Risk of haemorrhagic stroke in patients with total hip/knee replacements and matched controls: A population-based cohort study in Denmark

Introduction: Haemorrhagic stroke is a potentially fatal complication of total hip and knee replacements (THR/TKR), mainly associated with extensive thromboprophylaxis. However, timing of haemorrhagic stroke in THR/TKR patients, against matched controls, remains unknown. Objective of this study was to determine risk of haemorrhagic stroke in patients with THR/TKR against matched control subjects. Methods: A nationwide cohort study was conducted within the Danish registers (1998-2007). Patients included those with a primary THR/TKR in the study period (n=95,359), and were matched by age, sex, and region to three referent subjects without THR/TKR. Time-dependent cox models were used to derive hazard ratios (HR), and were adjusted (adj.) for disease history and drug use. Results: A 2.3- fold increased risk of haemorrhagic stroke was found within two weeks following THR (adj. HR 2.25; 95% CI 1.38-3.67), compared against matched controls. The risk remained slightly elevated within 6-12 weeks post-THR (adj. HR 1.52; 95% CI 1.05- 2.20), and dropped to baseline after this period. The six-week risk of haemorrhagic stroke was only increased in patients who underwent THR as a result of hip fracture adj. HR 2.81; 95% CI 1.77-4.60), and not osteoarthritis (adj. HR 0.43; 95% CI 0.16-1.14). For TKR patients, we were not able to detect an increased risk, nor could we observe a time trend for haemorrhagic stroke. Conclusion: This study shows, for the first time, that THR patients have a 2.3-fold increased risk of haemorrhagic stroke in the first two weeks post-surgery. Risk assessment for haemorrhagic stroke may be indicated, in particular in patients with a THR as a result of a hip fracture.