Blood Clots After Hip Or Knee Replacement - Study Looks At Prevalence

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Main Category: Bones / Orthopedics
Also Included In: Blood / Hematology
Article Date: 18 Jan 2012 - 15:00 PST

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According to a study in the January 18 issue of JAMA, approximately 1 in every 100 patients undergoing knee replacement surgery, and 1 in every 200 patients undergoing hip replacement surgery who use current preventive medications for venous thromboembolism (VTE; a blood clot that develops within a vein that might become serious), will develop VTE before being discharged from hospital.

In acute care hospitals, a crucial safety issue is postoperative VTE, which includes pulmonary embolism and deep vein thrombosis (DVT). The researchers write:

"Without prophylaxis, VTE (both symptomatic and asymptomatic) is the most frequent surgical adverse event after infections. Large numbers of patients world-wide undergo hip and knee replacement [arthroplasty] 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. Also, symptomatic VTE after total or partial knee arthroplasty (TPKA) and after total or partial hip arthroplasty (TPHA) are proposed patient safety indicators, but data are lacking."

In order to establish a contemporary literature-based estimate of symptomatic VTE event rates before patients undergoing TPHA or TPKA, who received VTE prophylaxis were discharged from hospital, Jean-Marie Januel, R.N., M.P.H., of the Lausanne University Hospital, Switzerland, and colleagues reviewed 47 relevant investigations (6 observational, and 41 randomized human trials).

The studies included a total of 44,844 patients (21,369 undergoing TPHA and 23,475 undergoing TPKA). 20 studies included patients undergoing knee arthroplasty, 21 included patients undergoing hip arthroplasty, and 6 studies included both.

The pooled incidence rates for patients undergoing total or partial knee arthroplasty were: 1.09% for symptomatic postoperative VTE0.27% for pulmonary embolismand 0.63% for DVTFor those undergoing total or partial hip arthroplasty the pooled incidence rates were: 0.53% for symptomatic postoperative VTE0.14% for pulmonary embolismand 0.26% for DVTThe researchers write: "In patients undergoing TPKA, the pooled incidence rates of symptomatic postoperative VTE were significantly heterogeneous [dissimilar]; the pooled incidence rates of symptomatic postoperative DVT and pulmonary embolism indicated less heterogeneity. For patients undergoing TPHA, similar heterogeneity was observed for the pooled incidence rates of symptomatic postoperative VTE and DVT.

These pooled rate estimates indicate that, under contemporary prophylactic regimens, approximately 1 in every 100 patients undergoing TPKA, and 1 in every 200 patients undergoing TPHA, will experience a VTE event before hospital discharge.

These estimates are of value to individual patients and clinicians in the consideration of risks and benefits of TPKA and TPHA, as well as to individuals and organizations seeking to evaluate institutional VTE event rates against contemporary benchmarks. Our above-mentioned rate estimates provide these contemporary benchmarks."

In an associated report, John A. Heit, M.D., of the Mayo Clinic, Rochester, Minn., comments about the accuracy of the estimates in this investigation:

"Of the patients included in their meta-analysis, more than 80 percent were enrolled in randomized clinical trials. The generalizability of the estimated in-hospital VTE rates to all patients undergoing TPHR and TPKR is uncertain.

Because the authors did not have individual patient-level data on the dates of surgery, postoperative VTE events, and death or other loss to follow-up, their VTE rates are not adjusted for differing periods of observation.

Since clinical trials typically mandate some form of leg vein imaging between postoperative days 7 and 10 and patients with identified asymptomatic DVT were usually treated, the study by Januel et al likely underestimated the true rate of symptomatic VTE for the reported mean durations of follow-up (13 days). However, because the current duration of hospitalization for TPHR and TPKR is only 3 to 4 days, the current rates of symptomatic VTE prior to hospital discharge likely are lower than those reported by Januel et al."

Written By Grace Rattue
Copyright: Medical News Today
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