Background
Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy [
1] in America. The prevalence of CTS is from 1% to 3% [
2,
3]; with an incidence that peaks in the late 50s [
4]. There is a high rate of CTS within certain occupational groups such as meatpackers, poultry processors and automobile assembly workers [
5] which is attributed to job tasks that require intensive manual exertion. In addition, CTS is associated with some systemic conditions, such as rheumatoid arthritis, hypothyroidism, diabetes mellitus, gout, and pregnancy [
6]. Both conservative and surgical treatments are used to manage CTS. The non-surgical treatment options include splinting, steroids, activity modification, non-steroidal anti-inflammatory drugs, diuretics, vitamin B-6 and others. However, of the conservative approaches only splinting [
7] and steroids [
8] are supported by high quality evidence.
Surgical release of the carpal tunnel is known to be effective and is typically used for patients who fail to achieve adequate relief with conservative managements and for those with moderate to severe symptoms [
9]. Although surgical intervention is considered as the definitive treatment to the CTS, it is not considered a first line of treatment. Conservative intervention may not be curative; but may provide sufficient relief in a proportion of cases. It may also be a patient preference due to concerns about the discomfort, inconvenience or safety of surgery. Conservative management is typically preferred for transient cases of CTS such as those associated with pregnancy or short-term overuse. In other cases conservative management might be used for partial relief of symptoms while awaiting surgery or for diagnostic purposes in determining patient response. Despite, potential variations in indications for one treatment and the associated expectations, there are a substantial proportion of patients for whom conservative management may have provided incomplete relief. These patients require evidence that surgical intervention has is more effective to proceed to surgery.
Systematic reviews provided the best evidence. In 2008, Verdugo et al. [
7] conducted a systematic review comparing surgical and non-surgical treatment for CTS; were able to locate four randomized controlled trials. The objective of this study was to build on this work by adopting boarder inclusion criterion, locating more recent trials that conducting a meta-analysis to synthesize evidence in a more quantitative manner.
Methods
Literature search
A literature search of four databases was conducted in June 2010 for studies addressing effectiveness of surgical or conservative interventions for CTS. The research strategy is list in Additional File
1.
These databases were Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2010), MEDLINE (1980 to June 2010), EMBASE (1980 to June 2010), PEDro (searched in June 2010). Only English language papers were included. Searching of international guidelines, computer searches based on key words, and hand searching for references from previously retrieved articles was used to extend the search strategy.
Research articles were included for review if they met the following criteria:
1.
The study was written in English.
2.
The study was designed as a prospective controlled trial.
3.
The study subjects/patients had a diagnosis of CTS, irrespective of the diagnostic criteria used, etiology of the syndrome, associated pathology, gender and age.
4.
The study compared any surgical with non-surgical intervention.
The surgical treatments include:
1.
Standard open carpal tunnel release (OCTR).
2.
Endoscopic carpal tunnel release (ECTR).
3.
Open carpal tunnel release with additional procedures such as internal neurolysis, epineurotomy or tenosynovectomy.
4.
Open carpal tunnel release using various incision techniques.
The non-surgical treatment includes:
1.
Drugs: oral or local steroids, non-steroidal anti-inflammatory drugs (NSAIDs), diuretics, pyridoxine, etc.
3.
Physical therapy, therapeutic exercises and manipulations. (ultrasound, laser therapy, yoga, and acupuncture, etc).
Research articles were excluded from review if they met the following criteria:
1.
The study investigated the efficacy of two surgical interventions or two non-surgical managements.
2.
The study did not provide data on intervention effectiveness).
3.
The study published before 1970.
Types of outcome measures
Primary outcome:
The primary outcome measure was patient self-reported functional and symptoms improvement at six months of follow-up. We selected this time point because most studies discussed the post operative status 6 months after the intervention.
Secondary outcomes:
1.
Patient self-reported functional and symptoms improvement at three months of follow-up.
2.
Patient self-reported functional and symptoms improvement at twelve months of follow-up.
3.
Improvement of neurophysiological parameters.
4.
Complications and side-effects.
Data collection
Study authors (QS and JM)) independently performed the study selection, assessment of methodological quality and data abstraction. Structured data extraction forms were used to extract data on the characteristics of individual studies. Information was collected on participants (age, sex, diagnostic criteria used to confirm CTS, severity of symptoms, duration of symptoms, inclusion/exclusion criteria, trial setting, allocation procedure, blinding, number of participants or hands randomized), interventions (description of interventions, treatment length, number and explanation for any drop-outs) and outcome measures (description of measures used, continuous/dichotomous nature). We used the Cohen's (unweighted) kappa to assess the agreement between the two reviewers on study selection.
Validity assessment
All the articles were assessed by two reviewers (QS, JM) using Jadad et al. scale [
10] (see Additional File
2) and the Structured Effectiveness Quality Evaluation Scale (SEQES) (see Additional File
3) independently. All the disagreement was solved by consensus discussion.
Jadad et al. scale is used to assess the methodology quality of each study. There are 3 criteria for this scale and total score ranges from 0 to 5. We decided that the study was high quality if the cumulative score was 3 or more. To add additional detail on the quality of studies we also used the SEQES [
11]. The scale has 24 items, scored 2, 1, or 0 based on congruence with specific descriptors. In this review, each study was ranked as low, moderate, or high quality based on the cumulative score (/48) using the following metric:
Data synthesis
Statistical analysis was performed using Review Manager (RevMan) version 5.0 [
12]. Relative risks (RR) were calculated for dichotomous outcomes and weighted mean differences (WMD) for continuous outcomes. Studies were compared for heterogeneity using the Chi-square statistic (P-value < 0.05 considered statistically significant) and an I
2 test ( I
2 >50% considered substantial heterogeneity). A fixed- effects model was initially used in this systematic review. A random-effects model was applied if heterogeneity existed. We conducted a priori hypothesis to explain the heterogeneity that might exist between the studies. The potential sources were: difference in populations, severity of the disease, duration of the symptoms, intervention techniques, length of treatment and methodological quality.
Discussion
Despite, the limitation in the number of randomized controlled trials available in current literature, this systematic review was able to provide evidence that CTS symptoms improved in both interventions.
All the studies reported that both conservative managements (splinting, steroid and laser therapy) and surgery result in clinically significant improvement in symptoms. Some authors [
13,
15,
17‐
19] concluded that surgical decompression produces long-term systematic improvement compared with the non-surgical intervention. We found that the positive impact of conservative management plateaus within 3 months whereas, the clinical effect of surgical intervention up until 12
th months after the treatment. The relative advantage of surgery at 6 months (WMD = 0.35) indicated that patient with surgical release had approximately 0.35 points lower functional scores than those receiving conservative intervention.. Although there was a similar trend at 12 months, no further improvement was observed at 12 months of follow-up. Thus, the current treatment approach of providing a conservative management as a front-line treatment in mild to moderate cases before considering surgery is justified.
However, surgery was superior to the non surgical intervention regarding the improvement of electrophysiological study. The relative advantage of surgery (RR = 2.3) indicated that approximately twice as many patients achieve better outcomes with surgery. This is important information for patient who fails conservative management to understand when deciding whether they should consent to surgery.
Prognosis was not addressed in these study trials but others have indicated that patients presenting with higher symptom severity scores and those not responding within the first six weeks are more likely to proceed to surgery following conservative management [
23]. Given that the size of the treatment advantage for surgical management is relatively small, and that improvements are noted with both conservative and surgical approaches the evidence does not support proceeding directly to surgery. The presenting symptoms/nerve damage, response/relief after conservative management, comorbid issues and patient circumstances/preferences will determine the optimal decision about surgery. There are potential complications that patients must consider, in particular for surgical management or steroid injection. Given the huge variation of how complications are defined, this systematic review was not well positioned to determine accurate rates of these complications.
Our review indicates substantial heterogeneity in effects between studies. This may have resulted from variations between the studies in terms of intervention techniques, length of treatment, methodological quality, etc. For example, all the patients in splinting group received 6 weeks treatment in Gerritsen study [
19] while patients in Ucan study [
15] used the splinting for 3 months. For this reason future systematic reviews that included larger numbers of studies might be useful to differentiate subgroups who would benefit most from conservative versus surgical management or factors associated with successful treatment in either treatment arm.
Critical appraisal of trials involving surgery, or hands-on interventions within the scope of conservative management have some inherent challenges in blinding that affect their scores on most critical appraisal instruments. While the Jadad scale is commonly used, others have pointed out its lack of reliability and validity with respect to surgery and rehabilitation research [
24,
25]. For this reason we used a 24-item structured evaluation instrument [
26] that has been used in other hand surgery/therapy systematic reviews [
27,
28]. This instrument also provides extra credit for blinding, but has an intermediary score for cases where blinding is not possible. In addition, because it addresses a variety of aspects of study in addition to blinding there is an opportunity for well-designed surgery trials to be favorably rated despite a lack of blinding.
One limitation of this systematic review is only studies written in English were included, which might introduce a publication bias. However, one recent assessment reported that non-English papers are likely to be of low quality and could result in bias into a review [
29].
Further Research
We observed a small to moderate incremental benefit in surgical group for patients with carpal tunnel syndrome. However, given that conservative management is effective in relieving symptoms and can circumvent the need for surgery in a certain proportion of cases it remains a justified first line treatment. Therefore, we do not see a need for further trials comparing conservative management versus surgical management but rather a need for better prognostic studies that would identify the characteristics of patients most likely to respond to each type of intervention. This would form a basis for clinical prediction rules and clearer criteria for which patients should be fast tracked to surgery and how long conservative management should be sustained before making decisions about transitioning into a surgical procedure.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
QS Participated in the design of the study, performed the statistical analysis and drafted the manuscript. JM participated in its design and coordination and helped to draft the manuscript. All authors read and approved the final manuscript.