Cause for concern: the pathology of the non-ulcerative foot
This article was first published in DiabetesVoice, journal of the International Diabetes Federation in November 2005.
Cause for concern: the pathology of the non-ulcerative foot
Those people with diabetes who are aware of the threat that is posed by diabetes foot complications are right to be terrified by the worst-case scenario: the loss by amputation of one of their feet or legs. People with diabetes are at risk of developing a series of common conditions that can represent a conduit for infection to their vulnerable feet. Andrew Clarke describes the apparently minor conditions that in fact require adequate attention or need to be prevented before chronic ulcers develop and the consequences become tragic.
In its consensus document, “The International Working Group on the Diabetic Foot” states: “There is no such thing as a trivial lesion of the diabetic foot.” The group recognises that hyperkeratosis (corns & calluses), blisters, dry cracked heels, thickened or ingrown nails, fungal infections of the nails or skin or foot deformity such as flat feet or bunions, are all cause for concern to people with diabetes. In addition, many people have other medical conditions, such as arthritis.
Probably the most serious non-ulcerative foot condition is called Charcot foot, known medically as diabetic neuroarthropathy. Figure. 1. This condition affects people who have developed neuropathy and lost their sense of protective pain. This is the sense that protects the foot from being pushed beyond its limits when walking, standing or exercising. For health professionals, the acute Charcot foot is difficult to detect and is often treated as an infection, because the foot has an area of redness and swelling. Figure. 2. An alerting factor is a history of an injury such as tripping or falling. Charcot foot can be divided into three stages:
- Acute onset
- Bony destruction
Any person with diabetic neuropathy, with a sudden onset of redness and swelling as a result of some injury should be treated as a suspect Charcot foot.
Skin and subcutaneous tissues
Hyperkeratosis (Corns & callus)
Thickened skin is the normal physiological response of the foot to pressure and friction and, if asymptomatic, should be left alone. The usual cycle of events leading to hyperkeratosis begins with intermittent compression and release, which causes the skin cells to become inflamed and overactive. These cells seem to stick to each other, reducing the rate of skin shedding. If the bulk of this normal hyperkeratosis increases to cause pain and deformation of the normal skin, it is considered pathological. Figure. 3. Callus and corns are defined as:
• Callus – a diffuse area of thickened skin
• Corn – an area of callus moulded into a nucleus by concentration of stresses
Dry skin (anhidrosis)
This can be the result of aging, but is usually associated with changes to the nervous system (neuropathy), which reduce the body’s sweating mechanism.
Fissures or cracks in the skin occur in two main sites: around the heel and between the toes. Figure. 4 a & b. Both indicate the skin’s inability to cope with local stresses. The skin at the heels is usually dry and between the toes it is moist.
A virus causes verrucae. Figure.5. The causative organism is one of the papova group of viruses, which cause benign spontaneously regressing tumours in the skin.
Fungal infections (Athlete’s foot or Tinea pedis)
Yeasts and moulds that infect the skin between and underneath the toes and on the soles of the feet cause fungal infections. Fungal spores are found in many different environments, including communal showers, sandy beaches, carpets and mats, animals and soil. The condition develops due to skin scales becoming infected with elements called hyphae, which can remain dormant until suitable growing conditions arise. Between the toes, moist cracks occur; on the soles, small, itchy blisters develop. Figure. 6. Tinea pedis may also present on the sole as inflamed, thickened, dry and scaly skin.
Disorders of the nails
Damage to the growth matrix of a toenail causes uniform thickening of the nail plate (onychauxis), or deformed thickening (onychogryphosis). Figure. 7. This causes pain, discomfort and sometimes hampers mobility. Abnormal curvature is usually not painful until an external factor such as pressure from shoes or poor self-treatment cause pain.
Ingrown nail (onychocryptosis)
Figure. 8. is caused by a shoulder or splinter of nail piercing the skin at the edge of a nail. As nail growth continues, normal healing granulation tissue forms but is unable to bring about healing because the piece of nail is still inside the skin. This causes hypergranulation or ‘proud flesh’.
Fungi and yeasts can also infect the toenails (onychomycosis) Figure. 9. The infecting organism usually begins at the front of the nail and slowly softens the nail, leaving yellow/brown streaks and possibly an odour.
The connective tissues
The foot is an amazing structure of bones, joints, ligaments and muscles, all of which are designed to work in harmony. Few people have perfect feet and we rely on being free of pain and deformity as the measure of structural foot health. There are certain foot structures that need special mention because they reflect alterations in the alignment and therefore function of the feet. These changes usually put an increased load on another part of the foot.
Highly-arched (pes cavus) or low-arched (pes planus) feet can both cause pain and increased pressures on the feet, especially the soles. Deformities such as hallux valgus and bunions are also evidence of an unbalanced foot structure and lead to increased local pressures, causing callus or corns.
As a person with diabetes, it is essential to have a regular foot examination and know your foot risk status. If you have neuropathy you will not feel the pain normally associated with some foot conditions. If you have poor circulation your skin will be unable to withstand the stresses and strains applied to your feet. Keeping good foot health reduces the risk of ulcers and amputation.
Andrew Clarke is a podiatrist in private practice at the Wits University Donald Gordon Medical Centre, Johannesburg, South Africa and works at the Chris Hani Baragwanath Hostpital diabetes and arthritis clinics in Soweto, South Africa