Carpal tunnel syndrome (CTS) is a disorder characterized by entrapment of the median nerve at the wrist, which may lead to symptoms of pain, paresthesia, and, ultimately, thenar muscle atrophy. Surgical intervention is indicated with persistent or progressive symptoms despite nonoperative management. Timely surgical decompression aims to halt progression of this disorder and prevent permanent peripheral nerve injury.
Carpal tunnel release (CTR) is the most common hand and wrist surgery in the United States, with about 400,000 operations performed annually.1,2 Several methods of decompressing the carpal tunnel have been described.3 These include standard open CTR (OCTR), mini-open approaches, and various endoscopic techniques. OCTR was initially described by Sir James Learmonth in 1933,4 and it remains the gold-standard surgical treatment for patients with symptomatic CTS. Uniform excellent results with high patient satisfaction and low complication rates have been reported in several series.5-9 Common to all techniques is complete proximal-to-distal division of the transverse carpal ligament (TCL). Magnetic resonance imaging studies have shown that TCL transection and the resulting diastasis between the radial and ulnar leaflets cause a significant increase in the volume of the carpal tunnel, leading to decreased pressure.10,11
Endoscopic CTR (ECTR) techniques were developed in an effort to reduce complications, scar sensitivity, and pillar pain and facilitate more rapid return to work.12-17 Outcome studies have demonstrated that both open and endoscopic releases yield patient-reported subjective improvements over preoperative symptoms.18-22 A randomized, controlled trial by Trumble and colleagues23 in 2002 found that ECTR led to improved patient outcomes in the early postoperative period (first 3 months), though differences in outcomes were reduced at final follow-up. More recently (2007), a Cochrane review of 33 trials concluded there was no strong evidence favoring use of alternative techniques over OCTR.3 Further, OCTR has been found to be technically less demanding and associated with decreased complications and costs.24
Indications
The benefit of median nerve decompression at the wrist for CTS is clear.6,7 Indications for surgery in patients with CTS include persistent symptoms despite nonoperative treatment, objective sensory disturbance or motor weakness, and thenar atrophy. Symptomatic response to corticosteroid injection is predictive of success after carpal tunnel surgery.25 More than 87% of patients who gain symptomatic relief from corticosteroid injection have an excellent surgical outcome.
Technique
OCTR allows direct visualization of the TCL and the distal volar forearm fascia (DVFF) and evaluation for the presence of anomalous branching patterns of the median nerve. OCTR traditionally was performed through a 4- to 5-cm longitudinal incision extending from the wrist crease proximally to the Kaplan cardinal line distally. The mini-open technique is identical with the exception of incision length. We routinely use a 2.5- to 3-cm incision. Regardless of incision length, each OCTR should proceed through the same reproducible steps.
We perform OCTR under tourniquet control. Choice of anesthesia is surgeon and patient preference. We prefer local anesthesia with conscious sedation. After conscious sedation is administered, we infiltrate the carpal tunnel and surrounding subcutaneous tissue with 10 mL of a 50:50 mixture of 0.5% bupivacaine and 1% lidocaine without epinephrine.
A 2.5- to 3-cm longitudinal incision is made along the axis of the radial border of the ring finger from the Kaplan cardinal line26 and extending about 3 cm proximally toward the wrist flexion crease ulnar to the palmaris longus if present (Figure 1).
After the skin is incised longitudinally, the subcutaneous fat is mobilized and cutaneous sensory branches identified and protected. The underlying superficial palmar fascia is incised in line with the skin incision. The underlying midportion of the TCL is now visualized.
Transverse Carpal Ligament Release
Occasionally, the investing fascia along the ulnar edge of the thenar musculature is mobilized radialward (if the thenar musculature is well developed) to visualize the proximal limb of the TCL. Injury to any anomalous motor branch of the median nerve is avoided by directly visualizing and then incising the TCL (Figure 2). The TCL is incised along its ulnar border just radial to the hook of hamate from distal to proximal in line with the radial border of the ring finger. Staying near the ulnar attachment of the TCL keeps the plane of ligament division farther away from the median nerve and its recurrent motor branches. Although the ulnar neurovascular bundle typically resides ulnar to the hook of hamate in the canal of Guyon, the surgeon must be aware that it can be located radial to the hook in some instances.27,28 In the elderly, the ulnar artery may be tortuous and enter the field and require retraction. The TCL is incised distally until the sentinel fat pad, which marks the superficial palmar arterial arch, is visualized. This bed of adipose tissue marks the distal edge of the TCL.29
