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What you can't feel can hurt you

2010; Elsevier BV; Volume: 52; Issue: 3 Linguagem: Inglês

10.1016/j.jvs.2010.06.005

1097-6809

Andrew J.M. Boulton,

Pressure Ulcer Prevention and Management

Throughout our medical training, we are taught how to manage patients who present with symptoms, which usually leads to a clinical examination, a diagnosis, and a management plan. However, virtually no time is spent on teaching how to manage patients who have no symptoms because they have lost the ability to feel pain; that is, they have peripheral neuropathy. The lifetime incidence of foot ulceration in people with diabetes has been estimated to be as high as 25%, and a number of contributory factors result in a foot being at risk of ulceration. Most important amongst these factors is peripheral neuropathy, or the loss of the ability to feel pain, temperature, or pressure sensation in the feet and lower legs. Up to 50% of older patients with type 2 diabetes have evidence of sensory loss that puts them at risk of foot ulceration. If we are to succeed in reducing the high incidence of foot ulcers, regular screening for peripheral neuropathy is vital in all patients with diabetes. Those found to have any risk factors for foot ulceration require special education and more frequent review, particularly with podiatrists. The key message is therefore that neuropathic symptoms correlate poorly with sensory loss, and their absence must never be equated with lack of risk of foot ulceration. If we are to succeed in reducing the high incidence of foot ulceration and, particularly, recurrent ulceration, we must realize that with loss of pain there is also diminished motivation in the healing and the prevention of injury. Throughout our medical training, we are taught how to manage patients who present with symptoms, which usually leads to a clinical examination, a diagnosis, and a management plan. However, virtually no time is spent on teaching how to manage patients who have no symptoms because they have lost the ability to feel pain; that is, they have peripheral neuropathy. The lifetime incidence of foot ulceration in people with diabetes has been estimated to be as high as 25%, and a number of contributory factors result in a foot being at risk of ulceration. Most important amongst these factors is peripheral neuropathy, or the loss of the ability to feel pain, temperature, or pressure sensation in the feet and lower legs. Up to 50% of older patients with type 2 diabetes have evidence of sensory loss that puts them at risk of foot ulceration. If we are to succeed in reducing the high incidence of foot ulcers, regular screening for peripheral neuropathy is vital in all patients with diabetes. Those found to have any risk factors for foot ulceration require special education and more frequent review, particularly with podiatrists. The key message is therefore that neuropathic symptoms correlate poorly with sensory loss, and their absence must never be equated with lack of risk of foot ulceration. If we are to succeed in reducing the high incidence of foot ulceration and, particularly, recurrent ulceration, we must realize that with loss of pain there is also diminished motivation in the healing and the prevention of injury. Pain is God's greatest gift to mankind.—Paul Brand It was Dr Paul Brand, working with patients suffering from Hansen's disease in South India, who recognized that it was the loss of peripheral sensation in the limbs that resulted in the terrible scarring and ulceration that occurred in these individuals. Pain is indeed a gift, but the gift of pain is only recognized when it is lost as it is a protective sensation that prevents us from further damaging areas of injury. In a very similar way to leprosy, patients with sensory loss secondary to diabetes, which predominates in the lower limb, frequently develop ulcers and even more serious conditions, such as Charcot neuroarthropathy, because they have lost this gift of pain. A reduction in neuropathic foot problems will only be achieved if we remember that those with insensitive feet have lost this warning signal of pain that ordinarily brings the patients to their doctors. The identification and care of a patient with no pain sensation is a new challenge for which most of us have little if any training. It is difficult for us to understand, for example, that an intelligent patient would buy and wear a pair of shoes several sizes too small and come to our clinic with an extensive shoe-induced ulcer. The explanation, however, is simple: with reduced sensation, a very tight fit stimulates the remaining pressure nerve endings and the individual interprets this as a normal fit; hence, the common complaint when we provide patients with custom-designed shoes is "these shoes are too loose." We can learn much about the management of patients with diabetic neuropathy from the treatment of patients with leprosy.1Brand P.W. Diabetic foot.in: Ellenberg M. Rifkin H. Diabetes mellitus: theory and practice. 3rd ed. Medical Examination Publishing, New York1983: 829-849Google Scholar If we are to succeed, we must realize that with loss of pain there is also diminished motivation in the healing of and the prevention of injury. Because the lifetime incidence of foot ulceration in diabetic patients has been estimated to be as high as 25%,2Singh N. Armstrong D.G. Lipsky B.A. Preventing foot ulcers in patients with diabetes.JAMA. 2005; 293: 217-228Crossref PubMed Scopus (1782) Google Scholar understanding the pathways that result in the development of an ulcer is increasingly important. It was the Scottish poet, Thomas Campbell who wrote, "Coming events cast their shadows before." These words can usefully be applied to the breakdown of the diabetic foot because ulceration does not spontaneously occur but is caused by a combination of factors that result in the development of a lesion. Thus, there are many warning signs or "shadows" that can identify those at risk. Other articles in this issue will cover the important area of peripheral vascular disease in the causation of lower extremity problems, and in this review I will focus on the commonest of the diabetic neuropathies, chronic sensorimotor neuropathy, which is a major contributory factor in the pathway to ulceration in diabetes. The final section will discuss simple methods to screen for the high-risk patient of foot ulcer, which will be based on the recently published Comprehensive Diabetic Foot Examination by a task force of the American Diabetes Association.3Boulton A.J.M. Armstrong D.G. Albert S.F. Frykberg R.G. Hellman R. Kirkman M.S. et al.Comprehensive foot examination and risk assessment: a report of the Task Force of the Foot Care Interest Group of the American Diabetes Association, with endorsement by the American Association of Clinical Endocrinologists and risk assessment: a report of the task force of the foot care interest group of the American Diabetes Association, with endorsement by the American Association of Clinical Endocrinologists.Diabetes Care. 2008; 31: 1679-1685Crossref PubMed Scopus (37) Google Scholar Of all the neuropathies of diabetes, the chronic sensorimotor variety, diabetic peripheral neuropathy (DPN), is by far the commonest. Indeed, it has been estimated that up to 50% of older type 2 diabetic patients may have evidence of sensory loss on clinical examination and therefore must be considered at risk of insensitive foot injury.4Boulton A.J.M. Malik R.A. Arezzo J.C. Sosenko J.M. Diabetic somatic neuropathies: technical review.Diabetes Care. 2004; 27: 1458-1486Crossref PubMed Scopus (632) Google Scholar In the large United Kingdom Prospective Diabetes Study, 13% of patients at diagnosis of type 2 diabetes had sensory loss of sufficient severity to put them at risk of insensitive foot lesions. This provides a clear message: People with any duration of type 2 diabetes might have significant risk of developing foot problems.4Boulton A.J.M. Malik R.A. Arezzo J.C. Sosenko J.M. Diabetic somatic neuropathies: technical review.Diabetes Care. 2004; 27: 1458-1486Crossref PubMed Scopus (632) Google Scholar DPN commonly results in a sensory loss confirmed on examination by a deficit in the stocking distribution to all sensory modalities. Evidence of motor dysfunction in the form of small muscle wasting is also often present, whereas some patients might give a history (past or present) of typical neuropathic symptoms such as burning pain, stabbing discomfort, and paraesthesia with nocturnal exacerbation, others might develop sensory loss without ever having any such history. Some patients might have the "painful-painless" leg with spontaneous discomfort secondary to neuropathic symptoms, but who on examination have both small and large fiber sensory deficits, and these patients are also at great risk of painless injury to their feet. From the above, it should be clear that a spectrum of symptomatic severity may be present, with some patients experiencing severe pain, and at the other end of the spectrum, patients who have no spontaneous symptoms; however, both groups may have significant sensory loss on clinical examination. The most challenging patients are indeed those who develop sensory loss with no history of symptoms. It is often difficult to convince them that they are at risk of foot ulceration because they feel no discomfort, and motivation to perform regular self-foot care is difficult. The key message is that neuropathic symptoms correlate poorly with sensory loss and their absence mustneverbe equated with lack of foot ulcer risk. Thus, in the assessment of foot ulcer risk, a careful foot examination after removal of shoes and socks must always be included whatever the history of the symptoms.4Boulton A.J.M. Malik R.A. Arezzo J.C. Sosenko J.M. Diabetic somatic neuropathies: technical review.Diabetes Care. 2004; 27: 1458-1486Crossref PubMed Scopus (632) Google Scholar Hence the clinical observation, again by Dr Paul Brand, that any patient who walks into the clinic with a foot ulcer but without a limp must have neuropathy because those with normal pain sensation would not be able to put weight on the lesion. Most patients with significant risk of foot ulceration due to sensory loss also have peripheral autonomic dysfunction affecting the sympathetic nervous system. This results in reduced sweating and, in the absence of large vessel obstructive vascular disease, increased blood flow to the foot with arteriovenous shunting leading to the warm, but insensate foot. The neuropathic insensate foot does not ulcerate spontaneously. A combination of factors ultimately results in breakdown and ulceration. Those factors that increase the risk of foot ulceration are listed in Table I. The highest-risk populations are those with a history of previous ulceration or even amputation. Several studies have shown that patients with other late complications of diabetes include nephropathy (particularly those on dialysis or post-transplantation) and retinopathy (particularly if there is visual loss). There appears to be a temporal relationship between starting dialysis and risk of foot ulcers.5Game F.L. Chipchase S.Y. Hubbard R. Burden R.P. Jeffcoate W.J. Temporal association between the incidence of foot ulceration and the start of dialysis in diabetes mellitus.Nephrol Dial Transplant. 2006; 21: 3207-3210Crossref PubMed Scopus (59) Google ScholarTable IFactors increasing risk of diabetic foot ulceration• Peripheral neuropathy – Somatic – Autonomic• Peripheral vascular disease• Past history of foot ulcers or amputation• Other long-term complications – End-stage renal disease—on dialysis – Visual loss—post-transplantation• Plantar callus• Foot deformity• Edema• Ethnic background• Poor social background Open table in a new tab Other important contributory factors to ulcers include the presence of callus or hard skin under weight-bearing areas, which occurs as a consequence of pressure plus dry skin due to autonomic neuropathy, and also foot deformity. A combination of motor neuropathy, limited joint mobility, and altered gait patterns are thought to result in the "high-risk" neuropathic foot with clawing of the toes, prominent metatarsal heads, a high arch, and small-muscle wasting. The combination of two or more risk factors ultimately results in breakdown of the diabetic foot. In a study of instant foot ulcers, Reiber et al6Reiber G.E. Vileikyte L. Boyko E.J. del Aguila M. Smith D.G. Lavery L.A. et al.Causal pathways for incident lower-extremity ulcers in patients with diabetes from two settings.Diabetes Care. 1999; 22: 157-162Crossref PubMed Scopus (738) Google Scholar showed that the commonest triad of component causes resulting in ulceration are neuropathy (loss of pain sensation), foot deformity, and trauma. Edema and ischemia are among the other important component causes in the pathway to ulceration. Superior doctors prevent the disease: mediocre doctors treat the disease before evident: inferior doctors treat the full blown disease.—Huang DEE, China, 2600 bc. The Chinese proverb is probably true, and there needs to be a shift from mostly being inferior doctors to mostly being superior, and that by preventing foot ulcers by identifying those at risk, and by foot care education and regular assessments and treatment, preventing the ulcers from actually occurring. Many countries have now adopted the principle of "the annual review," where every diabetic patient is screened at least annually for evidence of diabetic complications. Such a review can be carried out in primary care or in a hospital diabetic clinic. A task force of the American Diabetes Association recently addressed the question of what should be included for the annual review in the "Comprehensive Diabetic Foot Examination (CDFE)."3Boulton A.J.M. Armstrong D.G. Albert S.F. Frykberg R.G. Hellman R. Kirkman M.S. et al.Comprehensive foot examination and risk assessment: a report of the Task Force of the Foot Care Interest Group of the American Diabetes Association, with endorsement by the American Association of Clinical Endocrinologists and risk assessment: a report of the task force of the foot care interest group of the American Diabetes Association, with endorsement by the American Association of Clinical Endocrinologists.Diabetes Care. 2008; 31: 1679-1685Crossref PubMed Scopus (37) Google Scholar This group addressed and concisely summarized the recent literature in the area and recommended, where possible, using evidence-based medicine that should be included in the CDFE for adult patients with diabetes. The main emphasis of this report was on a concise clinical examination to identify the patient at risk. A summary of the key components of the CDFE is provided in Table II. Whereas each potential simple neurologic clinical assessment has advantages and disadvantages, it was felt that the 10-gauge monofilament had much evidence to support its use, hence the recommendation that assessment of neuropathy should always comprise the use of such a filament plus one other confirmatory test. In addition to the simple tests listed in Table II, one possible test that was also included was use of vibration perception threshold by using a biothesiometer or vibration perception threshold meter. Although this is a semi-quantitative test of sensation, it was included because many centers in North America and Europe have such equipment. As can be seen from Table II, however, this is not regarded as essential so these CDFE can be performed with simple clinical tools that do not require any external power source.Table IIKey components of the diabetic foot examinationAdapted from Boulton et al.3Boulton A.J.M. Armstrong D.G. Albert S.F. Frykberg R.G. Hellman R. Kirkman M.S. et al.Comprehensive foot examination and risk assessment: a report of the Task Force of the Foot Care Interest Group of the American Diabetes Association, with endorsement by the American Association of Clinical Endocrinologists and risk assessment: a report of the task force of the foot care interest group of the American Diabetes Association, with endorsement by the American Association of Clinical Endocrinologists.Diabetes Care. 2008; 31: 1679-1685Crossref PubMed Scopus (37) Google ScholarInspection•Evidence of past/present ulcers?•Foot shape?•Prominent metatarsal heads/claw toes•Hallux valgus•Muscle wasting•Charcot deformity•Dermatologic? – Callus – Erythema – SweatingNeurologic•10-g monofilament at 4 sites on each foot + 1 of the following Vibration using 128 HZ tuning fork•Pinprick sensation•Ankle reflexes•Vibration perception thresholdVascular•Foot pulses•Ankle brachial index, if indicated Open table in a new tab As can be seen, whereas the neuropathic foot is at great risk of ulceration, this need not occur and almost all such ulcers should be entirely preventable. This depends on realization by the patients themselves that they have risk of foot ulcers and the application of simple foot self-care such as regular inspection and podiatric care. However, it remains depressing that there are still reports that many patients are not receiving regular foot screens: if we as physicians fail to examine patients' feet when we occasionally see them, can we honestly expect them to examine their feet on a daily basis?