Hematologic effects of total knee arthroplasty. A prospective evaluation.

Abstract

In a prospective evaluation of 41 patients (57 knees) treated with index cemented total knee arthroplasty, perioperative blood testing was performed on blood counts, fibrinogen, and fibrin degradation products (FDP). The preoperative platelet count averaged 314/nl (range, 160-502/nl), whereas postoperatively, the count nadired at an average of 173/nl (range, 60-305/nl). Fibrinogen levels increased from 304 mg/dl (range, 170-442 mg/dl) to an average high of 647 mg/dl (range, 317-1018 mg/dl). Patients were also classified according to whether they had been treated with unilateral or bilateral procedures. Postoperatively, unilateral patients had an average 32% decrease in the platelet count, compared with the 64% decrease seen in bilateral patients. Analysis of fibrin split products revealed a trend toward greater elevation of these degradation products after bilateral procedures. The hematologic changes represented evidence of activation of the coagulation and fibrinolytic systems. These changes tended to be more pronounced in patients treated with bilateral procedures, and were manifested in postoperative elevation of fibrinogen and fibrin degradation products, with reductions in the platelet count. The degree of relative thrombocytopenia raises concerns about careful evaluation of candidates for bilateral arthroplasty, especially when determining the preoperative platelet count.