Table 2.

Risk of bias in included trials

First author (yr) [ref]	Random sequence generation	Allocation concealment	Patient and practitioner blinding	Assessor blinding	Reporting drop-out or withdrawal	Intention-to-treat analysis	Selective outcome reporting	Other potential bias
Oh (2010) [11]	L	U	L	L	L	H	L	U
Kim (2009) [12]	U	U	L	U	U	U	U	H
Kim (2012) [13]	L	U	L	U	L	L	U	U
Wiklund (1999) [14]	U	U	L	U	L	L	L	U

L, low risk of bias; U, unclear; H, high risk of bias.