Pachowsky 2012.

Methods	Study design: randomised controlled trial Ethics and informed consent: ethics approved and consent obtained. Sample size calculation: no ITT analysis: yes number randomised: 19 number analysed: 19 Follow‐up period: 10 days Funding: support received from Smith & Nephew. The authors were responsible for trial design, data analysis, and manuscript writing. The decision to publish trial results was made between study authors and study sponsors. Pre‐registration: no
Participants	Location: University Hospital Erlangen, Germany Intervention group: n = 9control group: n = 10 Mean age: intervention group = 66.2 years (SD 17.83)control group = 70.0 years (SD 11.01) Inclusion criteria: "consecutive patients who were scheduled for a total hip arthroplasty (THA) for osteoarthritis of the hip were randomised" Exclusion criteria: not stated
Interventions	Aim/s: to evaluate the use of NPWT to improve wound healing after total hip arthroplasty Intervention/s in both groups: "the surgical intervention was identical for both groups. All patients received two Redon drains, one in the deep area of the wound close to the prostheses and one above the closed fascia. The postoperative physiotherapy and mobilisation was also identical for both groups. Both groups received perioperative prophylaxis with antibiotics either Augmentin (amoxicillin trihydrate with potassium clavulanate) or ciprofloxacin" Group 1 (NPWT) intervention: "the NPWT group was treated with a PREVENA™ system (KCI, San Antonio, USA). The PREVENA system was left on the wound for five days including the day of surgery" Group 2 control: the control group received "the standard wound dressing of our department, consisting of a dry wound coverage". Study date/s: not stated
Outcomes	incidence of seroma (by ultrasound) amount of wound drainage in the Redon drain canisters duration of prophylactic antibiotics secretion from the wound Validity of measure/s: "all patients underwent an ultrasound (Zonare, Z.one Ultra SP 4.2, Erlangen, ZONARE Medical Systems, Inc., Mountain View, USA) of the wound" Time points: day 5 and day 10 of postoperative period
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated
Allocation concealment (selection bias)	Unclear risk	Not stated
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	Unclear risk	Dressings were left in place for 5 days. The ultrasound was performed on day 5. It was unclear if the person performing the ultrasound was aware of the group to which the participant had been allocated.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All enrolled participants were accounted for in the analyses.
Selective reporting (reporting bias)	Low risk	Results for outcomes identified in the methods section were reported. We did not see the original protocol.
Other bias	High risk	Evidence: quote: "Matthias H. Brem gave scientific presentations for KCI. The PREVENA wound treatment system was provided by KCI free of charge". Support was received from Smith & Nephew. The authors were responsible for trial design, data analysis, and manuscript writing. The decision to publish trial results was made between study authors and study sponsors. 1 participant in the NPWT group removed the Redon drain by himself on the first postoperative day.