Haemoglobin levels following unicompartmental knee arthroplasty: influence of transfusion practice and surgical approach.

A retrospective review was undertaken of preoperative and day 3 postoperative haemoglobin (Hb) levels in all unicompartmental knee arthroplasty (UKA) procedures performed by a single surgeon. Sixty-six UKAs were performed using the same prosthesis through an open approach with patella eversion. This group was compared with 212 UKAs performed using a minimally invasive approach without patella eversion, with an implant and instrumentation specifically devised for this approach. Both groups were well matched for patient demographics, surgical and anaesthetic techniques, thromboprophylaxis, and postoperative regimes. All patients received transfusions with pre-donated blood, except the unilateral minimally invasive approach group. An analysis of covariance was undertaken to examine the influence of the surgical approach and whether surgery was unilateral or bilateral, taking into account preoperative Hb levels and units of blood transfused. The average fall in Hb following UKA, adjusted for other variables, was 2.73 g/dl with an open approach compared to 1.82 g/dl with a minimally invasive approach. This difference was significant (p=0.0044). The average postoperative Hb in the minimally invasive group was 12.05 g/dl (range, 8.8 to 15.8 g/dl). Patients undergoing unilateral minimally invasive UKA are unlikely to develop symptomatic anaemia and should not be required to predonate blood or undergo transfusion.