Introduction to diabetic foot ulcers

What is the correct definition of a diabetic foot ulcer?

To be classified as a diabetic foot ulcer, at least three of the following aspects have to be represented:

 

a) the patient must have diabetes mellitus- either type I or type II.

b) the wound must be located at the height of the ankle or distally from here

c) the patient must have impaired sensory function or impaired arterial circulation or a combination of both.

So if a patient with diabetes has a chronic ulcer on the leg area, this is not a true diabetic ulcer! If a diabetic patient has an ulcer on the foot but has completely normal sensory function and good arterial circulation, this is by definition not a true diabetic foot ulcer! Yes, we understand that this is a bit picky, but this is the international definition. Anyway, most diabetic patients with foot ulcers will have an impairment of either sensory function or circulation.

Note that the term « diabetic foot» is a more loose definition. Diabetic foot basically refers to one or more complications that can arise in the foot area in diabetic patients. Suppose a patient with diabetes has a completely normal foot, without sensory loss or impaired circulation and no deformities or ulcers. In that case, this is not a diabetic foot- It is simply a normal foot. The term diabetic foot does not imply that the patient necessarily has an ulceration on the foot. Deformities of the foot due to diabetes are classified as "diabetic foot." Loss of sensation in the foot due to diabetes can be termed "diabetic foot" as well. 

Diabetic foot ulcers often have elements of other types of chronic wounds. They are often pressure-related (  like pressure ulcers) due to poor footwear. There is often some impaired arterial circulation ( like arterial ulcers). And not rarely do we apply compression bandages to promote healing ( like venous ulcers). For these reasons, some like to refer to diabetic foot ulcers as the « kings of all wound types,» although obviously, this is debatable.

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Figure 1  Diabetic foot ulcers often contain elements from other wound types like pressure ulcers ( upper left) or arterial ulcers ( lower left). Usually, they will heal better if we apply compression bandages as we would do with venous ulcers ( upper right). Because diabetic foot ulcers often combine these elements and should preferably be treated by specialists,  some refer to them as the “kings of ulcers.”

Diabetic foot ulcers in Africa

Diabetes mellitus is the most common, non-communicable chronic disease globally. It is estimated that there are about 19 million people with diabetes in sub-Saharan Africa (2021). It is further estimated that about60% of them are not aware of their condition! These numbers are expected to grow exponentially over the next 25 years. In sub-Saharan Africa, the number of people with diabetes is expected to more than double to 45 million by 2045

Diabetes affects most organs in the body and can cause severe complications. Especially when poorly controlled, it commonly leads to eye complications, renal disease, heart disease, and other vascular complications. Most patients develop sensory neuropathy ( and other neuropathies) during the course of the disease. We do not know the exact prevalence of diabetic foot ulcers amongst diabetic patients in Africa. There are several studies from various countries on the continent, but foot ulcer prevalence rates vary greatly even within regions of one country. In Nigeria, for example, prevalence rates varied from between 4%-19% between regions. That is an enormous range, so you will appreciate that it is difficult to generalize these numbers for an entire continent. Without a doubt, however, there is a significant increase in diabetes in Africa, and we will witness a marked increase in complications like diabetic foot ulcers in the future. 

 

Most patients who develop diabetic foot ulcers in African countries have sensory neuropathy. These patients do not necessarily feel pain when they step on something sharp or get a blister from inadequate shoe wear. Even minor damage to the skin can easily get infected in diabetic patients. Unfortunately, most patients that develop foot ulcers in Africa do not seek medical attention before the ulceration has advanced significantly. This patient delay is one of the factors for high amputation rates and high mortality of advanced diabetic foot ulcers.  

There are many important principles concerning the treatment of diabetic foot ulcers. The list below summarizes some of the essential principles all caregivers should know. 

Ten essential principles of treating diabetic foot ulcers

 

  • Always check both feet!

  • One of the most crucial principles is providing offloading for risk areas of the foot, especially where an ulcer has already developed. Many caregivers are unaware that offloading is one of the most critical aspects.

  • We repeat this once more, so everybody remembers this: The first thing you have to think about when you see a diabetic foot ulcer is how you will offload it!

  • If you have the tools available: do an ABI reading. If the patient has an ABI <, eight and a diabetic foot ulcer, refer them for a vascular assessment if that is available in your area.

  • Do a monofilament ( or tuning fork ) test of the patient's feet. If you detect sensory neuropathy, the patient needs extra information about taking good care of the feet. Most patients with sensory neuropathy require custom-made insoles or even special shoes. In most areas of Africa, there is limited access to this type of service.

  • If the patient has a foot ulcer and you probe to bone, you should suspect osteomyelitis until otherwise proven. Ideally, the patient should be referred for at least a plain x-ray of the affected area. An MRI should be performed if the x-ray is negative, but there is still a strong suspicion of osteomyelitis. Again, an MRI is not available to the majority of African patients.  

  • It is quite rare to encounter true dry necrosis in diabetic ulcers. Very often, infection and pus are hiding beneath dry areas. Contrary to dry necrosis in purely arterial ulcers, we have a low threshold for debriding dry necrosis in diabetic patients.

  • Ideally, diabetic foot ulcerations should be treated by an interdisciplinary specialist team or at least a specialized wound clinic. Such a team is not a reality in most parts of Africa.

  • If a diabetic foot ulcer has signs of infection, the patient should ideally be referred to a specialist center as an emergency. Infected diabetic ulcers often deteriorate quickly, and what looks manageable today may look like a catastrophe tomorrow. Diabetic foot ulcers that are not infected and show no other signs of immediate complications should be referred to a specialist team within the week.

  • Remember that there can be a severe infection in a diabetic foot without this being very apparent. Sometimes the classical clinical signs of infection like warmth, redness, and pain can be absent in diabetic patients, and we will go into a trap. Especially in dark skin, signs of infection may be more challenging to detect.

  • Remember that there exists a condition called Charcot's foot and that we encounter this more often in diabetic patients. Unless treated correctly, it will often leave behind a severely damaged foot with gross deformities. Please also refer to the separate chapter on this condition.