entrapment with the decompression
• Failing to recognize a double crush syndrome
• Infection, failure to heal, thrombophlebitis, atelectasis, and failure of the operation due to unknown cause

OUTCOME AND PROGNOSIS

Section 9 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Further Reading
• References

With appropriate decompression performed in a timely manner, the result of surgery for ulnar nerve entrapment should be a return to normal function. If decompression in situ is performed appropriately, return to normal function is almost immediate. With transposition of the nerve following decompression, postoperative immobilization, and the rehabilitative process, 3-6 months may pass before the patient is returned to normal function.

In chronic palsy (>3-4 mo in duration) associated with pain, muscle weakness, and/or atrophy, surgical outcome is less certain. Duration of entrapment and severity of numbness and muscle weakness are important factors in prognosis. Improvement may be limited or may not occur following decompression and transposition in these chronic cases, but further progression can be halted with proper decompression.

FUTURE AND CONTROVERSIES

Section 10 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Further Reading
• References

The only controversy is over which type of transposition produces the best result. At this time, each procedure has advocates. Results appear to be satisfactory in all 3 procedures.

FURTHER READING

Section 11 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Further Reading
• References

Chronic elbow pain.
American College of Radiology - Medical Specialty Society.  1998 (revised 2005).  5 pages.  NGC:004605

REFERENCES

Section 12 of 12

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Further Reading
• References

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5. Kleinman WB. Cubital tunnel syndrome: anterior transposition as a logical approach to complete nerve decompression. J Hand Surg [Am]. Sep 1999;24(5):886-97. [Medline].
6. Merolla G, Staffa G, Paladini P, Campi F, Porcellini G. Endoscopic approach to cubital tunnel syndrome. J Neurosurg Sci. Sep 2008;52(3):93-8. [Medline].
7. Gellman H. Compression of the ulnar nerve at the elbow: cubital tunnel syndrome. Instr Course Lect. 2008;57:187-97. [Medline].
8. Seddon HJ. Surgical Disorders of the Peripheral Nerves. Edinburgh, Scotland:. Churchill Livingstone;1972.
9. Sunderland S. Nerves and Nerve Injuries. 2nd ed. London, England:. Churchill Livingstone;1978:780-95.
10. Dunselman HH, Visser LH. The clinical, electrophysiologic and prognostic heterogeneity of ulnar neuropathy at the elbow. J Neurol Neurosurg Psychiatry. Jul 17 2008;[Medline].
11. Caliandro P, Foschini M, Pazzaglia C, La Torre G, Aprile I, Granata G, et al. IN-RATIO: a new test to increase diagnostic sensitivity in ulnar nerve entrapment at elbow. Clin Neurophysiol. Jul 2008;119(7):1600-6. [Medline].
12. Bartels RH, Meulstee J, Verhagen WI, Luttikhuis TT. Ultrasound imaging of the ulnar nerve: correlation of preoperative and intraoperative dimensions. Clin Neurol Neurosurg. Jul 2008;110(7):687-90. [Medline].
13. Yoon JS, Hong SJ, Kim BJ, Kim SJ, Kim JM, Walker FO, et al. Ulnar nerve and cubital tunnel ultrasound in ulnar neuropathy at the elbow. Arch Phys Med Rehabil. May 2008;89(5):887-9. [Medline].
14. Ruchelsman DE, Lee SK, Posner MA. Failed surgery for ulnar nerve compression at the elbow. Hand Clin. Aug 2007;23(3):359-71, vi-vii. [Medline].

Article Last Updated: Aug 25, 2008