The Second Look: Navigating Revision Surgery for Carpal and Cubital Tunnel Syndromes

Revision surgery for nerve compression in the upper extremity presents unique challenges. While primary decompression procedures for conditions like Carpal Tunnel Syndrome (CTS) and Cubital Tunnel Syndrome (CuTS) are common, addressing persistent or recurrent symptoms requires a specialized approach. Dr. Dy, also a host of his own hand surgery podcast The Upper Hand, provides an in-depth look at the workup and surgical philosophy for these complex revision cases.

Understanding Compression Neuropathy: A Quick Primer

Compression neuropathies affect the major nerves in the arm, leading to symptoms like numbness, tingling, and weakness.

Carpal Tunnel Syndrome (CTS)

• What it is: The most common compression neuropathy, involving the median nerve at the wrist.
• Symptoms: Numbness/tingling in the thumb, index, middle, and radial side of the ring finger, often worse at night.
• Primary Management: Nonoperative treatment includes nighttime wrist splinting, activity modification, NSAIDs, and steroid injections. Operative management is carpal tunnel release to divide the transverse carpal ligament.
• Revision Rates: Revision surgery is relatively uncommon, with reported rates ranging from approximately 1% to 5%.

Cubital Tunnel Syndrome (CuTS)

• What it is: The second most common compression neuropathy, involving the ulnar nerve at the elbow.
• Key Difference from CTS: CuTS can occur from both compression and traction of the nerve, particularly when the elbow is bent.
• Symptoms: Numbness/tingling in the small finger and ulnar side of the ring finger, hand weakness, and atrophy, often exacerbated by elbow flexion.
• Primary Management: Nonoperative care involves avoiding prolonged elbow flexion and night bracing. Operative techniques include in situ decompression, or anterior subcutaneous/submuscular transposition of the ulnar nerve.
• Revision Rates: Re-operation rates for CuTS are more variable and generally higher than CTS, with recurrence rates ranging from 7% to 25% and revision surgery rates between 3% to 19%. Outcomes after revision are generally inferior to primary surgery, but symptomatic improvement is still reported in 75-80% of patients.

The Classification of Post-Surgical Symptoms

When a patient returns with symptoms after primary nerve decompression, Dr. Dy refers to the helpful classification system attributed to Dr. Susan McKinnon:

• Persistent Symptoms: The patient’s pre-operative symptoms never fully resolved after surgery. This may suggest the initial diagnosis was wrong (e.g., undiagnosed cervical radiculopathy) or a double crush component (compression at multiple sites).
• Recurrent Symptoms: Symptoms resolved initially after surgery but returned after a symptom-free interval. This might be due to reformation of the transverse carpal ligament or a late point of compression.
• New Onset of Symptoms (Worsening): New or different symptoms develop that were not present before surgery, often attributed to a nerve injury, such as iatrogenic injury or neuroma formation.

Workup for Recurrent Compression

For a patient presenting with symptoms after a primary decompression, a careful, objective workup is essential.

The Role of Diagnostics

• Electrodiagnostic Studies (Nerve Tests): While not always necessary for textbook primary CTS, Dr. Dy advises getting a nerve test for any questionable diagnosis or routinely for CuTS, as it helps quantify axonal loss and look for concurrent diagnoses like cervical radiculopathy.
• Ultrasound: This is a crucial tool for revision workup.
  • It helps confirm the diagnosis and engages the patient.
  • For CuTS, it is vital to determine if the nerve is stable or unstable with elbow flexion, as the surgeon’s physical exam is only about one-third as accurate.
  • For revisions, it can check if the nerve was actually transposed, look for increased cross-sectional area, or see if the nerve is trapped in scar tissue (neuroma).

Dr. Dy’s Clinical Pearl for Ulnar Nerve Instability

To reliably assess ulnar nerve stability:

1. Stabilize the medial epicondyle with your thumb.
2. With your index or middle finger, attempt to pull the ulnar nerve from behind the epicondyle to the front as you passively flex the patient’s elbow.
3. If the nerve is unstable, you will feel it slip back down as you passively extend the elbow.

Surgical Approach for Revision CuTS

Dr. Dy’s philosophy for revision surgery is to optimize the chances of recovery and minimize the need for future operations, aiming to make it the patient’s last surgery.

• Revision Technique Preference: For almost all second-time ulnar nerve surgeries, Dr. Dy recommends a submuscular transposition. This is regardless of the prior primary surgery (whether it was in situ or subcutaneous transposition).
• Rationale: The submuscular transposition provides the smoothest and straightest course for the ulnar nerve, minimizing traction and compression.
• Exclusions: A submuscular approach may be avoided if the elbow joint is inflamed or irritated due to a prior fracture or capsular release.
• Role of Supercharging Nerve Transfer: For more advanced cases, an Anterior Interosseous Nerve (AIN) to Ulnar Nerve supercharging transfer is considered. This is reserved for patients who still have active signs of denervation but significant axonal loss.
  • Criteria for Nerve Transfer:
    1. Active Denervation: Fibrillations and sharp waves are present in the intrinsic muscles (FDI and ADM) on pre-operative EMG.
    2. Significant Loss: The Compound Muscle Action Potential (CMAP) amplitude loss is greater than 40% of the normal value, suggesting a significant number of functioning axons are lost.

Post-Operative Management

• Primary Carpal Tunnel: Typically, no formal therapy is needed.
• Revision Carpal Tunnel (with neurolysis/flap): Intentional therapy with early nerve gliding exercises is initiated within three to five days post-op.
• Ulnar Nerve Transposition (Submuscular): The arm is initially placed in a long arm splint at 60 to 70 degrees of elbow flexion. The splint is typically removed at the first post-op visit (3 to 5 days) to start motion, though the patient may continue using a long arm splint for a total of four weeks as a reminder to limit activity.

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The podcast host, Ethan Song, and Dr. Dy also discussed the importance of continually expanding one’s surgical bag of tricks and encouraging listeners to learn many different techniques for complex nerve problems.