Abstract
Background Application of negative pressure wound therapy (NPWT) on free flaps not only reduces
edema but also increases the pressure from outside. The impact of these opposite effects
on flap perfusion remains elusive. This study evaluates the NPWT system's influence
on macro- and microcirculation of free flaps and edema reduction to better assess
the clinical value of this therapy in microsurgical reconstructions.
Methods In this open-label, prospective cohort study, a total of 26 patients with free gracilis
muscle flaps for distal lower extremity reconstruction were included. Flaps were covered
with an NPWT (13 patients) or a conventional, fatty gauze dressing (13 patients) for
5 postoperative days (PODs). Changes in flap perfusion were analyzed by laser Doppler
flowmetry, remission spectroscopy, and an implanted Doppler probe. Flap volume as
a surrogate parameter for flap edema was evaluated by three-dimensional (3D) scans.
Results No flap showed clinical evidence of circulatory disturbances. The groups showed significant
differences in the dynamic of macrocirculatory blood flow velocity with an increase
in the NPWT group and a decelerated flow in the control group from PODs 0 to 3 and
PODs 3 to 5. No significant differences in microcirculation parameters were observed.
3D scans for estimation of edema development demonstrated significant differences
in volume dynamics between the groups. Flap volume of the controls increased, while
the volume in the NPWT group decreased during the first 5 PODs. The volume of NPWT-treated
flaps decreased even further after NPWT removal from PODs 5 to 14 and significantly
more than the flap volume in the control group.
Conclusion NPWT is a safe form of dressing for free muscle flaps that enhances blood flow and
results in a sustainable edema reduction. The use of NPWT dressings for free flaps
should therefore be considered not only as a pure wound covering but also as a supportive
therapy for free tissue transfer.
Keywords
free flap - negative pressure wound therapy - VAC - flap edema - flap perfusion
