RESUMEN
BACKGROUND: The intraoperative blood loss of unicompartmental knee arthroplasty is lower than that of total knee arthroplasty, but the difference of postoperative occult blood loss between them has not been widely studied. OBJECTIVE: To compare the difference of occult blood loss between unicompartmental knee arthroplasty and total knee arthroplasty, and to analyze whether patients with preoperative anemia can also undergo unicompartmental knee arthroplasty without the risk of blood transfusion. METHODS: 148 patients with knee osteoarthritis treated in 904 Hospital of the Joint Service Support Force of Chinese PLA from January 2014 to December 2016 were selected. Among them, 58 cases underwent unicompartmental knee arthroplasty and 90 cases underwent total knee arthroplasty. Hemoglobin levels and hematocrit were measured before and 1, 4, 21 and 42 days after operation, and the occult blood loss and blood transfusion rate were calculated. The trial was approved by the Ethics Committee of 904 Hospital of the Joint Service Support Force of Chinese PLA (approval No. 2019-01-03). RESULTS AND CONCLUSION: (1) The hemoglobin level of unicompartmental knee arthroplasty group was higher than that of total knee arthroplasty group at 1 and 4 days after operation (P 0.05). (2) Hematocrit in the unicompartmental knee arthroplasty group was higher than that in the total knee arthroplasty group at 1 and 4 days after operation (P 0.05).(3) From day one to day four after surgery, there was no occult blood loss in the female of unicompartmental knee arthroplasty group, and the average occult blood loss in the male was 4 g/L. The average occult blood loss was 10 g/L in female and 7 g/L in male in total knee arthroplasty group. The occult blood loss in male and female in unicompartmental knee arthroplasty group was lower than that in total knee arthroplasty group (P < 0.05 or P < 0.01). (4) The blood transfusion rate was 0% in unicompartmental knee arthroplasty group and 4.4% in total knee arthroplasty group. In patients with preoperative moderate anemia (hemoglobin 60-89 g/L), there was no need for blood transfusion in unicompartmental knee arthroplasty group (n=3), but blood transfusion was needed in 2 of 6 patients in total knee arthroplasty group (33%). (5) The results showed that unicompartmental knee arthroplasty had obvious advantages over total knee arthroplasty in postoperative occult blood loss.