Although the use of thromboprophylaxis is well established, there is no consensus on the preferred thromboprophylaxis regimen after THA; large, population-based studies offer an opportunity to examine this problem in a robust way that can complement results from randomized trials.
Using data from a large national registry, we asked: (1) Is there any difference between low-molecular weight heparin (LMWH) and new oral anticoagulants in preventing symptomatic deep vein thrombosis (DVT) and pulmonary embolism (PE), after THA? (2) Are there any differences in safety parameters, such as bleeding, reoperations and mortality, between LMWH and new oral anticoagulants?
Between 2008 and 2012, 78,066 THAs were performed in Sweden. This study evaluated 32,663 (42%) of them, selected through the merger of several national registries. These patients underwent unilateral THA due to primary osteoarthritis. They had not experienced any venous thromboembolic events 5 years before the index operation and were not prescribed potent antithrombotic agents, of any type, in the 6 months before the index operation. Additionally, their postoperative thromboprophylaxis was confirmed in a national registry by purchase of prescribed medications. We divided the cohort into two groups: those patients who received new oral anticoagulants (5752, 18%) and those who received LMWH (26,881, 82%) as postoperative thromboprophylaxis. Our primary endpoints were the frequencies of symptomatic DVT and symptomatic PE within 3 months of surgery. Our secondary comparison was a between-group comparison of bleeding (by way of diagnostic coding), reoperation, and mortality within 3 months of surgery. Odds ratios (OR) are presented with 95% confidence intervals (CIs) as pooled results for the two groups after adjustment for duration of thromboprophylaxis (short or extended for at least 28 days), year of the index operation, Elixhauser comorbidity index, sex, age and previous treatment with platelet aggregation inhibitors.
The risk of symptomatic DVT was lower in the group that received new oral anticoagulants than the group that received LMWH (0.3% versus 0.6%, OR, 0.47; 95% CI, 0.27–0.76; p = 0.026). The risk of symptomatic PE was lower in the group that received new oral anticoagulants than the group that received LMWH (0.1% versus 0.4%, OR, 0.36; 95% CI, 0.16–0.69; p = 0.005). There was no difference in the risk of bleeding (by way of diagnostic coding) (OR, 1.03; 95% CI, 0.82–1.28; p = 0.688), reoperation (OR, 1.02; 95% CI, 0.71–1.44; p = 0.860) or mortality (OR, 0.83; 95% CI, 0.31–1.88; p = 0.883) between groups.
New oral anticoagulants were associated with a lower risk of symptomatic DVT and symptomatic PE in this large, registry study, and we observed no differences in the risk of bleeding, reoperation, or death between the groups. Although we were able to control for a number of potential confounding variables, we cannot ascertain the indications that drove the prescription decisions in this setting, and there were important between-group differences in terms of duration of thromboprophylaxis (new oral anticoagulants generally were used for a longer period of time after surgery). Future studies, preferably large randomized trials with pragmatic inclusion criteria, to analyze symptomatic DVT, symptomatic PE and death are needed to confirm or refute our findings.
Level III, therapeutic study.
P. Kasina, L. J. Lapidus, Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden
A. Wall, O. Rolfson, J. Kärrholm, S. Nemes, B. I. Eriksson, M. Mohaddes, Department of Orthopedics, Institute of Clinical Sciences, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
O. Rolfson, J. Kärrholm, B. I. Eriksson, M. Mohaddes, University of Gothenburg, Sahlgrenska University Hospital, Mölndal, Sweden
O. Rolfson, J. Kärrholm, B. I. Eriksson, M. Mohaddes, Department of Orthopedics, Sahlgrenska University Hospital, Mölndal, Sweden
O. Rolfson, J. Kärrholm, S. Nemes, M. Mohaddes, Swedish Hip Arthroplasty Register, Registercentrum VGR, Gothenburg, Sweden
S. Nemes, Svenska Höftprotesregistret, Registercentrum Västra Götaland, Göteborg, Sweden
P. Kasina, Dept. of Orthopedics, Södersjukhuset, Sjukhusbacken 10 , SE-118 83 Stockholm, Sweden, Email: firstname.lastname@example.org
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request.
One of the authors certifies that he (OR) has received personal fees during the study period, in an amount of less than USD 10,000, from Zimmer Biomet (Winterthur, Switzerland) as reimbursement for presentation (Gothenburg, Sweden), outside the submitted work.
One of the authors certifies that he (MM) has received personal fees during the study period, in an amount of less than USD 10,000, from Zimmer Biomet (Winterthur, Switzerland) as reimbursement for presentation (Copenhagen, Denmark); and grants as institutional support in an amount of less than 10,000 USD, from Link (Hamburg, Germany), all outside the submitted work.
Clinical Orthopaedics and Related Research® neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA approval status, of any drug or device before clinical use.
Each author certifies that his institution approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research.
This study was performed in Sweden as a nationwide study, based on national registries with continuous data collection from all performing centers in the country. The authors in their respective centers in Gothenburg and Stockholm, Sweden performed the analysis and writing.
Received September 11, 2018
Accepted February 18, 2019