Fig. 1

PRISMA flow diagram for the systematic review process. The step-by-step process of the application of inclusion and exclusion criteria generated the final number of studies included in the systematic review. ^†Note: Kristjánsdóttir et al. (2013) was published as part 1 [22] and part 2 [23] with respect to a short-term follow-up and long-term follow-up; thus, the results are based on 12 studies from 13 published articles