Table 2.

Quality of included studies

Studies	Randomization	Allocation concealment	Assessor blinding	Loss of followup	Quality grade
Davison et al. [5]	RCT	Yes	Single blinding	17.9%, untreated	B
Frihagen et al. [6]	RCT	Yes	Unknown	Unknown	B
Johansson et al. [12]	RCT	Yes	Unknown	9%, untreated	B
Jónsson et al. [13]	RCT	Yes	Unknown	4%, untreated	B
Bjorgul and Reikeras [3]	RCT	Yes	Unknown	1%, untreated	B
Leonardsson et al. [16]	RCT	Yes	Unknown	3.9%	B
Heetveld et al. [9]	Inadequate	Yes	Double blinding	Unknown	B
Neander et al. [19]	RCT	Yes	Unknown	No	B
Parker et al. [21]	RCT	Yes	Unknown	No	B
Puolakka et al. [22]	RCT	Yes	Unknown	3%	B
Ravikumar and Marsh [23]	RCT	Yes	Unknown	Unknown	B
Rödén et al. [24]	RCT	Yes	Unknown	Unknown	B
Rogmark et al. [25]	RCT	Yes	Unknown	10.2%, untreated	B
Sikorski and Barrington [30]	RCT	Yes	Unknown	Unknown	B
Skinner et al. [31]	Inadequate	Unknown	Unknown	Unknown	C
Söreide et al. [35]	Inadequate	Unknown	Unknown	Unknown	C
Svenningsen et al. [34]	Inadequate	Yes	Unknown	< 5%	C
Keating et al. [15]	RCT	Yes	Double blinding	< 5%	A
Tidermark et al. [37]	RCT	Yes	Double blinding	7.2%, untreated	A
van Vugt et al. [38]	RCT	Yes	Unknown	< 5%	B