Thursday, March 18, 2010

Mayo Clinic study shows that dental procedures are not a risk factor in prosthetic hip or knee infections

Thanks to the good folks at Lexi-Comp. The following info was in their March 2010 Dental e-Newsletter. As dental professionals we're often "caught in the middle" in some areas. Perhaps none is so well known in the profession as prosthetic joint premedication. The guidelines surrounding this situation have changed frequently over the last few years and many dentists have been left confused and without much science to help in the decision making process.

Now comes a new study from the Mayo Clinic that sheds new light on this topic:

Mayo Clinic study shows that dental procedures are not a risk factor in prosthetic hip or knee infections. Authors call for reconsideration of administering antibiotics to all patients with prosthetic hip or knee joints who undergo dental treatment.

A report from the Mayo Clinic, published in January, described a large case-control study which examined the association between dental procedures - with or without antibiotic prophylaxis - and prosthetic joint infections. The study found no increased risk of prosthetic joint infections after dental procedures. And to top that, the study found that antibiotic prophylaxis was not associated with any reduction in risk of infection. The study data indicated that there is no need for antibiotic prophylaxis in patients with total hip or knee replacements undergoing dental procedures.

This report comes on the heels of the recent information statement by the American Association of Orthopaedic Surgeons (AAOS) that advocated using antibiotic prophylaxis in all patients with a joint prosthesis. The Mayo Clinic study was designed to determine whether dental procedures, with and without antibiotic prophylaxis, are risk factors for prosthetic hip or knee infection. It was designed as a prospective study, case controlled, in a single-institution and conducted between 2001-2006. The full report can be found in Clinical Infectious Diseases, January 1, 2010 issue. The lead author was E.F. Berbari from the Mayo Clinic College of Medicine, along with a bevy of authors, some of which were from the Department of Periodontics, Burnsville, Minnesota, and the Department of Endodontics, Virginia Commonwealth University.

There were 339 case patients and 339 control patients evaluated between December 2001 and May 2006. Case patients were those diagnosed with prosthetic hip or knee infections who were hospitalized at the Mayo Clinic. The control subjects were patients with prosthetic hips or knees with no infections, but who were hospitalized for: (1) an arthroplasty of a different site or side of the index total hip or knee arthroplasty, (2) for aseptic revision of the index arthroplasty, or (3) for other orthopedic procedures. Dental records were obtained from each patient's dentist. Dental procedures were categorized into low-risk and high-risk procedures. Low-risk procedures included restorative dentistry, dental filling, endodontic treatment, and fluoride treatment. High-risk procedures included dental hygiene, mouth surgery, periodontal treatment, dental extraction, and therapy for dental abscess. Hip or knee infections were determined using routine microbiological techniques that isolated the bacterial flora. In addition, a dental propensity score was calculated for each patient that predicted the propensity of each patient to visit a dentist.

The primary risk factor was whether a patient had a high risk or low risk dental procedure and whether, at the time of the procedure closest to the study date, the patient had antibiotic prophylaxis. The risk factor was defined at 4 levels: (1) patient did not have dental procedure in the observation period (reference level), (2) was an edentulous patient, none of whom had a dental visit , (3) patient had a dental procedure without antibiotic prophylaxis, and (4) patient had a dental procedure with antibiotic prophylaxis.


The total numbers of patients enrolled in the study were 339 case patients with prosthetic hip or knee infections and 339 control patients with prosthetic hip or knee replacement but no infections. There was no increased risk of prosthetic hip or knee infection for patients undergoing a high-risk or low-risk dental procedure who were not administered antibiotic prophylaxis (adjusted odds ratio (OR) 0.8; 95% confidence interval (CI), 0.4-1.6), compared with the risk for patients not undergoing a dental procedure (adjusted OR, 0.6; 95% CI, 0.4-1.1) respectively.

Of the case patients, 292 were dentate individuals and 47 were edentulous. Of the control patients, 313 were dentate individuals and 26 were edentulous. Among the dentate case patients, 192 (66%) had undergone a low-risk dental procedure over a 2-year observation period. Among the dentate control patients, 161 (51%) had undergone a low-risk dental procedure over the same 2-year observation period. In addition, 164 of the case patients and 146 of the control patients had undergone a high-risk dental procedure over the 2-year period.

The status of oral health was then compared between case patients and control patients during the 24 months that preceded the enrollment date. Among dentate case patients, the mean number of tooth brushings per week (mean + standard deviation) was 11.7 + 5.7 for case patients and 11.9 + 5.5 for control patients. Eighty-eight of the dentate case patients had >1 dental hygiene visit; 152 of the dentate control patients had >1 dental hygiene visit. Statistically, it was determined that there was no difference in the risk of developing prosthetic hip or knee infection between a patient with at least 1 dental hygiene visit relative to a patient with no visits.

Among the 339 case patients, 259 (76%) had a diagnosis of prosthetic hip or knee infection established within 10 days before or after the study date. Staphylococci were the most commonly encountered organisms isolated from the infection sites. Thirty-five (13.5%) of the prosthetic hip or knee infection cases were associated with bacterial flora of potential oral or dental origin.

Low-risk and high-risk dental procedures performed within 6 months or 2 years of the hospital admission of infected prosthetic joints were not significantly associated with an increased risk of prosthetic hip or knee infection, compared with no dental procedure.

Odds ratio (OR) estimates were used to assess the effect of antibiotic prophylaxis on the risk of prosthetic joint infections. Low-risk and high-risk dental procedures with antibiotic prophylaxis were compared with the same risk procedure without prophylaxis. The OR estimate was 0.7 (95% CI 0.3-1.5) for low-risk procedures and 0.7 (95% CI 0.3-1.4) for high-risk procedures performed within 6 months of hospital admission. The OR estimate was 1.2 (95% CL 0.7-2.2) for low-risk procedures and 0.9 (95% CI 0.5-1.6) for high-risk procedures performed within 2 years before hospital admission date. These odd ratios and 95% confidence limit values indicated no significant differences between the risk of prosthetic joint infections with and without antibiotic prophylaxis.

The 35 patients with prosthetic hip or knee infection associated with dental flora pathogens were compared to a randomly selected group of 35 control patients. The data showed no increased risk of total hip or knee infection regardless of the use of antibiotic prophylaxis.

The study also addressed whether dental procedures were a risk factor for subsequent prosthetic hip or knee infections in patients who were immunocompromised, had diabetes, had a prior arthroplasty, had duration of prosthetic joint infection symptoms of <8>

  • There was no increased risk of prosthetic hip or knee infection for patients undergoing a high-risk or low-risk dental procedure who were not administered antibiotic prophylaxis compared with the risk for patients not undergoing a dental procedure.
  • Antibiotic prophylaxis in high-risk or low-risk dental procedures did not decrease the risk of subsequent total hip or knee infection.

  • Discussion Points

    1. The results of this large, prospective, case-controlled study at the Mayo Clinic showed that the use of antibiotic prophylaxis prior to dental procedures did not alter the subsequent risk of prosthetic hip or knee infection.
    2. The ADA/AAOS 2003 advisory panel recommends that antibiotic prophylaxis be considered in those patients who are believed to be at increased risk, and that prophylaxis is not needed in otherwise healthy patients after two years of implant surgery.
    3. The recent information statement by the AAOS (see May 2009 Clinical Perspective) has advocated using antibiotic prophylaxis in all patients with a joint prosthesis.
    4. This Mayo Clinic study suggests that the risk of prosthetic hip or knee infection following dental procedures is not increased in those groups previously identified as being at risk.
    5. The majority of prosthetic hip or knee infections are due to staphylococci. Bacterial species from dental procedures include viridians group streptococci, beta-hemolytic streptococci, and gram-positive anaerobes, species not ordinarily associated with prosthetic hip or knee infections.

    Oral Hygiene and Risk of Joint Infection

    Poor dental hygiene, periodontal, and periapical infections probably produce bacteremia in the absence of dental procedures. In the Mayo Clinic study, the authors indicated that patients with >1 dental hygiene visit were 30% less likely to develop prosthetic hip or knee infection. The authors' suggested that the reported prosthetic joint infections attributed to dental procedures were more likely to have been caused by bacteremia related to routine daily activities than by bacteremia related to dental procedures.

    In view of the previous statement, the authors emphasize that it is inconsistent to recommend prophylaxis of prosthetic hip or knee infection for dental procedures but not to recommend prophylaxis for the same patients during routine daily activities. Of course, a recommendation for universal prophylaxis for routine daily activities is impractical and impossible. However, it is important to emphasize that maintaining good oral hygiene and eradicating dental disease is a key to decreasing the frequency of bacteremia from routine daily activities.

    Accompanying Editorial to the Mayo Clinic Report

    In the same issue of Clinical Infectious Diseases, there is an editorial entitled "Antibiotics for Prevention of Periprosthetic Joint Infection Following Dentistry: Time to Focus on Data," by W. Zimmerli and P. Sendi. This editorial made the following points:

    1. Prosthetic joint infections occur in 0.3% to 1% of patients undergoing total hip arthroplasty and in 1% to 2% in patients after knee arthroplasty. Most of episodes are sequalea of Staphylococcus aureus sepsis, skin infection, or infections of the urinary tract.
    2. Although it is conceivable that a small portion of the infections are caused by transient bacteremia during dental procedures, clinical experience does not favor this hypothesis.
    3. The present statement by the AAOS recommends that clinicians consider antibiotic prophylaxis for all total joint replacement patients prior to any invasive procedure that may cause bacteremia. Physicians and dentists will follow these latest recommendations. But here are the consequences: general prophylaxis increases the unjustified use of antibiotics, the risk of adverse effects (toxicity and allergy) will probably outweigh any prevention of prosthetic joint infection, and the dentist could be sued for not giving antibiotics according to the AAOS guidelines.
    4. Clear conclusive data obtained from clinical studies can help in resolving the question of whom to premedicate with antibiotics.
    5. This editorial reminds the physicians and the dental community that the Mayo Clinic study has the potential to reassure the responsible physicians and dentists that antibiotic prophylaxis is not needed for all patients with total joint replacement prior to any dental procedure and to convince individuals with joint replacement that meticulous dental hygiene is important.


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