Causes of Foot Problems in Diabetes
Foot problems are responsible for significant morbidity in diabetics. Surgical operations, at times repeated, are often required in the management of this problem. Foot problem is a common cause of hospitalization, often prolonged, resulting in loss of income and considerable medical expenses. The tissue damage and surgery lead to loss of part of the lower limb.
Why Foot Problems Occur in Diabetes?
As already discussed, in Chapter 14, narrowing and hardening of arteries and affection of minute blood vessels occur in diabetes. These changes reduce blood flow to the lower limbs. The resultant lack of nutrition makes the skin of the feet dry, vulnerable to blistering and susceptible to infections. Moreover, it delays healing of a wound or a sore. Pressure due to a tight shoe gives rise to a sore on the side of the foot.
In diabetes, the sensations of the feet may become blunt due to involvement of the nerves of the lower limbs. Hence, a diabetic may not feel pain, even when the foot is injured or when there is an infection. The severity of the foot problem is often underestimated because of lack of pain. The affection of the nerves of the lower limbs results in weakness of the muscles of the feet with consequent abnormal architecture of the feet and pressure points like head of the metatarsals and heel. Thickening of the skin-callus-develops at these points due to constant friction of walking. The callus breaks down, producing a sore. Involvement of the autonomic nervous system diminishes sweating of the feet, making the feet dry.
Disorganization of the ankle joint and midfoot joints often painless, may occur when sensations of the lower limbs are impaired.
Glycation of hemoglobin has already been discussed m Chapter 4. As mentioned in Chapter 4, glycation of proteins is a widespread process in diabetes. The glycation of protein in the skin makes the latter thick. Changes in collagen, a protein present in tendons and bones is one cause of the hammertoe deformity of the foot. This deformity produces excessive pressure on the skin under the head of the metatarsal bone and pressure of the shoe on the upper part of the foot.
Microbes cannot enter an intact skin. Fungus infection between the toes, a cut, an injury, a blister or a sore serve as a portal of entry for microbes. Defence mechanisms of the body are impaired in uncontrolled diabetes. White blood cells and factors in the serum essential for defence against infections are not mobilized at the site of infection due to impaired blood flow. Infection can provoke occlusion of. small arteries leading to further reduction in blood flow.
A combination of all these factors, that is, poor blood supply, involvement of nervous system and infection may give rise to serious complications of diabetes. A part of the foot like toes, may die when blood supply is very poor. Such a local death of the part of the body is known as gangrene.
AT RISK FEET
The following foot related risk conditions are associated with an increased risk of amputation.
- Involvement of nerves of lower limbs with loss of protective sensation
- Altered biomechanies (in presence of above)
- Evidence of increased pressure (redness, haemorrhage under a callus)
- Bony deformity
- Decreased or absent foot pulses
- History of ulcers or amputation. Severe nail problems
Management
Except minor foot problems, hospitalization is essential in a majority of cases. Radiograph and other imaging techniques of the foot are necessary to ascertain involvement of the bones. Material from the site of infection is cultured to identify the offending organisms and their sensitivity to antibacterial agents. The adequacy of blood flow to the lower limbs is assessed by appropriate investigations (see Chapter 14). Removal of dead tissue has to be thorough and often has to be repeated. Antibiotics as dictated by the culture and sensitivity tests are administered orally or by injection. Local application of antibiotics is not of any value. Pressure on the affected part is avoided and bed rest is essential initially. One should ensure that there is no pressure on the other heel, as this can lead to ulceration. Pressure is taken off the affected part by modification of footwear or a light plaster cast. Surgical procedures to improve blood supply to the affected part are carried out in suitable cases. Strict control of diabetes is essential and insulin is required. Consumption of tobacco in any form is totally prohibited Amputation is considered for removal of the dead tissues, when there is severe pain due to markedly poor blood supply, a life-threatening infection (not amenable to antibiotics) or when prolonged rest is not. possible for one or the other reason. The level of amputation compatible with healing and rehabilitation is selected.