Background:It has rarely been reported about the changes of hemoglobin (Hb) and hematocrit (Hct) in elderly patients receiving total knee arthroplasty (TKA) or total hip arthroplasty (THA).This study aimed to evaluate the changes of Hb and Hct after TKA or THA in elderly patients,and analyze its relationship with sex and type of arthroplasty.Methods:This is a prospective cohort study,including 107 patients receiving TKA or THA without allogeneic blood transfusion.There were 54 males and 53 females,with a mean age of 69.42 years.Levels of Hb and Hct were examined preoperatively and during the 6 months follow-up after operation.Results:Levels of Hb and Hct decreased postoperatively and reached their minimum points on postoperative day 4.Thereafter,Hb and Hct recovered to their preoperative levels within 6-12 weeks.No significant differences in the levels of Hb and Hct were noticed between different sexes.THA patients showed significantly greater drop in Hb and Hct than TKA patients in the first 4 days postoperatively (P ＜ 0.05).Conclusions:Levels of Hb and Hct decreased during the first 4 days after arthroplasty and gradually reted to their normal levels within 6-12 weeks postoperatively.THA may be associated with higher postoperative blood loss than TKA.