Surgical Management of Cubital Tunnel Syndrome: Ulnar Nerve Transposition

Introduction to Ulnar Nerve Transposition

Ulnar nerve transposition is a surgical procedure performed to relieve pressure on the ulnar nerve, which runs from the neck down to the hand, supplying sensation to the forearm and hand. This nerve is responsible for the fine motor control of the hand and the sensory information from the fingers. Compression of the ulnar nerve, often at the elbow (cubital tunnel syndrome), can lead to pain, tingling, and weakness in the hand, making ulnar nerve transposition an essential surgical option for affected patients.

Indications for Ulnar Nerve Transposition

Ulnar nerve transposition is typically indicated in patients with cubital tunnel syndrome, which is the second most common compressive neuropathy of the upper extremity after carpal tunnel syndrome. The following are common indications for ulnar nerve transposition:

1. Persistent Symptoms: Patients with persistent symptoms of ulnar nerve compression, such as numbness, tingling, and pain in the ring and little fingers, despite conservative treatment, are candidates for surgery.
2. Muscle Weakness: Progressive weakness in the intrinsic muscles of the hand, particularly in the hypothenar, interosseous, and lumbrical muscles, warrants surgical intervention.
3. Muscle Atrophy: Evidence of muscle wasting, especially in the hand, indicates severe and chronic nerve compression that may benefit from surgical decompression.
4. Failure of Conservative Management: When non-surgical treatments such as splinting, physical therapy, and anti-inflammatory medications fail to alleviate symptoms, surgery is often considered.
5. Severe Nerve Compression: In cases where electromyography (EMG) or nerve conduction studies indicate significant slowing of the nerve conduction velocity at the elbow, surgery may be recommended.

Preoperative Evaluation

A thorough preoperative evaluation is crucial for the successful outcome of ulnar nerve transposition. The following steps are typically involved:

1. Clinical Assessment: A detailed history and physical examination to assess the severity and duration of symptoms. Tinel's sign and elbow flexion test are commonly used clinical maneuvers to elicit symptoms.
2. Electrodiagnostic Studies: Nerve conduction studies and electromyography are performed to confirm the diagnosis, assess the severity of the compression, and rule out other conditions like cervical radiculopathy or thoracic outlet syndrome.
3. Imaging: While not always necessary, imaging studies such as ultrasound or MRI may be used to visualize the ulnar nerve and surrounding structures, particularly if there is suspicion of anatomic abnormalities or mass lesions.
4. Risk Assessment: Evaluation of the patient's overall health, comorbid conditions, and any potential risks associated with surgery. Patients should be informed of the potential risks and benefits of the procedure.

Contraindications

Ulnar nerve transposition is generally a safe procedure, but certain conditions may contraindicate surgery or require special consideration:

1. Active Infection: The presence of an active infection in the surgical area is a contraindication until the infection is resolved.
2. Poor Surgical Candidate: Patients with significant comorbidities or poor overall health may not be suitable candidates for elective surgery.
3. Nerve Regeneration Concerns: In patients with long-standing and severe nerve compression, where nerve regeneration potential is poor, the benefits of surgery may be limited.
4. Non-compliance: Patients who are unlikely to comply with postoperative rehabilitation and care may not achieve the desired outcomes from surgery.

Surgical Techniques and Steps

Several techniques for ulnar nerve transposition exist, with the choice depending on the surgeon’s preference, patient anatomy, and the specifics of the case. The three main types of ulnar nerve transposition are:

1. Subcutaneous Transposition: The ulnar nerve is moved anteriorly and placed under the skin but above the muscle layers. This technique is relatively simple and less invasive but may be associated with higher recurrence rates.
2. Intramuscular Transposition: The nerve is relocated within the muscle tissue, which provides a cushion and protection. This method requires more dissection and may have a higher risk of postoperative stiffness.
3. Submuscular Transposition: The most invasive of the three, this technique involves placing the nerve beneath the muscle. It provides excellent protection and minimizes the risk of nerve compression but requires a longer recovery time.

Steps in Submuscular Transposition:

1. Incision and Exposure: A curvilinear incision is made over the medial epicondyle, and dissection is carried down to expose the ulnar nerve.
2. Identification of the Nerve: The ulnar nerve is carefully identified and dissected free from surrounding structures, taking care to preserve the blood supply.
3. Release of the Nerve: Any compressive structures, including the Osborne's ligament and the intermuscular septum, are released to free the nerve.
4. Transposition: The nerve is carefully transposed anteriorly, and a new tunnel is created beneath the flexor-pronator muscle mass.
5. Closure: The muscle is sutured over the nerve to secure its position, and the incision is closed in layers.

Postoperative Care

Postoperative care is critical for the success of ulnar nerve transposition and includes the following components:

1. Immobilization: The elbow is typically immobilized in a flexed position (about 90 degrees) for 1-2 weeks to allow initial healing.
2. Pain Management: Pain is managed with oral analgesics, and patients are encouraged to avoid activities that strain the elbow.
3. Physical Therapy: Early mobilization is encouraged once the immobilization period is over. Physical therapy focuses on gentle range-of-motion exercises, followed by strengthening exercises to restore function.
4. Follow-up: Regular follow-up appointments are necessary to monitor nerve recovery and ensure there are no complications such as wound infection or nerve re-compression.

Possible Complications

While ulnar nerve transposition is generally successful, there are potential complications that surgeons should be aware of:

1. Infection: As with any surgical procedure, there is a risk of infection, which can delay healing and worsen outcomes.
2. Nerve Injury: There is a risk of inadvertent nerve injury during dissection or transposition, which can lead to worsening symptoms or new deficits.
3. Recurrent Compression: Despite successful transposition, the nerve can become re-compressed, necessitating revision surgery.
4. Elbow Stiffness: Especially with submuscular transposition, there may be a risk of postoperative elbow stiffness.
5. Hematoma: Accumulation of blood in the surgical site can compress the nerve and complicate recovery.

Prognosis and Outcome

The prognosis after ulnar nerve transposition is generally favorable, especially in patients with early to moderate compression. Most patients experience significant relief of symptoms, improved hand function, and a return to normal activities. However, the outcome depends on several factors:

1. Severity of Compression: Patients with mild to moderate compression tend to have better outcomes than those with severe, long-standing compression.
2. Type of Transposition: Submuscular transposition, while more invasive, tends to have the best long-term outcomes due to the protection it offers the nerve.
3. Patient Compliance: Adherence to postoperative rehabilitation plays a critical role in the success of the surgery.
4. Time to Surgery: Early intervention, before significant muscle atrophy or nerve damage occurs, is associated with better outcomes.

Recent Advances

Recent advances in ulnar nerve transposition focus on improving outcomes and reducing complications. Some of these include:

1. Minimally Invasive Techniques: Endoscopic ulnar nerve decompression is a less invasive option that may reduce recovery time and postoperative pain.
2. Bioabsorbable Materials: The use of bioabsorbable materials to create a tunnel for the transposed nerve is being explored to reduce the risk of nerve re-compression.
3. Intraoperative Monitoring: Real-time intraoperative nerve monitoring is being used to ensure the nerve is not damaged during surgery.