Table 2. Risk of bias in included studies.

Study	Random Sequence Generation	Allocation concealment	Blinding of participants	Blinding of outcome assessment	Incomplete Outcome data	Selective reporting	Other bias
Zhang 2013	Yes (Not reported)	Unclear	Unclear	Unclear	Yes	Unclear	Unclear
Pongcharoen 2013	Yes (Computer-generated numbers)	Unclear	Unclear	Unclear	Yes	Unclear	Unclear
Heekin 2013	Yes (Randomization table)	Unclear	Yes	Unclear	Yes	Unclear	Unclear
Cho 2013	Yes (Not reported)	Unclear	Unclear	Unclear	Yes	Unclear	Unclear
Guy 2012	Yes (Randomization table)	Yes (Sealed envelope)	Unclear	Yes	Yes	Unclear	Unclear
Varnell 2011	Yes (Not reported)	Unclear	Unclear	Unclear	Yes	Unclear	Unclear
Lee 2011	Yes (Computer-generated numbers)	Yes (Sealed envelope)	Unclear	Yes	Yes	Unclear	Unclear
Kim 2011	Yes (Randomization table)	Yes (Sealed envelope)	Yes	Yes	Yes	Unclear	Unclear
Hernandez-Vaquero2010	Yes (Randomization table)	Unclear	No	Yes	Unclear	Unclear	Unclear
Nestor 2010	Yes (Randomization table)	Unclear	Yes	Yes	Yes	Unclear	Unclear
Karpman 2009	Yes (Computer-generated numbers)	Unclear	Yes	Yes	Yes	Unclear	Unclear
Juosponis 2009	Yes (Randomization table)	Yes (Sealed envelope)	Unclear	Unclear	Yes	Unclear	Unclear
Dalury 2008	Yes (Randomization table)	Unclear	Unclear	Yes	Yes	Unclear	Unclear
Karachalios 2008	Yes (Computer-generated numbers)	Yes (Sealed envelope)	Unclear	Yes	Yes	Unclear	Unclear
Fu 2008	Yes (Not reported)	Unclear	Yes	Yes	Yes	Unclear	Unclear
Walter 2007	Yes (Randomization table)	Yes (Sealed envelope)	Unclear	Yes	Yes	Unclear	Unclear
Kolisek 2007	Yes (Randomization table)	Yes (Sealed envelope)	Unclear	Unclear	Yes	Unclear	Unclear
Chin 2007	Yes (Randomization table)	Yes (Sealed envelope)	Yes	Yes	Yes	Unclear	Unclear