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Carpal Tunnel Release Surgery- A Systematic Review of Open and Endoscopic Approaches

Context Carpal tunnel syndrome (CTS) is the most frequent peripheral compression-induced neuropathy observed in patients worldwide. Surgery is necessary when conservative treatments fail and severe symptoms persist. Traditional Open carpal tunnel release (OCTR) with visualization of carpal tunnel is considered the gold standard for decompression. However, Endoscopic carpal tunnel release (ECTR), a less invasive technique than OCTR is emerging as a standard of care in recent years. Evidence Acquisition Criteria for this systematic review were derived from Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Two review authors searched PubMed, MEDLINE, and the Cochrane Database in May 2018 using the following MeSH terms from 1993-2016: ‘carpal tunnel syndrome,’ ‘median nerve neuropathy,’ ‘endoscopic carpal tunnel release,’ ‘endoscopic surgery,’ ‘open carpal tunnel release,’ ‘open surgery,’ and ‘carpal tunnel surgery.’ Additional sources, including Google Scholar, were added. Also, based on bibliographies and consultation with experts, appropriate publications were identified. The primary outcome measure was pain relief. Results For this analysis, 27 studies met inclusion criteria. Results indicate that ECTR produced superior post-operative pain outcomes during short-term follow-up. Of the studies meeting inclusion criteria for this analysis, 17 studies evaluated pain as a primary or secondary outcome, and 15 studies evaluated pain, pillar tenderness, or incision tenderness at short-term follow-up. Most studies employed a VAS for assessment, and the majority reported superior short-term pain outcomes following ECTR at intervals ranging from one hour up to 12 weeks. Several additional studies reported equivalent pain outcomes at short-term follow-up as early as one week. No study reported inferior short-term pain outcomes following ECTR. Conclusions ECTR and OCTR produce satisfactory results in pain relief, symptom resolution, patient satisfaction, time to return to work, and adverse events. There is a growing body of evidence favoring the endoscopic technique for pain relief, functional outcomes, and satisfaction, at least in the early post-operative period, even if this difference disappears over time. Several studies have demonstrated a quicker return to work and activities of daily living with the endoscopic technique.

of function of associated structures if CTS remains untreated (1). The incidence of CTS is higher in the U.S. compared to Sweden and the United Kingdom (U.K.). CTS is an important cause of work disability with profound and well-described implications for psychological and financial hardship among affected patients (2). CTS is frequently multifactorial or idiopathic, but may also be associated with trauma, diabetes, pregnancy, acromegaly, hypothyroidism, rheumatoid arthritis, vibration, and certain repetitive motions of the hands and wrists.

Data Sources and Search Strategy
Criteria for this systematic review were derived from Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) (3).
Two review authors searched PubMed, MEDLINE, and the Cochrane Database in May 2018 using the following MeSH terms: 'carpal tunnel syndrome,' 'median nerve neuropathy,' 'endoscopic carpal tunnel release,' 'endoscopic surgery,' 'open carpal tunnel release,' 'open surgery,' and 'carpal tunnel surgery.' Additional sources, including Google Scholar, were added. In addition, based on bibliographies and consultation with experts, appropriate publications were identified.

Eligibility Criteria
Inclusion Criteria: The present investigation included studies that met the following criteria: randomized controlled trials (RTCs) or quasi-RCTs, inclusion of an endoscopic carpal tunnel release (ECTR) treatment arm, and reporting of pain, function, or satisfaction outcomes. Studies with follow-up time greater than one month were included in our search. Exclusion Criteria: Excluded categories were non-English papers, studies available in abstract or poster form only, and retrospective studies and case reports.

Outcomes of the Studies
The primary outcome measure was pain relief. The most commonly reported pain scores were VAS for pain, Carpal Tunnel Syndrome Symptom Severity Score (CTS-SSS), Boston Carpal Tunnel Syndrome Questionnaire Symptom severity scale (BCTQ-S), Levine Symptom Severity Score, and subjective reporting of pain. The most commonly reported secondary outcomes included Carpal Tunnel Syndrome Functional Status Score (CTS-FSS), Boston Carpal Tunnel Syndrome Questionnaire Functional status scale (BCTQ-F), pinch/grip strength, sensation (twopoint discrimination, monofilament), satisfaction, operating time, and time to return to work.

Data Extraction
The final evaluation included RCTs and quasi-RCTs and observational studies. The following data were extracted and compiled into a table: author's last name, publication year, average age, percent of sample size that was female, study size, treatment arm, endoscopic technique, follow-up time, outcomes reported, pain relief outcomes, secondary outcomes, complications, and significant conclusions. When available, mean pain scores were extracted with the intent of doing meta-analysis if possible. Please see Table 1.

Assessment of Study Quality
Two authors (SO and VO) used the Cochrane Risk of Bias to measure the methodological quality of the RCTs. The Cochrane Risk of Bias has seven items included to assess the internal validity of each of the RCTs. Each of the studies are scored via the allocation of "+," "-," or "?" to each criterion that is met or unmet (29). Please see Table 2.

Analysis of Evidence
For this systematic review, evidence synthesis was performed utilizing a qualitative modified approach to the grading of evidence, modified and collated from multiple available criteria, including Cochrane review criteria and the United States Preventive Services Task Force (USPSTF) criteria (32).

Meta-Analysis
Meta-analysis was not performed in this systematic review because of the nature of active control trials showing no significant difference between the two groups, and both approaches have been shown to be effective in the past. Please see Table 1.

Search Results
Thirty-four studies were identified for preliminary review. After applying inclusion and exclusion criteria, 27 studies with 1,920 patients were included for systematic review ( Figure 1). The mean age was 49, with 78.1% of patients being female. The techniques used for ECTR, listed in descending order, were the Chow (33), Agee (19), and Okutsu (34). The studies were published between 1992 and 2018, and the follow-up time ranged from one week to 16 years. A summary of the studies included in this review is displayed in Table 1. Our search identified 15 RCTs and 12 observational studies ( Figure 1). 2 Anesth Pain Med. 2020; 10(6):e112291.

Pain Relief
In 24 studies, both open and endoscopic techniques resulted in significant pain relief postoperatively. Endoscopic surgery resulted in a significantly greater pain relief in 10/24 studies, usually in the early post-operative period. For example, Aslani et al. (30) showed that postoperative pain at the incision site was greater for the open surgery group at weeks 2 and 4, but the difference disappeared at four months post-surgery. MacDermid et al. (6) showed that open surgery resulted in significantly more pain at weeks 1 and 6, but this difference did not persist at 12 weeks post-surgery. Trumble et al. (10) demonstrated that CTS-SSS and CTS-FSS improved more for the endoscopic group at weeks 2, 4, 8, and 12 post-surgery. Other significant findings in favor of the endoscopic group were improvement of night-time hand and wrist pain at week 4 postsurgery (12), improvement of symptoms and function (13), improvement in VAS pain scores at hours 1, 2, 4, and 24 postsurgery (18), improvement of scar tenderness at weeks 1, 2, 3, and 9 post-surgery and radial pillar tenderness at weeks 3 and 9 (19), and improvement of VAS pain up to 1-month post-surgery (26).

Secondary Outcomes
Several studies showed that endoscopic release produced a greater improvement of grip and/or pinch strength in the early post-operative period (7, 12, 18, 20, 21, 25, 26). According to Orak et al. (18), there was less analgesic use in the endoscopic group in the first 24 hours postoperatively. According to two studies, satisfaction was significantly greater for the endoscopic group in the early post-operative period, but this difference disappeared at later time points (10, 30). Several other studies showed similar satisfaction between open and endoscopic groups (5). Overall, endoscopic surgery resulted in a faster return to work in most studies (5,13,15,19,20,(25)(26)(27). Two studies showed a longer operating time for endoscopic surgery versus open surgery.

Complications
Adverse events between endoscopic and open surgery were about equal (ECTR = 43, OCTR = 44). In the endoscopic group, the most commonly reported complications were post-operative numbness/tingling (n= 13), pillar pain (n = 6), and persistence or exacerbation of symptoms (n = 6). In the open group, the most commonly reported complications were pillar pain (n = 9), reflex sympathetic dystrophy (n = 7), and hypertrophic/painful scar (n = 5). There were four instances of re-operation in the endoscopic group and three instances of re-operation in the open group.

Conclusions
For this analysis, 27 studies met inclusion criteria. Results indicate that ECTR produced superior post-operative pain outcomes (decreased pain score) during short-term follow-up. Of the studies meeting inclusion criteria for this analysis, 17 studies evaluated pain as a primary or secondary outcome and 15 studies evaluated pain, pillar tenderness, or incision tenderness at short-term follow-up. Most studies employed a VAS for assessment and the majority reported superior short-term pain outcomes following ECTR at intervals ranging from 1 hour up to 12 weeks (6, 12, 18-20, 24, 30, 31). Several additional studies reported equivalent pain outcomes at short-term follow-up as early as one week (5, 14, 15, 21, 25). No study reported inferior short-term pain outcomes following ECTR.
Interestingly, pain scores following endoscopic and OCTR techniques were equivalent in long-term follow-up, even after superiority of post-operative pain scores in the early post-operative period. Several studies report equalization or narrowing of benefit at follow-up time points ranging from 12 weeks to one year (6, 10, 18, 19, 24, 26, 31). No study reports superior pain outcomes at longterm follow-up exceeding one year for endoscopic, open, or mini-incision carpal tunnel release techniques.
Of the included studies, 24 studies reported outcomes pertaining to grip strength, pinch strength, and functional status. Most studies reported equivalent outcomes in grip or pinch strength at post-operative time points ranging from 1 week to one year (5,9,14,15,20,(23)(24)(25)27). Several studies also reported equivalent functional status using BCTQ-F and CTS-FFS scales at time points as early as 6 weeks (11,17,18).
A subset of studies reported contradicting findings related to transient superiority or inferiority of functional status following endoscopic release. Of groups reporting favorable outcomes following endoscopic release, Aslani et al. Predictably, this early trend in pain and functional outcomes following ECTR was mirrored in patient-reported satisfaction scores. Studies either reported equivalent patient satisfaction (5, 27, 28, 31) or higher patient satisfaction following endoscopic release as late as 6 months postoperatively (4, 10, 11, 30). Superior short-term pain and functional status outcomes following endoscopic release did translate to improved short-term patient satisfaction scores in select studies. However, like pain and functional status assessments, patient satisfaction became equivalent at intermediate and long-term follow-up.
Based on 27 RCTs published from 1993-2016, ECTR and OCTR produce satisfactory results in pain relief, symptom resolution, patient satisfaction, time to return to work, and adverse events. There is a growing body of evidence favoring the endoscopic technique in pain relief, functional outcomes, and satisfaction, at least in the early postoperative period, even if this difference disappears over time. Several studies have demonstrated a quicker return to work and activities of daily living with the endoscopic technique.  Abbreviations  Table 2 data is reported from time of intervention, not time of follow-up.