Vertical Laminar Airflow Research Articles

Quantitative Evaluation of the Transmission and Removal of Harmful Smoke Particles in the Operating Room: Full-Scale Experimental and Numerical Study

A large amount of surgical smoke in electrosurgery seriously deteriorates the clean environment of the operating room and can potentially harm medical staff and patients. Exploring the distribution and removal of indoor particulate matter and selecting efficient ventilation patterns are effective ways to control harmful smoke. Therefore, in this study, we combined simulations and full-scale experiments to quantitatively explore the high-concentration spatial regions of particles and compared three ventilation patterns: vertical laminar airflow (VLAF), horizontal laminar airflow (HLAF), and hybrid ventilation, wherein unidirectional airflow (UDAF) was applied to the operating table along with peripheral mixing (UDAF + mixing). We found that simple laminar flow ventilation was significantly affected by the equipment layout and air change rate (air changes per hour; ACH), and the smoke particles were distributed in large amounts in the operating area and could not be removed completely. Conversely, hybrid ventilation can work effectively, and the optimal ACH is approximately 60, which can remove nearly 72% of smoke particles. The airflow distribution in the operating room is also an important factor affecting the distribution and removal of smoke particles. Therefore, medical staff should avoid prolonged exposure to areas with high particle concentrations and particle removal paths.

Numerical investigation of indoor air quality in health care facilities: A case study of an intensive care unit

The risk of healthcare-associated infections (HAIs) is higher in patients admitted to intensive care units (ICU) and high dependency units (HDU). Currently, most ventilation studies focus on specialized areas, mainly isolation rooms and operating rooms. This paper focuses on the ventilation of multiple-bed hospital wards in developing countries. This study uses computational fluid dynamics (CFD) simulation to model and investigate airflow and the spread of pollutants. The study aims to investigate ICUs with various ventilation system designs. These predicted behaviors and characteristics were compared numerically to determine compliance with the requirements of airflow patterns, airborne contaminant distribution, and current international standards. The case study simulations were carried out using ANSYS Fluent simulation software as a solution tool. Three different ventilation systems, Vertical Laminar Airflow Ventilation (VLAF), Horizontal Laminar Airflow Ventilation (HLAF), and Temperature-Controlled Airflow Ventilation (TcAF), were modeled within five different designs to determine the most effective possible distribution of air inside the patient's room, based on different categories, primarily temperature distribution, CO2 concentration, and airflow distribution. The authors applied the TcAF technique in an ICU room, comparing the results of the proposed technique with those of other common techniques (HLAF and VLAF). It was found that TcAF showed the most effective airflow distribution around patients, isolating each patient from the others. However, the temperature distribution was excluded from the ASHRAE standard. HLAF with two exhausts is the most suitable option, with a lower CO2 concentration than the alternatives and a temperature that meets ASHRAE standards.

Bacteria-carrying particles diffusion in the operating room due to the interaction between human thermal plume and ventilation systems: An experimental-numerical simulation study

During surgery, the release of bacterial-carrying particles (BCPs) by surgeons is one of the major pollution sources in operating rooms (ORs), which may cause surgical site infection (SSIs) or health problems. The human thermal plume emitted by the human body may affect the airflow in the surgical micro-environment, leading to the further spread of BCPs. Therefore, this paper aimed to evaluate and compare the diffusion of human thermal plume and BCPs under the design conditions of four ventilation systems (vertical laminar airflow ventilation (VLAF1), horizontal laminar airflow ventilation (HLAF), vertical laminar airflow ventilation (VLAF2), and temperature-controlled airflow ventilation (TAF)). The experiments of airspeed measurements and biological particle emission were carried out in a standard vertical laminar ventilation operating room. Computational fluid dynamics (CFD) was used to extend the investigation of the different ventilation systems. In summary, both the VLAF and TAF systems were able to interact effectively with the human thermal plume, and the TAF ventilation system was superior to the other three systems in reducing BCPs levels in the air of the operating room. The TAF system was able to control the BCPs concentration in the surgical area to 20 CFU/m3. The interaction between human thermal plume and ventilation plays an important role in the clearance of BCPs in the operating room, so it is significant to systematically compare the performance of different ventilation systems.

A vertical laminar airflow system to prevent aerosol transmission of SARS-CoV-2 in building space: Computational fluid dynamics (CFD) and experimental approach

Respiratory aerosol particles carrying the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) are a primary cause of the long-distance infection, and insufficient ventilation systems make building occupants highly prone to the coronavirus disease-2019 (COVID-19). As a preventive measure of the aerosolized viable SARS-CoV-2 suspension in building space, we seek to propose an optimal design of the upper-room/drop-ceiling aeration grid system generating vertical laminar airflow (VLAF) as an aerosol barrier. On a test plan (6.1 × 4.7 m) representing the standard hospital patient room in South Korea (a 2.7 m-height room of 77.4 m3 in volume), we investigated the air-terminal size, spacing and air speed that shape uniform downflow of fresh air, minimizing horizontal spread. Our simulation results using the Taguchi method and computational fluid dynamics (CFD) in presence of indoor human expiration indicated that a steady vertical air supply of 0.3 m/s through 0.04m-diameter air diffusers deployed by 0.5 m spacing is the most effective to form VLAF. Physical particle detection tests at the height of 1.5 m in mockup setting of the optimal system design, revealed that expiratory aerosols produced by a single person were almost entirely removable in 20 s. Investigations also confirmed that the proposed design could minimize stagnant airflow regions and would potentially satisfy the indoor air-speed condition for occupant thermal comfort.

Prevention of surgical site infection under different ventilation systems in operating room environment.

Biological particles in the operating room (OR) air environment can cause surgical site infections (SSIs). Various ventilation systems have been employed in ORs to ensure an ultraclean environment. However, the effect ofdifferent ventilation systems on the control ofbacteria-carrying particles (BCPs) released from the surgical staff during surgery is unclear. In this study, the performance of four different ventilation systems (vertical laminar airflow ventilation (VLAF), horizontal laminar airflow ventilation (HLAF), differential vertical airflow ventilation (DVAF), and temperature-controlled airflow ventilation (TAF)) used in an OR was evaluated and compared based on the spatial BCP concentration. The airflow field in the OR was solved by the Renormalization Group (RNG) k-ε turbulence model, and the BCP phase was calculated by Lagrangian particle tracking (LPT) and the discrete random walk (DRW) model. It was found that the TAF system was the most effective ventilation system among the four ventilation systems for ensuring air cleanliness in the operating area. This study also indicated that air cleanliness in the operating area depended not only on the airflow rate of the ventilation system but also on the airflow distribution, which was greatly affected by obstacles such as surgical lamps and surgical staff.

Conflicting effects of a portable ultra-clean airflow unit on the sterility of operating rooms: A numerical investigation

The onset of post-operatory surgical-site infections is significantly correlated with the concentration of viable airborne bacteria that are shed from the surgical team or entering the operating room during door openings and are deposited directly on the patient's wound or on surgical instruments.The ultra-clean vertical laminar airflow ventilation system is often used to protect the main surgical area of operating rooms. The clean zone provided by the laminar airflow system is crowded with staff and furniture. As a result, some surgical instruments might remain outside the protected area. We use a numerical simulation to investigate the capability of a portable ultra-clean airflow unit to reduce the contamination of the principal instrumentation table by airborne bacteria, during a sham operation. The numerical model is thoroughly validated against the experimental data available for a test room. The portable air-cleaning device maintains sterile conditions on the principal instrumentation table over a range of flow rates of the general ventilation, although it induces higher levels of bacterial contamination in other zones of the room at the same time.

Influence of the Arrangement of Surgical Light Axes on the Air Environment in Operating Rooms.

Purpose Surgical lights in the operating rooms are typically installed in a single axis in the center of the room or in two axes on both sides of the operating table. In the single-axis installation, the air-conditioning outlet cannot be placed in the center of the ceiling, which may affect the air current. Therefore, we measured the air current and cleanliness in two equivalent operating rooms using a vertical laminar airflow system equipped with either single-axis or double-axis surgical lights. Methods Air current was measured using a three-dimensional ultrasonic anemometer. Cleanliness was evaluated by measuring the amount of dust before and after air-conditioner activation. To visualize the air current, smoke was illuminated on a sheet of laser light while the air-conditioning was stopped, and changes after air-conditioning activation were observed. Results In the single-axis room, an oblique fast air current flowing from the surrounding air outlet toward the center was observed, and the flow velocity fluctuated greatly. In the double-axis room, uniform downward laminar airflow was observed. The amount of dust at the center decreased significantly faster in the double-axis room; thus, the cleanliness at the center was higher in the double-axis room. Persistent stagnation of smoke was observed below the single-axis lighting, whereas smoke below the double-axis lighting was immediately dispersed and the air cleared even when surgical lights were in the position for surgery. Conclusion Uniform vertical laminar airflow was formed and high cleanliness was achieved in the center of the room when the surgical lights were arranged in two axes.

Temperature-controlled airflow ventilation in operating rooms compared with laminar airflow and turbulent mixed airflow

To evaluate three types of ventilation systems for operating rooms with respect to air cleanliness [in colony-forming units (cfu/m3)], energy consumption and comfort of working environment (noise and draught) as reported by surgical team members. Two commonly used ventilation systems, vertical laminar airflow (LAF) and turbulent mixed airflow (TMA), were compared with a newly developed ventilation technique, temperature-controlled airflow (TcAF). The cfu concentrations were measured at three locations in an operating room during 45 orthopaedic procedures: close to the wound (<40cm), at the instrument table and peripherally in the room. The operating team evaluated the comfort of the working environment by answering a questionnaire. LAF and TcAF, but not TMA, resulted in less than 10cfu/m3 at all measurement locations in the room during surgery. Median values of cfu/m3 close to the wound (250 samples) were 0 for LAF, 1 for TcAF and 10 for TMA. Peripherally in the room, the cfu concentrations were lowest for TcAF. The cfu concentrations did not scale proportionally with airflow rates. Compared with LAF, the power consumption of TcAF was 28% lower and there was significantly less disturbance from noise and draught. TcAF and LAF remove bacteria more efficiently from the air than TMA, especially close to the wound and at the instrument table. Like LAF, the new TcAF ventilation system maintained very low levels of cfu in the air, but TcAF used substantially less energy and provided a more comfortable working environment than LAF. This enables energy savings with preserved air quality.

Impact of surgical lights on the velocity distribution and airborne contamination level in an operating room with laminar airflow system

The presence of surgical lights disturbs the flow of ultraclean air in operating rooms (ORs) with vertical laminar airflow systems (LAF) by creating a wake downstream of the lights. The wake may be characterised by velocities low enough to directly influence the level of airborne microbe-carrying particles (MCP) close to the surgical site in an OR, eventually leading to surgical site infections (SSIs). The influence of surgical lights on airflow distribution during non-operating conditions and on airborne contamination level close to the operating table during mock surgeries was analysed in ORs with vertical LAF systems. The velocity and turbulence intensity (TI) distributions were recorded through a cross-sectional grid of points under surgical lights during non-operating conditions. In order to detect microbiological contamination during operating conditions, four mock surgeries were performed mimicking real surgeries on a porcine tissue. Three of the surgeries were performed under different types of surgical lights and one surgery did not include surgical lights at all. The mean velocity under all three surgical lights was significantly lower (≤0.07 m/s) compared with the mean velocity measured when the LAF was not obstructed by lights (0.24 m/s). At several points in the grid under all three lights, velocities as low as ≤0.02 m/s were measured. Air sampling during mock surgeries recorded at least 1 CFU/m3 for 43% of the samples (n = 16; mean = 1.25; range 0–4) using surgical lights, while not a single bacteria count was recorded without the use of lights (n = 7).

Effect of an anaesthetic screening drape on vertical laminar airflow

Effective operating room ventilation is required to reduce the risk of surgical site infection. Vertical laminar airflow from above the surgical field provides a source of 'ultra-clean' air, carrying contaminants away from the operative site. An anaesthetic screening drape is often used to shield the operative site from the anaesthetic team, and this defies the principles of vertical laminar airflow. A mock theatre set-up for a total knee replacement was constructed with and without the use of an anaesthetic screening drape. A 10×10 grid was set up within the surgical canopy, and the downward air velocities were measured using a hot air anemometer. The average velocity and range of velocities at each grid point were measured in both set-ups. The range was used as the marker of turbulence. Within the surgical canopy, the average downward air velocity was 0.35m/s. With the use of an anaesthetic screening drape, the mean downward air velocity in the area above the patient decreased from 0.36m/s to 0.29m/s (P=0.02). In the area immediately above the drape, the average velocity was 0.18m/s. Turbulent air currents were produced in the areas adjacent to the drape near to the mock surgical site. For the area above the patient, the range increased from an average of 0.034m/s to 0.05m/s (P=0.04). In the area directly above the drape, the average range was 0.08m/s. Use of an anaesthetic screening drape causes disruption to normal vertical laminar airflow.

FIELD MEASUREMENT OF AIRBORNE PARTICULATE MATTERS CONCENTRATION IN A HOSPITAL’S OPERATING ROOM

In a hospital operating room, adequate air flow and cleanliness are crucial to protect the patient from surgical site infection (SSI) during a procedure. The probability of the patient to get the infection is related to the concentration of bacteria carrying particles inside the room. This paper presents a field measurement study to quantify the concentration of particulate matters (PM) in a hospital operating room which complies with the ISO Class 7 requirements. The operating room was equipped with High Efficiency Particulate Air (HEPA) filters and a vertical laminar air flow (LAF) system. The measurements were conducted at three height levels from the floor namely 1.2 m, 1.8 m and 2.4 m. The data was logged at a rest condition, in accordance to the ISO 14644-1 requirements. A HPC300 particle counter was used to measure the concentrations of particulate matters namely PM0.5, PM1 and PM5. The results show that the concentrations of all particulate matters were higher at the height level of 1.2 m compared to other height levels. The concentration of PM0.5 was relatively higher than PM1 and PM5 in the vicinity of operating table.

A numerical investigation of vertical and horizontal laminar airflow ventilation in an operating room

The effectiveness of vertical and horizontal ventilation systems in terms of reducing sedimentation and distribution of bacteria-carrying particles in an operating room is investigated. The exploration is carried out numerically using computational fluid dynamics. Both airborne particle concentration and sedimentation are simulated under different ventilation flow conditions. Model validation is performed through comparisons with experimental data from the literature. Achieved results reveal that the preferred selection between vertical and horizontal ventilation scenario in an operating room is highly depend on internal constellation of obstacles, work practice and supply airflow rate. Improper positioning of operating room personnel may remarkably reduce the ventilation efficiency. Increasing the airflow rate reduces particle concentration in the surgical zone. Efficient ventilation, however, is not only a matter of increasing airflow rate. Inappropriate airflow rates result in flow pattern transition from laminar to less efficient turbulent mixing. A laminar and well- organized (unidirectional) flow pattern is retired for a good result. Innovative further solutions are suggested to be found in cross-disciplinary collaboration.

Simulation-based feasibility study of improved air conditioning systems for hospital operating room

The goal of the air distribution inside a hospital operating room (OR) is to protect the patient and staff from cross-infection while maintaining occupant comfort and not affecting the facilitation of surgical tasks. In ORs, HEPA-filtered air and vertical (downward) laminar airflow are often used to achieve a unidirectional flow of fresh air from ceiling, washing over the patient and flowing out of exhaust vents on the side walls, near the floor. However, previous research has shown that this method does not necessarily achieve the desired unidirectional flow pattern or adequately achieve optimal air asepsis. The results from this study show that maximizing the area of the laminar flow diffusers remedies this issue and provides very low contamination levels. The use of air curtains as specified by manufacturers of commercial products may not provide satisfactory results, with noticeable contamination levels at the wound site.

Clean operating rooms for optimizing surgical outcome

The National President of orthopedic surgeons of India has dedicated his efforts this year to surgical training in order to optimize surgical outcome. With the ongoing technological advances taking leaps and bounds worldover, our concern has always been to keep pace with the art and science of surgery. Many of the rituals and beliefs about practices in the operation theater were derived from wishful thinking and good ideas rather than scientific evidence. In an effort to develop these guidelines it would be good to know the standards of practice worldover. In this editorial I hope to review few facts in world literature and would expect your thoughtful minds to be stimulated regarding this important issue. WHO has come out with guidelines for safe surgery and have propagated – Safe surgery saves life, surgical site infection being one of the important issues. Surgical wound infection accounts for 20% of all nosocomial infections which most commonly occur because of contamination of wound during surgery. 1 Improvement in theater techniques, antibiotics, theater clothings and ventilation has reduced postoperative infection to as low as 0.3%. 2 Wound contamination can be reduced by a number of practices including: Limiting the number of personnel in the operation theater, Disrupting the flow of bacteria to the wound, Filtering the bacteria from the theater air, Disinfecting the air and the wound, Use of systemic antibiotics and Removing bacteria by physical methods such as disinfection and surgical techniques. The traffic in and out of the operating room should be restricted and the number of personnel should also be minimized. It is known that addition of 5 operating room personnel increased the microbiological counts by more than 15 folds. Also bacterial contamination in an operating room has been shown to increase significantly when the door is left open to the corridor. 3 The contamination rate of surgical instruments exposed to the air in an operation theater was 1.18 times higher than that of instruments that have been covered with a sterile guard. 4 The exposure time also had a positive correlation with bacterial contamination rate. Research on the clean air technology has brought certain facts which can help designing the operating rooms. Firstly vertical laminar airflow units generally reduce airborne contamination better than horizontal units. Secondly there is an inconsistent relationship between the surface and air bacterial counts, indicating that measurement of air contamination represents an unhelpful method for assessment of

Assessment of horizontal laminar air flow instrument table for additional ultraclean space during surgery

The area in a vertical ultraclean laminar air flow (LAF) theatre is usually too small to accommodate all the equipment needed for major surgery. We investigated the addition of an instrument table supplied with fixed ultraclean LAF and placed alongside the existing main LAF unit, to determine its physical and bacteriological effect on the main unit. In phase 1, with two investigators but without a patient, smoke tests showed no intrusion of air from the table into the main unit and particle counts did not show any adverse effect on the main LAF unit. In phase 2, during patients undergoing two total knee replacements, the LAF table and a table without LAF were placed alongside the main LAF unit. The tables were subjected to the activity of an extra operating room (OR) nurse working from inside the main LAF vigorously simulating handling of instruments. During this activity, the >5μm particle counts were 275/m(3) at the instrument table with LAF and 8550/m(3) at the table without LAF (P<0.0001). Also, without the OR nurse activity, the particle counts, just inside the main unit and adjacent to the LAF table, were significantly reduced (P<0.03-0.003). Sedimentation plates on the LAF table and in the main unit registered 22 and 25cfu/m(2)/h respectively compared with 45cfu/m(2)/h at the instrument table without LAF. In conclusion, the results from the smoke tests, particle counts and bacteriological evaluation showed that the additional instrument table supplied with LAF is efficient and can be safely used as an extension additional to a main OR LAF unit.

Operating Room Ventilation With Laminar Airflow Shows No Protective Effect on the Surgical Site Infection Rate in Orthopedic and Abdominal Surgery

To evaluate whether operating room (OR) ventilation with (vertical) laminar airflow impacts on surgical site infection (SSI) rates. Retrospective cohort-study based on routine surveillance data. Sixty-three surgical departments participating voluntarily in the German national nosocomial infections surveillance system "KISS" were included (a total of 99,230 operations). Active SSI surveillance was performed according to the methods and definitions given by the US National Nosocomial Infection Surveillance system. Surgical departments were stratified according to type of OR ventilation used: (1) turbulent ventilation with high-efficiency particulate air-filtered air, and (2) HEPA-filtered (vertical) laminar airflow ventilation. Multivariate analyses were performed by the generalized estimating equations method to control for the following variables as possible confounders: (a) Patient-based: wound contamination class, ASA score, operation duration, patients' age and gender, endoscopic operation; (b) Hospital-based: the number of beds in the hospital, its academic status, operation frequency, and long-term participation in KISS. The risk for severe SSI after hip prosthesis implantation was significantly higher using laminar airflow OR ventilation (1.63 < 1.06; 2.52>), as compared with turbulent ventilation. The adjusted odds ratios for the other operative procedures analyzed were: knee prosthesis 1.76 < 0.80, 3.85>; appendectomy 1.52 < 0.91, 2.53>; cholecystectomy 1.37 < 0.63, 2.97>; colon surgery 0.85 < 0.49, 1.49>; and herniorrhaphy 1.48 < 0.67; 3.25>. Unexpectedly, in this analysis, which controlled for many patient and hospital-based confounders, OR ventilation with laminar airflow showed no benefit and was even associated with a significantly higher risk for severe SSI after hip prosthesis.

Adherence to Recommendations Designed to Decrease Intra-Operative Wound Contamination

The incidence of wound infection following total hip and knee arthroplasty has fallen with the introduction of laminar vertical laminar airflow, occlusive clothing and prophylactic antibiotics. However, infection still occurs after prosthetic joint replacement and can have devastating consequences. Intra-operative wound contamination is the major source of infection. Measures proven to decrease intra-operative wound contamination include chlorhexidine lavage, removal of jewellery, covering old jewellery, ears, nose, mouth and hair and wearing theatre clothing in an occlusive manner. Posters explaining this practice were placed at eye level in the scrub area of orthopaedic theatres and adoption of these techniques was observed covertly before and after. Eighty-two personnel were audited before the poster was erected and 90 afterwards. Only 2 of 12 observed standards were adhered to 100% of the time. Education by posters did not significantly improve adherence to protocols. Compliance with protocols was worse amongst non-scrubbed theatre personnel.

A Case Study: Surface Contamination of Cyclophosphamide due to Working Practices and Cleaning Procedures in Two Italian Hospitals

The efficacy of preventive and organisational measures implemented in Italy to prevent the contamination of cytotoxic drug preparation rooms has been investigated, and oncologic wards of two Italian hospitals were examined. The sampling strategy was based not only on potential sources of contamination but also on responses to detailed questionnaires on workplace practices and work organisation. Wipe samples were taken from different surfaces of preparation rooms, before and after the work shift, over a span of a month. Cyclophosphamide was taken as the marker drug that reflects exposure to cytotoxic drugs, being measurable by GC/MS. In one of the two hospitals (Hospital A), a large amount of cyclophosphamide was found, both before and after shift, on the workbench (median value, 2.55 microg dm(-2), before shift), on the floor between the operator working position and the waste bin (>10 microg dm(-2), after shift), as also on door handles and storage shelves. No quantifiable levels of cytotoxic drug were detected in the second hospital investigated (Hospital B). These results could be attributed to the efficacy of cleaning procedures and working practices. In fact, both hospitals were provided with vertical-laminar airflow hoods and the (male) nurses had attended special training courses; but in Hospital A, cleaning procedures were carried out without substances used specifically for the cleaning of surfaces contaminated by cytotoxic drugs such as sodium hypochlorite. Working practices did not include Luer Lock devices. Cyclophosphamide concentrations found in both hospitals, compared with the quantities of drug handled, gave evidence of the importance of the correct handling of cytotoxic agents as a major tool in reducing contamination levels. The results reveal the insufficiency of the risk management measures which do not take into account working practices that are prevailing, and stress the necessity for periodic environmental monitoring, indispensable for evolving effective procedures to prevent antineoplastic drug exposure.

Sterility validity period of vials after multiple sampling under vertical laminar airflow hood

The aim of this study is to validate the sterility period of vials after multiple sampling under Grade A vertical laminar airflow hood. Vials filled aseptically with a sterile culture medium have been sampled with syringes three times a week over one month under Grade A vertical laminar airflow hood and in the mean-while, keeping the vials out of the laminar airflow hoods. No microbial growth has been observed. On the basis of these results, it has been decided to modify our standard operating procedures, to allow keeping the vials for two weeks in a box out of the laminar airflow hoods (ambient temperature Grade B) or any controlled environment (under refrigeration). This study validates the multiple use of vials of small to large volumes (5-100 mL), to simplify handling and to reduce the costs in centralized cytostatic reconstitution units in hospital pharmacies, with no microbial risk.

Primary total knee replacement: a comparison of a nationally agreed guide to best practice and current surgical technique as determined by the North West Regional Arthroplasty Register

In 1999, a statement of best practice in primary total hip replacement was approved by the Council of the British Orthopaedic Association (BOA) and by the British Association for Surgery of the Knee (BASK) to provide a basis for regional and national auditable standards: we have compared practice in the North West of England to this document to ascertain adherence to this guide to best practice. A direct comparison of data held on the North West Hip Arthroplasty Register for 2001/2002 and BASK/BOA guidelines was performed. 86 surgeons from 26 hospitals were included in the study. A mean of 93.3% of operations were performed in the surgeon's usual theatre. All of these theatres had vertical laminar air flow systems. 42.2% of respondents routinely used exhaust suits and 68.1% of respondents routinely used impermeable disposable gowns. All surgeons use some form of anti-thromboembolic prophylaxis; 66.2% use a combination of both mechanical and chemical means. All surgeons used antibiotic prophylaxis. The most popular choice of antibiotic was a cephalosporin. 93.7% of surgeons routinely use antibiotic-loaded cement. The PFC and Kinemax prostheses were the most commonly used prostheses. Interestingly, 97.7% of all first-choice implants were cemented. Only 2 surgeons used uncemented total knee replacement. 69.8% of surgeons used a posterior cruciate retaining design. A midline longitudinal skin incision is used by 87.2% of surgeons, a medial longitudinal skin incision by 7.0% and a lateral longitudinal skin incision by 5.8% of surgeons. A medial parapatellar capsular incision is preferred by 91.9% with the remainder using mid vastus or trivector retaining capsulotomy. Closure of capsulotomies is performed in flexion by 65.1% and in extension by 34.9%. In patients with osteoarthritis, 38.4% routinely resurfaced the patella, 34.9% never resurfaced the patella and 26.7% selectively resurfaced. This was in direct contrast to practice for patients with rheumatoid arthritis in whom 66.3% routinely resurfaced the patella, 22.1% never resurfaced the patella and 11.6% selectively resurfaced. This study has demonstrated variation of practice in hip arthroplasty across the North West region and significant divergence from the BASK/BOA statement of best practice. The introduction of a properly funded national arthroplasty register will surely help to clarify the effect of such diverse practice on patient outcome.