Material and Methods
Design
This study was a single-blinded, multicenter, randomized controlled trial.
The patients were randomly allocated to either TENS group or Placebo TENS group in a ratio 1:1. All patients had an equal probability of assignment to the groups.
External randomization was achieved by Random Allocation Software(Ver. 2.0) [14] in blocks of 4 stratified by 4 hospitals.
This study protocol was approved by the institutional review board of Sahmyook University.