By: 22 October 2013

F Arnaout, A Ismail and P Shewell examine laminar flow areas to help reduce post-operative infections




The consequences of deep infection following orthopaedic operations can be catastrophic. A low incidence of infection depends upon operating theatre design, meticulous surgical technique and rigid aseptic discipline within the operating theatre suite.

The Department of Health has recommended in the Health Technetium Memorandum (HTM) that the use of lines or a coloured area on the floor delineating the extent of the clean zone is essential.


We conducted an audit in one of the orthopaedic theatres in our District General Hospital before and after the implementation of DH guidelines to mark the floor corresponding to the laminar flow area. We also contacted all hospitals in the region to find out who is implementing the recommendations.


Theatre team members, except surgeons, were blinded to the study and the patients selected were all lower limb arthroplasty cases. We used a scoring system based on the position of the trolleys in the marked area.


This re-audit has shown significant improvement in theatre staff practice following the implementation of DH guidelines. Therefore, we recommend that all regional and national hospitals should have the floor corresponding to laminar airflow marked.

Key words

Laminar, flow, theatre, infection



The consequences of deep infection following orthopaedic operations can be catastrophic. Revision arthroplasty following infection is technically difficult and both the operating time, duration of hospital admission and costs may be two to three times higher than for primary joint replacement.

The early infection rate following total hip replacement in standard operating theatres without modern aseptic precautions was as high as 11%, but a combination of prophylactic antibiotics and clean air can reduce the infection rate to 0.3%.3

In a multi-centre study of sepsis after total hip or knee replacement,1 the operations performed by each surgeon were allocated at random between control and ultraclean-air operating rooms. Records were obtained from over 8,000 such operations. In the patients whose prostheses were inserted in an operating room ventilated by an ultraclean-air system the incidence of joint sepsis confirmed at re-operation within the next one to four years was about half that of patients who had had the operation in a conventionally ventilated room at the same hospital.

A low incidence of infection depends upon operating theatre design, meticulous surgical technique & rigid aseptic discipline within the operating theatre suite. Therefore, the British Orthopaedic Association recommends the use of ultraclean theatres and laminar airflow.

In the Laminar Air Flow (LAF) system, the entire body of air within a designated space moves with uniform velocity in a single direction along parallel flow lines, and is restricted to an area in the centre of the operating theatre (room within a room principle). Theatres are usually designed with a vertical downward airflow concept. This results in statistically significant reduction in colony-forming unit per cubic metre (CFU/m3) in the air.

The Department of Health (DH) has recommended in the Health Technetium Memorandum (HTM), that the use of lines or a coloured area on the floor delineating the extent of the clean zone will assist staff and is therefore essential, as any air outside this zone cannot be guaranteed to be ultra-clean.5

The aim of study is to look into the practice of orthopaedic theatres and whether theatre staff has improved their practice of placing instruments trolleys within the laminar air flow area, following the implementation of the national guidelines by marking the floor.


Aims & objectives

  1. To close the audit cycle and re-audit the practice in the orthopaedic theatre before and after marking the floor corresponding to the laminar air flow area.
  2. To conduct a survey to monitor the application of the DH recommendation to mark the floor in the West Midlands area.


Methodology & Design

medicaltrolleyPart One

We have previously conducted an audit in our District General Hospital before marking the floor, which showed inadequate placement of trolleys within the walls of the laminar flow room; none of the procedures had 100% trays completely within the zone, and 6% recorded had 0% trays within.

This audit was followed by marking the floor to help theatre team identify the clear air area. We then closed the audit loop by repeating the audit following the same methodology.

This was a single-blinded study; the theatre staff were not aware that a study was being done. Cases were selected randomly based on the availability of an orthopaedic registrar in theatre to conduct the necessary observations.

We looked at primary lower limb joint arthroplasty operations from September 2010 to April 2011 and included 48 cases in total; both total hip replacements (THR) and total knee replacement (TKR), the same total number as the original audit.

The information recorded were: procedure undertaken (THR /TKR), date of operation and position of trolleys in theatre (appendix I).

For each standard lower limb arthroplasty operation, a total of six trolleys were used; four instrument trolleys and two bowel trolleys.

The position of the trays was observed at the time of opening the drapes. We used the following scoring system based on trolley position within the marked area:

Fully inside: 2 points        
Partially inside: 1 point        
Fully outside: 0 points

Therefore, the Minimum score possible is 0 and the maximum score possible is 12. The higher the score means better adherence to the guidelines.


Part Two

We called all NHS and private hospitals in the West Midlands and asked the following three questions:

  1. How many trauma & orthopaedics theatres available?
  2. How many of them have laminar flow area marked on the floor?
  3. What is the method used to mark the floor (line or shadow)?



Part One Results

The table below explains the results of the repeated audit with the percentages of operations that scored each point, and gives the final median score at the end:




The above results show clearly that the average score for operations has increased from 7 to 9 points out of a maximum 12 points, following the implementation of the guidelines. This is significant and confirms real improvement in the practice of pacing trays within the designated laminar flow area, which will subsequently lead to decreased infection rates.


Part Two Results

We contacted 27 hospitals, the total number of orthopaedic theatres was 80, all of them had laminar flow, and 49 of them had the laminar flow area marked on the floor (61.25%) with lines or shadows. Details are in appendix II.

This part of the study shows that although all regional hospitals had laminar air flow, but almost 40% of them have failed to use this system effectively in reducing operative infections, when they did not marked the laminar air flow area on the floor, making it less noticeable to theatre staff.


Discussion and Conclusion

The re-audit has shown increased awareness in the orthopaedic theatre in the placement of surgical instruments within the clean air area, following the implantation of HTM guidelines. In particular, there has been avoidance of placing the trays completely outside the laminar flow field. This will potentially reduce the risks of infection and its catastrophic consequences to patients, which are also associated with huge costs to the health budget.

A similar study was performed in an eye hospital,6 which showed an increase in positioning the trolley within the laminar flow area from 6.1% to 53.8%. This is consistent with the results of our study. However, they used only one instrument trolley for these cases unlike our experiment, which included a more complicated six trolleys. 

We recommend that all orthopaedic theatres should have floor marking delineating the clean air zone to help setting up the instruments within this zone to reduce the risk of infection. We also recommend submitting a request to the trust board to arrange for all orthopaedic theatre floors to be marked, which helps increase sterility in theatre environments, and maintain patient safety in accordance with the HTM guidelines from the Department of Health.




Firas Arnaout, Speciality Doctor; Aemin Ismail, Senior House officer; Peter Shewell, Consultant

Department of Trauma & Orthopaedics, Hereford County Hospital, UK




  1. Effect of ultraclean air in operating rooms on deep sepsis in the joint after total hip or knee replacement: a randomised study. Lidwell OM, Lowbury EJ, Whyte W, Blowers R, Stanley SJ, Lowe D. Br Med J (Clin Res Ed) 1982 Jul 3;285(6334):10-4
  2. BOA guidelines
  3. Infection rates after 3175 total hip and total knee replacements performed with and without a horizontal unidirectional filtered air-flow system, EA Salvati, RP Robinson, SM Zeno, BL Koslin, BD Brause and PD Wilson, The Journal of Bone and Joint Surgery, Vol 64, Issue 4 525-535
  4. BOA, PRIMARY TOTAL HIP REPLACEMENT, 1999; revised August 2006
  5. Heating and ventilation systems Health Technical Memorandum 03-01: Specialised ventilation for healthcare premises.
  6. Safety by design: effects of operating room floor marking on the position of surgical devices to promote clean air flow compliance and minimise infection risks. de Korne DF, van Wijngaarden JD, van Rooij J, Wauben LS, Hiddema UF, Klazinga NS. BMJ Qual Saf. 2011 Aug 18