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© 1998 The Journal of Bone and Joint Surgery, Inc.
CorrespondenceTO THE EDITOR: The article "Current Concepts Review. Prophylactic Use of Antibiotics for Procedures after Total Joint Replacement" (78-A: 1755-1770, Nov. 1996), by Deacon et al., appears to contain several factual errors. First, on page 1756, in the section entitled "Dental Procedures," the authors state: "We know of only one randomized placebo-controlled trial confirming the benefits of such prophylaxis in the prevention of late prosthetic-valve endocarditis." The authors then go on to cite a study by Horstkotte et al.3. However, that study was not a randomized placebo-controlled trial. I have read and translated parts of that article from German and have also read an article in English by Horstkotte et al.2 that appears to describe the same research. It is clear from these articles that this was a retrospective clinical study, which is similar in design to a retrospective cohort study. There is no mention of placebos, randomization, or prospective planning. Indeed, the last line of the English-language abstract in the German article and of the abstract in the English-language version states that "this retrospective study documents the benefit" of prophylaxis against infective endocarditis2,3. In fact, I am not aware of any prospective, randomized, controlled trials that have been conducted to measure the efficacy of antibiotic prophylaxis in the prevention of endocarditis, and the performance of such a study is fraught with both logistical and ethical problems as endocarditis is rare and prophylaxis is now accepted therapy1. However, several recent case-control studies have been performed that estimated the efficacy of prophylaxis among patients with native-valve endocarditis who had had recent invasive procedures. In those four studies, the relative risk (RR), which is approximated by the odds ratio, can be used in the formula 1 - RR to calculate the efficacy of prophylaxis. The odds ratios, and corresponding efficacy (with 95 per cent confidence intervals when given), were 0.09 or 91 per cent efficacy (7.0 to 100)4, 0.51 or 49 per cent efficacy (0 to 89)7, and 0.54 or 46 per cent efficacy (0 to 90)5; in a recent study, the odds ratio was more than one, indicating 0 per cent efficacy6. Second, when Deacon et al. referred to the study by Horstkotte et al.3, they mistakenly cited the number of procedures as the number of patients. For example, Deacon et al. stated that "in 1986, Horstkotte et al. reported no cases of late prosthetic-valve endocarditis in 287 patients with prosthetic heart valves who had been given antibiotics." Actually, Horstkotte et al. reported no instances of late prosthetic-valve endocarditis in 229 patients who had had a total of 287 procedures. Deacon et al. also stated that "of the 390 patients [in the study by Horstkotte et al.] who did not receive antibiotics prophylactically, eight had late prosthetic-valve endocarditis." In fact, Horstkotte et al. reported late prosthetic-valve endocarditis in eight of 304 patients who had had a total of 390 procedures. Although these latter errors are minor, the first one is important because the efficacy of antibiotic prophylaxis for patients who have a prosthesis in place is an important issue in both medical and dental practice today and incorrect information could mislead readers and possibly slow down advances in this area.
Mark T. Drangsholt, D.D.S., M.P.H.: Department of Oral Medicine, School of Dentistry, University of Washington, Box 356230, Seattle, Washington 98195-6370
Dr. Deacon, Dr. Pagliaro, Dr. Zelicof, and Dr. Horowitz reply: Dr. Drangsholt correctly points out our errors in the citing of the study by Horstkotte et al.3. Indeed, the study was neither prospective nor randomized and we reported the number of procedures rather than the number of patients. We agree that it is unlikely that a randomized, placebo-controlled study will be performed to examine the efficacy of antibiotic prophylaxis in patients who have a prosthetic heart valve. It is also unlikely that such a study will be performed to determine the effectiveness of prophylaxis in patients with prosthetic joints who have an invasive procedure. Our intention in the section entitled "Dental Procedures" was to note that there are few data to support the use of prophylactic antibiotics in patients with a total joint replacement who are having an invasive procedure. Although not comprehensive, there are markedly more data to support the use of antibiotic prophylaxis for patients who have native heart-valve disease or a prosthetic heart valve. In our review, we wrote that the interest in providing antibiotic prophylaxis for patients with a total joint prosthesis who are having an invasive procedure is at least partly based on the belief that this situation parallels that of the use of prophylactic antibiotics for patients who have heart-valve disease. We reported the conflicting results in animal models of infection around heart valves and noted that failures in humans were well reported, but we omitted other relevant human studies (which Dr. Drangsholt supplies in his letter). The study by Horstkotte et al.3 was just one of several studies that were used to support the notion that antibiotic prophylaxis should be used for patients with prosthetic heart valves who are having an invasive procedure. We are sorry that our miscitation of the data presented by Horstkotte et al.3 caused confusion. Regrettably, this was the only secondary reference in our review of the literature that we did not review firsthand. The error, however, does not change our argument or the results regarding the major theme of the review.
John M. Deacon, M.D.: Division of Emergency Medicine, University of California, Davis, Sacramento, California 95817 Andre J. Pagliaro, M.D.; Steven B. Zelicof, M.D., Ph.D.; Harold W. Horowitz, M.D.: Departments of Orthopaedic Surgery (A. J. P. and S. B. Z.) and Internal Medicine, Division of Infectious Diseases (H. W. H.), New York Medical College, Westchester County Medical Center, Room 209, Macy Pavilion, Valhalla, New York 10595
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