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by the American Institute of Ultrasound in Medicine J Ultrasound Med 22:409-411 • 0278-4297
Gas Bubbles as Sonographic Signs of Buried Muscle Flap NecrosisDepartment of Plastic and Reconstructive Surgery and the Ludwig Boltzmann Institute for Quality Control in Plastic Surgery (A.H.S., M.S., R.G.) and Department of Radiology (G.B.), Leopold-Franzens University, Innsbruck, Austria. Address correspondence and reprint requests to Anton H. Schwabegger, MD, Department of Plastic and Reconstructive Surgery, Leopold-Franzens University, Anichstrasse 35, A-6020 Innsbruck, Austria.
Over the past 3 decades, tissue transfer has evolved into a highly reliable tool for the reconstructive surgeon. Conventional flap-monitoring techniques (clinical observation, handheld Doppler sonography, photometer oxygen measurement, surface temperature probes, and pinprick testing) are proven methods for monitoring vascularized flaps at the body surface. For vascularity surveillance of buried flaps, more sophisticated devices such as a PO2 probe or Doppler sonography must be used when exteriorization of a part of the flap for monitoring is not feasible. Because of the high success rate of flap surgery nowadays and the relatively high material and personnel costs of vascularity surveillance, some surgeons tend to refrain from frequent controls, especially in pedicled flaps. Thus, identification of failure of eventual buried flaps is rather delayed; therefore, flaps are found to be unsalvageable at reexploration. Here we report a case in which gas bubbles were detected on sonography in a buried muscle flap 8 days after surgery. Gas bubbles initially misinterpreted as normal trapped air between the folds of a muscle flap could be early indicators of tissue necrosis in a buried muscle flap, necessitating surgical revision to avoid major complications.
A 20-year-old man had a soft tissue defect due to a previous gunshot injury in the left shoulder with disability of the full range of shoulder movement. This defect was reconstructed by transfer of a latissimus dorsi muscle island flap covered with a full-thickness skin graft. Because of misdiagnosis of a postoperative hematoma as small and not critical, bruising pressure to the muscle flap was neglected at that time, and revision or hematoma evacuation was not considered.
Sonographic examination 8 days postoperatively showed multiple trapped gas bubbles between the muscle fibers (Fig. 1
One week after discharge of the patient, severe secretion of dark red liquid appeared. That situation forced us to perform surgical revision, which revealed complete necrosis of the flap (Fig. 2  ).
Multiple large series of free flap transfers have documented overall success rates greater than 95%.1–4 Throughout this development and evolution of free tissue transfer, surgeons increasingly have sought reliable means of monitoring their flaps. Conventional free flap–monitoring techniques (clinical observation, handheld Doppler sonography, surface measurement probes, and pinprick testing) are widely used for monitoring flaps with external components.5–7 The external component permits direct visualization of signs of vascular compromise. However, conventional monitoring of buried flaps is more problematic. By virtue of their location, buried flaps cannot be visualized directly. This placement limits conventional monitoring techniques to Doppler evaluation of the vascular pedicles of free flaps as well as pedicled or island flaps.8,9 Despite a surgeon’s attempt to accurately assess a pedicle by using a handheld Doppler probe, it is possible to overlook a compromise in overall flap perfusion. This method can lead to the false impression that the flap pedicle is patent. The inability to reliably monitor the above-mentioned buried flaps leads to a delay in recognition of failing flaps. In a study in which buried flaps were compared with nonburied flaps,10 nonburied flap vascular compromise was identified earlier (generally <48 hours postoperatively). On the contrary, vascular compromise in buried flaps was not recognized until it manifested itself as a wound complication (generally >7 days postoperatively).10 Also, in our case, the ischemia of the buried flap was not detected at the beginning. The only clear abnormal sign on sonography was the presence of the gas bubbles, which was misinterpreted by the surgeon as rest air between the folds of the latissimus dorsi muscle flap. To the best of our knowledge, the presence of gas bubbles as a clinical observation or a sign of muscle necrosis has not been described previously in the sonographic literature. The sonographic detection of gas as a sign of liver tissue necrosis has been described in literature on liver tumor surgery.11–14 In cases of unclear indications for surgical revision, however, because of hematoma and the potentially impaired viability of a buried muscle flap, detection of gas bubbles by sonographic assessment may be the earliest sign in a buried flap with vascular compromise.15 Early observation of hyperechoic spots on a sonogram as signs of gas development due to necrosis and autolysis may not facilitate salvage of a flap, but it may prevent delayed recognition of further disastrous complications and ensuing sequelae such as sepsis.
Received November 14, 2002, from the Department of Plastic and Reconstructive Surgery and the Ludwig Boltzmann Institute for Quality Control in Plastic Surgery (A.H.S., M.S., R.G.) and Department of Radiology (G.B.), Leopold-Franzens University, Innsbruck, Austria. Revision requested November 25, 2002. Revised manuscript accepted for publication November 27, 2002.
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