Table 1 Study characteristics of the randomized controlled trials included in the meta-analysis

Agee et al. [28]

US

OCTR (n = 65): conventional release

ECTR (n = 82): one-portal (2 cm)

1, 2, 3, 6, 9, 13, 26 week(s)

Return of hand use for ADL, time to RTW, grip strength, pinch strength, lateral/key and pulp strength, SW monofilament test, Phalen’s wrist flexion test, Tinel’s test, scar tenderness, radial and ulnar pillar tenderness, record of medication use, complications

Atroshi et al. [9]

Sweden

OCTR (n = 65): 4 cm

ECTR (n = 63): two-portal (1 cm)

3, 6 weeks;

3, 12 months

Pain, time to RTW, BCTQ-S, BCTQ-F, SF-12, sensation, grip strength, key pinch strength, DL, quality of life, SW monofilament test, 2PD test, complications

Atroshi et al. [29]

Sweden

OCTR (n = 63): 4 cm

ECTR (n = 63): two-portal (1 cm)

1, 5 year(s)

Operative time, satisfaction rating, symptom relief, BCTQ-S, BCTQ-F, pain score, complications

Atroshi et al. [25]

Sweden

OCTR (n = 61): 4 cm

ECTR (n = 63): two-portal (1 cm)

1, 11–16 year(s)

BCTQ-S, BCTQ-F, pain score, numbness and tingling, satisfaction score, quick DASH, pain scale, complications

Aslani et al. [30]

Iran

OCTR (n = 36): conventional release

OCTR (n = 28): mini-incision

ECTR (n = 32): two-portal (length NR)

4 weeks;

4 months

Numbness, nocturnal pain, wrist pain, weakness and stiffness, Tinel’s test, Phalen’s wrist flexion test, EMG, NCV, strength to grasp, time to RTW and ADL, satisfaction rating, operative time, complications

Brown et al. [31]

US

OCTR (n = 82): conventional release

ECTR (n = 78): two-portal (2 cm)

3, 6, 12 weeks

2PD test, SW monofilament test, APB strength, thenar atrophy, grip strength, key pinch strength, pain, numbness, paresthesia, weakness, Tinel’s test, Phalen’s wrist flexion test, interstitial carpal tunnel pressure, satisfaction rating, time to RTW, rate of ADL impairment, ADL score, operative time, hospital cost, complications

Dumontier et al. [32]

France

OCTR (n = 40): conventional release

ECTR (n = 56): two-portal (Chow [12])

2 weeks;

1, 3, 6 month(s)

Paresthesia, pain, time to RTW, grip strength, finger mobility, complications

Ejiri et al. [33]

Japan

OCTR (n = 50): 3 cm vertical incision

ECTR (n = 50): one-portal (Okutsu et al. [13])

1, 3 month(s)

Paresthesia, nighttime pain, impairment of ADL, APB-DL, SW monofilament test, 2PD test, grip strength, pinch strength, key pinch strength, complications

Erdmann [34]

UK

OCTR (n = 52): NR (short length)

ECTR (n = 53): two-portal (Chow [12])

1, 2 week(s);

1, 3, 6 month(s);

1 year

Grip and pinch strength, time to normal grip strength, time to normal pinch strength, time to RTW, ADL, time to relief of symptoms, median nerve motor and sensory DL, VAS pain score, complications

Ferdinand and MacLean [35]

UK

OCTR (n = 25): NR

ECTR (n = 25): one-portal

6, 12, 26 weeks;

13 months

VAS scores (numbness, pain, and paresthesia), ADL, return to full activities, time to RTW, thenar muscle strength, lateral pinch strength, grip strength, wrist and finger movement, 2PD test, Jebson score, operative time, satisfaction rating, complications

Gümüştaş et al. [36]

Turkey

OCTR (n = 20): NR (Taleisnik [37])

ECTR (n = 21): two-portal (Chow [12])

6 months

BCTQ-S, BCTQ-F, median nerve motor DL, CMAP, SCV, sensory nerve action potential, complications

Jacobson and Rahme [38]

Sweden

OCTR (n = 16): conventional release

ECTR (n = 16): two-portal (Chow [12])

2, 6, 24 weeks

Symptom relief, total number of analgesics, 2PD test, time to RTW, nerve conduction test, complications

Kang et al. [39]

South Korea

OCTR (n = 52): mini-incision (1.5 cm)

ECTR (n = 52): one-portal (Agee et al. [28])

3 months

BCTQ-S, BCTQ-F, DASH, complications

Larsen et al. [40]

Denmark

OCTR (n = 30): classic incision, 7 cm

OCTR (n = 30): short incision, 3 cm

ECTR (n = 30): one-portal (Menon [41])

1, 2, 3, 6, 12, 24 week(s)

VAS (pain), grip strength, range of motion, pillar pain, VAS (paresthesia), time to RTW, complications

Macdermid et al. [42]

Canada

OCTR (n = 32): conventional release

ECTR (n = 91): two-portal (Chow [12])

1, 6, 12 week(s)

Time to RTW, McGill pain questionnaire, key pinch strength, tripod pinch strength, grip strength, symptom severity score (Likert score), sensory threshold, self-report scale, SF-36, complications

Mackenzie et al. [43]

US

OCTR (n = 14): 2.5 cm palmar incision

ECTR (n = 22): one-portal (Agee et al. [28])

1, 2, 4 week(s)

Grip strength, pinch strength, BCTQ-S, BCTQ-F, complications

Martínez et al. [24]

Spain

OCTR (n = 52): 1 cm mini-incision

ECTR (n = 35): one-portal (Menon [41])

1 week;

1, 6, 12 month(s)

Grip strength, pinch strength, VAS pain score, satisfaction questionnaire, complications

Michelotti et al. [44]

US

OCTR (n = 25): 3 cm palmar incision

ECTR (n = 25): one-portal (Agee et al. [28], 1.5 cm)

2, 4, 8, 12, 24 weeks

2PD test, SW monofilament test, thenar strength, grip strength, BCTQ-S, BCTQ-F, satisfaction rating, complications

Michelotti et al. [45]

US

OCTR (n = 30): 3 cm palmar incision

ECTR (n = 30): one-portal (Agee et al. [28], 1.5 to 2 cm)

2, 4, 8, 12, 24 weeks

VAS pain score, 2PD test, SW monofilament test, thenar strength, grip strength, BCTQ-S, BCTQ-F, satisfaction rating, complications

Oh et al. [46]

South Korea

OCTR (n = 32): mini-incision (1.5 cm)

ECTR (n = 35): one-portal (Agee et al. [28], 1.5 cm)

24 weeks

BCTQ-S, BCTQ-F, DASH, CSA, CSA-I, CSA-M, CSA-O, flattening ratio, complications

Rab et al. [47]

Austria

OCTR (n = 10): two mini-incisions

ECTR (n = 10): two-portal (Chow [12])

2, 4, 6, 12 weeks; 6, 12 months

VAS pain score, grip strength, pinch strength, key pinch strength, ADL, BCTQ-S, BCTQ-F, 2PD, DL, NCV, complications

Saw et al. [48]

UK

OCTR (n = 42): 2 cm palmar incision

ECTR (n = 43): one-portal (Agee et al. [28])

1, 3, 6, 12 week(s)

BCTQ-S, BCTQ-F, grip strength, VAS pain score, time to RTW, operation time, complications

Sennwald and Benedetti [49]

Switzerland

OCTR (n = 22): Sennwald incision

ECTR (n = 25): one-portal (Agee et al. [28], 2–3 cm)

4, 8, 12 weeks

Grip strength, key pinch strength, time to RTW, complications

Tian et al. [50]

China

OCTR (n = 36): S-shaped incision

ECTR (n = 34): one-portal (Okutsu et al. [13], 1 cm)

2 years

Symptom improvement, operation time, hospital stay time, time to RTW, 2PD test, grip strength, scar tenderness, complications

Trumble et al. [51]

US

OCTR (n = 95): palmar incision (3 ~ 4 cm)

ECTR (n = 97): one-portal (Agee et al. [28], 1 cm)

2, 4, 8, 12, 26, 52 weeks

BCTQ-S, BCTQ-F, 2PD test, satisfaction rating, grip strength, pinch strength (key pinch, three-jaw), hand dexterity, time to RTW, thenar atrophy, strength of APB, complications

Wong et al. [52]

Hong Kong

OCTR (n = 30): mini-incision

ECTR (n = 30): two-portal (Chow [12])

2, 4, 8, 16 weeks; 6, 12 months

VAS pain score, grip strength, pinch strength, 2PD test, operation time, symptom relief, incision length, complications

Zhang et al. [53]

China

OCTR (n = 72): double small incision

OCTR (n = 65): standard incision (5–7 cm)

ECTR (n = 69): two-portal (Chow [12])

3 years

BCTQ-S, BCTQ-F, patient satisfaction, VAS pain score, cylindrical strength, lateral strength, pinch strength, grip strength, time to RTW, 2PD test, SW monofilament test, hospital cost, complications

Zhao et al. [54]

China

OCTR (n = 21): S-shaped incision

ECTR (n = 26): one-portal (Okutsu et al. [13], 1 cm)

2 years

EMG, operation time, hospital stay time, 2PD test, time to RTW, complications