Abstract

Carpal tunnel syndrome (CTS) is the most common compressive neuropathy of the upper extremity. It is caused by increased pressure on the median nerve between the transverse carpal ligament and the carpal bones. Surgical treatment consists of the release of the nerve by cutting the transverse carpal ligament. This can be done either with an open approach or endoscopically.

To assess the effectiveness and safety of the endoscopic techniques of carpal tunnel release compared to any other surgical intervention for the treatment of CTS. More specifically, to evaluate the relative impact of endoscopic techniques in relieving symptoms, producing functional recovery (return to work and return to daily activities) and reducing complication rates.

This review fully incorporates the results of searches conducted up to 5 November 2012, when we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE and EMBASE. There were no language restrictions. We reviewed the reference lists of relevant articles and contacted trial authors. We also searched trial registers for ongoing trials. We performed a preliminary screen of searches to November 2013 to identify any additional recent publications.

We included any randomised controlled trials (RCTs) and quasi-RCTs comparing endoscopic carpal tunnel release (ECTR) with any other surgical intervention for the treatment of CTS.

We used standard methodological procedures expected by the Cochrane Collaboration.

Twenty-eight studies (2586 hands) were included. Twenty-three studies compared ECTR to standard open carpal tunnel release (OCTR), five studies compared ECTR with OCTR using a modified incision, and two studies used a three-arm design to compare ECTR, standard OCTR and modified OCTR.

At short-term follow-up (three months or less), only one study provided data for overall improvement. We found no differences on the Symptom Severity Scale (SSS) (scale zero to five) (five studies, standardised mean difference (SMD) -0.13, 95% CI -0.47 to 0.21) or on the Functional Status Scale (FSS) (scale zero to five) (five studies, SMD -0.23, 95% CI -0.60 to 0.14) within three months postoperatively between ECTR and OCTR. Pain scores favoured ECTR over conventional OCTR (two studies, SMD -0.41, 95% CI -0.65 to -0.18). No difference was found between ECTR and OCTR (standard and modified) when pain was assessed on non-continuous dichotomous scales (five studies, RR 0.69, 95% CI 0.33 to 1.45). Also, no difference was found in numbness (five studies, RR 1.14; 95% CI 0.76 to 1.71). Grip strength was increased after ECTR when compared with OCTR (six studies, SMD 0.36, 95% CI 0.09 to 0.63). This corresponds to a mean difference (MD) of 4 kg (95% CI 1 to 6.9 kg) when compared with OCTR, which is probably not clinically significant.

In the long term (more than three months postoperatively) there was no significant difference in overall improvement between ECTR and OCTR (four studies, RR 1.04, 95% CI 0.95 to 1.14). SSS and FSS were also similar in both treatment groups (two studies, MD 0.02, 95% CI -0.18 to 0.22 for SSS and MD 0.01, 95% CI -0.14 to 0.16 for FSS). ECTR and OCTR did not differ in the long term in pain (six studies, RR 0.88, 95% CI 0.57 to 1.38) or in numbness (four studies, RR 0.64, 95% CI 0.31 to 1.35). Results from grip strength testing favoured ECTR (two studies, SMD 1.13, 95% CI 0.56 to 1.71), corresponding to an MD of 11 kg (95% CI 6.2 to 18.81). Participants treated with ECTR returned to work or daily activities eight days earlier than participants treated with OCTR (four studies, MD -8.10 days, 95% CI -14.28 to -1.92 days).

Both treatments were equally safe with only a few reports of major complications (mainly with complex regional pain syndrome) (15 studies, RR 1.00, 95% CI 0.38 to 2.64).

ECTR resulted in a significantly lower rate of minor complications (18 studies, RR 0.55, 95% CI 0.38 to 0.81), corresponding to a 45% relative drop in the probability of complications (95% CI 62% to 19%). ECTR more frequently resulted in transient nerve problems (ie, neurapraxia, numbness, and paraesthesiae), while OCTR had more wound problems (ie, infection, hypertrophic scarring, and scar tenderness). ECTR was safer than OCTR when the total number of complications were assessed (20 studies, RR 0.60, 95% CI 0.40 to 90) representing a relative drop in the probability by 40% (95% CI 60% to 10%).

Rates of recurrence of symptoms and the need for repeated surgery were comparable between ECTR and OCTR groups.

The overall risk of bias in studies that contribute data to these results is rather high; fewer than 25% of the included studies had adequate allocation concealment, generation of allocation sequence or blinding of the outcome assessor.

The quality of evidence in this review may be considered as generally low. Five of the studies were presented only as abstracts, with insufficient information to judge their risk of bias. In selection bias, attrition bias or other bias (baseline differences and financial conflict of interest) we could not reach a safe judgement regarding a high or low risk of bias. Blinding of participants is impossible due to the nature of interventions.

We identified three further potentially eligible studies upon updating searches just prior to publication. These compared ECTR with OCTR (two studies) or mini-open carpal tunnel release (one study) and will be fully assessed when we update the review.

In this review, with support from low quality evidence only, OCTR and ECTR for carpal tunnel release are about as effective as each other in relieving symptoms and improving functional status, although there may be a functionally significant benefit of ECTR over OCTR in improvement in grip strength. ECTR appears to be associated with fewer minor complications compared to OCTR, but we found no difference in the rates of major complications. Return to work is faster after endoscopic release, by eight days on average. Conclusions from this review are limited by the high risk of bias, statistical imprecision and inconsistency in the included studies.