Fig. 4

a Correlation between cortisol at 6 h after THA and IL-6 at 24 h after THA in the aged group. b Correlation between IL-6 at 6 h after THA and VAS at 24 h after THA in the aged group. c Correlation between CRP at 6 h after THA and VAS at 24 h after THA in the middle-aged group