Dear Sir,

Over the past two decades, the use of perforator flaps in microsurgical reconstruction has increased; free muscle flaps are still though widely used, especially in lower extremity reconstruction.[1] A disadvantage of free muscle flaps is the necessary use of skin graft that can interfere with flap monitoring.[2] Although clinical exam remains the gold standard for monitoring, assessing the perfusion of a skin grafted muscle can be challenging.[2] [3] To that end, monitoring of free muscle flaps is performed with Doppler ultrasound—either with implantable devices or a pencil Doppler.[2] [3]

Negative pressure wound therapy (NPWT) has revolutionized wound care since its introduction.[4] Besides a favorable impact in wound healing, NPWT has been shown to increase the take of skin grafts[4] and is routinely used as a bolster postoperatively. NPWT reduces wound complications and increases the timing flexibility of soft tissue reconstruction, while its application in cutaneous flaps has been hypothesized to reduce flap edema and associated complications.[3] The NPWT applicability in free flaps has been controversial, secondary to concerns of creating pressure on the pedicle, but studies have demonstrated its safety.[2] [3] NPWT is still seldom applied over a free muscle flap covered with skin graft as it would interfere with flap monitoring, unless an implantable Doppler device was used.[2] Henry et al first reported the successful use of NPWT over skin grafted free muscle flaps, making windows in the foam over areas where a strong Doppler signal can be heard.[5] In our experience, the direct contact of the NPWT adhesive drape and the skin graft can interfere with the Doppler signal and occasionally create concerns over flap perfusion.

We have been successfully using a modified technique of NPWT application that reliably allows the monitoring of muscle flaps through the NPWT device. At the completion of free tissue transfer and split thickness skin graft, the area of muscle where a strong Doppler signal can be heard is marked. The muscle is covered with a nonadhesive occlusive dressing (Xeroform™ Occlusive Dressing, Cardinal Health™, Dublin, OH) and the NPWT sponge is applied (V.A.C.® GranuFoam™ Dressing; 3M KCI International Inc., San Antonio, TX). A piece of the sponge and underlying dressing is then excised to expose the area of the muscle that will be used for flap monitoring ([Fig. 1]). The formed “well” is then filled with ultrasound conducting gel (Aquasonic Ultrasound Transmission Gel, Parker Laboratories Inc. Fairfield, NJ) and the adhesive drape is applied over the sponge. The pencil Doppler probe can then be used over the clear adhesive dressing of NPWT for flap monitoring. The high viscosity of the ultrasound gel does not allow it to be suctioned through the NPWT. In our practice, the NPWT is set at 75 mm Hg of continuous pressure and the dressing stays in place for 5 days. This modification in NPWT application enhances the ability to reliably monitor flap perfusion over free muscle flaps, obviating the need for implantable Doppler devices.