The critical relationship between airborne microbiological contamination in an operating theatre and surgical site infection (SSI) is well known. The aim of this annotation is to explain the scientific basis of using settle plates to audit the quality of air, and to provide information about the practicalities of using them for the purposes of clinical audit. The microbiological quality of the air in most guidance is defined by volumetric sampling, but this method is difficult for surgical departments to use on a routine basis. Settle plate sampling, which mimics the mechanism of deposition of airborne microbes onto open wounds and sterile instruments, is a good alternative method of assessing the quality of the air. Current practice is not to sample the air in an operating theatre during surgery, but to rely on testing the engineering systems which deliver the clean air. This is, however, not good practice and microbiological testing should be carried out routinely during operations as part of clinical audit.

Cite this article: Bone Joint J 2024;106-B(9):887–891.

Introduction. Infection is disastrous in arthroplasty surgery and requires multidisciplinary treatment and debilitating revision surgery. Between 80-90% of bacterial wound contaminants originate from colony forming units (CFUs) present in operating room air, originating from bacteria shed by personnel present in the operating environment. Steps to reduce bacterial shedding should reduce wound contamination. These steps include the use of unidirectional laminar airflow systems and the introduction of theatre attire modelled on this principle (e.g. total body exhaust suits). Our unit introduced the use of the Stryker Sterishield Personal Protection System helmet used with laminar flow theatre systems. This study compares an enclosed helmet system used with standard gowns, with standard hood and mask attire. Method. 12 simulated hip arthroplasties were performed, six using disposable sterile impermeable gown, hood and mask and a further 6 using a Sterishield helmet and hood. Each 20 minute operation consisted of arm and head movements simulating movements during surgery. Air was sampled at wound level on a sterile draped operating table using a Casella slit sampler, sampling at 700l/minute. Samples were incubated on Blood agar for 48 hours at 37°c and the CFUs grown were counted. Results. Mean number of CFUs for the helmet was 9.33 with hood and mask attire having 49.16 CFUs (S. Ds 6.34 and 26.17; p value 0.0126). In all cases a coagulase negative staphylococcus was isolated. Conclusion. Although the sample size was small, we demonstrated a fivefold increase in the number of CFUs shed when using hood and mask attire compared to personal helmet and sterile hood. We conclude that the helmet system is superior to non-sterile hood and mask at reducing bacterial shedding by theatre personnel

Introduction Infection is a disastrous complication of arthroplasty surgery, requiring multidisciplinary treatment and debilitating revision surgery. As between 80–90% of bacterial wound contaminants originate from colony forming units (CFU’s) present in operating room air tending to originate from bacteria shed by personnel present within the operating environment, any steps that can reduce this bacterial shedding should reduce the chances of wound contamination. These steps have included the use of unidirectional downward laminar airflow theatre systems, and the introduction of theatre attire modelled on this principle (e.g. total body exhaust suits). Our unit has introduced the use of the Stryker T4 Personal Protection System helmet in conjunction with laminar flow theatre systems. This study compares an enclosed helmet system used with standard gowns, with standard hood & mask attire. Method 12 simulated hip arthroplasty operations were performed, six using disposable sterile impermeable gown, hood and mask, with a further 6 using the T4 helmet & hood. Each 20 minute operation consisted of a series of arm and head movements simulating movements performed during surgery. Air was sampled at wound level on a sterile draped operating table using a Casella slit sampler, sampling at 700l/minute. Samples were incubated on Blood agar for 48 hours at 37oc & the CFU’s grown were counted. Results The mean number of CFU’s for the helmet was 9.33 with hood and mask attire yielding 49.16 CFU’s (S.Ds 6.34 & 26.17; p value 0.0126). In all cases, the organism isolated was a coagulase negative staphylococcus. Conclusion Although the sample size was small, we demonstrated a fivefold increase in the number of CFU’s shed when using hood and mask attire compared to personal helmet and sterile hood. We conclude that the helmet system is superior to non-sterile hood & mask at reducing bacterial shedding by theatre personnel

Introduction Infection is a disastrous complication of arthroplasty surgery, requiring multidisciplinary treatment and debilitating revision surgery. As between 80–90% of bacterial wound contaminants originate from colony forming units (CFU’s) present in operating room air tending to originate from bacteria shed by personnel present within the operating environment, any steps that can reduce this bacterial shedding should reduce the chances of wound contamination. These steps have included the use of unidirectional downward laminar airflow theatre systems, and the introduction of theatre attire modelled on this principle (e.g. total body exhaust suits). Our unit has introduced the use of the Stryker Sterishield Personal Protection System helmet in conjunction with laminar flow theatre systems. This study compares an enclosed helmet system used with standard gowns, with standard hood & mask attire. Method 12 simulated hip arthroplasty operations were performed, six using disposable sterile impermeable gown, hood and mask, with a further 6 using a Sterishield helmet & hood. Each 20 minute operation consisted of a series of arm and head movements simulating movements performed during surgery. Air was sampled at wound level on a sterile draped operating table using a Casella slit sampler, sampling at 700l/minute. Samples were incubated on Blood agar for 48 hours at 37°c & the CFU’s grown were counted. Results The mean number of CFU’s for the helmet was 9.33 with hood and mask attire having 49.16 CFU’s (S.Ds 6.34 & 26.17; p value 0.0126). In all cases, the organism isolated was a coagulase negative staphylococcus. Conclusion Although the sample size was small, we demonstrated a fivefold increase in the number of CFU’s shed when using hood and mask attire compared to personal helmet and sterile hood. We conclude that the helmet system is superior to non-sterile hood & mask at reducing bacterial shedding by theatre personnel

Background: Ultraclean air (UCA) in the operating theatre has been defined as less than 10 colony forming units (CFU)/m3. Wearing a Body Exhaust Suit (BES) in clear air has been shown to reduce infection from 1.0% to 0.1%. A trial in our unit in 2003 found bacterial air counts of 1 CFU/m3 with Rotecno gowns made from polyester T85392 compared to 0.5 CFU/m3 with BES. The same Rotecno gowns have since been used for arthroplasty surgery in our unit as this difference was not felt to be clinically significant. A new type of gown, manufactured by Gore ltd. was offered to our hospital. These gowns consist of a three layer laminate containing polyester and polytetrafluoroethylene (PTFE) and were advertised as impervious to liquids, bacteria and viruses. Their laboratory results were deemed to be superior to Rotecno gowns on standard testing. Aim: The aim of this study was to compare bacterial air counts using the existing Rotecno gowns with this new type of occlusive gown made by Gore ltd. Methods: 56 joint replacements were allocated randomly to either the Rotecno or Gore gowns and also stratified to Total Knee Arthroplasty (TKR), Total Hip Arthroplasty (THA) or Revision THA. Bacterial air counts were measured for the first ten minutes of surgery using a Casella slit sampler which sampled air at 700 lt/min onto a nutrient agar plate. These plates were then incubated for 48 hours at 37 degrees Celcius and colonies were counted. Results: The new gowns were associated with higher air counts (3.7 CFU/m) than the Rotecno gowns (1.2 CFU/m) (p=0.01). All Rotecno air samples were < 10 CFU/m3 but three of the Gore samples exceeded the clean air standard. The bacterial counts with the Rotecno gowns were the same as those in the 2003 study. TKA was associated with higher air counts than THA or Revision THA (p=0.04). Conclusions: The new gowns may have been superior on the standard tests but they were not superior at preventing airborne bacterial dispersal. Rotecno gowns made from polyester T85392, although many years old, were still associated with very low air counts. This study highlights the importance of testing new materials in a clinical environment with UCA; in vitro testing alone is not an adequate assessment. This is especially important for TKA which was associated with higher counts

Deep infection was identified as a serious complication in the earliest days of total hip arthroplasty. It was identified that airborne contamination in conventional operating theatres was the major contributing factor. As progress was made in improving the engineering of operating theatres, airborne contamination was reduced. Detailed studies were carried out relating airborne contamination to deep infection rates.

In a trial conducted by the United Kingdom Medical Research Council (MRC), it was found that the use of ultra-clean air (UCA) operating theatres was associated with a significant reduction in deep infection rates. Deep infection rates were further reduced by the use of a body exhaust system. The MRC trial also included a detailed microbiology study, which confirmed the relationship between airborne contamination and deep infection rates.

Recent observational evidence from joint registries has shown that in contemporary practice, infection rates remain a problem, and may be getting worse. Registry observations have also called into question the value of “laminar flow” operating theatres.

Observational evidence from joint registries provides very limited evidence on the efficacy of UCA operating theatres. Although there have been some changes in surgical practice in recent years, the conclusions of the MRC trial remain valid, and the use of UCA is essential in preventing deep infection.

There is evidence that if UCA operating theatres are not used correctly, they may have poor microbiological performance. Current UCA operating theatres have limitations, and further research is required to update them and improve their microbiological performance in contemporary practice.

Cite this article: Bone Joint J 2018;100-B:1264–9.

Patient warming significantly decreases the risk of surgical site infection. Recently there have been concerns that forced air warming may interfere with unidirectional airflow, potentially posing an increased risk of infection. Our null hypothesis was that forced air and radiant warming devices do not increase the temperature and the number of particles over the surgical site when compared with no warming device. A forced air warming device was compared with a radiant warming device and no warming device as a control. The temperature and number of particles were measured over the surgical site. The theatre was prepared as for a routine lower-limb arthroplasty operation, and the same volunteer was used throughout the study.

Forced air warming resulted in a significant mean increase in the temperature (1.1°C vs 0.4°C, p < 0.0001) and number of particles (1038.2 vs 274.8, p = 0.0087) over the surgical site when compared with radiant warming, which raises concern as bacteria are known to require particles for transport.