Neuropathic Diabetic Foot Ulcers

A 58-year-old man with type 2 diabetes mellitus has an asymptomatic plantar ulcer on the left foot that remains unhealed after four months. The ulcer measures 2 by 1 cm and is surrounded by callus under the first metatarsal head. Neurologic examination reveals loss of sensation of touch, pinprick, and vibration below the midcalf level bilaterally and the absence of ankle reflexes; the foot pulses are normal. How should this patient be evaluated and treated?