Table 2 Risk of bias assessment of included studies
Quality item | Sugawara et al. 2002 [22] | Deguchi et al. 2011 [23] | Buschang et al. 2011 [24] | Akan et al. 2013 [25] | Xun et al. 2007 [26] | Erverdi et al. 2004 [27] | Erverdi et al. 2007 [28] | Scheffler et al. 2014 [29] | Foot et al. 2014 [30] | kuroda et al. 2007 [10] | Hart et al. 2015 [32] | Lee and Park 2008. [31] |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1. A clear stated aim | 1 | 2 | 1 | 2 | 2 | 2 | 2 | 1 | 2 | 2 | 2 | 2 |
2. Inclusion of consecutive patients | 0 | 2 | 2 | 0 | 0 | 0 | 0 | 2 | 1 | 0 | 2 | 0 |
3. Prospective collection of data | 0 | 1 | 2 | 1 | 1 | 0 | 1 | 0 | 2 | 1 | 1 | 1 |
4. Endpoints appropriate to the aim of the study | 2 | 2 | 1 | 2 | 2 | 2 | 1 | 2 | 2 | 2 | 2 | 1 |
5. Unbiased assessment of the study end point | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
6. Follow-up period appropriate | 2 | 2 | 0 | 0 | 0 | 0 | 1 | 2 | 0 | 0 | 0 | 2 |
7. Loss to follow-up less than 5 % | 2 | 2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 |
8. Prospective calculation of the study size | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Additional criteria in the case of comparative study | ||||||||||||
9. An adequate control group | 2 | 2 | – | – | – | – | – | – | – | 2 | – | – |
10. Contemporary groups | 0 | 2 | – | – | – | – | – | – | – | 2 | – | – |
11. Baseline equivalence of groups | 0 | 1 | – | – | – | – | – | – | – | 1 | – | – |
12. Adequate statistical analyses | 2 | 2 | 0 | 2 | 2 | 1 | 2 | 2 | 2 | 2 | 2 | 2 |
Total | 11 | 18 | 6 | 7 | 7 | 5 | 7 | 9 | 9 | 12 | 9 | 10 |