Table 2: Risk of bias assessment.
Study	Random Sequence Generation	Allocation Concealment	Blinding	Incomplete Outcome Data	Selective Reporting	Other Sources of Bias
Akkaya et al. [3]	Randomization tickets	Sealed envelopes	Yes	Yes	Unclear	Unclear
Chisholm et al. [12]	Excel-compatible randomizing program	Sealed envelopes	Yes	Yes	Unclear	Unclear
El-Ahl [23]. [3]	Block randomization	Sealed envelopes	Yes	Yes	Unclear	Unclear
Espelund et al. [21]	Unclear	Unclear	Yes	Yes	Unclear	Unclear
Espelund et al. minor [20,22]	Unclear	Unclear	Yes	Yes	Unclear	Unclear
Espelund et al S. pain. [22]	Unclear	Unclea	Yes	Yes	Unclear	Unclear
Hanson et al.<">[2]	Unclear	Sealed envelopes	Yes	Yes	Unclear	Unclear
Hsu et al. [4]	Random-number generator	Sealed envelopes	Yes	Yes	Unclear	Unclear
Westergaard et al. [19]	Random number list	Sealed envelopes	Yes	Yes	Unclear	Unclear
Lundblad et al. [1]	Computer-generated random numbers	Sealed envelopes	Yes	Yes	Unclear	Unclear