Comparative analysis of acute blood loss anemia in robotic assisted vs. manual instrumented total knee arthroplasty

Robotic assisted total knee arthroplasty has become an increasingly popular technique over the past several years. Manual total knee arthroplasty can be associated with acute blood loss anemia. Instrumentation of the femoral canal with the alignment guide may in part contribute to this blood loss. Because the femoral canal is not entered during robotic assisted total knee arthroplasty, the blood loss may be lower compared to that seen in manual total knee arthroplasty. The purpose of this study was to determine if acute blood loss is greater in manually instrumented total knee arthroplasty versus robotic assisted total knee arthroplasty. This retrospective cohort study was performed in a large tertiary academic hospital network by two fellowship trained surgeons. Patients underwent either robotic assisted or manually instrumented total knee arthroplasty and were assessed for postoperative acute blood loss anemia, defined as hemoglobin < 13 g/dL for males or < 12 g/dL for females plus a 2g/dL drop from preoperative levels, as well as postoperative drop in hemoglobin. A total of 75 patients were included in each study arm. There was no significant difference (p>0.05) in postoperative hemoglobin in robotic assisted (2.1 g/dL) compared to manually instrumented total knee arthroplasty (2.1 g/dL). There was no significant difference in the incidence of postoperative acute blood loss anemia between robotic assisted (45%) and manually instrumented total knee arthroplasty (39%). Higher BMI and increased age were protective against postoperative drop in hemoglobin. These protective effects were not significant when controlling for confounding variables. Surgical time was significantly longer for robotic assisted (99 minutes) versus manually instrumented total knee arthroplasty (86 minutes) (p <0.001). There is no significant difference in acute blood loss when comparing patients undergoing robotic assisted and manually instrumented total knee arthroplasty.