Ortho Dx: Black Necrosis of the Left Foot - Clinical Advisor

Ortho Dx: Black Necrosis of the Left Foot

Slideshow

  • Figure 1. Photograph of the left foot.

  • Figure 2. Photograph of the left foot.

A 61-year-old man presents to the emergency department with a 2-month history of an infection in his left foot. The patient has poorly controlled insulin-dependent diabetes and underwent a below the knee amputation on his right side 2 years ago. His infection started as cellulitis but has progressed to full necrosis of the lateral aspect of the left foot over the course of 2 months. The patient has limited mental capacity and has not been taking his insulin routinely. Images of the gangrenous foot are obtained (Figures 1 and 2) and blood cultures reveal Staphylococcus aureus bacteremia.

The patient presents with an ischemic foot due to uncontrolled diabetes that has resulted in a gangrenous infection. The first priority of treatment for this patient is to remove the infected tissue. Gangrene is irreversible tissue death due to loss...

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The patient presents with an ischemic foot due to uncontrolled diabetes that has resulted in a gangrenous infection. The first priority of treatment for this patient is to remove the infected tissue. Gangrene is irreversible tissue death due to loss of blood supply; it is often divided into dry or wet gangrene.1

Dry gangrene causes skin and tissues to dry, shrink, and turn black; it progresses slowly and may result in an auto-amputation of the involved finger or toe. By contrast, wet gangrene can occur if bacteria starts to invade the avascular tissue, which causes swelling, drainage, and a foul smell. Treatment of wet gangrene is more emergent as the infection can spread quickly.1

It is crucial to assess the extremity for arterial occlusive disease with ultrasound or arteriogram studies. If ateriovascular reperfusion can be established, a more limited debridement has a higher chance of healing. For example, a partial foot amputation may be viable if foot perfusion is re-established as opposed to a below the knee amputation for an ischemic foot.2,3 

The patient in this case underwent an arteriogram of the left lower extremity that showed an occlusion of the superficial femoral artery (FSA) and distal left anterior tibial artery. A percutaneous balloon angioplasty was performed to perfuse the anterior tibial artery and the FSA. The anterior tibial artery supplies the dorsum of the foot whereas the posterior tibial artery enters the sole of the foot through the tarsal tunnel and supplies most of the plantar aspect of the foot. A left foot transmetatarsal amputation was performed to remove the dead tissue associated with his ischemic foot.3

Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopedics for Physician Assistants.

References

1. Noor S, Khan RU, Ahmad J. Understanding diabetic foot infection and its management. Diabetes Metab Syndr. 2017;11(2):149-156.

2. Kota SK, Kota SK, Meher LK, Sahoo S, Mohapatra S, Modi KD. Surgical revascularization techniques for diabetic foot. J Cardiovasc Dis Res. 2013;4(2):79-83.

3. Kinlay S. Management of critical limb ischemia. Circ Cardiovasc Interv. 2016;9(2):e001946.

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