Venous thromboembolism in patients having knee replacement and receiving thromboprophylaxis: a Danish population-based follow-up study.

BACKGROUND: We examined the rate of venous thromboembolism, as well as changes over time, in a population-based cohort of patients who underwent knee arthroplasty.
METHODS: Using medical databases, we identified all patients who underwent primary knee arthroplasties with pharmacological thromboprophylaxis performed in Denmark from 1997 to 2007. The outcome was hospitalization with symptomatic venous thromboembolism within ninety days of surgery. We examined several potential patient and surgery-related predictors for venous thromboembolism using Cox regression analyses.
RESULTS: The overall rate of hospitalization for venous thromboembolism among 37,223 patients within ninety days after primary knee arthroplasty was 1.2% (441 patients) at a median of fifteen days. The rate of hospitalization was 0.9% (323 patients) for deep venous thrombosis and 0.3% (127 patients) for pulmonary embolism, with nine patients who had both. The rate of venous thromboembolism increased during the ten-year study period. Patients with a high score on the Charlson comorbidity index had an increased relative risk for venous thromboembolism compared with patients with a low score (adjusted relative risk = 1.73; 95% confidence interval, 1.24 to 2.41). Patients with a history of cardiovascular disease or a previous venous thromboembolism had an increased risk for postoperative venous thromboembolism compared with patients without these conditions. Surgery-related factors were not predictors for venous thromboembolism.
CONCLUSIONS: Despite pharmacological thromboprophylaxis, patients undergoing knee arthroplasty remain susceptible for venous thromboembolism events after surgery. Future efforts should focus on the improvement of prophylaxis following hospital discharge, particularly among elderly patients and those with a history of cardiovascular diseases or previous venous thromboembolism.