Diabetic foot ulcers and infections

Why diabetes affects the feet

Long-standing diabetes can damage the nerves that carry sensation from the feet (neuropathy). When feeling is reduced, blisters, cuts and areas of high pressure can go unnoticed. Diabetes can also narrow the arteries of the legs, so less blood reaches the foot to heal a wound. An unnoticed injury combined with poor circulation can progress into an ulcer, and sometimes into a serious infection.^[1]

Nerve damage can also change the shape of the foot. Toes can bend into hammertoes, and rarely the bones can fracture and collapse (see Charcot foot). Both create new pressure points where ulcers develop.^[1,5]

Signs of an ulcer or infection

Because feeling is reduced, the signs below matter more than pain:

• a blister, cut, sore or crack in the skin that isn’t healing
• redness, warmth or swelling of part of the foot, or a foot that looks different from the other
• drainage, or a bad smell, from a sore
• skin that is very pale, blue, black or cold
• fever or chills, or feeling unwell^[1,6]

Preventing ulcers

Prevention is far easier than treatment.

• Regular foot screening. People at very low risk of foot ulceration should be screened at least once a year for loss of protective sensation and for peripheral artery disease. People at higher risk should be screened more often.^[5]
• Daily foot checks for cuts, blisters, red spots and warm areas, using a mirror if needed. Don’t walk barefoot, indoors or outdoors.^[1,5]
• Proper shoes. People at moderate to high risk should wear properly fitting, accommodative therapeutic footwear. After an ulcer has healed, footwear that has a demonstrated pressure-relieving effect helps prevent recurrence.^[5]
• Treating problems early. Calluses and other pre-ulcer lesions should be treated. For a bent, flexible hammertoe with a pre-ulcer lesion, a small tendon release can be considered.^[5]
• Blood sugar control and regular checkups, with foot examinations at each visit for people at high risk.^[1]

How an ulcer is evaluated

The evaluation looks at the ulcer itself (size, depth, and whether bone is exposed), signs of infection, sensation, pulses and circulation, the shape of the foot, and the shoes you wear. Tests may include X-rays, blood tests, measurements of blood flow, and sometimes MRI when bone infection is suspected.^[6,3] Because PAD is common in people with diabetic foot ulcers, the circulation assessment is an essential part of the plan.^[3]

Treatment

Healing a diabetic foot ulcer takes several treatments working together:

• Offloading. For a neuropathic ulcer on the ball or middle of the sole, the international guideline recommends a non-removable, knee-high offloading device as the first choice. If that isn’t suitable, a removable knee-high or ankle-high device is the second choice.^[2]
• Wound care. Removal of dead tissue (debridement), keeping the wound bed clean and appropriately dressed, and, in selected cases, other therapies to help healing, all alongside multidisciplinary care.^[7]
• Treating infection. Infections range from superficial to deep infections of soft tissue and bone. The International Working Group on the Diabetic Foot and the Infectious Diseases Society of America have guidelines for diagnosing and treating them, including when surgery is needed.^[6,8]
• Restoring blood flow. When PAD is present, a vascular specialist evaluates whether the circulation can be improved.^[3]
• Blood sugar control and treatment of other health conditions.^[9]

The role of surgery

Foot and ankle surgery has several roles in diabetic foot disease. A deep infection or abscess usually needs prompt surgical drainage and removal of infected or dead tissue. Bone that is infected (osteomyelitis) may need to be partly removed. Deformities that keep causing ulcers, such as a bent toe, a bony prominence, or a tight Achilles tendon, can sometimes be corrected to take pressure off the area. And when a foot has collapsed, reconstruction may be considered. The aim is to preserve a foot that can walk and fit in a shoe.^[9,5,8]

Surgery in people with diabetes carries higher risks, particularly of infection, and the risk is highest in people with neuropathy and complications of diabetes. In one study, the rate of surgical site infection after foot and ankle surgery was 9.5% in people with diabetes and 2.4% in people without it; neuropathy, Charcot neuroarthropathy and smoking were associated with infection.^[10,11] Careful preparation, including optimizing blood sugar, is part of the plan. See preparing for foot and ankle surgery.

Nerve decompression is not a recommended way to prevent foot ulcers.^[5]

When to seek care

If you have diabetes, look at your feet every day, and get care early. Don’t wait for pain, since nerve damage can hide it.