We compared thromboembolic events, major haemorrhage and death after knee replacement in patients receiving either aspirin or low-molecular-weight heparin (LMWH). Data from the National Joint Registry for England and Wales were linked to an administrative database of hospital admissions in the English National Health Service. A total of 156 798 patients between April 2003 and September 2008 were included and followed for 90 days. Multivariable risk modelling was used to estimate odds ratios adjusted for baseline risk factors (AOR). An AOR < 1 indicates that risk rates are lower with LMWH than with aspirin. In all, 36 159 patients (23.1%) were prescribed aspirin and 120 639 patients (76.9%) were prescribed LMWH. We found no statistically significant differences between the aspirin and LMWH groups in the rate of pulmonary embolism (0.49% vs 0.45%, AOR 0.88 (95% confidence interval (CI) 0.74 to 1.05); p = 0.16), 90-day mortality (0.39% vs 0.45%, AOR 1.13 (95% CI 0.94 to 1.37); p = 0.19) or major haemorrhage (0.37% vs 0.39%, AOR 1.01 (95% CI 0.83 to 1.22); p = 0.94). There was a significantly greater likelihood of needing to return to theatre in the aspirin group (0.26% vs 0.19%, AOR 0.73 (95% CI 0.58 to 0.94); p = 0.01). Between patients receiving LMWH or aspirin there was only a small difference in the risk of pulmonary embolism, 90-day mortality and major haemorrhage.
These results should be considered when the existing guidelines for thromboprophylaxis after knee replacement are reviewed.
The authors would like to thank the patients and staff of all the hospitals in England and Wales who have contributed data to the National Joint Registry. We are grateful to the Healthcare Quality Improvement Partnership (HQIP), the NJR steering committee and the staff at the NJR centre for facilitating this work.
The National Joint Registry for England and Wales is funded through a levy raised on the sale of hip and knee replacement implants. The cost of the levy is set by the NJR Steering Committee. The NJR Steering Committee is responsible for data collection. This work was funded by a fellowship from the National Joint Registry. The authors have conformed to the NJR’s standard protocol for data access and publication. The views expressed represent those of the authors and do not necessarily reflect those of the National Joint Register Steering committee or the Health Quality Improvement Partnership (HQIP) who do not vouch for how the information is presented.
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
Supplementary material. Two tables detailing i) the International Statistical Classification of Diseases and Related Health Problems (10th revision) (ICD-10) and Office of Population, Censuses and Surveys Classification of Surgical Operations and Procedures (4th revision) (OPCS-4) codes and ii) the Charlson score are available with the electronic version of this article on our website www.jbjs.boneandjoint.org.uk
- Received January 13, 2012.
- Accepted February 23, 2012.
- ©2012 British Editorial Society of Bone and Joint Surgery