Cubital Tunnel Release (Cadaver)

Cubital tunnel syndrome is a condition that affects the ulnar nerve as it crosses the medial elbow through the retrocondylar groove. It is the second most common compressive neuropathy, causing tingling and numbness in the ring and small fingers. In advanced cases of symptomatic cubital tunnel syndrome, weakness, altered dexterity, and atrophy of the intrinsic muscles of the hand may develop.¹ Cubital tunnel syndrome can be treated with either a cubital tunnel release or an ulnar transposition. In this case, the former is demonstrated on a cadaveric arm.

The ulnar nerve originates from the C8–T1 nerve roots, forming part of the medial cord of the brachial plexus. It descends down the arm medial to the brachial artery, up until the insertion point of the coracobrachialis muscle. It then pierces the medial intermuscular septum and enters the posterior compartment of the arm. It runs along the posteromedial aspect of the humerus, passing behind the medial epicondyle in the cubital tunnel. The roof of the cubital tunnel is formed by Osborne’s ligament and the flexor carpi ulnaris fascia. The floor of the tunnel is formed by the posterior and transverse bands of the medial collateral ligament and elbow joint capsule. The medial epicondyle and the olecranon process form the walls of the cubital tunnel. In the cubital tunnel, the ulnar nerve is palpable by hand. After passing through the cubital tunnel, the ulnar nerve enters the anterior compartment of the forearm between the two heads of flexor carpi ulnaris. It runs through the forearm between the flexor digitorum superficialis laterally and the flexor digitorum profundus medially. In the forearm, the ulnar nerve gives off several branches: muscular branches, palmar branches, dorsal branches, and articular branches. The ulnar nerve enters the palm of the hand via Guyon’s canal. In the hand, it gives off several additional branches including the superficial sensory branch, the deep motor branch, and additional articular branches.

Functionally, the ulnar nerve provides sensory innervation to the fifth digit, the medial half of the fourth digit, and the corresponding parts of the palm. Additionally, the ulnar nerve’s motor function controls the fine movements of the fingers via the intrinsic muscles of the hand.

Most commonly, there are three sites of ulnar nerve entrapment in the elbow that lead to cubital tunnel syndrome. Proximally, the ulnar nerve may become entrapped within the arcade of Struthers (the hiatus in the medial intermuscular septum). Moving distally, the ulnar nerve may also become entrapped between Osborne’s ligament and the medial collateral ligament. Most distally, the ulnar nerve may become entrapped in the aponeurosis between the two heads of flexor carpi ulnaris.

Surgically, there are two broad approaches to cubital tunnel syndrome. The first approach is to release the nerve where it lies in an in situ release (neuroplasty of ulnar nerve). The second approach is a transposition, which involves neurolysis of the ulnar nerve and transposition anteriorly. This surgical video and accompanying article only deal with the former approach: in situ release of the ulnar nerve. Several techniques fall under the category of in situ release of compressive ulnar neuropathy. These include the extensile-open, the mini-open, and the endoscopic techniques.² The difference between the extensile-open and the mini-open techniques is limited to the length of the incision. In the extensile-open technique, an incision is made centered on the medial epicondyle of the elbow. The incision is made 6–8 cm proximally to the medial epicondyle to a distance 6–10 cm distally to the medial epicondyle. The mini-open technique uses the same incision line, but the incision can be made smaller both proximally and distally. The mini-open technique for cubital tunnel release is performed in this video and discussed below in more detail.

The third surgical technique under the category of in situ ulnar nerve release is the endoscopic technique.³ The potential advantages of an endoscopic cubital tunnel release over an open procedure to surgically treat cubital tunnel syndrome include smaller incision, less surgical pain, earlier recovery, minimized manipulation of the ulnar nerve, and reduced risk of nerve devascularization. Yet, several contraindications may exist that hinder the use of the endoscopic technique. Severe cubital valgus or elbow deformity, osteoarthritis of the elbow, or recurrent ulnar nerve compressions after previous surgeries are all contraindications for endoscopic cubital tunnel release. Additionally, if endoscopic release is performed and the ulnar nerve begins to sublux over the medial epicondyle, an incision may need to be made to perform a medial epicondylectomy or anterior nerve transposition.

Before the operation begins, the patient should be kept supine on the operating table. The operative limb is extended across a hand table. Standard preparation and draping of the limb should be performed, and a sterile tourniquet should be applied.

To begin an open, in situ ulnar nerve release, the patient’s elbow should be flexed slightly and the shoulder externally rotated, looking at the posteromedial aspect of the elbow behind the medial epicondyle. Before making the incision, it is important to examine the position of the ulnar nerve and to ensure that it lies stably behind the medial epicondyle. Examination of the ulnar nerve before making the incision allows the surgeon to determine if the ulnar nerve is subluxing over the medial epicondyle into the surgical field. A subluxing ulnar nerve preoperatively or postoperatively may be an indication for an ulnar nerve transposition as opposed to the in situ release. After careful examination of the ulnar nerve and determination of its stability behind the medial epicondyle, the incision can be made.

After the incision is made, the tissue should be dissected down to the level of the medial epicondyle to find the ulnar nerve. The ulnar nerve will be palpable before it is visible behind the medial epicondyle. Branches of the medial antebrachial cutaneous nerve may be found to be crossing the medial epicondyle and the ulnar nerve, and should be identified and retracted.

With the ulnar nerve palpated, it is sharply incised longitudinally behind the medial epicondyle. Once the ulnar nerve is clearly exposed, the decompression can begin. Proximally, Metzenbaum scissors can be used to carefully decompress the nerve. Distally, the Metzenbaum scissors can similarly be used to release the ulnar nerve distally through the cubital tunnel, under Osborne’s ligament, and through the aponeurosis of the two heads of flexor carpi ulnaris.

Once the ulnar nerve is released, the elbow joint is ranged in flexion and extension, and the ulnar nerve is observed. The nerve may roll or perch over the epicondyle, but it should not sublux or dislocate. Flexing and extending the elbow ensures the ulnar nerve’s stability after it has been released.

The wound is washed and closed in layers. A soft dressing is applied.

Use of the operative limb for activities of daily living is allowed immediately after surgery. However, strenuous activity is discouraged for a period of 2–4 weeks postoperatively until the surgical wound is healed and surgical site pain has resolved.

Several studies have reported on the outcomes of the cubital tunnel release procedure. Generally, regardless of the surgical treatment employed, release of the ulnar nerve at the elbow improves symptoms of pain, numbness, and tingling within and outside of the elbow. As discussed previously, cubital tunnel release can be performed with an in situ release or transposition. Bacle et al. reviewed 375 patients undergoing surgery for ulnar nerve entrapment. Regardless of surgical technique, 90% of patients were cured or showed improvement.⁴ Neither of the techniques aggravated symptoms, and the study concluded that surgery was effective in treating cubital tunnel syndrome. Transposition proved to be as effective as in situ decompression.

To some degree, however, transpositions were associated with more complications and slower recovery. Results from studies conducted by Bartels et al., Nabhan et al., and Caliandro et al. also support these findings.^5–7 More specifically, research has compared results of the different techniques used for in situ ulnar nerve release. In a meta-analysis comparing results of 556 endoscopic versus 425 open cubital tunnel release procedures, Aldekhayel et al. concluded that the two methods of in situ cubital tunnel release produce similar outcomes, complication profiles, and reoperation rates.³ In both groups, approximately 80% of patients experience “good” or “excellent” results as defined by specific study criteria.

To date, the literature does not seem to agree on a superior method for repair of ulnar nerve entrapment. The choice of surgical technique to repair cubital tunnel syndrome remains in question and should be an individualized decision based on the surgeon’s discretion.

Nothing to disclose.