13: In Situ Cubital Tunnel Decompression

Published on 18/04/2015 by admin

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Procedure 13 In Situ Cubital Tunnel Decompression

Pao-Yuan Lin, Sandeep J. Sebastin, Kevin C. Chung

See Video 11: In Situ Cubital Tunnel Decompression

Indications

In situ decompression of the ulnar nerve is indicated for patients with symptoms that are mild or intermittent (Table 13-1). If there is subluxation or instability of the ulnar nerve and/or ulnar nerve palsy owing to an abnormal osseous architecture of the elbow, in situ decompression is not indicated. In these situations, an anterior transposition is more appropriate to correct the anatomic problem.

Table 13-1 Ulnar Nerve Entrapment

Examination/Imaging

Clinical Examination

Palpation: The ulnar nerve is palpated to check for enlargement or subluxation.

The elbow joint is checked for range of motion.

Check Tinel sign from the distal forearm to above the elbow along the course of the ulnar nerve. In cubital tunnel syndrome, Tinel sign is present at the medial epicondylar groove or over the proximal end of the flexor carpi ulnaris (FCU) muscle.

A provocative test for ulnar nerve subluxation is performed by placing the elbow in full flexion with the wrist hyperextended, whereas manual pressure is applied to the nerve for 60 seconds. If the patient’s ring and small finger become numb, the ulnar nerve is likely compressed.

Intrinsic muscle function is tested by asking the patient to cross the long finger over the index finger (i.e., the crossed finger test). Patients with severe ulnar nerve entrapment will not be able to perform this task.

Imaging

Radiographs of the elbow may be obtained if elbow pathology is suspected, such as valgus cubitus, bone spurs or fragments, a shallow epicondylar groove, osteochondroma, and/or destructive lesions. In most cases of idiopathic ulnar nerve entrapment, however, radiographs are not necessary.

Electromyography tests and nerve conduction studies are indicated to confirm the area of entrapment and to document the extent of the pathology.

Nerve conduction studies showing a diminished signal conduction rate of less than 50 meters per second (33% decrease from normal) across the elbow are indicative of nerve compression.

Surgical Anatomy

The ulnar nerve is the terminal branch of the medial cord of the brachial plexus. Initially, the ulnar nerve lies medial to the axillary artery. In the upper arm, the ulnar nerve lies posteromedial to the brachial artery, posterior to the intermuscular septum, and anterior to the medial head of the triceps muscle. Approximately 8 cm proximal to the medial epicondyle is the arcade of Struthers, a thin fibrous band. At the elbow, the ulnar nerve travels posterior to the medial epicondyle and medial to the olecranon at the subcutaneous level, then it enters the cubital tunnel. The cubital tunnel is covered by fibroaponeurotic bands and the Osborne fascia (a ligament over the epicondylar groove), which is the fibroaponeurotic tissue between the two heads of the FCU. After passing through the cubital tunnel, the ulnar nerve travels deep into the forearm between the humeral and ulnar heads of the FCU. Distally, the ulnar nerve follows through the FCU to the deep flexor-pronator aponeurosis (Fig. 13-1).

The posterior branch of the medial antebrachial cutaneous nerve is at risk of injury during cubital tunnel surgery. The proximal crossing branch lies approximately 1.8 cm proximal to the medial epicondyle, whereas the distal crossing branch is about 3.1 cm distal to the medial epicondyle (Fig. 13-2).

The ulnar nerve may be easily compressed at five sites (see Fig. 13-1).

• The arcade of Struthers, a thin aponeurotic band extending from the medial head of the triceps to the medial intermuscular septum. The ulnar nerve passes through the arcade of Struthers in 70% to 80% of patients.

• The medial epicondyle, where a valgus cubitus deformity caused by malunion or nonunion of a condylar fracture may compress the nerve.

• The epicondylar groove (proximal part of cubital tunnel), which is a fibro-osseous tunnel bound anteriorly by the medial epicondyle and laterally by the olecranon and ulnohumeral ligament and covered by fibroaponeurotic bands (Osborne fascia).

• The middle part of the cubital tunnel, where the nerve passes between the two heads of the FCU, which is a continuation of the fibroaponeurotic covering of the epicondylar groove. During elbow flexion, the Osborne fascia is stretched and the tunnel flattened, resulting in a 7- to 20-fold increase in tunnel pressure, ultimately causing pressure on the ulnar nerve. The distal part of the cubital tunnel is formed by the muscle bellies of the FCU.

• Flexor-pronator aponeurosis. Fascia is located at the point of exit from the FCU.

The most common sites of ulnar nerve compression are the epicondylar groove and the cubital tunnel.

FIGURE 13-1

FIGURE 13-2

Positioning

The procedure is performed under tourniquet control. It can be done under regional or general anesthesia. The patient is positioned supine with the affected extremity on a hand table. The elbow is in 90-degree flexion, with some towels under the elbow to keep the elbow in flexion and supination posture. Placing these towels under the elbow will help in locating the medial epicondyle (Fig. 13-3).

FIGURE 13-3

Exposures

The medial epicondyle and olecranon are marked first. A 3-cm skin incision line between the medial epicondyle and olecranon is marked, which is generally drawn a little closer to the medial epicondyle (Fig. 13-4).

FIGURE 13-4

Pearls

Using short (3- to 5-cm) skin incisions will help to avoid injury to the medial antebrachial cutaneous nerve (see Fig. 13-2).

Procedure

Step 1

After tourniquet inflation, the skin and subcutaneous tissue are dissected and divided with a blade, and the Osborne fascia is identified (Fig. 13-5).

FIGURE 13-5

Step 1 Pitfalls

Care should be taken to avoid injury to the medial antebrachial cutaneous nerve. Injury of the cutaneous nerve will result in a painful neuroma (see Fig. 13-2).

Step 3

The elbow is moved through a range of movements to check whether the ulnar nerve subluxes.

If subluxation of the ulnar nerve over the medial epicondyle is noticed, medial epicondylectomy or anterior transposition of the ulnar nerve should be performed to avoid postoperative discomfort from nerve impingement.

Step 4

Tourniquet is deflated and the wound is compressed for 5 minutes to allow the vessels to retract. In most cases, bleeding will stop spontaneously.

The skin and subcutaneous tissue are closed with absorbable sutures and then covered with skin strip tapes.

The patient’s elbow is protected in a soft bulky dressing.

Postoperative Care and Expected Outcomes

The dressings are removed 2 to 3 days after surgery, and active range of motion of the elbow is started at that time.

In mild to moderate nerve compression, the in situ decompression procedure should result in marked relief of paresthesias in the ulnar nerve distribution. The motor weakness may take a much longer time to recover.

Miller RG, Hummel EE. The cubital tunnel syndrome: treatment with simple decompression. Ann Neurol. 1980;7:567-569.

A retrospective review of 12 patients with progressive cubital tunnel syndrome treated with simple decompression of the ulnar nerve. Eleven of the 12 patients had clinical and electrophysiologic evidence of improvement. Patients with the best outcomes had (1) mild weakness, (2) recent onset of symptoms, and (3) a mild abnormality of the sensory action potential preoperatively. (Level IV evidence)

Nathan PA, Istvan JA, Meadows KD. Intermediate and long-term outcomes following simple decompression of the ulnar nerve at the elbow. Chir Main. 2005;24:29-34.

A retrospective review of 102 cases of cubital tunnel syndrome in 74 patients treated with simple decompression of the ulnar nerve. Overall, 82% of patients were regarded as having 75% or more improvement in range of motion at the elbow following the surgery. Most patients (61%) were found to have improved ulnar nerve conduction velocities at follow-up. In this study, simple decompression resulted in excellent intermediate and long-term relief of symptoms in a substantial majority of patients. (Level IV evidence)

Tanigughi Y, Takami M, Tamake T, et al. Simple decompression with small skin incision for cubital tunnel syndrome. J Hand Surg [Br]. 2002;27:559-562.

A retrospective review of 18 elbows in 17 patients treated by simple decompression using only a 1.5- to 2.5-cm skin incision with no endoscopic assistance. Clinical results were evaluated as “excellent” for 4 elbows, “good” for 10, and “fair” for 4. The 4 patients with a “fair” outcome had diabetes mellitus, with marked atrophy of the interosseous muscle and unmeasurable nerve conduction velocities. (Level IV evidence)

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