Chapter 18 Ulnar Nerve Transposition

Amy Barenholtz-Marshall, OTR, CHT

At the elbow, the ulnar nerve passes posterior to the medial epicondyle through a narrow space known as the cubital tunnel. Because of the anatomical configuration and the superficial course of the nerve, this is a common entrapment site and is referred to as cubital tunnel syndrome. At this level the nerve is responsible for motor activity of the fourth and fifth flexor digitorum profundus (FDP) tendons, flexor carpi ulnaris (FCU) muscle, intrinsic hand muscles, and sensation of the fifth and ulnar one-half of fourth fingers.

Injury to the nerve can be caused by a blunt trauma to the elbow (such as a fracture or fracture dislocation), compression, traction, friction, or subluxation. Compression to the nerve can originate from external or internal sources. Externally sustained, prolonged pressure on the medial side of the elbow, or repetitive motion, results in compression of the nerve. Internal sources of compression include tight fascial bands, arthritic spurs, rheumatoid synovitis, and soft tissue tumors. Other conditions that contribute to compression by lowering the nerve threshold include diabetes, chronic alcoholism, and renal disease.

Ulnar nerve compression symptoms can mimic other conditions. A differential diagnoses must be made to exclude thoracic outlet syndrome (TOS), cervical disc lesion with nerve root compression, and ulnar nerve entrapment at Guyon’s canal. Early symptoms of ulnar nerve compression include sharp or aching pain on the medial side of the proximal forearm, that radiates proximally or distally. This is accompanied by intermittent paresthesias in the fourth and fifth fingers. Symptoms are aggravated by elbow flexion and frequently awaken the patient at night. Later symptoms include muscle atrophy of the intrinsics, slight clawing of the fourth and fifth digits accompanied by sensory changes, hand weakness, and impaired dexterity. The last changes to appear are FDP and FCU weakness.

Nerve compression that is detected early, with the compression attributed to external sources, is treated conservatively by anti-inflammatory medication, nighttime splinting (to avoid prolonged elbow flexion), postural education, and activity modification. If a 4- to 6-week trial of conservative treatment fails, surgery is considered. Electromyography (EMG) testing before surgery confirms compression of the nerve.

Surgical procedures to decompress the nerve range from a simple ligament release (in situ decompression) to an anterior transposition of the nerve to a medial epicondylectomy. Functional results vary depending on the severity and duration of nerve compression, clinical symptoms, and surgical procedure. Symptoms that have been present for less than 6 months and limited to paresthesias can expect complete recovery.

Anatomic Overview

• The ulnar nerve arises from the medial cord of the brachial plexus.

• As the ulnar nerve courses medially toward the elbow, it pierces the medial intermuscular septum through the arcade of Struthers. This is a fascial band that lies 8 cm proximally to the medial epicondyle and traverses the medial head of the triceps to the medial intramuscular septum.

• The nerve descends subfascially on the medial aspect of the triceps muscle and changes to a more posterior course.

• Before the nerve enters the forearm, it passes posteriorly to the medial epicondyle through the cubital tunnel.

1 The tunnel begins at the condylar groove between the medial epicondyle of the humerus and the olecranon of the ulna.

2 The floor of the tunnel is composed of the medial collateral ligament of the elbow joint, and the two heads of the FCU form the sides.

3 The roof is formed by the triangular arcuate ligament, which bridges the medial epicondyle of the humerus and the medial tip of the olecranon.

4 The capacity of the cubital tunnel is greatest when the elbow is extended, because this puts the arcuate ligament on slack.

• The nerve then passes into the forearm between the ulnar and humeral heads of the FCU muscle.

• Compression at the elbow can occur at various sites along the course of the nerve, including the arcade of Struthers, the medial intermuscular septum, the medial epicondyle, the cubital tunnel, or between the two heads of the FCU origin.

Surgical Overview

• The purpose of surgical intervention is to decompress the nerve while retaining adequate blood supply.

• If in situ decompression cannot adequately relieve compression, the nerve is removed from the tunnel and transposed anteriorly either subcutaneously or submuscularly. The nerve is moved to lie anteriorly to the elbow flexion/extension axis of motion to avoid compression and traction with elbow flexion.

• The approach is a posteromedial longitudinal incision approximately 8 to 10 cm long, with proximal exposure of the medial intermuscular septum and the arcade of Struthers and distal exposure of the nerve between the two heads of the FCU.

• The arcade of Struthers is released, and the intermuscular septum is removed.

• The nerve is then identified and freed in the proximal forearm at the level deep to the FCU origin.

• It is elevated from its bed and placed anteriorly to the medial epicondyle.

• At this point the nerve is placed in an intermuscular, subfascial, subcutaneous, or submuscular position.

Subcutaneous Transposition

• The ulnar nerve and its neurovascular bundle are transposed anteriorly beneath the elevated skin flap.

• A loose fasciodermal sling, created from the flexor muscle mass or the intermuscular septum, is created to support the nerve in the new position.

• This approach is appropriate for mild cases of compression.

• Clinical symptoms are present, but EMG tests are normal.

Submuscular Transposition (Learmonth Procedure)

• This procedure places the nerve in a protected position and is indicated in moderate to severe neuropathies, thin-skinned individuals, or high demand elbows, such as throwing athletes.

< div class='tao-gold-member'>

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

Total Knee Arthroplasty Contracture Release of the Elbow Extensor Tendon Repairs Volar Plate Arthroplasty Flexor Tendon Repairs Meniscal Repair and Transplantation

Stay updated, free articles. Join our Telegram channel

Join

Full access? Get Clinical Tree