Indications

Failure of conservative treatment for idiopathic carpal tunnel syndrome (CTS).

Patient prefers the endoscopic procedure.

The authors’ preferred technique is the limited incision open carpal tunnel release (LOCTR) (see Procedure 12). Studies have not demonstrated significant differences in outcomes between endoscopic carpal tunnel release (ECTR) and LOCTR. ECTR has a steep learning curve, needs a sizeable initial capital investment in video equipment, and incurs the recurring cost of the single-use disposable blade. Although the time taken to perform ECTR is less than for LOCTR, the time expended to set up the equipment mitigates this advantage.

Occasionally, patients request the endoscopic procedure. They are counseled with regard to the cost and complications. We prefer the single-portal Agee technique to the double-portal Chow technique because the Agee technique avoids a scar in the palm.

Examination/Imaging

Clinical Examination

The clinical examination for CTS is described in Procedure 12.

It may be difficult to introduce the scope in patients with a very narrow wrist.

Imaging

None required

Surgical Anatomy

The carpal tunnel is a fibro-osseous tunnel that contains the median nerve and the nine flexor tendons to the thumb and the fingers. The roof of the carpal tunnel is formed by the flexor retinaculum, which extends between four bony prominences (proximally: pisiform and tubercle of scaphoid, distally: hook of the hamate and tubercle of trapezium) (Fig. 11-1).

The flexor retinaculum can be divided into three components (see Fig. 11-1).

• Proximal: Direct continuation of the deep antebrachial fascia

• Middle: Transverse carpal ligament (TCL)

• Distal: Aponeurosis between the thenar and hypothenar muscles

Some authors consider the flexor retinaculum and the TCL to be synonymous.

The carpal tunnel is narrowest in both palmar-dorsal and ulnar-radial planes at the level of the hook of the hamate. The other narrow portion of the carpal tunnel is at the proximal edge of the TCL (see Fig. 11-1).

The important surface landmarks and surrounding neurovascular structures related to the carpal tunnel are as follows (Fig. 11-2):

• The hook of the hamate is palpable 1 cm distal and radial to the pisiform and is in line with the ulnar border of the ring finger.

• The Kaplan cardinal line (KCL) connects the apex of the first web with the thumb in abduction to the hook of hamate. This line is usually parallel to the proximal palmar crease.

• The distal aspect of the flexor retinaculum lies 1 cm distal to the hook of the hamate.

• The superficial palmar arch (SPA) lies about 2.5 cm distal to the hook of the hamate.

• The origin of the recurrent motor branch is surface-marked at the intersection of a vertical line from the radial border of the long finger and KCL. The recurrent motor branch arises from the palmar and ulnar aspect of the median nerve (Fig. 11-3), and three courses of this branch have been described (Fig. 11-4).

♦ Extraligamentous (46%)

♦ Subligamentous (31%)

♦ Transligamentous (23%)

• The third common digital nerve is surface-marked by an oblique line joining the midpoint of the palmar digital crease of the ring finger to the scaphoid tubercle. This nerve is always located distal to the KCL at an average distance of 0.5 cm.

• The palmar cutaneous branch of the median nerve arises from the radial aspect of the median nerve about 5 cm proximal to the wrist crease (see Fig. 11-2). It runs parallel to the median nerve for 1.6 to 2.5 cm and then passes under the antebrachial fascia between the palmaris longus (PL) and the flexor carpi radialis (FCR). About 0.8 cm proximal to the wrist crease, it pierces the antebrachial fascia, becoming superficial to the flexor retinaculum.