Table 1 The risk of bias assessment of non-randomized studies (MINORS)

1.A clearly stated aim

2

2

2

2

2

2.Inclusion of consecutive patients

1

1

2

2

2

3.Prospective collection of data

2

2

2

2

2

4.Endpoints appropriate to the aim of the study

2

2

2

2

2

5.Unbiased assessment of the study endpoint

0

0

0

0

0

6.Follow-up period appropriate to the aim of the study

2

2

2

2

2

7.Loss to follow up less than 5%

2

2

2

0

2

8.Prospective calculation of the study size

0

0

0

0

0

9.An adequate control group

0

0

1

0

2

10.Contemporary groups

0

0

2

0

2

11.Baseline equivalence of groups

0

0

2

0

2

12.Adequate statistical analyses

0

0

2

0

2

Total score

11

11

19

10

20