Manoharan 2016.

Methods	Study design: randomised controlled trial Study grouping: bilateral knees were randomised to intervention or control knees Ethics and informed consent: yes Sample size estimate: yes, but sample did not reach target, stopped due to financial constraints Follow‐up period: 10 days ITT analysis: yes number randomised: 21 number analysed: 21 Funding: KCI, Acelity Inc provided the negative pressure wound therapy dressings for the study. Pre‐registration: retrospectively registered as ANZCTR 12615001350516
Participants	Location: Queensland, Australia Intervention group: n = 21 kneescontrol group: n = 21 knees Mean age (range): 66 (45 to 80) Inclusion criteria: patients undergoing a bilateral knee arthroplasty Exclusion criteria: aged < 18 years or pregnant
Interventions	Aim/s: to assess the effect of NPWT on outcomes after primary arthroplasty Group 1 (NPWT) intervention: the intervention group received PREVENA Incision Management System, Acelity, KCI, which was placed over the closed surgical incision under sterile conditions at the end of the procedure. The NPWT device provided a continuous negative pressure of 125 mmHg for a duration of 8 days. Group 2 (control) intervention: the conventional dry dressing was placed over the closed surgical incision under sterile conditions at the end of the procedure. Neither the type of control dressing nor when the dressing was removed was reported. Study date/s: February to December 2014
Outcomes	SSI blisters cost QoL Validity of measure/s: no Time points: 10 to 12 days postsurgery
Notes	Investigator contacted for additional details.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Simple randomisation was performed by the research assistants via online computer software that indicated the side to which the intervention, NPWT, would be applied.
Allocation concealment (selection bias)	High risk	The surgeons were notified on the day of surgery, before the commencement of the procedure. It was also unclear if consecutive patients for each of the 3 surgeons were recruited.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Evidence for participants: not possible Comment: unlikely to affect outcomes Evidence for personnel: not possible Comment: unlikely to affect outcomes
Blinding of outcome assessment (detection bias) All outcomes	High risk	The final incision assessment was performed by the surgeon and clinic nurse and witnessed by 1 of the research assistants. There were no independent observers attached to this assessment.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	It was unclear if all participants were accounted for in the results as the numbers analysed for each outcome are not stated.
Selective reporting (reporting bias)	Low risk	Expected outcomes reported. Protocol retrospectively registered as ANZCTR 12615001350516.
Other bias	Low risk	No other biases detected.