This patient has an arterial ulcer, and determination of the ankle-brachial index would be the next appropriate step in management. Arterial ulcers occur in the setting of significant peripheral vascular disease and result from inadequate perfusion of the lower extremities. Ulceration tends to occur at the distal aspects of the arterial supply (such as the distal toes) or in areas of trauma (such as overlying the metatarsal heads or shins and ankles). The ulcers are usually tender, have a well-demarcated border with a “punched out” appearance, and are surrounded by erythematous, tight skin. Dry, shiny skin is often present, and elevation of the legs often results in worsening pain. Changes consistent with venous stasis, such as stasis dermatitis and lipodermatosclerosis, are usually lacking. The presence of peripheral vascular disease may be suggested by a decreased ankle-brachial index, with a value less than or equal to 0.9 suggestive of significant arterial occlusion. If the ankle-brachial index is decreased in this patient, lower extremity Doppler ultrasound arterial studies are indicated to confirm impaired arterial flow as a cause of the ulceration. If significant arterial compromise is found, referral to a vascular surgeon is indicated for consideration of a revascularization procedure.

Biopsy is not useful for distinguishing between venous stasis ulcers and arterial ulcers, although it can be useful to rule out other causes of ulceration such as infection or malignancy. Skin biopsy in the setting of arterial insufficiency can lead to an enlargement of the ulcer and thus should be performed with caution.

External compression, a mainstay of treatment for venous stasis ulcers, is contraindicated for arterial ulcers as it may further interfere with perfusion. As venous stasis and arterial insufficiency may sometimes coexist, vascular studies should be considered prior to starting compression therapy for venous stasis if there is significant concern for the presence of arterial disease.

Oral antibiotics are useful when overt signs of infection are present; however, they are not indicated otherwise. Common signs of infection include purulent discharge, swelling, and increasing tenderness. Overuse of antibiotics has been shown to lead to the development of resistant bacteria, a situation that is particularly problematic in the setting of chronic wounds.