Study offers benchmark for VTE risk after joint replacement; follow-up needed

January 27, 2012

Approximately 1 in 100 patients undergoing total or partial knee replacement surgery and 1 in 200 patients undergoing total or partial hip replacement surgery will experience a venous thromboembolism event, including deep vein thrombosis and pulmonary embolism, before being discharged from the hospital, according to a new study.

Approximately 1 in 100 patients undergoing total or partial knee replacement surgery and 1 in 200 patients undergoing total or partial hip replacement surgery will experience a venous thromboembolism (VTE) event, including deep vein thrombosis (DVT) and pulmonary embolism, before being discharged from the hospital, according to a new study.

The study was reported January 18 in the Journal of the American Medical Association.

“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,” wrote the researchers, led by Jean-Marie Januel, RN, MPH, of the Institute of Social and Preventive Medicine at Lausanne University Hospital in Switzerland.

Januel and his team conducted a systematic review and meta-analyses that reported pooled in-hospital incidence rates of acute symptomatic VTE events among patients receiving appropriate prophylaxis after total or partial hip arthroplasty (TPHR) and total or partial knee arthroplasty (TPKR). Their analysis included 44,844 patients within 47 clinical trials and observational studies. Twenty-one studies evaluated patients undergoing hip replacement, 20 evaluated patients undergoing knee replacement, and 6 included both.

The pooled rates of symptomatic postoperative VTE before hospital discharge were 1.09% (95% CI, 0.85–1.33) for patients undergoing TPKR and 0.53% (95% CI, 0.35–0.70) for those undergoing TPHR.

For patients undergoing knee replacement, the pooled rates of symptomatic DVT were 0.63% (95% CI, 0.47–0.78) and for those undergoing hip replacement, the rates were 0.26% (95% CI, 0.14–0.37).

The pooled rates for pulmonary embolism in patients undergoing knee replacement were 0.27% (95% CI, 0.16–0.38) and corresponding rates for patients undergoing hip replacement were 0.14% (95% CI, 0.07–0.21).

The researchers propose that the results can be used to provide a benchmark to evaluate patient safety indicators where there are currently none available.  However,  John A. Heit, MD, of the Division of Cardiovascular Diseases, Department of Internal Medicine, College of Medicine, at the Mayo Clinic in Rochester, Minn., said in an editorial accompanying the study that the values may be suboptimal “because the period of VTE risk extends beyond the length of hospitalization for surgery.”

“Based on the studies conducted to date,” Dr Heit noted, “the postoperative period of risk for VTE after THR and TKR is about 10 to 12 and 4 to 6 weeks, respectively, and substantially beyond the period of initial hospitalization for surgery.”

Acknowledging this limitation, the researchers suggest future studies might widen the observation window to encompass a longer period to obtain a more stable and accurate estimate of VTE risk after TPHR and TPKR.