An ultrasound-based approach to preoperative confirmation of reverse radial forearm flap perfusion.

Abstract

Sir: The reverse radial forearm flap serves as a workhorse for reconstruction of dorsal hand defects with denuded tendon exposure following trauma, burns, and tumor excision. Successful flap perfusion following proximal division of the radial artery relies on reversal of arterial flow through the superficial and deep palmar arch branches of the ulnar artery.1,2 Preoperative assessment of radioulnar collateralization must be performed to ascertain adequate digital perfusion following radial artery division. In most cases, an Allen test can aid in determining whether sacrificing the radial or ulnar artery will result in compromised digital blood flow.3 However, some situations, such as severe hand burns, undermine the utility of an Allen test, which relies on visualizing skin color changes and manual compression over potentially sensitive areas.4 In this communication, we present a case using a novel Doppler ultrasound method of assessing the adequacy of an ulnar-based flap and digital perfusion with direct visualization of radial artery flow reversal. A 43-year-old man with a history of posttraumatic stress disorder and multiple substance abuse sustained third-degree burns to his left lateral arm, dorsal forearm, and dorsal hand in a motor vehicle collision. On postburn day 7, the patient underwent tangential excision and allografting of all of his left upper extremity burns. Whereas his left arm and dorsal forearm burns showed subsequent improvement in their wound beds, the dorsal hand deteriorated, revealing exposed and desiccated extensor tendon over the radial dorsal hand, index, and long finger proximal interphalangeal joints. Soft-tissue coverage with a reversed radial forearm flap was planned. Because of extensive hand and wrist burns precluding Allen testing, alternatives were considered. Computed tomographic and traditional angiography were undesirable because of deteriorating renal function. To assess digital and flap perfusion preoperatively, we combined the use of two Doppler-based examinations. First, the patient underwent a Doppler ultrasound-based examination of the radial artery near the level of the proximal wrist crease. We obtained ultrasound waveforms and flow velocities before and after manual occlusion proximal to this site, simulating arterial division. Preocclusion waveforms showed arterial, proximal-to-distal directional signals, with a peak velocity of 83 cm/second; whereas postocclusion waveforms showed arterial, distal-to-proximal flow, with a peak velocity of −15 cm/second and color change indicating reversal of flow (Figs. 1 and 2). We supplemented this test with a traditional Doppler Allen test by verifying the presence of triphasic signals in all five digits during occlusion of the radial artery. The patient subsequently underwent a reverse radial forearm flap. He required a 3-day course of leeching postoperatively, but the flap remained viable thereafter.Fig. 1: Left radial artery before occlusion. Red color indicates anterograde flow. Pulsatile waveform with a peak velocity of 83 cm/second is shown.Fig. 2: Left radial artery after proximal occlusion. Blue color indicates retrograde flow. Pulsatile waveform with peak velocity of −15 cm/second is shown.In this case, we demonstrate a convenient bedside method for directly visualizing and quantifying the reversal of radial artery flow in anticipation of performing a reverse radial forearm flap for soft-tissue coverage of dorsal hand defects. This is a simple and useful method for verifying flap perfusion and digital perfusion when supplemented with a Doppler Allen test. This combination of Doppler-based modalities represents a previously unreported method of verifying adequate digital and flap perfusion when traditional modalities are not possible. DISCLOSURE The authors have no financial interest to declare in relation to the content of this article. Leo M. Gribelyuk, M.D., M.B.A. Peter F. Koltz, M.D. Joshua T. Waltzman, M.D., M.B.A. Jeffrey A. Fink, M.D. Derek E. Bell, M.D. Division of Plastic Surgery University of Rochester Medical Center Rochester, N.Y.