Diabetic foot ulcers (DFUs) affect around 15 to 25% of all patients with diabetes mellitus.

While DFU formation is complex, the leading causes are neuropathy and peripheral artery disease (PAD), which develop as diabetes progresses.

Neuropathy impairs foot function and sensation, increasing the likelihood of blisters and calluses developing into wounds. PAD reduces blood flow to the foot, decreasing the body’s healing and immune response. Consequently, even small wounds to the foot may fail to heal and develop into ulcers.

The foot becomes vulnerable to infection and possibly gangrene once a foot ulcer develops. The majority of ulcers can typically heal with conservative treatment, while 5 to 25% require amputation.

With timely intervention, diabetic foot ulcers are far more likely to heal, preventing severe outcomes.

In this article, we’ll explore the causes of diabetic foot ulcers and how to treat them.

What Are Diabetic Foot Ulcers?

Diabetic foot ulcers (DFUs) are open sores or wounds that develop on the feet of individuals with diabetes. Ulcers are wounds that don’t heal in the expected time-frame of around two to three weeks.

Instead of healing, ulcers remain open wounds, which vastly increases the chance of infection.

DFUs typically develop on the bottom of the foot but can occur elsewhere on the top, side, or bottom of the foot.

Keep in mind that DFUs vary in severity and can range from small ulcers that heal independently with wound treatment to larger, more complex ulcers that are considerably harder to treat.

What Causes Diabetic Foot Ulcers?

The causes of diabetic foot ulcers are complex and can involve a number of factors.

Most ulcers develop through a combination of neuropathy, which weakens feeling and sensation in the limb, and peripheral artery disease (PAD), which causes impaired circulation.

Ulcers can occur at any stage of diabetes and are more common in older individuals living with diabetes for a long time.

For example, a 2005 study published in JAMA Network found that the risk of developing foot ulcers increases with age, with a mean age of 56, primarily due to the progression of PAD and neuropathy.

Here are the key mechanisms behind DFUs:

Neuropathy

Diabetic neuropathy is fundamental to the formation of DFUs.

Neuropathy affects the foot’s ability to sense, leading to deformities such as hammer toe and Charcot’s foot which is a rare complication of diabetes.

Since the foot is not its usual shape, it’s more likely to rub in contact with the floor or ill-fitting footwear. This increases the likelihood of calluses, bunions, and blisters forming on the foot, which eventually erode and flake away, forming an open wound that develops into an ulcer.

Since the body cannot sense the presence of the wound – as the nerves are damaged – it doesn’t attempt to heal it. As neuropathy reduces pain and sensation, lesions are often ignored, causing them to worsen.

Peripheral artery disease (PAD)

One of the later-stage complications of diabetes is peripheral artery disease (PAD), which decreases blood flow to the feet.

It is estimated that 20% of people with diabetes develop PAD. With decreased blood flow to the extremities, the body’s ability to heal the foot is reduced, leaving the feet vulnerable to ulceration and infection.

Advanced PAD makes it difficult for the body to heal even minor and seemingly benign wounds.

Foot deformities

Diabetic neuropathy leads to muscle weakness, resulting in foot deformities such as hammertoes, bunions, and Charcot’s foot.

Deformities increase pressure on specific areas of the foot, making them more vulnerable to calluses which eventually develop into ulcers. This is exacerbated by ill-fitting footwear, which increases stress on certain parts of the foot, hence why most ulcers form on the ball of the foot or the heel.

Trauma

Minor injuries, such as cuts or blisters, can quickly develop into ulcers in diabetic patients.

Since the foot nerves are damaged, the body cannot sense the presence of a wound and as a result, does not attempt to heal it. Moreover, neuropathy renders minor injuries relatively painless and easy to ignore.

People with diabetes should never ignore foot trauma of any kind, no matter how minor the wound is. Contact your physician as soon as possible if you have diabetes and injure your foot or notice calluses forming, regardless of how minor.

How Diabetic Foot Ulcers Form: An Example Case

Let’s take a closer look at an example of how diabetic foot ulcers form in diabetic individuals.

The formation of DFUs is complex and involves multiple factors, including:

  • Peripheral neuropathy causes loss of sensation in the foot, impairing the body’s ability to sense the presence of a wound.
  • Foot deformity resulting from nerve damage, which, even in minor cases, can accelerate the formation of calluses and bunions.
  • Local autonomic neuropathy in the foot, which prevents the foot from sweating. This causes the skin to dry out and flake away or erode, increasing the likelihood of wound formation. For example, dry skin is prone to cracking.
  • Peripheral artery disease, which impairs the body’s ability to divert fresh blood to the area to heal wounds.

Diabetic foot ulcers usually form from calluses. A study published in Diabetic Medicine found that calluses precede 82% of DFUs. Normally, calluses form, degrade, and heal at their own accord, but in diabetic individuals, calluses are more likely to degrade into lesions that develop into DFUs.

Due to impaired blood circulation and reduced immune response, the lesion left behind by a callus doesn’t heal and develops into a foot ulcer. As a result, the ulcer and surrounding tissues are left vulnerable to infection.

In some cases, an untreated ulcer may deepen and spread to underlying structures such as tendons, bones, and joints, increasing the risk of complications such as abscess, bone infection (osteomyelitis), and gangrene.

Types and Grades of Diabetic Foot Ulcers

Diabetic ulcers vary in severity. Minor ulcers are more likely to heal than advanced ulcers with early intervention – don’t delay contacting your physician if you notice a wound on your foot that isn’t healing.

The most commonly used grading system for DFUs is the Wagner scale, which grades ulcers from 0 to 5:

  • Grade 0: Pre-ulcerative lesion
  • Grade 1: Superficial ulcer, not involving tendon or bone
  • Grade 2: Deep ulcer, penetrating down to tendon or bone
  • Grade 3: Ulcer with abscess, osteomyelitis, or sepsis
  • Grade 4: Localized gangrene
  • Grade 5: Extensive gangrene involving the entire foot

Grades 1 to 3 are typically treated with combo therapy of dressings, antibiotics, and offloading, which aims to take the weight off the foot to promote healing.

Grades 4 and 5 may prove challenging to treat and are considerably more likely to require amputation. Again, this highlights the importance of timely intervention.

Treatment of Diabetic Foot Ulcers

Treating diabetic foot ulcers varies depending on the severity and depth of the ulcer, the level of infection, and the structures affected (e.g., bones and tendons). Treatments range from straightforward conservative treatment with dressings to surgical intervention.

Glycemic control

Maintaining optimal blood glucose levels is paramount in the treatment of DFUs. High blood sugar levels and poor glycemic control impair wound healing and increase the risk of infection.

Keeping blood glucose levels stable is crucial to avoiding neuropathy and PAD, which are prerequisites to diabetic foot ulcers.

The American Diabetes Association recommends a target HbA1c level of <7% for most diabetic patients.

Wound care

Wound care for diabetic foot ulcers can include debridement (cleaning), dressings, and topical treatment.

Debridement is pivotal for neglected wounds, which often contain decaying tissues and foreign materials, like fluff or dirt.

Dressings protect the wound from infection and maintain an environment that promotes healing.

Hydrocolloids and alginate dressings are often used to absorb septic discharge from exuding ulcers. Additionally, topical creams and gels are applied to the wound area to kill and deter microbes.

Offloading

Offloading means relieving weight from the affected foot. It is essential for reducing pressure on the ulcerated area and promoting healing.

The most effective offloading techniques include total contact casting (TCC), removable cast walkers (RCWs), and therapeutic footwear.

TCC is considered the gold standard for offloading plantar DFUs, as it redistributes pressure evenly across the foot.

Infection management

Infections are a significant complication of DFUs and can lead to severe outcomes which can include amputation. A variety of different antibiotics are often used depending on the severity of the infection.

Early diagnosis and treatment of infection with antibiotics is crucial to prevent amputation.

Revascularization

In some cases, physicians treat peripheral artery disease with revascularization procedures.

Revascularization re-diverts blood flow to the ulcer, enhancing natural healing and potentially avoiding the need for amputation.

Do Foot Ulcers Heal?

Fortunately, 60-80% of diabetic foot ulcers heal. However, successful healing of foot ulcers may take weeks to months depending on the ulcer’s size, depth, and location. Physicians should monitor the wound for signs of infection during the healing process.

In some scenarios, foot ulcers may not heal despite appropriate treatment. If so, alternative therapies or surgical interventions, such as amputation are proposed depending on the ulcer’s potential to heal and its risk to the individual.

While amputation seems like a drastic intervention, it may be necessary to prevent an infection from developing into a serious case of sepsis which can be life-threatening.

Amputation in Diabetic Foot Ulcers

Amputation is sometimes necessary for ulcers that do not respond to conservative treatments, are severely infected, or have extensive tissue necrosis.

The primary goal of amputation is to remove nonviable tissue and prevent the spread of infection. Of course, the decision to amputate is never taken lightly.

Amputations can be categorized as minor or major:

Minor amputations

Minor amputations involve the removal of part of the foot, such as a toe or a portion of the metatarsal bone. The aim is to preserve as much of the foot as possible while removing nonviable tissue and infection.

Major amputations

Major amputations involve the removal of a significant portion of the limb, such as a below-knee amputation (BKA) or an above-knee amputation (AKA).

Physicians will only consider major amputation for severe cases where extensive tissue necrosis, uncontrolled infection, or ischemia makes it impossible to salvage the limb.

While viewed as a last resort, major amputations can save a patient’s life.

If You Have a DFU: What Next?

If you suspect a diabetic foot ulcer (DFU), consult a healthcare provider for assessment and treatment.

Your provider will create a bespoke plan tailored to you and your ulcer, including managing glycemic treatment, wound care, offloading, infection control, debridement, and vascular intervention.

Regularly monitor the ulcer’s healing and maintain proper foot care by washing and inspecting your feet daily, moisturizing, wearing appropriate footwear, trimming toenails properly, and scheduling regular foot exams. Don’t ignore wounds to the feet, no matter how small.

The risk of amputation increases the longer the ulcer is ignored. However with early intervention and good foot care management can reduce serious complications and promote healthy healing.

Sources

https://www.unitypoint.org/news-and-articles/top-5-causes-of-diabetic-foot-ulcers-and-how-to-prevent-them
https://www.healthline.com/health/diabetic-foot-pain-and-ulcers-causes-treatments
https://www.medicalnewstoday.com/articles/324875#is-it-common
https://www.ncbi.nlm.nih.gov/books/NBK537328/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5875034/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4499529/
https://pubmed.ncbi.nlm.nih.gov/1551311/