Reporting pain as mean difference (MD) instead of standardized mean difference (SMD) is justified by the different measurements for the same outcome [13]: as mentioned in the results, the included studies measured pain with 10-point NRS [2,14,15] or mm-100 VAS [16,17], thus requiring the use of SMD.

Regarding the minimum detectable changes (MDC) and the minimum clinically important difference (MCID) of subjective pain intensity scales (VAS, NRS), while Cleland et al. [18] calculated them, these