12: Open Carpal Tunnel Release

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Procedure 12 Open Carpal Tunnel Release

Douglas Sammer

imageSee Video 10: Open Carpal Tunnel Release

Indications

image Diagnosis of carpal tunnel syndrome with one of the following:

• Mild symptoms unresponsive to conservative management (6 to 12 weeks of nocturnal use of neutral wrist splint)
• Substantial symptoms, with or without trial of conservative management (continuous symptoms, two-point discrimination changes, or thenar weakness or atrophy)
• Prolonged duration of symptoms (≥6 months), with or without trial of conservative management

Examination/Imaging

Clinical Examination

image Phalen test (Fig. 12-1): The patient’s wrist is held in a flexed position for up to 1 minute or until onset of symptoms. A positive test consists of the onset of numbness or paraesthesia in the median nerve distribution. Care must be taken to avoid direct pressure or flexion at the elbow when performing this examination, in order to avoid inducing ulnar nerve symptoms.

image Carpal tunnel compression test (Fig. 12-2): The examiner applies direct pressure to the carpal tunnel with his or her thumb for up to 1 minute or until onset of symptoms. A positive test consists of the onset of numbness or paresthesia in the median nerve distribution. As with Phalen test, care is taken to avoid direct pressure or flexion at the elbow when performing this examination.

image Tinel sign (Fig. 12-3): The examiner taps directly over the carpal tunnel with his or her long and index fingers. A positive test consists of paresthesia or pain in a median nerve distribution.

image Two-point discrimination (tests innervation density; abnormal test is a late finding)

image Semmes-Weinstein monofilament test (tests pressure threshold; more sensitive)

image

FIGURE 12-1

image

FIGURE 12-2

image

FIGURE 12-3

Imaging/Diagnostic Studies

image Three-view radiographs of the wrist (posteroanterior, lateral, oblique) plus carpal tunnel view: obtained when there is antecedent wrist trauma that may narrow the carpal tunnel. Otherwise, routine wrist x-rays are unnecessary.

image Nerve conduction studies (NCS) and electromyelogram (EMG)

• Increased distal median nerve sensory latency (>3.5 msec)
• Increased distal median nerve motor latency (>4.5 msec)
• Decreased conduction velocity (demyelination) or amplitude (axonal loss)
• Denervation of thenar muscles on EMG (fibrillation potentials, sharp waves, increased insertional activity)

Surgical Anatomy

image The superficial palmar fascia is a fanlike palmar fascial extension into which the palmaris longus inserts.

image The palmar cutaneous branch of the median nerve (PCN) lies between the flexor carpi radialis and palmaris longus tendons in the distal forearm, but its branches may be found up to 6 mm ulnar to the thenar crease in the palm (Fig. 12-4).

image The transverse carpal ligament (flexor retinaculum) forms the roof of the carpal tunnel.

image The walls of the carpal tunnel are formed by the hamate and triquetrum ulnarly and the scaphoid and trapezium radially.

image Nine tendons (four flexor digitorum profundus [FDP] tendons, four flexor digitorum superficialis [FDS] tendons, one flexor pollicis longus [FPL] tendon) travel within the carpal tunnel, along with the median nerve.

image The median nerve lies in the volar and radial quadrant of the carpal tunnel.

image The recurrent motor branch typically arises from the volar-radial aspect of the median nerve at the distal end of the transverse carpal ligament and turns proximally and radially to innervate the thenar muscles. Multiple variations may exist, including a transligamentous course (recurrent motor branch pierces transverse carpal ligament), subligamentous origin, multiple recurrent motor branches, origin of recurrent motor branch from ulnar side of median nerve, recurrent motor branch anterior to transverse carpal ligament, absence of recurrent motor branch (ulnar nerve supplies thenar muscles), and others. Overall, the incidence of an anomalous course is 19%, with a transligamentous recurrent motor branch being the most common anomalous variation.

image

FIGURE 12-4

Exposures

image A 2.5- to 3-cm longitudinal incision is made in the proximal palm.

image The incision does not cross the distal wrist flexion crease.

image The incision should be placed 6 mm ulnar to the thenar crease (Fig. 12-5).

image

FIGURE 12-5

Pearls

It is important to keep the incision at least 6 mm ulnar to the thenar crease to prevent injury to the PCN.

The incision should lie ulnar to the longitudinal course of the palmaris longus tendon.

Pitfalls

If the incision is made too ulnar in an effort to avoid the PCN, the dissection becomes more difficult owing to increased palmar fat (hypothenar fat) and the presence of the ulnar neurovascular bundle.

Procedure

Step 1

image The incision is made as described earlier (see Fig. 12-5).

image Double skin hooks are used to retract the skin (Fig. 12-6).

image A no. 15 blade is used to incise down to the superficial palmar fascia, which has longitudinal fibers (Fig. 12-7).

image A blunt self-retaining retractor is placed for radial and ulnar retraction, and blunt Senn retractors are used for distal and proximal retraction.

image

FIGURE 12-6

image

FIGURE 12-7

Step 1 Pearls

Retraction with skin hooks or blunt Senn retractors aids in dissection through the palmar fat.

Step 2

image The superficial palmar fascia is divided longitudinally with a no. 15 blade.

image The transverse carpal ligament is exposed and cleared off with a sponge (Fig. 12-8).

image

FIGURE 12-8

Step 3

image The hook of the hamate is palpated.

image The transverse carpal ligament is divided longitudinally with a no. 15 blade, just radial to the hook of the hamate (Fig. 12-9).

image

FIGURE 12-9

Step 4

image Tenotomy scissors are used to spread distally, just superficial to the transverse carpal ligament.

image Under direct visualization, the distal release is completed with scissors (Fig. 12-10).

image

FIGURE 12-10

Step 4 Pearls

The presence of perivascular fat indicates proximity to the superficial palmar arch and the distal end of the release.

The surgeon’s small finger can be passed distally into the palm; if the release is complete, it should pass easily. Alternatively, the close end of the scissors can be inserted into the wound and, with a pullback motion, can define whether there is residual ligament that has not been divided.

Step 5

image Tenotomy scissors are used to spread on top of the ligament proximally.

image A freer elevator is placed under the ligament, and the contents of the carpal tunnel are pressed down and away from the ligament.

image The proximal release is completed under direct visualization with scissors (Fig. 12-11).

image

FIGURE 12-11

Step 5 Pearls

Care is taken not to veer radially or ulnarly, to prevent injury to important structures (PCN and ulnar neurovascular bundle, respectively).

The surgeon’s small finger can be passed proximally into the distal forearm.

If tight bands are present, antebrachial fascia may be divided with scissors.

It is important to do this under direct visualization, as opposed to blindly advancing the scissors.

Synovectomy and neurolysis are not necessary unless specifically indicated (e.g., synovectomy in rheumatoid arthritis).

Step 6

image The skin is closed with 4-0 horizontal mattress Prolene sutures (Fig. 12-12).

image A soft bulky dressing is applied.

image Splinting is unnecessary.

image

FIGURE 12-12

Postoperative Care and Expected Outcomes

image Elevation and finger motion are encouraged.

image Light activity is encouraged when comfortable.

image The dressing can be removed in 3 to 4 days, and handwashing is encouraged.

image Lifting is limited to 5 lb for 6 weeks.

image At 6 weeks the patient can gradually resume full activity.

image With mild and/or intermittent symptoms, relief is often immediate.

image With prolonged or severe symptoms (two-point discrimination changes, thenar weakness), relief of symptoms may occur over many months, and the patient may not experience complete improvement.

Evidence

Freshwater MF, Arons MS. The effect of various adjuncts on the surgical treatment of carpal tunnel syndrome secondary to chronic tenosynovitis. Plast Reconstr Surg. 1978;61:93-96.

This classic study demonstrates that routine flexor synovectomy and external neurolysis are unnecessary in patients undergoing carpal tunnel release. In fact, patients who did not receive adjunctive procedures were able to return to work earlier than those who underwent synovectomy and neurolysis. (Level IV evidence)

Keith MW, Masear V, Amadio P, et al. Treatment of carpal tunnel syndrome. J Am Acad Orthop Surg. 2009;17:297-405.

Keith MW, Masear V, Chung K, et al. Diagnosis of carpal tunnel syndrome. J Am Acad Orthop Surg. 2009;17:389-396.

These two articles represent clinical practice guidelines for the diagnosis and treatment of carpal tunnel syndrome. These guidelines were developed by the American Academy of Orthopaedic Surgeons and subsequently endorsed by the American Association of Neurological Surgeons and the Congress of Neurological Surgeons.

Lanz U. Anatomical variations in the median nerve in the carpal tunnel. J Hand Surg [Am]. 1977;2:44-53.

In this classic study, 246 cadaveric hands were examined. The study describes four categories of variations in the anatomy of the median nerve. (Level V evidence)

Watchmaker GP, Weber D, Mackinnon SE. Avoidance of transaction of the palmar cutaneous branch of the median nerve in carpal tunnel release. J Hand Surg [Am]. 1996;21:644-650.

This is an excellent anatomic study of the course of the palmar cutaneous branch of the median nerve within the palm and its relationship to proposed carpal tunnel release incisions. (Level V evidence)

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