• The second year of the Department of Health’s mandatory surveillance of surgical site infection in orthopaedic surgery in NHS hospitals in England
  
  

• Quarterly Clostridium difficile and MRSA data published
  

 

The second year of the Department of Health’s mandatory surveillance of surgical site infection in orthopaedic surgery in NHS hospitals in England

The surveillance of surgical site infections (SSI) in four orthopaedic surgical categories was made mandatory in England from 1 April 2004 [1]. This was in response to the action plan on healthcare associated infections in the Chief Medical Officer’s strategy to combat infectious diseases, Getting ahead of the Curve [2].

The second report of the mandatory surveillance of SSI has been published on the Health Protection Agency’s website on <http://www.hpa.org.uk/infections/topics_az/surgical_site_infection/documents/SSI2ndMandatory29-01-07.pdf>.

This report presents data on the participation of hospital Trusts in the surveillance, the incidence of surgical site infection (SSI) by each of the four categories of procedure, differences between the first year (2004-05) and the second year (2005-06), the incidence by risk groups and summary data on the most common causative micro-organisms in a surgical site infection.

The key points of the report are:

• Data on 52,992 procedures has been collected by 152 Trusts in the second year of mandatory surveillance (2005-06) of surgical site infection compared with 41,286 procedures by 145 Trusts in the previous year (2004-05).
  
• More than one third of Trusts have undertaken surveillance in at least one category of orthopaedic procedure continuously. Most have been undertaking surveillance in the hip and knee replacement categories of procedure.
  
• The rates of SSI decreased between the first (2004-05) and second year (2005-06) of the mandatory surveillance for each category, although the reduction was only statistically significant for hip prosthesis surgery.
  
• In most Trusts, the rates of SSI in orthopaedic surgery were low.
  
• The rate of SSI increases with the number of risk factors present in the patient, three of which are captured by the Risk Index. This is a composite measure based on three important risk factors: wound class, underlying physical status and duration of operation.
  
• In both years, the rates of SSI were highest in the hip hemiarthroplasty category. This is partly explained by patients undergoing these procedures being at greater risk of infection and because they tend to have a longer post-operative stay in hospital, increasing the chance that SSIs will be detected.
  
• Most of the SSIs reported affected the superficial layers of the wound, but approximately a quarter involved the deeper tissues. In three categories of surgery, the proportion of SSI affecting the deeper tissues has increased in the second year.
  
• In 2005-06, S. aureus continues to be a major cause of SSIs and was responsible for nearly half of all SSIs, with 65% of being methicillin resistant. Nearly a third of the total SSIs were caused by methicillin resistant S. aureus.
  
• There are four NHS Trusts with rates of SSI that are higher than would be expected in the set of data contributed between April 2005 and March 2006. These Trusts are different from those identified as having high rates in the first year. They are aware that their rates are comparatively high and are investigating possible causes.
  
• Data from the second year of mandatory surveillance (2005-06) shows that there is continued decrease in the length of post-operative stay in hospital following elective surgery. This means that the rates reported in this surveillance are underestimates and this would affect the interpretation of changes in rates over time.

Other data presented are SSI rates by Trust and year:
<http://www.hpa.org.uk/infections/topics_az/surgical_site_infection/documents/trusttables04-06final.pdf>.

The rates at Trust level should be interpreted with caution as some represent estimates based on small numbers of orthopaedic procedures and are therefore imprecise. The number of procedures on which rates are based varies according to the throughput of the given type of surgical procedure at the Trust and the number of surveillance periods they have chosen to participate in.

The possibility that an SSI will be detected depends on the length of time that the patient spends in hospital post-operatively. Some of the variation in rates may therefore be explained by differences in length of post-operative follow-up. In addition, the rates included in these tables have not been adjusted for underlying risk factors related to the patient or their operation that could affect the risk of developing an SSI, for example age, underlying illness, complexity of the operation.

References
1. HPA. Mandatory surveillance of surgical site infections in orthopaedic surgery. Commun Dis Rep CDR Weekly [serial online] 2004 [cited 1 February 2007]; 14(4):News. Available at <http://www.hpa.org.uk/cdr/archives/2004/cdr0404.pdf>.

2. Department of Health (Chief Medical Officer). Getting ahead of the curve: a strategy for combating infectious diseases (including other aspects of health protection). London: Department of Health, 2002. Available at: <http://www.dh.gov.uk/assetRoot/04/06/08/75/04060875.pdf>.