A 52-year-old man presents to the clinic with a left foot ulcer that he noticed 6 days ago. He has a history of obesity, hypertension, type 2 diabetes mellitus, and depression. His current medications include metformin, aspirin, rosuvastatin, lisinopril, and fluoxetine. He has a 25-pack-year smoking history and drinks 1 glass of wine a day. His temperature is 98.6°F (37.0°C), blood pressure is 115/70 mmHg, pulse is 70/min, and respirations are 12/min. On physical exam, he has a 1.2 x 1.7 cm ulcer on the plantar surface of his left metatarsal head. Which of the following tests will most appropriately assess this patient’s future risk of foot ulcers?
Knee reflex testing
Monofilament testing
Contrast-enhanced foot magnetic resonance imaging
Ankle-brachial index
Monofilament testing
This patient with a history of diabetes, hypertension, and obesity now presenting with a foot ulcer most likely has a diabetic foot ulcer. He should undergo monofilament testing to assess the subsequent risk of developing foot ulcers.

Diabetic neuropathy is the most common underlying cause of diabetic foot ulcers. The pathophysiology of diabetic foot ulcers is thought to be the loss of pain and pressure sensation, which leads to muscular imbalance and foot deformities. This subsequently decreases microcirculation and impairs the integrity of the skin, leading to the formation of foot ulcers. Diabetic foot ulcers, like other neuropathic ulcers, occur commonly under bony prominences in the foot. During monofilament testing, a 10-g monofilament is placed on the plantar surface of the foot at a right angle, and pressure is applied until the patient can no longer tolerate it or the filament buckles. Patients with diabetic neuropathy have a higher-pressure threshold due to loss of sensation, and this is a useful predictor of the severity of diabetic neuropathy and future foot ulcer formation. The management of diabetic neuropathy consists of tight glycemic control, weight loss, blood pressure control, exercise, preventing complications, and pain management with pharmacotherapy (serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants, or gabapentinoid antiseizure medications).

Tesfaye et al. study the efficacy of various first-line medications for diabetic nephropathy including amitriptyline, duloxetine, pregabalin, or gabapentin. The authors found that there were no differences between any of the medications as monotherapy. The authors recommended adding combination pharmacotherapy for patients with painful diabetic neuropathy that do not respond to initial monotherapy.

Incorrect Answers:
Answer A: Ankle-brachial index is a calculation made in the assessment of peripheral arterial disease (PAD). While PAD can present with arterial ulcers, these are usually located at the tip of the toes and not the plantar surface. Furthermore, the ankle-brachial index does not accurately assess small vessel disease, which is associated with diabetic foot ulcers.

Answer B: Capillary refill time, when delayed, may suggest decreased limb perfusion. This is a nonspecific test, as decreased limb perfusion can be caused by peripheral arterial disease, volume depletion, or hypotension.

Answer C: Contrast-enhanced foot MRI is the most sensitive and specific test to identify soft tissue complications of acute osteomyelitis. This patient has no clinical features of osteomyelitis (fever, chills, or malaise, ulcer that probes to bone) and does not require imaging currently.

Answer D: Knee reflex testing is not useful in assessing diabetic neuropathy. While diabetic neuropathy can affect large nerve fibers in the lower extremities, it typically impairs ankle reflexes while sparing knee reflexes.

Bullet Summary:
Preventative measures for diabetic foot ulcers should focus on regular foot exams with monofilament testing to assess for diabetic neuropathy.