For the first time, researchers say they have established benchmarks for the rates of in-hospital venous thromboembolism that occur after total or partial hip arthroplasty and after total or partial knee arthroplasty, according to a report Jan. 18 in JAMA.
In a meta-analysis of 47 studies that documented venous thromboembolism (VTE) event rates in nearly 45,000 patients who received recommended prophylaxis during hospitalization for knee or hip arthroplasty, investigators estimated that approximately 1 in every 100 patients undergoing knee arthroplasty and 1 in every 200 undergoing hip arthroplasty will develop symptomatic VTE before they are discharged.
"These estimates are of value to individual patients and clinicians in the consideration of risks and benefits" of the two procedures. They also are important because rates of in-hospital VTE are increasingly used as indicators of patient safety at individual medical centers, even though the expected background rates haven’t been established until now, said Jean-Marie Januel, a registered nurse with the Institute of Social and Preventive Medicine, Lausanne (Switzerland) University Hospital, and his associates.
"Large numbers of patients worldwide undergo hip and knee replacement procedures annually, and VTE is a widely acknowledged complication. Yet no estimate of symptomatic VTE risk prior to hospital discharge is available from the literature that can be conveyed to patients in the informed consent process," they noted.
Mr. Januel and his colleagues performed a systemic search of the literature to identify studies performed between 1996 and 2011 in which subjects undergoing either hip or knee arthroplasty received VTE prophylaxis according to published guidelines, including either low-molecular-weight heparin or inhibitors of factor Xa or IIa. They found 41 randomized clinical trials and 6 observational studies to include in the meta-analysis.
A total of 22 of the studies were performed in Europe, 14 were in North America, and 11 were in other regions. The mean duration of follow-up after either surgery was 13 days.
This included 21 studies of partial or total hip arthroplasty, 20 of partial or total knee arthroplasty, and 6 studies of both procedures, with a total of 44,844 subjects.
There were 443 cases of symptomatic postoperative VTE that developed before hospital discharge: 288 in the 23,475 knee patients and 155 in the 23,475 hip patients. This included 182 cases of deep vein thrombosis in the knee patients and 93 in the hip patients, as well as 106 cases of pulmonary embolism in the knee patients and 43 in the hip patients.
The pooled incidence rates of VTE were approximately 1% after knee arthroplasty and approximately 0.5% after hip arthroplasty. This means that the background rate of VTE is approximately 1 in 100 knee patients and 1 in 200 hip patients, the investigators said (JAMA 2012;307:294-303).
When the data were broken down by type of VTE, the pooled incidence rates were 0.26% for deep vein thrombosis and 0.14% for pulmonary embolism after knee arthroplasty. The corresponding rates were 0.63% for deep vein thrombosis and 0.27% for pulmonary embolism after hip arthroplasty.
"Given that these rates are based on the results of rigorous studies, they may represent a lower incidence than actual rates observed in clinical practice, in which patients are selected less rigorously and prophylaxis is administered less assiduously," Mr. Januel and his associates noted.
The pooled incidence rates of deep vein thrombosis were lower for both knee patients and hip patients when factor Xa or IIa inhibitors, rather than low-molecular-weight heparin, were given for prophylaxis. "However, we cannot make assertions regarding comparative efficacy among treatments, because our meta-analysis did not directly compare [these agents] as an efficacy meta-analysis would have done," they said.
This study was supported by Alberta Innovates Health Solutions, a government research funding agency, and the International Methodology Consortium for Coded Health Information, a collaboration of health sciences researchers to promote quality of care. Dr. Heit reported ties to Daiichi Sankyo, GTC, Ortho-McNeil-Jansen, the National Heart, Lung, and Blood Institute, the National Human Genome Research Institute, the National Institutes of Health, the Centers for Disease Control and Prevention, and the Mayo Foundation.