Risk of myocardial infarction in Dutch patients following discharge for total hip/knee replacement and matched controls: a population-based cohort study

Abstract

Introduction Total joint replacement surgery of the hip and knee has been associated with an increased risk of acute myocardial infarction. However, this risk has not been compared with matched controls without surgery after discharge from the hospital. The aim of this study was to estimate the risk of myocardial infarction in Dutch patients following discharge for total hip/knee replacement and matched controls. Materials and methods A population-based retrospective cohort study was conducted with the Dutch PHARMO Record Linkage System. All patients with a primary elective total hip replacement (n = 13,952) or total knee replacement (n = 8239) between 2000 and 2009 were selected, and matched to 47,864 controls (no total hip replacement/total knee replacement) by age, sex and geographical location. Timedependent Cox regression was used to derive disease- and medicationadjusted (adj.) hazard ratios for a readmission due to acute myocardial infarction. Results The mean age of patients who sustained total hip replacement surgery was 68.5 years (standard deviation: 10.1), which was similar to patients who sustained total knee replacement surgery (68.4 years, standard deviation: 9.9). As compared with controls, the risk of myocardial infarction was not increased within 1 year after discharge for total hip replacement [adj. hazard ratio = 0.83, 95% confidence interval: 0.60–1.16] or total knee replacement [adj. hazard ratio = 0.97, 95% confidence interval: 0.63–1.48]. The corresponding cumulative incidence was 0.4% 1 year after total hip/knee replacement discharge. Furthermore, the hazard ratio of myocardial infarction was not different between patients exposed to total hip/knee replacement and controls, when the surgery was performed more than 1 year ago. Conclusion The hazard ratio of acute myocardial infarction was not increased in the year following discharge for total hip/knee replacement surgery or in the subsequent period, as compared with controls without surgery. The incidence of post-discharge acute myocardial infarction was low, which is possibly related to the current treatment regimen, including lowmolecular-weight-heparins for an extended duration of 6 weeks and early revalidation after surgery.