Timing of stroke in patients undergoing total hip replacement and matched controls: a nationwide cohort study.

BACKGROUND AND PURPOSE Stroke is a potentially fatal complication of total hip replacements (THR). However, timing of stroke in THR patients compared with matched controls and influence of drug use remain unknown. The objective of this study was to determine timing of stroke in patients with THR compared with matched control subjects. METHODS A nationwide cohort study was conducted within the Danish registers (1998-2007). Included patients were those with a primary THR in the study period (n=66,583) and were matched by age, sex, and region to three referent subjects without THR or total knee replacements. Time-dependent Cox models were used to derive hazard ratios and were adjusted for disease history and drug use. RESULTS A 4.7-fold increased risk of ischemic stroke (adjusted hazard ratio, 4.69; 95% CI, 3.12-7.06), and a 4.4-fold increased risk of hemorrhagic stroke (adjusted hazard ratio, 4.40; 95% CI, 2.01-9.62) were found within 2 weeks following THR, compared with matched controls. The risk remained elevated during the first 6 postoperative weeks for ischemic stroke, and the first 12 weeks for hemorrhagic stroke. Outpatient antiplatelet drug use lowered the 6-week hazard ratios for ischemic stroke by 70%, although not affecting risk of hemorrhagic stroke. CONCLUSIONS This study shows, that THR patients have a 4.7-fold increased risk of ischemic stroke, and a 4.4-fold increased risk of hemorrhagic stroke during the first 2 weeks postsurgery. Risk assessment of stroke in individual patients undergoing THR (ie, evaluate other risk factors for stroke) should be considered during the first 6 to 12 weeks.