Negative pressure wound therapy reduces the ischaemia/reperfusion-associated inflammatory response in free muscle flaps

Background: We recently established negative pressure wound therapy (NPWT) as a safe postoperative care concept for free muscle flaps; however, the molecular effects of NPWT on free muscle flaps remain elusive. Here we investigated the effects of NPWT on pathological changes associated with ischaemia/reperfusion injury in free flap tissue. Methods: From July 2008 to September 2010, 30 patients receiving skin-grafted free muscle transfer for defect coverage were randomly assigned to two treatment groups: In one group the skin-grafted free flap was covered by a vacuum dressing (NPWT); in the second group, flaps were covered by conventional petroleum gauze dressings (conv). Biopsies were taken intraoperatively prior to clipping of the pedicle and on postoperative day 5. Samples were analysed by immunohistochemistry for infiltration of inflammatory cells, real-time polymerase chain reaction (RT-PCR) for the analysis of expression levels of interleukin-1 beta (IL-1 beta) and tumour necrosis factor (TNF)-alpha as markers of inflammation. Histological samples were also examined for interstitial oedema formation, and apoptosis was detected by a terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay. Results: NPWT leads to a significantly reduced tissue infiltration of CD68 + macrophages and reduced expression of the inflammatory cytokines IL-1 beta and TNF alpha. None of these parameters was significantly elevated in the pre-ischaemic biopsies. Furthermore, NPWT reduced the interstitial oedema formation and the number of apoptotic cells in free flap tissue. Conclusion: NPWT of skin-grafted free muscle flaps leads to a reduced inflammatory response following ischaemia/reperfusion, resulting in reduced oedema formation improving the microcirculation and ultimately reduced tissue damage. We thereby deliver new insight into the effects of NPWT. (C) 2011 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.