Radial Nerve Entrapment Treatment & Management

Immediate exploration of a palsied nerve after a closed fracture of the humerus is contraindicated. A 6- to 12-week period of expectancy is indicated to allow the swelling and palsy to subside. With a palsy developing after a closed manipulation, a further gentle remanipulation is carried out. Open exploration is indicated if there is no relief of the palsy or if it is felt that the nerve may be entrapped between the fracture fragments.

In an open fracture or with a gunshot wound to the humerus with an associated palsy, exploration of the nerve at the time of debridement, as well as possible fixation, is the treatment of choice. ^{[13, 14, 15, 16, 17]}  Nerve injuries in continuity to an open fracture are gently explored and followed for 6-12 weeks before any further treatment is initiated.

In radial tunnel syndrome, prolonged conservative treatment is indicated if the only symptom is pain. If pain does not resolve after 12 weeks, surgery may be indicated. ^{[3, 18, 19, 20]}

In posterior interosseous nerve syndrome, institute conservative treatment for 6-12 weeks. Surgery is indicated if no improvement occurs or paralysis increases.

Wartenberg syndrome is best treated nonoperatively. Local application of steroids or iontophoresis is used. Nerve decompression is indicated only in resistant cases.

Conservative treatment varies according to the level and the cause of radial nerve neuropathy. ^[30] A period of immobilization and anti-inflammatory pharmacologic therapy may diminish swelling and improve symptoms. In addition, functional splints help prevent contracture and improve function as signs of nerve healing follow. For example, an appropriate functional splint for a high palsy includes a static extension splint for the wrist and a dynamic extension apparatus for the proximal phalanges.

The initial treatments for radial tunnel syndrome and posterior interosseous nerve syndrome are similar. Splints and activity modification help limit repetitive elbow extension, forearm pronation, and wrist flexion. Anti-inflammatory drugs and a single cortisone shot in the affected area are administered for both conditions, but in posterior interosseous nerve syndrome, weakened muscles are protected with a cock-up splint.

Compression of the superficial radial sensory nerve (RSN) in the distal forearm is best treated conservatively by eliminating any possible external compression, decreasing inflammation by utilizing a thumb spica forearm-based splint (allowing interphalangeal motion), and administering anti-inflammatory medications and cortisone injections. Injections for de Quervain disease should fill the first extensor compartment, whereas those for Wartenberg syndrome are placed in the subcutaneous tissues just dorsal to the compartment. If symptoms continue unabated after 4-6 months and the diagnosis is clear, consider neurolysis or neuroma excision, followed by burying of the nerve ends in bone.

Choice of surgical approach

Surgical treatment of the radial nerve in the arm is carried out through either the anterolateral approach or the posterior approach. The anterolateral approach offers excellent nerve exposure over the distal half of the humerus. For more proximal exposure, the posterior approach is recommended. If needed, both approaches can be employed together for wide exposure. ^{[23, 16, 18, 20, 12]}

Preparation for operation

Appropriate preoperative blood work, a chest radiograph (if indicated), and a careful physical examination are warranted preoperatively. Standard preoperative laboratory studies are required. The patient is positioned supine with the arm on an arm board. A tourniquet is essential. For proximal nerve lesions, a sterile tourniquet may be needed, and the lateral decubitus position is preferred. Prophylactic antibiotics are used. General anesthesia without complete paralysis is preferred for proximal lesions so that intraoperative nerve stimulation may be utilized.

Procedure

The favored approach begins posterolaterally in the interval between the deltoid and the lateral head of the triceps. It proceeds distally between the biceps and the lateral head of the triceps, crossing the lateral intermuscular septum 10 cm proximal to the lateral epicondyle. The incision continues in the biceps-brachialis interval. At this point, the incision joins the anterolateral approach recommended for exposure of the radial nerve at the elbow.

The superficial fascia is incised, and the lateral antebrachial cutaneous nerve is isolated and protected as it emerges between the biceps and brachialis. The deep fascia is incised in line with the skin incision and the radial nerve located deep within the intermuscular interval between the brachialis and brachioradialis. The nerve is traced proximally and distally, releasing any possible points of compression.

Proximally, compression of the radial nerve at the lateral intermuscular septum must be suspected, especially in cases associated with humerus fractures. In these cases, the nerve may be encased in scar, buried in the fracture, or surrounded by callus. Meticulous dissection and a complete neurolysis are required.

To explore and release the nerve in the supinator and surrounding area, the incision is started 20-25 cm above the elbow and is continued to the dorsum of the forearm. Care must be taken during the dissection because 5-6 cm above the elbow, branches are given off to the brachioradialis and the extensor carpi radialis longus and brevis. The nerve is followed distally beneath the brachioradialis and into the supinator. The distal margin of the supinator is identified, and the fascia is incised between the extensor carpi radialis longus and brevis and the extensor digitorum communis. Once the nerve is exposed, it is followed proximally to the distal margin of the supinator, where numerous branches are given off.

Once these branches have been protected, the superficial layer of the supinator is incised at right angles to the direction of its fibers, and the fibrous arcade of Frohse is incised to complete exposure of the posterior interosseous nerve. In this exposure, all the potential sites of compression of the posterior interosseous nerve (ie, arcade of Frohse, supinator muscle, and distal fascia) are released.

Great care must be exercised in exposing the posterior interosseous nerve. The following should be kept in mind:

• Proximally, watch for the branches to the brachioradialis and the extensor carpi radialis longus and brevis, as well as the superficial branch of the radial nerve
• Release the supinator along its entire course
• Remember that compression may be present not only at the arcade of Frohse but also where the nerve exits the muscle
• Incise the superficial layer of the supinator very carefully to avoid injuring the enclosed nerve
• Protect the numerous muscular branches given off distal to the supinator
• Distally, protect branches of the RSN and lateral antebrachial cutaneous nerve

In exposing the superficial radial nerve at the wrist for relief of a chronic Wartenberg syndrome that is not responsive to conservative treatment, the incision is made over the suspected area of compression; however, it must be transverse rather then longitudinal in order to prevent further scarring in this area. The incision is very superficial, and any area of compression is released. If a neuroma is present, it is resected and the ends buried in healthy tissue.

Immediately after release of the radial nerve in the arm, a splint is used to put the arm, forearm, and wrist at rest, with the elbow flexed to 90° and the forearm in neutral pronosupination. Motion is initiated quickly with graduation to the appropriate functional splint. Rehabilitation emphasizes motor and sensory reeducation and must be tailored to the individual patient.

After posterior interosseous nerve exploration and release, a similar long arm splint is used for a short duration postoperatively. A range of motion (ROM) exercise program is started at 1 week and is continued throughout treatment. Protective splints may be utilized along with graduated muscle stretching and then strengthening. The patient may not be able to return to normal activities for 3-4 months.

RSN decompression or neuroma excision is followed by a short-arm thumb spica splint. Again, ROM is initiated quickly. Protective splints are frequently needed, and sensory reeducation and desensitization are the mainstays of treatment in the postoperative phase.

A major complication of radial nerve entrapment is injury to the nerve during surgical exploration. Severing or stretching the nerve is not uncommon while attempting to extricate the nerve in the middle and distal thirds of the arm from a bony spicule or healing callus. Counsel the patient about this risk. In exploring the posterior interosseous nerve, a large ganglion or lipoma may be seen encompassing the nerve, and during dissection, the nerve may be severed or severely stretched.

Another complication is failure of the patient to seek medical help until the affected muscles have atrophied or fibrosed. Although nerve decompression should still be strongly considered, the possibility of a satisfactory outcome from neurolysis alone is slim, and tendon transfers may need to be performed at the same time.

Other complications are those that can occur with any form of surgery, including infection, wound dehiscence, keloid formation, and incomplete recovery of function for no apparent reason.

If nerve entrapment has caused only mild damage to the nerve (neurapraxia), recovery should be rapid and complete in a short period of time—approximately 2-8 weeks. If the injury is more severe (axonotmesis), recovery will take longer, and the timetable is determined by how far the regenerating axon must grow to reinnervate the paralyzed muscles. Nerves typically heal at a rate of 1 mm/day. The most severe form of nerve injury (neurotmesis) rarely results from nerve entrapment. If there is discontinuity of the axon and sheath, there is no chance for a full recovery.

The result of any surgery is dependent on the damage to the nerve preoperatively. With neurapraxia—whether it is in the arm, elbow, or wrist—following early release, the result should be a return to normal function in 80-90% of cases. With axonotmesis, the results, even after early release, will not be as favorable as those with neurapraxia; complete return of function is rare. With neurotmesis, the results are unsatisfactory even with surgical repair.