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The use of antibiotic-laden cement in primary TKR may not be justified
Our chief medical editor poses his 4 Questions about choosing the ideal prophylactic antibiotic following total knee replacement to Robert S. Namba, MD.
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Introduction
Antibiotic-laden cement is used by an increasing number of orthopedic surgeons each year during both primary and revision knee replacement. An immediate question is which antibiotic should be used and at what concentration is the most ideal? Is there any scientific basis for choosing to use one that justifies adding an additional cost to the procedure? Is it more to alleviate surgeon’s concerns or are the outcomes actually improved for the patient?
To shed some light on these issues for our readers, and me, I have turned to Robert S. Namba, MD, for his insights and experience.
Douglas W. Jackson, MD
Chief Medical Editor
Douglas W. Jackson, MD: What evidence is there that antibiotic-laden cement alters the infection rate in primary total knee replacement?
Robert S. Namba, MD: There is no evidence that the prophylactic use of commercially available (low dose) antibiotic-laden bone cement (ALBC) significantly alters infection rates in primary total knee arthroplasty (TKA). Much of the early success of ALBC was originally reported out of Scandinavia for cemented total hip arthroplasty, where reduction of infection rates led to a nationwide adoption of hand-mixed ALBC.
Commercial ALBC became available in the United States in 2003. Prior to pre-mixed ALBC, there were reports of the efficacy of hand-mixed ALBC in primary TKA. These include a single-surgeon series of 178 cases where cefuroxime was mixed with Simplex P cement (Stryker) and the same author’s experience with cefuroxime impregnated cement in 41 patients with diabetes. Decreased infection rates were noted in the ALBC group compared with the control group, but the surgical environment in which the procedures were performed did not include clean-air measures (potentiating the risk of infection in the control group).
There is no commercially available ALBC containing cephalosporins, and the potential for allergic reactions likely preclude future development.
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An analysis of infection rates in primary TKA with, and without, commercially available ALBC was performed using the Kaiser Permanente Total Joint Registry, which has been prospectively tracking arthroplasty cases since 2001 and now contains over 100,000 joint replacement procedures. Clinical outcomes are followed annually with detailed information on patient factors, the surgical technique, the surgical implants and the institution where surgical care is provided.
Specifically, the retrospective study compared 2,030 TKA procedures using ALBC and 20,859 cases without ALBC. Paradoxically, a statistically significant increased infection rate was noted in the ALBC cohort (1.4%) compared to the standard cement cohort (0.9%). Antibiotic-laden bone cement was chosen by surgeons for patients considered to be at higher risk for infection, but the addition of low-dose antibiotics in the cement did not reduce TKA infection rates.
Current usage of low dose ALBC within Kaiser Permanente is about 17%, but is slowly increasing.
In a recent study performed at an academic Canadian institution, it was observed again that commercially prepared ALBC did not significantly reduce infection rates of primary TKA.
With contemporary surgical clean air facilities, prophylactic intravenous antibiotics, and proper patient selection, commercially available ALBC has not been shown to reduce infection rates of TKA procedures in North America.
Jackson: How does a clinician choose the ideal prophylactic antibiotic?
Namba: The only commercially available ALBC contain either tobramycin (1 g per 40 g bone cement) or gentamicin (0.5 g to 1 g per 40 g bone cement). There is no clinical evidence identifying greater efficacy of either of these aminoglycosides. However, gentamicin-resistant bacteria have been demonstrated during revision of primary arthroplasties performed with gentamicin-containing bone cement. Therefore, if ALBC were to be used in a revision procedure, a different antibiotic could be considered for the re-operation.
Jackson: What are the cost considerations related to justifying, or not, of its use?
Namba: Typically, a 40-mg bag of ALBC costs three times that of standard polymethylmethacrylane (PMMA). If prosthetic infections could be reduced, the cost would be justified by avoidance of costly revision procedures and prolonged intravenous antibiotics.
However, as discussed earlier, no clinical study has demonstrated efficacy of commercially available ALBC in reducing infection rates for TKA. Development of resistant bacteria is a concern if the low-dose gentamicin or tobramycin in commercially available ALBC provides only subinhibitory levels of the antibiotic. Exposing bacteria to such levels could lead to development of mutational resistance. In such a scenario, widespread use of low-dose ALBC could prove prohibitively costly.
Jackson:Many surgeons add additional antibiotics to the cement. What are the concerns related to changing the properties (and possible function) of the cement?
Namba: Admixture of antibiotics has been demonstrated to decrease the shear and compressive mechanical properties of PMMA. The uniform distribution and low dose of commercially available ALBC probably does not lead to a clinically significant reduction in fatigue strength. Hand-mixing, however, could lead to clumping, inclusion voids, and use of higher antibiotic doses (typical used with hand-mixing), causing potentially significant reduction in cement fatigue strength.
References:
- Chiu FY, Chen, CM, Lin CR, Lo WH. Cefuroxime-impregnated cement in primary total knee arthroplasty: A prospective randomized study of three hundred and forty knees. J Bone Joint Surg (Am). 2002;84:759-762.
- Espehaug B, Engesaeter LB, Vollset SE, et al. Antibiotic prophylaxis in total hip arthroplasty. Review of 10,905 primary cemented total hip replacements reported to the Norwegian arthroplasty registry 198 to 1995. J Bone Joint Surg (Br). 1997;79:590-595.
- Gandhi R, Razak F, Pathy R, et al. Antibiotic bone cement and the incidence of deep infection after total knee arthroplasty. J Arthroplasty. 2009;24(7):1015-1018.
- Jiranek WA, Hanssen AD, Greenwald AS. Current Concepts Review. Antibiotic-loaded bone cement for infection prophylaxis in total joint replacement. J Bone Joint Surg (Am). 2006;88: 2487-2500.
- Namba R, Chen Y, Paxton L, et al. Outcomes of routine use of antibiotic–loaded cement in primary total knee arthroplasty. J Arthroplasty. 2009; 24(6): 44-47.
Robert S. Namba, MD, is an orthopedic surgeon with Kaiser Permanente. He can be reached at 6670 Alton Parkway, Irvine, CA 92618; 949-932-5190; e-mail: robert.s.namba@kp.org.
