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Routinely using antibiotic bone cement in THA is justified by the literature
Overall it saves costs, and data indicate that its use may increase prosthesis survival.
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By way of statistics, it is true that in high-volume specialized centers in the United States, the infection rate has been lowered to less than 1%; however, the majority of the hip arthroplasty cases are being done in the trenches by community surgeons. For them, Medicare data on a large number of patients would suggest that the infection rate is about 2.2%.
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Infection is still a significant issue, particularly when you consider the number of procedures that are performed each year.
A 2003 award-winning study published in Acta Orthopaedica from the Norwegian Hip Registry looked at 22,000 hip replacements. The data is clear in regards to 10-year survivorship for all prostheses — with all reasons for revision — that using antibiotics in the cement improved the survivorship of both aseptic and septic loosening. This has not been lost on the Norwegians and you can see what is happening in terms of the utilization of antibiotic cement: The amount of hip arthroplasties performed without antibiotics are dwindling down basically to zero. Now, nearly all the cases implanted with cement also incorporate antibiotics.
Lowest risk ratio
We had seen for years the risk-ratio statistics that have been published by the Swedish Hip Registry, which show clearly that antibiotic- impregnated cement has the lowest risk ratio for both septic and aseptic loosening, which is an interesting fact in itself. I think that there is a homogenization toward the use of antibiotic-impregnated cement. Over 95% of all cemented implants incorporate antibiotics within the cement.
It is no coincidence that if you look at the cumulative survivorship curves, the cumulative revision rate is improving with every 5-year period. It is also no coincidence that, with this homogenization toward antibiotic-impregnated cement, the deep infection rate, as a reason for revision, is decreasing significantly over time.
We are seeing similar things in Canada where we have our own registry. Looking at the 2005 and 2006 data on all cemented implants, the majority incorporate antibiotic-impregnated cement. The evidence feeds back resulting in a quality improvement loop.
Non-registry data
What about nonregistry data? A meta-analysis of 22 papers from Block looked at the effect of antibiotic impregnated cement in joint arthroplasty and concluded that when surgeries are performed in ultra-clean air conditions, the revision rate decreased by half for those patients treated with antibiotic- loaded cement. They went on to say that antibiotic-impregnated cement is consistently superior to plain cement and it had an independent and additive effect when combined with other prophylactic measures.
Despite this evidence, we get a lot of arguments about why we shouldn’t be using antibiotic-impregnated cement and, for the sake of simplicity, we can break these down into four main areas: The cost is not justified; there are issues with resistance; the systemic toxicity; and there are adverse effects on mechanical properties.
Cost effective
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The meta-analysis indicted that you decrease your failure rate by half by using antibiotic-impregnated cement. Therefore, based on Medicare data, you go from 2% to 1%. As a result, in every 100 cases you are going to get one less infected hip. In Canada, it is about $340 per case to use antibiotic-impregnated cement; it is significantly less to use nonimpregnated cement. If you do the math, the difference is $25,000. However, we know that it is $50,000-plus to treat an infected hip; therefore, for every 100 hips you do, there is a $25,000 savings to the system considering the revisions for infection. So, I would say that it is highly cost effective.
What about the development of resistance? We know that the antibiotics in the cement elute over time; more than 50% of it is gone after the first week and then it tails off slowly after that. But, I submit to you two scenarios: Which do you think is more likely to cause resistance – using a low-dose prophylaxis that elutes quickly in a healthy environment in a healthy patient with a low virulence load, or where you have an established infection and you are using your big guns for 6 weeks or more and you have dead, denuded tissue with an unhealthy local environment and a high virulence load? I would suggest that you are more likely to get it in the latter scenario.
Toxicity
There are reported cases of toxicity in infected hips when antibiotics are added by the surgeon in high doses to treat the infection. A study from Australia that looked at patients with renal dysfunction and took their serum, urine and renal levels found no toxicity in terms of adverse effects – even in this challenged population.
Allergic reaction is a non sequitur to me; it is the same argument for the systemic antibiotic. If they have an allergy, you either pick a different cement with a different antibiotic, or you don’t use it and tell the patient that the risk for infection will be slightly higher.
Mechanical properties come up often as an issue. There are several papers that show when an antibiotic is added by the manufacturer, there is no effect on the tensile strength of the material. A follow-up paper by the Norwegian group on 56,000 patients shows that when you don’t use antibiotics in your cement, your infection rate is higher.
When you look at aseptic loosening as a reason for failure, hips with an antibiotic have a better survivorship. This may be due to the fact that some cases are being diagnosed as aseptic loosening that are actually infected, but it is clear that there are no adverse effects in terms of mechanical properties based on survivorship. This is backed up by the good RSA (roentgen stereo photogrammetric analysis) data in a randomized control trial in two different kinds of cement. The conclusion is that both cements give good fixation of the femoral component and good clinical results at 2 years.
In conclusion, I think that the registry and meta-analysis data are highly supportive of the use of antibiotic-impregnated cement. The data suggest that it is cost effective with no adverse effects on mechanical properties. I think we should conclude that antibiotic-impregnated cement should be used in all cemented total hip arthroplasties.
For more information:
- Michael J. Dunbar, MD, FRCS(C), PhD, associate professor, Department of Surgery, Division of Orthopaedics, and clinical research scholar, Dalhousie University, can be reached at 902-473-7337; e-mail: michael.dunbar@dal.ca. He has no direct financial interest in any products or companies mentioned in this article.
References:
- Adalberth G, Nilsson KG, Karrholm J, et al. Fixation of the tibial component using CMW-1 of Palacos bone cement with gentamicin: Similar outcomes in a randomized radiosterimetric study of 51 total knee arthroplasties. Acta Orthop Scand. 2002;73(5):531-538.
- Dunbar MJ. Antibiotic bone cements: Their routine use in primary THA is justified — affirms. Paper #101. Presented at Current Concepts in Joint Replacement Spring 2008 Meeting. May 18-21, 2008. Las Vegas.
- Engesaeter LB, Lie SA, Espehauug B, et al. Antibiotic prophylaxis in total hip arthroplasty: Effects of antibiotic prophylaxis systemically and in bone cement on the revision rate of 22,170 primary hip replacements followed 0-14 years in the Norwegian Arthroplasty Register. Acta Orthop Scand. 2003;74(6):644-651.