A 45-year-old man comes to the office due to mild pain in his left foot and difficulty walking for the past several months. He now walks with a cane and recently began using an ankle brace for support. Medical history is significant for type 1 diabetes mellitus, hypertension, and hypercholesterolemia. Physical examination is notable for a significantly deformed left ankle and a mildly deformed left foot. Peripheral pulses are full and symmetric. X-ray of the left foot and ankle with weight bearing reveals osseous fragmentation, new bone formation, and sclerosis, as seen in the exhibit. Which of the following is the most likely cause of this patient's foot condition?
Show Explanatory Sources
This patient has foot and ankle deformities and x-ray findings that indicate neuropathic (Charcot) arthropathy, which occurs most commonly in patients with diabetes mellitus (particularly those with peripheral neuropathy). Neuropathic arthropathy involves repetitive bone and tissue trauma caused by impaired sensation and joint proprioception that prevent the patient from adjusting weight bearing to avoid mechanically induced wear and tear.
Neuropathic arthropathy can present in either of 2 stages:
Acute: Characterized by inflammatory erythema, warmth, and edema of the foot 1-2 days after minor trauma. X-rays at this stage usually show only soft tissue swelling without bone involvement.
Chronic: Characterized by bone deformities noted on x-ray that typically include osseous fragmentation, new bone formation, and subluxation/dislocation predominantly in the mid and hind foot. Other common signs are loss of the metatarsal heads (pencil pointing) with osteopenia and phalangeal osteolysis. These changes often lead to neuropathic ulcers, arch collapse (rocker bottom feet), and callus formation.
(Choice A) Osteoarthritis of the foot typically affects the first metatarsophalangeal joint with subchondral sclerosis and osteophyte formation rather than diffuse bone destruction as found in neuropathic arthropathy.
(Choice B) Decreased perfusion of the extremities due to atherosclerosis of the tibial arteries (ie, peripheral artery disease) can cause pain (ie, claudication) but would not cause significant bone deformities. This patient's peripheral pulses are full and symmetric.
(Choice C) Isolated foot involvement due to autoimmune inflammatory arthritis is uncommon but may occur in patients with rheumatoid arthritis. When it does, it typically presents with bilateral involvement rather than unilateral as in this patient. However, x-ray findings in advanced rheumatoid arthritis commonly include periarticular osteoporosis, joint erosion, and joint space narrowing rather than grossly destructive changes.
(Choice D) Bony destruction from bacterial infection (ie, osteomyelitis) can manifest as periosteal thickening on x-ray, but infection would be unlikely to cause the significant bone deformities seen in this patient. Osteomyelitis typically occurs in association with a neuropathic ulcer with sinus tracts or exposure of the underlying bone.
Educational objective:
Chronic neuropathic (Charcot) arthropathy is characterized by bone deformities resulting from repetitive trauma to the foot and ankle. It develops in patients who have impaired sensation and joint proprioception (eg, diabetic peripheral neuropathy) that prevent the patient from adjusting weight bearing to avoid mechanically induced wear and tear.