A 42-year-old man comes to the office due to swelling and numbness in his foot. His symptoms have gradually worsened over one month. Medical history is significant for type 2 diabetes mellitus for five years, for which he takes metformin. However, he is non-compliant with his medications. He has smoked half a pack of cigarettes daily for 20 years. He does not consume alcohol or use illicit drugs. Temperature is 37.1 C (98.9 F), blood pressure 130/80 mm of Hg, pulse 77/min, and respirations 18/min. The cardiopulmonary examination is normal. There is swelling, erythema, and deformity of the left foot on examination. An X-ray of the foot is shown in the exhibit. A small ulcer of about 1 cm (0.9 inches) is present in the plantar surface of the foot under the first metatarsal head. Neurological examination reveals loss of sensation of the left foot. Reflexes are intact. Tibial and dorsalis pedis pulses are normal.