Surgery for carpal tunnel syndrome

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Surgery for carpal tunnel syndrome

Author

Alice A Hunter, MD

Barry P Simmons, MD

Section Editor

Jeremy M Shefner, MD, PhD

Deputy Editor

John F Dashe, MD, PhD

Last literature review for version 17.1: January 1, 2009 | This topic last updated:

September 11, 2007

INTRODUCTION — Carpal tunnel syndrome (CTS) is a common nerve entrapment disorder

manifested by pain, paresthesias, and ultimately muscle wasting of the hand. Appropriate

treatment can interrupt the progression of this disorder and avoid the development of permanent

disability. Conservative therapy may be sufficient, although many patients require surgery.

Surgical treatment may involve open or endoscopic technique. The goal of either approach is to

decrease pressure upon the median nerve at the wrist by dividing the transverse carpal ligament

and antebrachial fascia.

This topic review will discuss the surgical treatment of CTS. The clinical manifestations, diagnosis,

and conservative therapy of this disorder are reviewed elsewhere. (See "Clinical manifestations

and diagnosis of carpal tunnel syndrome" and see "Treatment of carpal tunnel syndrome").

GENERAL PRINCIPLES — Indications for surgery include persistent numbness and pain, motor

dysfunction with diminished grip or pinch grasping, or thenar eminence flattening.

Prior to contemplating surgical carpal tunnel release, one must be sure of the correct diagnosis.

Although median nerve entrapment at the wrist is the most common and most well-studied

manifestation of CTS, it is often confused with other disorders, especially cumulative trauma

disorder.

With a clearly defined history and physical examination, electrodiagnostic studies are not

necessary. The symptoms include numbness and tingling in the hand, especially if confined to the

median nerve distribution. The symptoms are often worse at night but can also be present in the

daytime in the worker with a provocative job. Symptoms are often worse with driving or holding a

book, newspaper, or telephone [1].

Electrodiagnostic studies are helpful if the history or physical examination is equivocal. The

American Association of Electrodiagnostic Medicine found high sensitivity and specificity with the

use of nerve conduction studies to evaluate CTS [2]. However, symptomatic median nerve

compression can occur in the presence of normal electrodiagnostic studies [3]. These observations

were made in patients with clinical evidence of CTS. One must be very skeptical about proceeding

to surgery in a patient with normal electrodiagnostic studies in combination with an equivocal

history and physical examination.

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ANATOMY OF THE CARPAL TUNNEL — To better appreciate the possible surgical approaches for

carpal tunnel release, one must understand the anatomy of the carpal tunnel and the median

nerve at the wrist. The carpal tunnel is a defined anatomic space with the following characteristics.

The dorsal surface is formed by the carpal bones, while the volar surface is formed by

the transverse carpal ligament (flexor retinaculum) which attaches ulnarly to the

hamate and pisiform and radially to the trapezium and scaphoid tuberosity (show figure

1).

The antebrachial fascia of the forearm is continuous with the transverse carpal ligament

of the palm. The four flexor digitorum profundus tendons, four flexor digitorum

superficialis tendons, the flexor pollicis longus tendon, and the median nerve pass

within this canal (show figure 2).

Median nerve — The median nerve lies directly under the transverse carpal ligament. The

median nerve at the level of the distal forearm and wrist has three main branches: two sensory

and one motor. The first sensory branch is the palmar cutaneous nerve which branches from the

median nerve approximately 5 cm proximal to the wrist crease. This nerve gives sensation to the

thenar eminence and, because its take off is proximal to the carpal canal, it is not affected by CTS.

However, it can easily be injured in the release of the transverse carpal ligament if the incision is

not meticulously placed.

The second sensory branch passes through the carpal canal as part of the main trunk. After

passing through the canal, it divides into multiple branches to innervate the thumb, index, middle

and radial half of the ring finger. Because these sensory branches pass through the canal, they are

affected by compression of the median nerve at the level of the transverse carpal ligament.

Branches of these sensory nerves can also be injured during surgery, more commonly with an

endoscopic carpal tunnel release.

The motor branch innervates the two radial lumbricals, opponens pollicis, abductor pollicis brevis,

and the superficial head of the flexor pollicis brevis. The motor branch takes a more variable route

to its destination. It most often branches off distal to the transverse carpal ligament. However, it

may branch off within the tunnel or pass directly through the transverse carpal ligament. The

motor branch is in jeopardy during carpal tunnel if meticulous planning is not carried out.

SURGICAL TECHNIQUES — Surgery can be divided into two main techniques:

The classic open carpal tunnel release, which can be performed through a standard

incision or a limited incision

Endoscopic carpal tunnel release, which can be performed through a single or double

portal

Each procedure has its risks and benefits, and there is controversy among prominent hand

surgeons as to the best technique. Proponents of open carpal tunnel release feel that it is the

safest means of decompressing the nerve. However, there is less trauma with the endoscopic

technique.

Surgery for carpal tunnel release is usually performed using local anesthesia only, or local

anesthesia with intravenous sedation, according to patient preference.


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Open technique — The classic open approach allows one to better view the anatomy and

possible anomalies, thereby decreasing the risk of injury to critical structures. Prior to making an

incision, the surgeon must keep in mind the location of the superficial palmar arch, the motor

branch of the median nerve, Guyon's canal and the palmar cutaneous branch.

Standard incision — A variety of longitudinal incisions describe the classic incision. Most

commonly, the incision starts just proximal to Kaplan's cardinal line. It moves in a curvilinear

manner staying just ulnar to the thenar crease. This keeps the incision ulnar to the palmaris

longus, which reduces the likelihood of affecting the small palmar cutaneous nerve branches that

pass from radial to ulnar in the palm.

Few surgeons carry this incision proximal to the wrist crease unless the patient needs a repeat

release. If the incision does cross the crease, it should do so obliquely to avoid a flexion

contracture at the wrist and it should be directed ulnarly to avoid the palmar cutaneous nerve. The

incision is then deepened either bluntly or sharply through the palmar fascia to the transverse

carpal ligament.

The transverse carpal ligament and antebrachial fascia are divided longitudinally and the median

nerve may be identified. The division should occur along the ulnar border of the transverse carpal

ligament to avoid damage to the motor branch. Care must be taken to obtain a complete release

while avoiding damage to the vital structures. The flexor tendons can be retraced radially to

inspect the floor of the canal for lesions. Meticulous hemostasis must be achieved prior to closure.

With open carpal tunnel release, the question often arises whether or not to perform internal

neurolysis. At one time, neurolysis was felt to be important to a primary carpal tunnel release

[4,5]. However, later studies found no significant difference between primary carpal tunnel release

performed with or without internal neurolysis [6,7]. This applies even to patients with severe CTS

defined by thenar atrophy and/or a fixed sensory deficit [7]. Neurolysis is accomplished by incising

the epineurium to further decompress the nerve fascicles.

Small palmar incision — Open carpal tunnel release can also be performed through a small

palmar (or "limited") incision [8]. This permits better exposure to avoid complications and keeps

the incision out of the painful portion of the palm.

Carpal tunnel release through a small palmar incision uses a longitudinal palmar incision that

starts just proximal to Kaplan's cardinal line and moves proximally for 2 to 2.5 cm. This allows

visualization of the transverse carpal ligament; the more proximal portion of the ligament can be

identified by elevating the tissue proximally above and below it. Then, under direct vision, the

ligament can be incised or cut with a carpal tunnel tome.

The improved exposure with this technique decreases the risk of injury to vital structures and

avoids a longer scar at the base of the palm that increases morbidity. Furthermore, the palmar

fascia is left intact over the proximal portion of the transverse carpal ligament, reducing

postoperative incision pain [8].

Endoscopic technique — Due to preservation of the palmar fascia, subcutaneous fat, and skin,

endoscopic median nerve decompression may result in less scar tenderness and an earlier return

to work compared with the open technique. However, good visualization is essential for the

endoscopic technique. If this cannot be achieved, one must switch to the open technique.


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Both a one-portal and a two-portal approach have been used [9-12]. The success rates are

equivalent, and the choice is surgeon-dependent [9,12].

One-portal approach — The one- and two-portal techniques use a transverse portal at the

wrist. A flap of antebrachial fascia is elevated and dilators are passed distally. The path is just

radial to the hook of the hamate, in line with the ring finger. Care must be taken not to pass

Kaplan's cardinal line in order to avoid injury to the palmar arch. The neurovascular bundle is 1 to

4 mm from the distal edge of the transverse carpal ligament [13].

If the one portal technique is used, the endoscopic device is then passed. One should immediately

see the fibers of the transverse carpal ligament. If these are not seen, an attempt to clear the

ligament of synovial tissue from the ligament is carried out. If the exact position of the transverse

carpal ligament cannot be determined, the endoscopic approach must be aborted. If the fibers are

clearly seen the device is inserted just distal to the fibers. The knife device is then elevated and

pulled proximally, cutting the transverse carpal ligament under endoscopic vision. Assessment to

verify complete transection of the fibers is carried out. The antebrachial fascia can be cut under

direct vision through the portal at the wrist using scissors.

Two-portal approach — If a second portal is desired, a transverse incision is made in the

palm just over the end of the transverse carpal ligament. This portal permits distal visualization

and can be used to depress structures such as the superficial palmar arch out of the operative

field.

Complications — Although infrequent, complications of surgery for CTS include the following

[14,15]:

Inadequate division of the transverse carpal ligament

Injuries of the recurrent motor and palmar cutaneous branches of the median nerve

Lacerations of the median and ulnar trunk

Vascular injuries of the superficial palmar arch

Postoperative wound infections

Painful scar formation

Complex regional pain syndrome

Incomplete release of the transverse carpal ligament may be the most frequent complication of

surgery for CTS, and is usually due to errors in surgical technique, such poor choice of incision and

inadequate exposure [15]. It is also the most common problem leading to reoperation for CTS, in

one series accounting for 49 percent of 185 reoperations [16].

In an early series of 186 patients, 34 various complications occurred in 22 patients (12 percent),

including incomplete division of the transverse carpal ligament in 11 (6 percent), and development

of complex regional pain syndrome in 4 (2 percent) [14].

With proper surgical training, experience, and technique, it is estimated that the combined

incidence of long-term disability related to complications from carpal tunnel release surgery should

not exceed 1 to 2 percent [15].


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Open versus endoscopic complications — The types of complications seen with open and

endoscopic techniques are similar [17-20]. Proponents of the endoscopic technique cite evidence

that it leads to less postoperative incision pain and an earlier return to work compared with open

techniques [17]. However, critics of the endoscopic approach cite an apparent increased rate of

complications, which are related to the experience of the surgeon [21,22].

ASSESSMENT OF OUTCOME — Outcome studies have demonstrated that both open surgery and

endoscopic release produce subjective improvement in preoperative symptoms [8,9,12,17,23].

The choice of technique is largely surgeon-dependent. Each has its advantages and disadvantages

and each technique has a learning curve, which is greatest with the endoscopic technique.

Evaluation of pain relief and function is essential in determining the effectiveness of treatment for

musculoskeletal disorders. One study used a standardized, self-administered questionnaire to

assess the severity of symptoms and functional status at six weeks, three months, six months,

and two years after open (primarily limited open) surgery [24]. The following findings were noted:

Nocturnal pain, tingling, and numbness improved within six weeks.

Weakness and functional status improved more gradually, grip and pinch strength

initially worsened, returned to preoperative levels at about three months, and improved

significantly by two years.

Although 90 percent of patients had relief of either nighttime or daytime pain, only 73

percent said that they were completely or very satisfied with the results of the surgery.

These temporal patterns should be discussed with the patient to promote realistic expectations

about the results of surgery.

Using the same questionnaire, a prospective study was performed to determine the predictors of

return to work after carpal tunnel release (primarily open surgery) in a community-based cohort

[11]. Within six months, 77 percent had returned to their previous employment. The major risk

factors for poor outcome were scar tenderness and failure to relieve symptoms. Other negative

predictors of return to work included lack of an education beyond high school, consumption of

more than two drinks per day, smoking, female sex, use of an attorney or workers compensation

before surgery, and the presence of physical stresses such as multiple repetitive motion in the

workplace. Later follow-up of a related cohort showed that 82 percent of worker's compensation

recipients had returned to work at 30 months [25].

The outcome of endoscopic carpal tunnel release was "satisfactory" in 86 percent of 42 operations

upon 35 patients [23]. The mean time to return to ordinary daily activities and work were 14 and

25 days, respectively. One year after surgery, night pain and paresthesia were absent in 95 and

81 percent, respectively.

Open versus endoscopic techniques — In controlled trials comparing open versus endoscopic

carpal tunnel release, the long-term outcomes appear to be equivalent [26-29].

While some trials suggest a more rapid postoperative recovery and earlier return to

work with the endoscopic technique [17,28,30], others have found no significant

difference for time to return to work between the two techniques [26,27,29].


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The endoscopic technique may result in less postoperative pain and tenderness of the

scar [17], but the degree of this benefit appears to be modest [29].

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REFERENCES

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assessment of severity of symptoms and functional status in carpal tunnel syndrome. JBone Joint Surg Am 1993; 75:1585.

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Jablecki, CK, Andary, MT, So, YT, et al. Literature review of the usefulness of nerve

conduction studies and electromyography for the evaluation of patients with carpaltunnel syndrome. AAEM Quality Assurance Committee. Muscle Nerve 1993; 16:1392.

2.

Grundberg, AB. Carpal tunnel decompression in spite of normal electromyography. J

Hand Surg [Am]1983; 8:348.

3.

Curtis, RM, Eversmann, WW Jr. Internal neurolysis as an adjunct to the treatment of the

carpal-tunnel syndrome. J Bone Joint Surg Am 1973; 55:733.

4.

Rhoades, CE, Mowery, CA, Gelberman, RH. Results of internal neurolysis of the median

nerve for severe carpal-tunnel syndrome. J Bone Joint Surg Am 1985; 67:253.

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Gelberman, RH, Pfeffer, GB, Galbraith, RT, et al. Results of treatment of severe carpal-

tunnel syndrome without internal neurolysis of the median nerve. J Bone Joint Surg Am1987; 69:896.

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Lowry, WE, Follender, AB. Interfascicular neurolysis in the severe carpal tunnel

syndrome. A prospective randomized double-blind controlled study. Clin Orthop 1988;227:251.

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8.

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GRAPHICS

Structures involved with carpal tunnel syndrome


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Cross-sectional anatomy of the wrist

Tendons and median nerve may be compressed by inflammation or infection because they

are encompassed by synovial sheath and flexor retinaculum.


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Surgery for carpal tunnel syndrome

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