A national SSI surveillance programme in England was launched in 1997 by the public Health Laboratory Service now hosted by PHE. Scotland (Health Protection Scotland), Wales (Public Health Wales) and Northern Ireland (Public Health Agency) have similar surveillance programmes. PHE identifies 17 categories of surgery in hospital can undertake surveillance, four of these are orthopaedic categories mandated by the DH. NHS trusts are asked to undertake surveillance in one of the four orthopaedic categories in financial year (PHE 2013b.) Hospital may choose to conduct surveillance in as many categories as they wish