Causes of diabetic foot
FOOT ULCERATION, is a leading cause of hospitalisation in patients with diabetes mellitus. The risk of lower extremity amputation is 14-46 times higher in diabetics than in persons who do not have diabetes mellitus.
A number of risk factors predispose patients to foot ulceration: most important amongst these are neuropathy which leads to reduced pain sensation, altered joint position sensation, dry skin, reduced blood flow and abnormalities of pressure loads under the feet during standing and walking.
Increased foot pressure has been associated with foot ulcers and risk of amputation. Prolonged exposure to repetitive moderately elevated pressure can result in ulceration in the neuropathic patient with reduced or absent pain sensation. Foot ulcers are expensive to manage. Therefore, treatment and prevention of ulcers is the central focus of amputation prevention programmes.
The causes of the increased foot pressure in diabetic people include structural alterations of the bone and connective tissue, limited joint mobility and changes in posture and gait. Pressures generated under apparently healthy feet can be high enough to cause ulceration in the presence of neuropathy.
Glycosylation of collagen in tendons and ligaments results in limited motion of joints found in feet. Limited joint mobility (LJM) is associated with an increased foot pressure and greater chances of foot ulceration. In the case of LJM, the foot is unable to provide its shock absorbing mechanism and may lose its ability to maintain normal foot pressures.
Relationship of joint limitation and plantar ulceration was established in a study conducted by the author and his colleagues at Diabetes Research Centre, Chennai. It was published in the journal Diabetes Research and Clinical Practice (DRCP).
LJM and the foot pressure were measured in 345 subjects of whom 295 had diabetes and the remaining 50 were non-diabetic controls. Diabetic patients were those with neuropathy and without neuropathy.
In this study, it was reported that the joint mobility at the ankle and at the big toe was significantly reduced in the diabetic patients when compared with the controls. Among the diabetic patients those with neuropathy and those with history of foot ulcer had significantly lesser joint mobility. LJM and increased foot pressure appear to be important determinants of foot ulceration in South Indian diabetic patients.
Footwear and appropriately fitted insoles may relieve the areas of high foot pressures and decrease the mechanical stress of walking. Orthoses and footwear, designed to distribute the pressures evenly under the feet are needed to compensate for joint mobility in the feet.
Diabetes Research Centre
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