Infected total hip arthroplasty - Bacteriology and the role of operating room ventilation in the reduction of postoperative infection

Each year approximately 7,000 patients receive a total hip arthroplasty (THA) in Norway. The most common indication is osteoarthritis and most patients experience substantial pain relief postoperatively. A rare but much feared complication after arthroplasty surgery is postoperative prosthetic joint infection (PJI). This is a huge burden for patients and a technical challenge for surgeons, generating huge costs for the health care system and society. Knowledge of how and why these infections arise is essential in order to provide the best possible prophylaxis against and treatment of PJI. The aim of the first part of this thesis was to assess what kind of bacteria cause revisions due to infection after THA (Paper I). We also wanted to assess correlations between bacteriology and haematological findings (Paper I) and antibiotic resistance amongst the bacteria found in THA revisions due to infection (Paper II). We used the Norwegian Arthroplasty Register (NAR) and supplemented this with bacteriological findings including antibiotic resistance patterns and preoperative blood samples including parameters of infection, collected from patient records. As expected, we found a large proportion of Staphylococci, a commensal organism known to be part of normal human skin flora. Coagulase negative staphylococci (CoNS) showed increased resistance to several antibiotics that are used both as prophylaxis and in empirical and definitive treatment of PJI. As the staphylococcus aureus (S. aureus) species led to significantly higher biochemical parameters of infection compared to CoNS, our results might inform the choice of empirical treatment based on haematological status in cases of arthroplasty infection with an unknown causative pathogen. In the second part of the thesis (Papers III and IV), we wanted to enhance understanding of the origin of these infections by assessing operating room ventilation as a prophylactic measure against revision due to infection. The air in the operating room is, in addition to other surgery- and patient-related factors, a possible risk factor for postoperative infection. In Norwegian hospitals there are mainly two ventilation principles that are used to increase the cleanliness of the air: conventional, turbulent, mixing ventilation (CV) and unidirectional airflow (UDF) ventilation, formerly known as laminar airflow (LAF) ventilation, where the latter has in recent years been recommended on a disputed scientific basis. Lack of evidence for reduction in postoperative infection has led to the implementation of UDF systems being questioned as a prophylactic measure against postoperative infection. The NAR holds surgeon-reported data on the type of ventilation used during primary THA. We validated these ventilation data by performing a comprehensive assessment of the historical and present ventilation systems in 40 hospitals in Norway during the period 1987-2015 (Paper III). This was done in cooperation with knowledgeable surgeons and engineers at the relevant hospitals. This assessment showed that not all surgeons knew exactly what kind of ventilation system they performed the THA in, and accordingly may have reported inaccurate data to the register. This might have led to erroneous conclusions in earlier register studies on this topic. A series of such studies using data on ventilation reported by the surgeon or surgical department contributed to the scientific basis for a report on infection reduction from the World Health Organization (WHO) from 2016. This report concluded that UDF systems should not be installed in new operating rooms where arthroplasty is performed. We continued the project by conducting new analyses on the risk of revision due to infection after THA using validated ventilation data (Paper IV). This included sub- analyses of technical specifications of the different systems. We concluded that UDF systems do not increase the risk of infection, as recent literature seems to imply. By performing a sub-classification based on technical specifications, we show that there is substantial variation between the different UDF systems and that the more modern and large UDF systems, offering high volumes of air, show a slight reduction in the risk of revision due to infection after THA compared to CV. This is in concordance with other studies showing that UDF/LAF systems are able to create cleaner air than CV systems. When taking our results into account, considering also the finding of increased antibiotic resistance amongst common causative bacteria of THA, it would be erroneous to discontinue the use of large, high volume, vertical UDF systems in the operating room of the future. We hope and believe that the results of this thesis will have an impact on the ongoing international discussion on operating room ventilation and perioperative care

Infected total hip arthroplasty - Bacteriology and the role of operating room ventilation in the reduction of postoperative infection

Each year approximately 7,000 patients receive a total hip arthroplasty (THA) in Norway. The most common indication is osteoarthritis and most patients experience substantial pain relief postoperatively. A rare but much feared complication after arthroplasty surgery is postoperative prosthetic joint infection (PJI). This is a huge burden for patients and a technical challenge for surgeons, generating huge costs for the health care system and society. Knowledge of how and why these infections arise is essential in order to provide the best possible prophylaxis against and treatment of PJI. The aim of the first part of this thesis was to assess what kind of bacteria cause revisions due to infection after THA (Paper I). We also wanted to assess correlations between bacteriology and haematological findings (Paper I) and antibiotic resistance amongst the bacteria found in THA revisions due to infection (Paper II). We used the Norwegian Arthroplasty Register (NAR) and supplemented this with bacteriological findings including antibiotic resistance patterns and preoperative blood samples including parameters of infection, collected from patient records. As expected, we found a large proportion of Staphylococci, a commensal organism known to be part of normal human skin flora. Coagulase negative staphylococci (CoNS) showed increased resistance to several antibiotics that are used both as prophylaxis and in empirical and definitive treatment of PJI. As the staphylococcus aureus (S. aureus) species led to significantly higher biochemical parameters of infection compared to CoNS, our results might inform the choice of empirical treatment based on haematological status in cases of arthroplasty infection with an unknown causative pathogen. In the second part of the thesis (Papers III and IV), we wanted to enhance understanding of the origin of these infections by assessing operating room ventilation as a prophylactic measure against revision due to infection. The air in the operating room is, in addition to other surgery- and patient-related factors, a possible risk factor for postoperative infection. In Norwegian hospitals there are mainly two ventilation principles that are used to increase the cleanliness of the air: conventional, turbulent, mixing ventilation (CV) and unidirectional airflow (UDF) ventilation, formerly known as laminar airflow (LAF) ventilation, where the latter has in recent years been recommended on a disputed scientific basis. Lack of evidence for reduction in postoperative infection has led to the implementation of UDF systems being questioned as a prophylactic measure against postoperative infection. The NAR holds surgeon-reported data on the type of ventilation used during primary THA. We validated these ventilation data by performing a comprehensive assessment of the historical and present ventilation systems in 40 hospitals in Norway during the period 1987-2015 (Paper III). This was done in cooperation with knowledgeable surgeons and engineers at the relevant hospitals. This assessment showed that not all surgeons knew exactly what kind of ventilation system they performed the THA in, and accordingly may have reported inaccurate data to the register. This might have led to erroneous conclusions in earlier register studies on this topic. A series of such studies using data on ventilation reported by the surgeon or surgical department contributed to the scientific basis for a report on infection reduction from the World Health Organization (WHO) from 2016. This report concluded that UDF systems should not be installed in new operating rooms where arthroplasty is performed. We continued the project by conducting new analyses on the risk of revision due to infection after THA using validated ventilation data (Paper IV). This included sub- analyses of technical specifications of the different systems. We concluded that UDF systems do not increase the risk of infection, as recent literature seems to imply. By performing a sub-classification based on technical specifications, we show that there is substantial variation between the different UDF systems and that the more modern and large UDF systems, offering high volumes of air, show a slight reduction in the risk of revision due to infection after THA compared to CV. This is in concordance with other studies showing that UDF/LAF systems are able to create cleaner air than CV systems. When taking our results into account, considering also the finding of increased antibiotic resistance amongst common causative bacteria of THA, it would be erroneous to discontinue the use of large, high volume, vertical UDF systems in the operating room of the future. We hope and believe that the results of this thesis will have an impact on the ongoing international discussion on operating room ventilation and perioperative care

Increasing Resistance of Coagulase-Negative Staphylococci in Total Hip Arthroplasty Infections: 278 THA-Revisions due to Infection Reported to the Norwegian Arthroplasty Register from 1993 to 2007

We investigated bacterial findings from intraoperative tissue samples taken during revision due to infection after total hip arthroplasty (THA). The aim was to investigate whether the susceptibility patterns changed during the period from 1993 through 2007. Reported revisions due to infection in the Norwegian Arthroplasty Register (NAR) were identified, and 10 representative hospitals in Norway were visited. All relevant information on patients reported to the NAR for a revision due to infection, including bacteriological findings, was collected from the medical records. A total of 278 revision surgeries with bacterial growth in more than 2 samples were identified and included. Differences between three 5-year time periods were tested by the chi-square test for linear trend. The most frequent isolates were coagulase-negative staphylococci (CoNS) (41%, 113/278) and Staphylococcus aureus (19%, 53/278). The proportion of CoNS resistant to the methicillin-group increased from 57% (16/28) in the first period, 1993–1997, to 84% (52/62) in the last period, 2003–2007 (P = 0.003). There was also significant increase in resistance for CoNS to cotrimoxazole, quinolones, clindamycin, and macrolides. All S. aureus isolates were sensitive to both the methicillin-group and the aminoglycosides. For the other bacteria identified no changes in susceptibility patterns were found

Bacterial Findings in Infected Hip Joint Replacements in Patients with Rheumatoid Arthritis and Osteoarthritis: A Study of 318 Revisions for Infection Reported to the Norwegian Arthroplasty Register

High rates of Staphylococcus aureus are reported in prosthetic joint infection (PJI) in rheumatoid arthritis (RA). RA patients are considered to have a high risk of infection with bacteria of potentially oral or dental origin. One thousand four hundred forty-three revisions for infection were reported to the Norwegian Arthroplasty Register (NAR) from 1987 to 2007. For this study 269 infection episodes in 255 OA patients served as control group. In the NAR we identified 49 infection episodes in 37 RA patients from 1987 to 2009. The RA patients were, on average, 10 years younger than the OA patients and there weremore females (70% versus 54%).We found no differences in the bacterial findings in RA and OA. A tendency towards a higher frequency of Staphylococcus aureus (18% versus 11%) causing PJI was found in the RA patients compared to OA. There were no bacteria of potential odontogenic origin found in the RA patients, while we found 4% in OA. The bacteria identified in revisions for infection in THRs in patients with RA did not significantly differ from those in OA. Bacteria of oral or dental origin were not found in infected hip joint replacements in RA

Virus transmission during orthopedic surgery on patients with COVID-19 – a brief narrative review

Background and purpose — COVID-19 is among the most impactful pandemics that the society has experienced. Orthopedic surgery involves procedures generating droplets and aerosols and there is concern amongst surgeons that otherwise rational precautionary principles are being set aside due to lack of scientific evidence and a shortage of personal protective equipment (PPE). This narrative review attempts to translate relevant knowledge into practical recommendations for healthcare workers involved in orthopedic surgery on patients with known or suspected COVID-19. Patients and methods — We unsystematically searched in PubMed, reference lists, and the WHO’s web page for relevant publications concerning problems associated with the PPE used in perioperative practice when a patient is COVID-19 positive or suspected to be. A specific search for literature regarding COVID-19 was extended to include publications from the SARS epidemic in 2002/3. Results — Transmission of infectious viruses from patient to surgeon during surgery is possible, but does not appear to be a considerable problem in clinical practice. Seal-leakage is a problem with surgical masks. Due to the lack of studies and reports, the possibility of transmission of SARS-CoV-2 from patient to surgeon during droplet- and aerosol-generating procedures is unknown. Interpretation — Surgical masks should be used only in combination with a widely covering visor and when a respirator (N95, FFP2, P3) is not made available. Furthermore, basic measures to reduce shedding of droplets and aerosols during surgery and correct and consistent use of personal protective equipment is important

Virus transmission during orthopedic surgery on patients with COVID-19 – a brief narrative review

Background and purpose — COVID-19 is among the most impactful pandemics that the society has experienced. Orthopedic surgery involves procedures generating droplets and aerosols and there is concern amongst surgeons that otherwise rational precautionary principles are being set aside due to lack of scientific evidence and a shortage of personal protective equipment (PPE). This narrative review attempts to translate relevant knowledge into practical recommendations for healthcare workers involved in orthopedic surgery on patients with known or suspected COVID-19. Patients and methods — We unsystematically searched in PubMed, reference lists, and the WHO’s web page for relevant publications concerning problems associated with the PPE used in perioperative practice when a patient is COVID-19 positive or suspected to be. A specific search for literature regarding COVID-19 was extended to include publications from the SARS epidemic in 2002/3. Results — Transmission of infectious viruses from patient to surgeon during surgery is possible, but does not appear to be a considerable problem in clinical practice. Seal-leakage is a problem with surgical masks. Due to the lack of studies and reports, the possibility of transmission of SARS-CoV-2 from patient to surgeon during droplet- and aerosol-generating procedures is unknown. Interpretation — Surgical masks should be used only in combination with a widely covering visor and when a respirator (N95, FFP2, P3) is not made available. Furthermore, basic measures to reduce shedding of droplets and aerosols during surgery and correct and consistent use of personal protective equipment is important

Virus transmission during orthopedic surgery on patients with COVID-19 – a brief narrative review

Background and purpose — COVID-19 is among the most impactful pandemics that the society has experienced. Orthopedic surgery involves procedures generating droplets and aerosols and there is concern amongst surgeons that otherwise rational precautionary principles are being set aside due to lack of scientific evidence and a shortage of personal protective equipment (PPE). This narrative review attempts to translate relevant knowledge into practical recommendations for healthcare workers involved in orthopedic surgery on patients with known or suspected COVID-19. Patients and methods — We unsystematically searched in PubMed, reference lists, and the WHO’s web page for relevant publications concerning problems associated with the PPE used in perioperative practice when a patient is COVID-19 positive or suspected to be. A specific search for literature regarding COVID-19 was extended to include publications from the SARS epidemic in 2002/3. Results — Transmission of infectious viruses from patient to surgeon during surgery is possible, but does not appear to be a considerable problem in clinical practice. Seal-leakage is a problem with surgical masks. Due to the lack of studies and reports, the possibility of transmission of SARS-CoV-2 from patient to surgeon during droplet- and aerosol-generating procedures is unknown. Interpretation — Surgical masks should be used only in combination with a widely covering visor and when a respirator (N95, FFP2, P3) is not made available. Furthermore, basic measures to reduce shedding of droplets and aerosols during surgery and correct and consistent use of personal protective equipment is important

Operating room ventilation and the risk of revision due to infection after total hip arthroplasty: assessment of validated data in the Norwegian Arthroplasty Register

Background The air in the operating room is considered a risk factor for surgical site infection (SSI) due to airborne bacteria shed from the surgical staff or from patients themselves. Aim To assess the influence of validated operating room (OR) ventilation data on the risk of revision surgery due to deep infection after primary total hip arthroplasty (THA) reported to the Norwegian Arthroplasty Register (NAR). Methods Forty orthopaedic units reporting THAs to the NAR during the period 2005–2015 were included. The true type of OR ventilation in all hospitals at the time of primary THA was confirmed in a previous study. Unidirectional airflow (UDF) systems were subdivided into: small, low-volume, unidirectional vertical flow (lvUDVF) systems; large, high-volume, unidirectional vertical flow (hvUDVF) systems; and unidirectional horizontal flow (UDHF) systems. These three ventilation groups were compared with conventional, turbulent, mixing ventilation (CV). The association between the end-point, time to revision due to infection, and OR ventilation was estimated by calculating relative risks (RRs) in a multivariate Cox regression model, with adjustments for several patient- and surgery-related covariates. Findings A total of 51,292 primary THAs were eligible for assessment. Of these, 575 had been revised due to infection. A similar risk of revision due to infection after THA performed was found in ORs with lvUDVF and UDHF compared to CV. THAs performed in ORs with hvUDVF had lower risk of revision due to infection compared to CV (RR = 0.8; 95% CI: 0.6–0.9; P = 0.01). Conclusion THAs performed in ORs with hvUDVF systems had lower risk of revision due to infection compared to THAs performed in ORs with CV systems. The perception that all UDF systems are similar and possibly harmful seems erroneous

Operating room ventilation and the risk of revision due to infection after total hip arthroplasty: assessment of validated data in the Norwegian Arthroplasty Register

Background The air in the operating room is considered a risk factor for surgical site infection (SSI) due to airborne bacteria shed from the surgical staff or from patients themselves. Aim To assess the influence of validated operating room (OR) ventilation data on the risk of revision surgery due to deep infection after primary total hip arthroplasty (THA) reported to the Norwegian Arthroplasty Register (NAR). Methods Forty orthopaedic units reporting THAs to the NAR during the period 2005–2015 were included. The true type of OR ventilation in all hospitals at the time of primary THA was confirmed in a previous study. Unidirectional airflow (UDF) systems were subdivided into: small, low-volume, unidirectional vertical flow (lvUDVF) systems; large, high-volume, unidirectional vertical flow (hvUDVF) systems; and unidirectional horizontal flow (UDHF) systems. These three ventilation groups were compared with conventional, turbulent, mixing ventilation (CV). The association between the end-point, time to revision due to infection, and OR ventilation was estimated by calculating relative risks (RRs) in a multivariate Cox regression model, with adjustments for several patient- and surgery-related covariates. Findings A total of 51,292 primary THAs were eligible for assessment. Of these, 575 had been revised due to infection. A similar risk of revision due to infection after THA performed was found in ORs with lvUDVF and UDHF compared to CV. THAs performed in ORs with hvUDVF had lower risk of revision due to infection compared to CV (RR = 0.8; 95% CI: 0.6–0.9; P = 0.01). Conclusion THAs performed in ORs with hvUDVF systems had lower risk of revision due to infection compared to THAs performed in ORs with CV systems. The perception that all UDF systems are similar and possibly harmful seems erroneous

Operating room ventilation-Validation of reported data on 108 067 primary total hip arthroplasties in the Norwegian Arthroplasty Register

Rationale, aims, and objectives: The true effect of laminar airflow (LAF) systems on postoperative infection is disputed, partly due to uncertainty regarding the validity of ventilation data in register studies. The aim of this study was to validate the information on operating room (OR) ventilation reported by the orthopaedic surgeons to the Norwegian Arthroplasty Register (NAR) after primary total hip arthroplasty (THA). Method: Forty of the 62 public orthopaedic units performing primary THA in Norway during the period 1987‐2015 were included. The hospitals' current and previous ventilation systems were evaluated in cooperation with the hospitals head engineer. We identified the type of ventilation system reported to the NAR and compared the information with the factual ventilation in the specific ORs at the time of primary THA. Results: A total of 108 067 primary THAs were eligible for assessment. None of the hospitals performed THA in true “greenhouse” (GH) ventilation. Fifty‐seven percent of the primary THAs were performed in ORs with LAF and 43% in ORs with conventional, turbulent ventilation (CV). Comparing the reported data with the validated data, LAF was reported with a sensitivity of 86%, specificity of 89%, and positive predictive value (PPV) of 92%, with an accuracy of 88%. CV was reported with a sensitivity of 89%, specificity of 87%, and PPV of 84%, with an accuracy of 88%. The total, mean misreporting rate was 12%. Conclusions: Surgeons were not fully aware of what kind of ventilation system they operated in. This study indicates that conclusions based on ventilation data reported on THA in the NAR should not be interpreted without considering the inaccuracy of the data