Prevention of deep infection in joint replacement surgery

Bacterial colonization and resistance patterns in 133 patients undergoing a primary hip- or knee replacement in Southern Sweden

BACKGROUND AND PURPOSE

Prosthetic joint infections can be caused by bacteria derived from the patient's skin. The aim of the study was: (1) to determine which bacteria colonize the nose and groin in patients planned for primary hip or knee arthroplasty, (2) to determine the antimicrobial resistance patterns, and (3) to monitor changes in bacterial colonization and resistance patterns connected to surgery.

PATIENTS AND METHODS

2 weeks before scheduled primary hip or knee arthroplasty, culture samples were taken from the anterior nares and from the groin of 133 consecutive patients. At surgery, cloxacillin was given prophylactically and cement with gentamicin was used. 2 weeks after surgery, another set of samples were taken from 120 of these patients. Bacterial findings and resistance patterns were analyzed.

RESULTS

Preoperatively, 95% of the patients had coagulase-negative staphylococci (CNS) in the groin and 77% in the nose. The proportion of patients with a methicillin-resistant CNS in the groin increased from 20% preoperatively to 50% postoperatively (p < 0.001), and the proportion of patients with a gentamicin-resistant CNS in the groin increased from 5% to 45% (p < 0.001). 28% of the patients had Staphylococcus aureus in the nose preoperatively, and 7% in the groin. Methicillin-resistant Staphylococcus aureus (MRSA) was found in the nose of 1 patient.

INTERPRETATION

In southern Sweden, beta-lactams were effective against 99% of the Staphylococcus aureus strains and 80% of the CNS strains colonizing the patients undergoing primary hip or knee arthroplasty. Gentamicin protects against most CNS strains in cemented primary joint replacements.

Metal-on-metal joint bearings and hematopoetic malignancy

This is a review of the hip arthroplasty era. We concentrate on new metal bearings, surface replacements, and the lessons not learned, and we highlight recent reports on malignancies and joint implants. A low incidence of blood malignancies has been found in bone marrow taken at prosthetic surgery. The incidence is increased after replacement with knee implants that release very low systemic levels of metal ions. A carcinogenic effect of the high levels of metal ions released by large metal-on-metal implants cannot be excluded. Ongoing Swedish implant registry studies going back to 1975 can serve as a basis for evaluation of this risk.

Monitoring the one year postoperative infection rate after primary total hip replacement

PURPOSE

Infection of a total hip replacement is potentially a devastating complication. Statistical process control methods have been generating interest as a means of improving the quality of healthcare, and we report our experience with the implementation of such a method to monitor the one year infection rate after primary total hip replacement.

METHOD

Infection was defined as the growth of the same organism in cultures of at least two aspirates or intra-operative specimens, or growth of one pathogen in a patient with local signs of infection such as erythema, abscess or draining sinus tract. The cumulative summation test (CUSUM test) was used to continuously monitor the one year postoperative infection rate. The target performance was 0.5% and the test was set to detect twice that rate.

RESULTS

Over the three year study period, 2006 primary total hip replacements were performed. Infection developed within one year after surgery in eight (0.4%) hips. The CUSUM test generated no alarms during the study period, indicating that there was no evidence that the process was out of control.

CONCLUSION

The one year infection rate after primary total hip replacement was in control. The CUSUM test is a useful method to continuously ensure that performance is maintained at an adequate level.

Variation in the IL1B, TNF and IL6 genes and individual susceptibility to prosthetic joint infection

Background

Prosthetic joint infection (PJI) is an important failure mechanism of total joint arthroplasty (TJA). Here we examine whether the particular genetic variants can lead to increased susceptibility to PJI development.

Results

We conducted a genetic-association study to determine whether PJI could be associated with functional cytokine gene polymorphisms (CGP) influencing on innate immunity response. A case–control design was utilized and previously published criteria for PJI were included to distinguish between cases and control subjects with/without TJA. Six single nucleotide polymorphisms (SNPs) located in the genes for interleukin-1beta (SNP: IL1B-511, +3962), tumour necrosis factor alpha (TNF-308, -238) and interleukin-6 (IL6-174, nt565) were genotyped in 303 Caucasian (Czech) patients with TJA (89 with PJI / 214 without PJI), and 168 unrelated healthy Czech individuals without TJA. The results showed that carriers of the less common IL1B−511*T allele were overrepresented in the group of TJA patients with PJI (69%) in comparison with those that did not develop PJI (51%, p = 0.006, p_corr = 0.037) and with healthy controls (55%, p = 0.04, p_corr = N.S.). There was no significant difference in the distribution of the remaining five investigated CGPs and their haplotypes between groups.

Conclusion

A functional variant of the gene encoding for IL-1beta was preliminarily nominated as a genetic factor contributing to the susceptibility to PJI. Our results should be independently replicated; studies on the functional relevance of IL1B gene variants in PJI are also needed.

Existing data sources for clinical epidemiology: The Danish Knee Arthroplasty Register

Purpose

We described the settings, organization, content, and data quality of the Danish Knee Arthroplasty Register (DKR), as well as the incidence and the first results of the knee replacement procedures captured by the DKR. Our aim was to draw researchers’ attention to the DKR and its potential use in clinical epidemiological research.

Patients and methods

The DKR has collected data on all knee replacement procedures performed in Denmark since 1997. The validity of the register was compared with the Danish National Registry of Patients (DNRP). Incidence rate was calculated per 100,000 inhabitants. Implant survival was estimated by Kaplan–Meier method. Cox regression analyses were used to estimate the relative risk (RR) for revision with a 95% confidence interval (CI).

Results

A total of 62,586 primary knee arthroplasties and 6,683 revisions were registered in the DKR between January 1, 1997 and December 31, 2010. More than 90% of the private and public hospitals performing knee replacement surgery in Denmark have entered data to the DKR. Registration completeness of primary procedures and revisions has increased since the DKR initiation and was 88% in 2010 for both procedures, compared with registration in the DNRP. For primary knee arthroplasties, the annual incidence rate increased from 35.8 in 1997 to 155.2 in 2010 per 100,000 inhabitants. Incidence was higher in females than in males during the entire study period, and increased with age for both sexes. The overall implant survival after 14 years was 89% irrespective of diagnosis for surgery. Male patients had higher revision risk than females, and revision risk decreased with increasing age. Risk for any revision was higher for uncemented implants (RR = 1.48; 95% CI: 1.32–1.66), and lower for hybrid implants (RR = 0.84; 95% CI: 0.75–0.95) compared to cemented implants. Implant survival did not improve but remained the same throughout the study period when comparing patients operated in the periods 1997–2000 versus 2001–2003, 2004–2006, and 2007–2010.

Conclusion

The DKR is a valuable tool for quality monitoring and research in knee arthroplasty surgery due to the high quality and completeness of prospective, routinely collected data. Large population-based epidemiological studies can be performed in order to study trends as well as risk factors for poor clinical outcome following knee arthroplasty surgery.

[Prevention of periprosthetic joint infections]

High numbers of primary joint replacement procedures lead to increasing numbers of revision surgeries due to periprosthetic joint infections. Several studies revealed different patient-associated and intervention-associated risk factors. Importance should be pointed on short operating times to avoid intraoperative colonisation of the implant with microorganisms. Patient-associated diseases such as diabetes and obesity should be influenced positively in the preoperative setting. Cessation of smoking should be started two months before surgery and continued until wound healing is completed. Intraoperative single-shot antibiotic prophylaxis has become clinical routine. Prolonged perioperative antibiotic prophylaxis is often conducted but has not shown to be effective in lowering infection rates.

Comparison of the Norwegian knee arthroplasty register and a United States arthroplasty registry

Several national total joint arthroplasty registries exist outside of the United States (U.S.) and have been used to compare rates and outcomes of total knee arthroplasty. Within the U.S., regional arthroplasty registries provide an opportunity to compare U.S. practices and outcomes with those of other countries. The purpose of this study was to compare the demographics, choice of implants, techniques, and outcomes of total knee arthroplasties in Norway to those from a large, U.S. integrated health-care system and to determine the feasibility of using aggregate-level data for international registry comparisons. The study sample consisted of 25,004 primary total knee arthroplasties performed in Norway and 56,208 from the Kaiser Permanente health-care system. Summary-level data were used to compare the two cohorts. At the time of the seven-year follow-up, the cumulative survival of the total knee prosthesis was 94.8% for the arthroplasties performed in Norway and 96.3% for those performed at Kaiser Permanente. The primary reasons for revision arthroplasty included infection, instability, pain, and aseptic loosening. Patient characteristics, selection of implants, surgical techniques, and outcomes differed between the cohorts. Harmonization of data elements and definitions is necessary for future international research.

A Scandinavian experience of register collaboration: the Nordic Arthroplasty Register Association (NARA)

BACKGROUND

The Nordic (Scandinavian) countries have had working arthroplasty registers for several years. However, the small numbers of inhabitants and the conformity within each country with respect to preferred prosthesis brands and techniques have limited register research.

METHODS

A collaboration called NARA (Nordic Arthroplasty Register Association) was started in 2007, resulting in a common database for Denmark, Norway, and Sweden with regard to hip replacements in 2008 and primary knee replacements in 2009. Finland joined the project in 2010. A code set was defined for the parameters that all registers had in common, and data were re-coded, within each national register, according to the common definitions. After de-identification of the patients, the anonymous data were merged into a common database. The first study based on this common database included 280,201 hip arthroplasties and the second, 151,814 knee arthroplasties. Kaplan-Meier and Cox multiple regression analyses, with adjustment for age, sex, and diagnosis, were used to calculate prosthesis survival, with any revision as the end point. In later studies, specific reasons for revision were also used as end points.

RESULTS

We found differences among the countries concerning patient demographics, preferred surgical approaches, fixation methods, and prosthesis brands. Prosthesis survival was best in Sweden, where cement implant fixation was used more commonly than it was in the other countries.

CONCLUSIONS

As the comparison of national results was one of the main initial aims of this collaboration, only parameters and data that all three registers could deliver were included in the database. Compared with each separate register, this combined register resulted in reduced numbers of parameters and details. In future collaborations of registers with a focus on comparing the performances of prostheses and articulations, we should probably include only the data needed specifically for the predetermined purposes, from registers that can deliver these data, rather than compiling all data from all registers that are willing to participate.

Infection after primary hip arthroplasty: a comparison of 3 Norwegian health registers

BACKGROUND AND PURPOSE

The aim of the present study was to assess incidence of and risk factors for infection after hip arthroplasty in data from 3 national health registries. We investigated differences in risk patterns between surgical site infection (SSI) and revision due to infection after primary total hip arthroplasty (THA) and hemiarthroplasty (HA).

MATERIALS AND METHODS

This observational study was based on prospective data from 2005-2009 on primary THAs and HAs from the Norwegian Arthroplasty Register (NAR), the Norwegian Hip Fracture Register (NHFR), and the Norwegian Surveillance System for Healthcare-Associated Infections (NOIS). The Norwegian Patient Register (NPR) was used for evaluation of case reporting. Cox regression analyses were performed with revision due to infection as endpoint for data from the NAR and the NHFR, and with SSI as the endpoint for data from the NOIS.

RESULTS

The 1-year incidence of SSI in the NOIS was 3.0% after THA (167/5,540) and 7.3% after HA (103/1,416). The 1-year incidence of revision due to infection was 0.7% for THAs in the NAR (182/24,512) and 1.5% for HAs in the NHFR (128/8,262). Risk factors for SSI after THA were advanced age, ASA class higher than 2, and short duration of surgery. For THA, the risk factors for revision due to infection were male sex, advanced age, ASA class higher than 1, emergency surgery, uncemented fixation, and a National Nosocomial Infection Surveillance (NNIS) risk index of 2 or more. For HAs inserted after fracture, age less than 60 and short duration of surgery were risk factors of revision due to infection.

INTERPRETATION

The incidences of SSI and revision due to infection after primary hip replacements in Norway are similar to those in other countries. There may be differences in risk pattern between SSI and revision due to infection after arthroplasty. The risk patterns for revision due to infection appear to be different for HA and THA.

Timing of preoperative antibiotics for knee arthroplasties: Improving the routines in Sweden

Background

A slight increase in revisions for infected joint arthroplasties has been observed in the Nordic countries since 2000 for which the reasons are unclear. However, in 2007 a Swedish study of the timing for prophylactic antibiotics in a random sample of knee arthroplasties found that only 57% of the patients had received the antibiotic during the optimal time interval 45-15 minutes before surgery. The purpose of the report was to evaluate the effect of measures taken to improve the timing of prophylactic antibiotics.

Findings

Reporting this finding to surgeons at national meetings during 2008 the Swedish Knee Arthroplasty Register (SKAR) introduced a new report form from January 2009 including the time for administration of preoperative antibiotics. Furthermore, the WHO's surgical checklist was introduced during 2009 and a national project was started to reduce infections in arthroplasty surgery (PRISS). The effect of these measures was found to be positive showing that in 2009, 69% of the 12,707 primary knee arthroplasties were reported to have received the prophylaxis within the 45-15 min time interval and 79% of the first 7,000 knee arthroplasties in 2010. A survey concerning the use of the WHO checklist at Swedish hospitals showed that 73 of 75 clinics had introduced a surgical checklist.

Conclusions

By registration and bringing back information to surgeons on the state of infection prophylaxis in combination with the introduction of the WHO checklist and the preventive work done by the PRISS project, the timing of preoperative prophylactic antibiotics in knee arthroplasty surgery was clearly improved.

Clinical outcome and microbiological findings using antibiotic-loaded spacers in two-stage revision of prosthetic joint infections

OBJECTIVES

Antibiotic-loaded spacers may improve antimicrobial efficacy in two-stage revision of prosthetic joint infections, but they may also interfere in the course of infection. This prospective study of prosthetic joint infections managed with two-stage revision and antibiotic-loaded spacers (2004-09) analyzes case outcomes and proposes a second-stage culture interpretation scheme.

METHODS

Second-stage infection was diagnosed upon second-stage cultures (synovial membranes, joint fluid, spacers), as either superinfection (≥2 samples, new organism) or persistence (≥1 samples, previously isolated organism). Isolated positive antibiotic-loaded spacers cultures were considered as colonizations.

RESULTS

Of 42 patients, two had two prosthetic infections (n = 44): 25 knees, 19 hips. Spacers contained gentamicin (33), vancomycin (10) and aztreonam (1). Three patients (7%) with wound healing impairment required debridement and spacer exchange. The remainder underwent second-stage surgery as planned: 34 (77%) new arthroplasties, five arthrodeses, one resection arthroplasty and one permanent spacer. Of 18 cases (44%) with ≥1 positive sample, only four (10%) were second-stage infections. Fourteen antibiotic-loaded spacers cultures (34%) were positive. Four new prostheses (9%) supervened further infections: one by the organism isolated in the spacer, three by new bacteria.

CONCLUSIONS

The findings of second-stage cultures show that the surgical site is frequently non-sterile at reimplantation. Isolated positive antibiotic-loaded spacer cultures usually have no clinical consequences, but together with tissue cultures they help to diagnose second-stage infections when clinical signs are absent.