The clinical management of diabetic foot and its medicolegal implications
Diabetes affects millions of people worldwide and its prevalence is increasing (1). Insulin treatment has overcome the acute problems of ketoacidosis and infection often associated with the disease, but vascular and neurological complications, including diabetic foot (DF), remain an issue (2). DF is defined as a structural or functional alteration of the foot, which may manifest as ulceration, infection and/or gangrene (1). It is the commonest complication associated with diabetes (2), occurring in 15–34% of diabetics during their lifetime (3, 4). Complications arising from DF are seen in around 25% of cases and are the leading cause of both hospitalisations and amputations in patients with diabetes (1, 5).
Many factors lead to the development of DF (4), and there is rarely a single cause (2, 5). The two biggest risk factors are diabetic neuropathy and peripheral vascular disease (1-4, 6). These arise as a result of sustained hyperglycaemia over a number of years (1, 2, 6) and their prevalence increases with both age and the duration of diabetes (2). When combined with other factors, such as trauma, microvascular disease, biomechanical abnormalities, limited joint mobility and increased susceptibility to infection, DF can result (1, 2, 4). In Western countries, most trauma to the feet is caused by ill-fitting shoes (4).
Neuropathy affects up to 60% of patients with diabetes (4, 5), and involves the motor, sensory and autonomic components of the nervous system (1, 2, 4). It is the result of multiple factors, including blood glucose concentration, blood lipids, the structure and permeability of the myelin sheath, axonal flow and micro and macroangiopathy of the peripheral nerves (2). Motor neuropathy typically presents as muscle wasting of the muscles of the foot, and leads to structural changes in its shape. These include clawing of the toes and changes to the architecture of the mid-foot, and subsequent redistribution of pressure over the metatarsal heads (4, 5). As a result, many standard shoes are unsuitable for patients with diabetes (4). This is compounded by the changes in pain stimulation caused by sensory neuropathy; the patient fails to recognise that their shoes no longer fit, and pressure injuries can result (2, 4). Patients with sensory loss due to neuropathy are around seven times more likely to develop a foot ulcer than those without neuropathy (4). The onset of sensory neuropathy is often insidious and many patients remain asymptomatic (2, 4). In others, it presents as a tingling or burning sensation, or numbness, in the affected area, while the loss of the Achilles reflex indicates that the condition is advanced. Autonomic neuropathy contributes to ulceration through changes to the structure of the skin, hair loss from the legs, and brittle, ridged toenails (4).
Peripheral vascular disease (PVD), typically affecting the small arteries below the knee and within the foot, is four times more common in patients with diabetes than in healthy individuals. The resulting poor blood supply increases the risk of ulceration and inhibits wound healing in lesions that do occur (4, 5). Therefore, evaluating the degree of ischaemia is vital. A history of intermittent claudication or pain at rest are suggestive of PVD (5, 6), whilst in patients with critical ischaemia (both in Diabetics and non-Diabetics) should be investigated further by arteriography (4, 5). A quick and reliable method of detecting PVD is with non-invasive arterial Doppler ultrasonography (2, 4-6), as other methods are less satisfactory. For example, the ankle–brachial pressure index measurement is often falsely elevated in diabetics, due to arterial calcification (4, 6). Management of PVD may be medical or surgical, and percutaneous transluminal angioplasty is also useful in high-risk patients unsuitable for surgery (2).
Initially, DF may manifest as a decrease in the patient’s ability to feel pain and temperature changes, which is followed by decreased sensitivity to vibrations and superficial touch. Thus, patients with DF are unable to feel normal painful mechanical, chemical or thermal stimuli (1). Callus formation and ulceration may then follow. The presence of infection is indicated by symptoms including pain or tenderness, redness and swelling at the affected site, and purulent discharge. Anorexia, nausea, vomiting, fever, chills, night sweats and change in mental status suggest that the infection has become systemic (2, 6). If not correctly treated, this ulceration may ultimately lead to amputation (3, 4). Approximately 85% of all amputations in diabetic patients are preceded by a foot ulcer that becomes infected or gangrenous (2, 3, 5). Therefore, early identification is vital so that the patient can be referred to a podiatrist for regular assessment and the provision of customised footwear (4). Underlying osteomyelitis can be identified through imaging (4, 5); while plain radiography is most commonly used, magnetic resonance imaging is the preferred method due to higher sensitivity and specificity. Computed tomography with IV contrast is also acceptable (4). Once an appropriate wound classification has been made, a treatment plan can be implemented (5).
The treatment of DF remains a challenge, partly because published guidelines vary considerably in their recommendations (1). Furthermore, the presence of neuropathy, PVD and infection all influence successful treatment, the main aims of which are to prevent amputation and to maintain a functional foot, capable of weight-bearing (3). Debridement, in which necrotic tissue is removed from a wound until only healthy tissue remains, is probably the most useful technique to encourage wound healing (1, 5). Debridement may be carried out using surgical, autolytic or larval techniques, all of which are equally effective (1). It is vital to recognise when an ulcer has become infected, as a lack of treatment may ultimately result in amputation (4, 6). There is no specific antibiotic suitable for all cases of DF; instead, drug choice will depend on the severity of the infection and known local drug resistance (1). Cases of osteomyelitis should always be treated with antibiotics, which can be modified according to treatment response (1, 4). Hyperglycaemia impairs wound healing; thus, diabetes control is also very important (4, 6, 7).
Most patients will also require pressure offloading treatment, which aims to reduce the pressure on the affected area through the provision of customised footwear, total contact casts or splints (1, 2, 4, 7). Removal of pressure from the site of the wound is particularly important for plantar neuropathic ulcers. Ideally, shoes should have a wide toe box, soft cushioned soles, extra depth to accommodate orthoses if necessary and laces or Velcro to allow for fine fitting adjustments (6). While it has been suggested that the use of specialist shoes should be restricted to patients with known foot deformities, their use in other patients can help to reduce the recurrence of foot problems, through a reduction in shearing forces and friction leading to damaged tissues (1). As the need for specialist footwear may be life-long, patient education should be provided, including a recommendation to wear shoes at all times to reduce the risk of incidental trauma to the feet (4).
Few effective adjuvant treatments exist: although granulocyte colony stimulating factor reduces surgical intervention and length of hospital stay, its effect on infection resolution is minimal. Whilst some evidence for the use of negative pressure therapy is contradictory (1), there is no doubt that such therapy in appropriate DF wounds provides a good wound management system and facilitates healing. Neuropathic pain can be treated with antidepressants, anticonvulsants and opioids (1, 2). Due to the different causes and range in clinical presentations of DF, a multidisciplinary approach will provide more effective treatment (1, 3, 4, 6, 7) and even reduce the frequency of amputations (1, 4). A team may include general practitioners, diabetologists; endocrinologists, podiatrists; general, orthopaedic and vascular surgeons; radiologists; infectious disease specialists, wound care nurses and orthotic technicians (3, 4).
Even if DF is successfully treated, the recurrence rate is very high (4-6). Around 40% of patients will develop another ulcer within 1 year of healing and 65% will do so within 5 years (4). Therefore, prevention is particularly important, with foot screening being the most effective way of achieving this (1, 4-6). This should include a thorough evaluation of the patient’s feet and footwear, identification of any deformities and analysis of the patient’s gait and mobility. Risk of future foot problems can be assessed by inspecting foot and clothing hygiene, toenail appearance and ankle strength and movement, as well as the neuropathic and vascular status of the foot (1, 4-6). Detection of any risk factors will allow for further investigations, management and referral for specialist care (4). As well as daily self-examination, all diabetic patients should have at least an annual foot examination carried out by a healthcare provider (1, 4-6). However, in patients with known risk factors, such as a foot deformity or diagnosis of neuropathy or PVD, screening should be performed every 1–6 months (4, 6). A major issue with foot screening is lack of compliance by patients (1). Therefore, patient education on the importance of foot care is vital (1, 7).
DF is a common condition among patients with diabetes, and one that can be both complex and costly to treat. It is also associated with significant morbidity and mortality (4). Due to the high prevalence of neuropathy and PVD in diabetic patients, primary and recurrent ulceration is common. Therefore, prevention remains the best strategy. Regular foot screening, including assessment of sensory and vascular status of the foot, is particularly effective, as well as being easy and cheap to perform. Education of patients on the importance of good foot care is also vital.
References
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