Abstract: BACKGROUND: Massive blood loss often produces during the perioperative period of total knee arthroplasty. Local injection of tranexamic acid can effectively reduce perioperative blood loss. However, the protortion of tranexamic acid solution has not been unified.  
OBJECTIVE: To study the effect of intra-articular tranexamic acid at different volumes and doses on blood loss in total knee arthroplasty.
METHODS:  A total of 120 patients aged 42-89 years who underwent unilateral total knee arthroplasty in the First Affiliated Hospital of Zhengzhou University from February 2019 to January 2020, including 45 males and 75 females, were randomly divided into four groups (n=30 per group). Patients undergoing total knee arthroplasty in the A, B, C, and D groups were injected with tranexamic acid solution 1 g/20 mL, 1 g/50 mL,1 g/100 mL, and 2 g/100 mL, respectively, along the incision after joint capsule suturing. Postoperative blood loss, inflammatory indexes, coagulation indexes, complications and adverse reactions, and visual analogue scale scores of the knee joint at resting and active states were compared among the four groups after operation.  
RESULTS AND CONCLUSION: (1) Blood loss and blood transfusion: the drain output, total blood loss and hemoglobin drop in the C and D groups were significantly lower than those in the A and B groups (P < 0.05), and hidden blood loss in the C and D groups was significantly lower than that in the A group (P < 0.05). The drain output, total blood loss, and hemoglobin drop in the B group were lower than those in the A group (P < 0.05). There were no significant differences in blood transfusion rate and blood transfusion among all the groups (P > 0.05). (2) Inflammation and coagulation indexes: There were no significant differences in erythrocyte sedimentation rate, C-reactive protein, D-dimer and fibrinogen among the four groups (P > 0.05). (3) Complications and adverse reactions: No deep vein thrombosis and other adverse reactions occurred in any patients. (4) There was no significant difference in visual analog scale scores at resting and active states among the four groups at 3 hours and 7 days after operation (P > 0.05). (5) In conclusion, intra-articular injection of 1 g/100 mL tranexamic acid solution is better than 1 g/20 mL and 1 g/50 mL in the reduction of blood loss during total knee arthroplasty, without increasing the risk of complications such as deep venous thrombosis and superficial wound necrosis. 1 g/100 mL and 2 g/100 mL tranexamic acid solutions have the same hemostatic effect, but 1 g/100 mL tranexamic acid solution is more economical and convenient in clinical practice. Therefore, 1 g/100 mL tranexamic acid solution is recommended for intra-articular injection in total knee arthroplasty.

Key words: orthopedic implant, artificial prosthesis, tranexamic acid, intra-articular injection, total knee arthroplasty, blood loss