BLOOD LOSS FOLLOWING TOTAL KNEE REPLACEMENT IS REDUCED WHEN USING COMPUTER-ASSISTED VERSUS STANDARD METHODS

Abstract

Introduction: Computer navigated total knee replacement does not require the use of intramedullary alignment rods, and is thus less invasive than traditional methods.

One previous study has suggested that the computer-assisted technique may reduce blood loss in comparison to traditional methods. This study (Kalairajah et al, 2005) used blood volume loss from drainage bottles as a primary outcome measure (n=60). Hidden (internal) blood losses were not accounted for.

Our study uses a more accurate method of assessing blood loss, and the sample size is larger (n=136; 68 standard TKR versus 68 computer assisted TKR).

Methods: 136 TKR patients were included, of which 68 had standard TKR and 68 computer assisted. Patients were matched such that in each group half had BMI in the range 20–30, and half had BMI between 30–40. Patients were also matched for gender. All patients had Tranexamic acid at the start of the procedure.

Total body blood volume was calculated using the formula of Nadler, Hidalgo & Bloch (1962). This was then used, together with haematocrit and volume re-infused or transfused, to calculate true blood loss, as described by Sehat, Evans, and Newman (2004). This method is considered to be more reliable than measuring drain output, as it takes account of “hidden” losses. The navigated and non-navigated groups were compared using Student’s t-test.

Results: The average blood loss was 583ml in the standard TKR group, and 442ml in the computer assisted TKR group. This difference was statistically significant (p=0.003).

Conclusions: A previous study found reduced blood loss when performing total knee replacement using computer navigation, compared with traditional methods. Our study confirmed this finding, using a larger sample size, and a more reliable method of assessing blood loss.

Our study found that overall blood loss was less for both groups, when compared to the findings of Kalairajah Y et al. We suspect that this difference was due to our departmental policy that all patients receive tranexamic acid at the start of joint replacement procedure.