Subcutaneous Ulnar Nerve Transposition

Cubital tunnel syndrome is one of the most common compression neuropathies affecting the upper extremity. Physical exam findings include loss of sensation, muscle weakness, and clawing of the fingers. More severe cases also show irreversible muscle atrophy, hand contractures, and loss of function. There are several approaches to treating cubital tunnel syndrome. Here, a subcutaneous anterior transposition was performed on this patient. The patient’s ulnar nerve subluxed upon elbow flexion and extension upon physical examination, which was a primary indication for choosing this surgical approach over other techniques. This procedure not only decompresses the affected nerve but also transposes the nerve anterior to the medial epicondyle so as to relieve strain on the nerve upon the full range of motion of the elbow.

This is a case of a 42-year-old female presenting with numbness in the ring and small fingers for several months that is worst at night or when sitting in a chair. Over time the patient notes tenderness in the inside part of the elbow and altered hand dexterity and strength.

Cubital tunnel syndrome is the second most common compression neuropathy affecting the upper extremity after carpal tunnel syndrome.¹ It affects approximately 1% of the general population in the US. However, information on the epidemiology of cubital tunnel syndrome is limited compared with that of carpal tunnel syndrome. Unlike carpal tunnel syndrome, active disease surveillance of cubital tunnel syndrome in the US is lacking, which has implications for establishing standard guidelines on its diagnosis and treatment.² In addition to affecting the patient’s activities of daily living, cubital tunnel syndrome also carries an additional economic burden. In a study conducted by Juratli et al., nearly half of the workers with this condition received disability benefits before diagnosis.³

First-line treatment for cubital tunnel syndrome is typically nonoperative. When conservative treatment fails to relieve symptoms, however, surgical intervention is needed. There are a variety of different surgical procedures that can be performed. Here, an anterior subcutaneous ulnar nerve transposition is performed on this patient. 

Physical exam findings will reveal decreased sensation in the ring and small fingers, and muscle weakness in the interossei of the hand. In more advanced cases, clawing of the ring and small fingers may also be evident upon inspection of the hand. Additionally, there are several tests that can be performed on the hand to help in the diagnosis of cubital tunnel syndrome. A positive Froment’s sign occurs when the patient’s interphalangeal joint of the thumb flexes when asked to pinch a flat object, such as a piece of paper. A positive Wartenberg’s sign will show persistent abduction of the fifth digit during attempted adduction of all digits. Lastly, provocative tests such as the Tinel sign, where slight percussion over the nerve elicits a tingling sensation, and reproduction of symptoms upon flexion of the elbow, can also be performed to support this diagnosis. 

Patients with cubital tunnel syndrome experience a range of symptoms such as discomfort, muscle weakness, and numbness in the ring and small fingers. Patients may also report night symptoms such as awakening as a result of sleeping with their elbow in a flexed position. Early symptoms are primarily sensory with motor changes occurring later. In more severe cases, loss of function, hand contractures, and irreversible muscle atrophy may also be evident if the patient is left untreated.⁴

Nonoperative therapies such as pain relief, inflammation reduction, and rehabilitation work for patients 50% of the time.⁵ These include NSAIDs, corticosteroid injections, and nighttime extension splints, which have all shown efficacy. Other measures such as elbow pads, physical therapy, and avoidance of provocative activities can also relieve symptoms.

Surgical intervention is only considered when conservative treatments fail to treat the patient’s symptoms. There are a variety of different surgical procedures to treat cubital syndrome. Among these are open or endoscopic ulnar nerve decompression, ulnar nerve transposition, and medial epicondylectomy. Simple decompression and anterior transposition (subcutaneous or submuscular) are the most common surgical treatments for cubital tunnel syndrome. However, there is a lack of consensus on determining the best and optimal surgical treatment for cubital tunnel syndrome. Thus, the choice of procedure is often determined by a variety of different factors: the severity of nerve compression, nonspecific patient factors, and surgeon preference.¹

As mentioned above, there is no standard approach to treating cubital tunnel syndrome surgically. However, in situ decompression such as a cubital tunnel release is generally considered the first surgical choice. However, when there is baseline ulnar nerve instability, then transposition may be better. In this case, it was evident upon physical examination that the patient’s ulnar nerve subluxed upon elbow flexion and extension. This key finding was the primary indication for performing an ulnar nerve transposition versus an in situ cubital tunnel release. 

Before incision, patients are typically given either general or regional anesthesia and are injected with Marcaine with epinephrine to minimize bleeding and pain postoperatively. During blunt dissection to the level of the ulnar nerve and cubital tunnel, the medial antebrachial cutaneous nerve was first identified and protected throughout the procedure, as injury to this nerve is common with this approach. Crossing veins in the surgical field were cauterized to prevent hematoma formation and bruising postoperatively.

Dissection of the ulnar nerve was started posterior to the medial epicondyle where the nerve is more easily mobilized and identified. The ulnar nerve was mobilized by releasing its fascia first distally and then proximally with care not to injure surrounding vessels and nerves. The intermuscular septum was then identified and mobilized to prevent any undue tension on the ulnar nerve upon transposition. 

The cubital tunnel was first closed before transposing the ulnar nerve in order to prevent subluxation or dislocation. In order to keep the ulnar nerve in an anteriorly subcutaneous transposed position, a mattress suture technique was used to attach the fascial sling to the anterior skin flap. Direct visualization and flexion of the elbow can confirm that the fascial sling is secure enough without compressing the ulnar nerve.

The wound was washed and closed with sutures in a layered fashion. Postoperatively, a sling was provided for protection and comfort. The patient was able to range the arm and resume activities of daily living immediately. However, it was advised to the patient that strenuous activity should be avoided for at least 2–6 weeks postoperatively until the wound is fully healed. After the sling is removed, physical therapy is generally advised to allow for the full range of motion of the elbow joint.

There are few complications associated with anterior transposition of the ulnar nerve. Among these are scar sensitivity, infection, and complex regional pain syndrome.⁶ These complications are due to the nature of the surgical technique itself; compared with a simple in situ decompression, ulnar nerve transposition requires a larger incision, more extensive dissection, greater manipulation of the nerve, and removal of the surrounding vasculature. Another common complication of this procedure is an injury to the posterior branch of the medial antebrachial cutaneous nerve, which can result in a painful neuroma, hyperesthesia, hyperalgesia around the medial elbow, and painful scarring.⁷

The best surgical technique for cubital tunnel syndrome is still under debate. Therefore, the choice of surgical procedure is largely up to surgeon preference. Simple decompression of the ulnar nerve is one of the more common and simple surgical approaches to cubital tunnel syndrome, and it can be done both openly or endoscopically. Medial epicondylectomy is a less common technique but is indicated when structural abnormalities of anatomy are evident.

Anterior transposition of the ulnar nerve is another common approach to treating cubital tunnel syndrome. Although the choice of procedure is largely up to surgeon preference, there is a general consensus amongst surgeons that anterior transposition is indicated when the patient shows subluxation of the nerve upon examination. Studies that have compared ulnar nerve transposition with in situ decompression have shown no statistical difference with regards to clinical outcomes. However, it should be noted that ulnar nerve transposition is associated with a higher number of complications due to the nature and extent of its dissection.

There are three types of ulnar nerve transposition: subcutaneous, intramuscular, and submuscular. Subcutaneous transposition was first introduced by Benjamin Curtis in 1898 and is considered one of the most common approaches to cubital tunnel syndrome.⁸ It is generally advised to do a subcutaneous transposition over the other two approaches whenever possible. However, if there are cases with excessive preoperative nerve instability or nerve irritability or sensitivity, an intramuscular or submuscular transposition may be the preferred method. Studies have shown similar clinical outcomes between submuscular and anterior transpositions. However, one advantage of the submuscular transposition is that the muscle offers an additional layer of protection over the ulnar nerve. This can be particularly useful for patients who have relatively little subcutaneous tissue.

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