This is a single-site trial, and it has been designed to compare a revision hip cohort with a revision knee cohort. All consecutive eligible patients, under the care of participating Co-Investigator Orthopaedic Surgeons, are approached for recruitment into the study.

Eligible patients wishing to participate must require either revision hip or revision knee surgery and consent to be randomised to either NPWT PICO dressing for 7-day therapy (PICO 7) or NPWT PICO 14-day therapy (PICO 14).

82 Revision Hips and 82 Revision Knee participants, with 41* of each cohort randomised to either a 7-day or a 14-day NPWT dressing treatment duration period. The 7-day cohort will be treated with PICO7 dressings and pumps, and the 14-day cohort will be treated with PICO14 dressings.

*Randomisation will be stratified, so it will continue until there are at least 41 participants in each cohort.

Although the efficacy of these dressings is well established in promoting wound healing, the duration of application particularly in revision surgeries, where the surgery has been carried out though old scar tissues is however undetermined at present. The few published studies regarding this do show a benefit, however, they do not address the potential issues surrounding late wound breakdown and the duration of the NPWT on the wound 4,5.

Therefore a proposed randomised study to evaluate whether one-week of negative pressure wound therapy is sufficient or whether a two-week therapy duration is warranted.

This will be done by randomising a minimum of 82 patients who are scheduled for revision hip surgery and 82 patients who are scheduled for revision knee surgery into either a "control group" or a "study group".

The 'control group' cohort will receive a NPWT PICO 7 dressing and pump for a period of week, followed by a hydrocolloid dressing or other standard dressing applied thereafter. The 'study group' cohort will receive a NPWT PICO 14 dressing and pump for a period of 2 weeks, with a dressing change at one week. The pump will be paused during the dressing change, restarting it again once the new dressing has been applied and sealed for another week's NPWT.

Inclusion Criteria:

• Subjects must be over the age of 18 years.
• Participants undergoing aseptic revision hip or aseptic revision knee surgery procedure (a single stage revision procedure).
• Participants must be willing and be able to make all the required study visits to be seen by the research team at the Outpatients department at RJAH.
• Participants must be able to follow instructions.

Exclusion Criteria:

• Revisions for infection, where the nature of the infection has a significant influence on the wound healing, discharge, and length of stay.
• Subjects with a history of poor compliance with medical treatment.
• Subjects with contraindications (as per the PICO Instructions for use) or hypersensitivity to the use of the NPWT PICO dressing product or its components e.g.: silicone adhesives, polyurethane films, acrylic adhesives, polyethylene fabrics and super- absorbent powders (polyacrylates) contained within the dressing.