Author Random
sequence
generation 		Allocation
concealment 		Blinding Incomplete
outcome
data 		Selective
reporting 		Other
bias
Astrand et al. [41] + ? ? + + +
Moberg et al. [42] ? ? ? + ? +
Ravald et al. [43] ? - - + + ?
Renvert et al. [44] ? ? ? + + +
Polizzi et al. [45] ? ? ? + + ?
Vandeweghe et al. [46] ? ? ? + + +
de Araújo Nobre and Malo [47] ? ? ? - - +

+ = low risk of bias; ? = unclear risk of bias; - = high risk of bias.