Literature search
A total of 559 articles were retrieved from PubMed (n=146), Embase (n=232), Cochrane Library (n=1), Scopus (n=180) and other resources (n=15). Apart from the repeated publications, 322 articles were expected for a further review. Then 313 studies were excluded by thoroughgoing screening; these consisted of letters (n=2), book section (n=3), adult patients (n =21), review articles (n =27), not comparisons (n =31), not original published (n=3), conference abstracts (n=69), irrelevant interventions (n=137) and not report outcome of interest (n=20). Eventually, 10 qualified articles were included for a systematic analysis (including one unpublished article). The specific search and selection process is represented in Figure 1.