A total of 822 articles were retrieved from the database using our search strategy, and 5 articles were obtained from other review references. After removing 439 duplicate articles, 388 articles were screened. Among these, 347 articles were excluded after reading the titles and abstracts, and 26 articles were excluded after reading the full text. This screening resulted in 15 articles enrolling a total of 1400 patients, all of which compared TKA with and without tourniquet use. After quality evaluation, two studies [17, 18] were excluded due to poor literature quality. Finally, 13 RCTs [19-31], enrolling a total of 1321 patients, were included in the meta-analysis; 721 participants were randomized to the tourniquet group, while 600 were randomized to the non-tourniquet group (Fig. 1). The data extracted from the included studies (age, tourniquet pressure, and operating time) are summarized in Table 1. In the included studies, tourniquets of varying pressures were used, and most of them were deflated after the incision was closed. The type of anesthesia and anticoagulant regimens used in all operations were dependent on the surgeon's experience and the patient's needs.
Table 1. Characteristics of the included studies
Author
|
Year
|
Age
(T/N T)
|
Number
of patients
|
T/N T
|
Tourniquet pressure
|
Operation time (min)
|
DVT
|
K-C
|
D-d
|
Pain
|
Abdelsalam
|
1995
|
72.0/74.0
|
80
|
40/40
|
Twice SBP
|
<90
|
√
|
|
|
√
|
Wakankar
|
1999
|
72.5/71.8
|
77
|
37/40
|
Twice SBP
|
NA
|
√
|
√
|
|
√
|
Aglietti
|
2000
|
70.0/68.0
|
20
|
10/10
|
0.8 bar
|
90.0
|
|
|
√
|
|
Vandenbussche
|
2002
|
72.5/68.5
|
80
|
40/40
|
350 mmHg
|
151.0
|
√
|
|
|
√
|
Wauke
|
2002
|
63.2/61.4
|
37
|
19/18
|
SBP+100 mmHg
|
75.1
|
√
|
|
|
|
Li
|
2008
|
71.0/70.0
|
80
|
40/40
|
SBP+100 mmHg
|
73.0
|
|
√
|
|
|
Zhang
|
2010
|
72.0/71.0
|
60
|
30/30
|
SBP+100 mmHg
|
<90
|
√
|
|
|
|
Yin
|
2011
|
63.1/61.9
|
39
|
20/19
|
NA
|
NA
|
|
|
√
|
|
Yin
|
2012
|
68.9/67.1
|
40
|
20/20
|
NA
|
NA
|
|
|
√
|
|
Ejaz
|
2014
|
68.0/68.0
|
92
|
33/31
|
250 mmHg
|
70.0
|
√
|
|
|
√
|
Mori
|
2016
|
72.8/74.6
|
103
|
51/52
|
250 mmHg
|
63.6
|
√
|
|
|
|
Zhang
|
2016
|
63.2/65.2
|
230
|
84/82
|
SBP+13.3 kPa
|
81.7
|
√
|
|
|
√
|
Zhou
|
2017
|
66.8/69.1
|
150
|
72/68
|
NA
|
77.2
|
√
|
√
|
|
√
|
Wu
|
2018
|
67.6/68.1
|
112
|
50/50
|
250 mmHg
|
67.2
|
√
|
√
|
|
√
|
Goel
|
2019
|
66.0/66.5
|
200
|
100/99
|
300/225 mm Hg
|
71.6
|
√
|
|
|
√
|
T: Tourniquet; N T: Non- tourniquet; DVT: Deep venous thrombosis; NA: Not available; K-C: knee circumference; D-d: D-dimers; SBP: systolic blood pressure
Quality assessment
The quality assessment of the primary studies is summarized in Table 2. The Jadad scores ranged from 0 to 7. thirteen of fifteen studies had a Jadad score of at least 4, and thus were considered high quality. Two studies, with a Jadad score of less than 3, were deemed low quality and ultimately excluded.
Effects on DVT
Based on the inclusion criteria, a total of 11 trials with 1106 patients provided data of DVT were included in the study (Fig. 2). There was a significant statistical difference in DVT between the tourniquet and non-tourniquet groups (RR 2.30, 95% CI: 1.51-3.49, P < 0.0001, I2 = 0%).
Table 2. Quality assessment of RCTs included in the review
Study
|
Explicit eligibility
criteria
|
Similarity of Baseline
Characteristics
|
Revised Jadad score
|
Random sequence
generation
|
Allocation
concealment
|
Double-
blind
|
withdrawals and dropouts
|
Sum (4-7
high quality)
|
Abdelsalam[30]
|
Yes
|
Yes
|
2
|
1
|
2
|
0
|
5
|
Wakankar[29]
|
Yes
|
Yes
|
2
|
1
|
0
|
1
|
4
|
Aglietti[28]
|
Yes
|
Yes
|
2
|
1
|
0
|
1
|
4
|
Vandenbussche[27]
|
Yes
|
Yes
|
2
|
2
|
2
|
1
|
7
|
Wauke[26]
|
Yes
|
Yes
|
2
|
1
|
0
|
1
|
4
|
Li[31]
|
Yes
|
Yes
|
2
|
2
|
1
|
1
|
6
|
Zhang[25]
|
Yes
|
Yes
|
2
|
2
|
0
|
1
|
5
|
Zhou[18]
|
Yes
|
Yes
|
0
|
0
|
0
|
1
|
1
|
Yin[17]
|
Yes
|
Yes
|
1
|
1
|
0
|
1
|
3
|
Ejaz[24]
|
Yes
|
Yes
|
2
|
2
|
0
|
1
|
5
|
Mori[23]
|
Yes
|
Yes
|
2
|
1
|
0
|
1
|
4
|
Zhang[22]
|
Yes
|
Yes
|
2
|
0
|
1
|
1
|
4
|
Zhou[21]
|
Yes
|
Yes
|
2
|
2
|
0
|
1
|
5
|
Wu[20]
|
Yes
|
Yes
|
2
|
2
|
2
|
1
|
7
|
Goel[19]
|
Yes
|
Yes
|
2
|
2
|
2
|
1
|
7
|
Effects on knee circumference
Four trials provided data of knee circumference, and three of these studies with 317 patients were included in analysis. The meta-analysis showed that the tourniquet group had a significantly larger knee circumference difference than the non-tourniquet group in the 1st, 3rd, and from the 5th to the 21st days, and from the 3rd to the 6th weeks after surgery (P < 0.05) (Fig. 3, Fig. 4, Fig. 5, Fig. 6). However, 4 to 6 months after the surgery, no significant difference in knee circumference difference was found between the two groups (MD 0.14, 95% CI: -0.02-0.31, P = 0.09, I2 = 0%) (Fig. 7).
Effects on D-dimers
Three trials provided data of D-dimers, but only one study with 20 patients was included because the two other trials had a revised Jadad scale score of less than 3 and were ruled out. Therefore, a meta-analysis of D-d dimers was not possible.
Effects on pain
Eight trials provided data of pain score measured using the visual analog scale (VAS). Three of these studies with 406 patients were included in the analysis. The results show that the VAS score in the tourniquet group was higher than in the non-tourniquet group on the 3rd and 5th days after surgery (P < 0.05) (Fig. 8, Fig. 9). However, there was no significant difference in VAS score between the two groups (MD 0.31, 95% CI: -0.05-0.66, P = 0.09, I2 = 89%). (Fig. 10)
Publication bias
In this study, with DVT after TKA as the main observation index, publication bias was analyzed in 11 studies. All the studies were distributed symmetrically with a small top and a large bottom indicating no significant publication bias in the 11 included studies (Fig. 11).