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Infections following total knee arthroplasty: Defining the role of the orthopedic surgeon
In this 4 Questions interview, Kevin L. Garvin, MD, explains infection rates, risk factors for infection and the needed preoperative preparation.
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Infection following a total knee replacement is often a devastating experience for the patient as it prolongs their ultimate recovery and generates significant additional expenses. I asked Kevin L. Garvin, MD, four questions this month that relate to what we know about the rate of infection and some of the common risk factors. Reducing the incidence of these infections takes constant vigilance as does the preoperative assessment to reduce risk factors. In addition, the information that Dr. Garvin shares will assist as a comparison for data generated in our institutions.
— Douglas W. Jackson, MD
Chief Medical Editor
Douglas W. Jackson, MD:What information do we have on the infection rate following total knee replacement in the United States?
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Kevin L. Garvin, MD: The information available to orthopedic surgeons about the infection rate of total knee replacement in North America is included in several articles. First, the Medicare data indicates that the rate of prosthetic infection within the first 2 years after knee arthroplasty is 1.55%. The infection rate in the next 2 years to 10 years following surgery is an additional 0.46%. The information does not include patients who develop an infection after revision knee surgery.
Jackson: What are some of the identified risk factors that have been associated with an increased chance of developing a postoperative infection?
Garvin: Several factors are known to increase the risk of prosthetic joint infection. The factors include diabetes, rheumatoid arthritis, malnutrition, smoking, obesity, steroids, excessive anticoagulation, chemotherapy, cancer, alcoholism, urinary tract infection, complex surgery or revision surgery and multiple blood transfusions.
Jackson: As obesity is a common entity in patients needing knee replacements, what information can you share with Orthopedics Today readers on the preoperative preparation of these patients?
Garvin: Winiarsky et al compared a group of morbidly obese patients who had 50 total knee arthroplasties (TKAs) with a control group of non-morbidly obese patients who had a total of 1,768 TKAs. In the morbidly obese group, there was a 22% rate of wound complications (11 patients) and 5 deep infections. In contrast, the control group had a 2% rate of wound complications and a 0.6% rate of deep infections. The information suggests that we should do as much as we can to lessen the risk of infection in these morbidly obese patients.
Nutritional status of these patients may not be normal, and it should be evaluated by measuring their serum albumin and transferrin levels as well as their total lymphocyte count. If their nutritional status is poor (transferrin <200 mg/dL), albumin level of < 0.35 g/dL or total lymphocyte count of <1500 cells/mm3), then the patients should be referred to their primary care provider or a nutritionist. The consultation should be done prior to the TKA so this can be approved.
Alternatively, the obese patients may be counseled about ways to reduce their weight. If a morbidly obese patient has an adequate nutritional status and is unable to lose the weight on their own, then he or she may be a candidate for bariatric surgery. Bariatric surgery would be performed prior to the TKA.
Jackson: Does Staphylococcus aureus remain the most common organism? Are we seeing any trends related to it and other organisms?
Garvin: Staphylococcal infections are the most common cause of prosthetic joint infection. Staphylococcus aureus and coagulase negative Staphylococcus account for these infections. It is troubling that a percentage of the Staphylococcus is methicillin-resistant.
Recent information has shown that there is a decrease in the number of health care-associated methicillin-resistant Staphylococcus aureus (MRSA) infections. The incidence rate of hospital-onset invasive MRSA infections decreased 9.4% per year from 2005 to 2008. The findings are corroborated by a second study on MRSA central line associated bloodstream infections that reported data from hundreds of different intensive care units and up to 50% to 70% decrease between 2001 and 2007. The reasons for the decrease are not clear, but are believed to be multifactorial. It is also unknown whether the trends will continue. Orthopedic surgeons play an important role in helping to lower this rate of methicillin-resistant infections by the judicious use of vancomycin and by avoiding prolonged hospitalization of their patients.
References:
- Bozic KJ, Kurtz SM, Lau E, et al. The epidemiology of revision total knee arthroplasty in the United States. Clin Orthop Relat Res. 2010;468(1):45-51.
- Kurtz SM, Ong KL, Lau E, et al J. Prosthetic joint infection risk after TKA in the Medicare population. Clin Orthop Relat Res. 2010;468 (1):52-56.
- Mahomed NN, Barrett J, Katz JN, et al. Epidemiology of total knee replacement in the United States Medicare population. J Bone Joint Surg Am. 2005;87(6):1222-1228.
- Wilson MG, Kelley K, Thornhill TS. Infection as a complication of total knee-replacement arthroplasty. Risk factors and treatment in sixty-seven cases. J Bone Joint Surg Am. 1990;72(6):878-83.
- Windsor RE, Bono JV. Infected total replacements. J Am Acad Orthop Surg. 1994; 2(1):44-53.
- Kevin L. Garvin, MD, can be reached at University of Nebraska Medical Center, 42nd and Emile, Omaha, NE 68198-1080; 402-559-5605; email: kgarvin@unmc.edu.
- Disclosure: Garvin has no relevant financial disclosures.