In the study of Nguyen Toan Thang [14], the average activating VAS score on move was 4.25 ± 0.93 while in the study of the author Nguyen Trung Kien [8], the activating VAS score on move of PCEA group was 1.6 ± 0.6 and of PCA group was 2.7 ± 0.5.