Table 1: Critical appraisal of the studies.

Articles Years Validity Relevance
Study designNumber of patientsRandomizationSimilarity treatment & controlBlindingComparable treatmentIntention to treatDeterminantMeasurement of outcomeLevel of evidence

Xiang and Feng [6]2015Retrospective study (case-control)151++++4
Sim and Tan [1]2013Randomized single-blind clinical trial67++++++2
Samalavicius et al. [9]2012Prospective study (case series follow-up)10++4
Sutherland et al. [10]2009Prospective study (case series follow-up)49++4