Table 2.

Quality assessment of non-randomized comparative studies

Study	Selection	Comparability	Outcome	Total
Alvin et al. [20]	4	2	3	9
Cho et al. [9]	3	1	3	7
Dunn et al. [26]	4	1	3	8
Forster et al. [18]	4	2	3	9
Korinth et al. [23]	4	1	3	8
Lin et al. [10]	4	1	3	8
Mansfield et al. [27]	3	1	3	7
Mok et al. [17]	4	1	2	7
Scholz et al. [19]	3	0	3	7
Selvanathan et al. [21]	3	1	3	7
Tumialan et al. [22]	3	2	3	8
Witiw et al. [16]	4	1	2	7