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Assessment of peripheral neuropathy in the diabetic foot
Journal of Tissue Viability 2000 Vol10 No 1 21
Assessment of peripheral neuropathy in the diabetic foot Jodi Booth Podiatry Department, School of Health Professions and Rehabilitation Sciences, University of Southampton Peripheral neuropathy is associated with major morbidity in the diabetic population. The detection of whether peripheral neuropathy is simply present or not in patients with diabetes is insufficient. What is required is a reliable measure of both the extent and severity of neuropathy, as this enables the appropriate allocation of resources and improves the quality of care for the patients who need it most. Standardized approaches involving the use of a neurothesiometer and a 10 g monofilament can provide a reliable and objective measure of the extent and severity of neuropathy, and should therefore be adopted into protocols for best practice in the assessment of neuropathy.
Introduction Of the estimated 110 million people worldwide who have diabetes mellitus 1, many will experience one or a number of syndromes affecting the foot, in which neuropathy, ischaemia and infection can result in major morbidity 2 . Foot ulceration remains one of the most prevalent and serious complications associated with diabetes 3•4 (Figure 1). A suggested 15% of the diabetic population are afflicted by ulceration during their lifetimes, and 6-20% of these require in-patient treatment for their ulcer management 1.
• • • •
peripheral neuropathy peripheral vascular disease poor glycaemic control bony deformity
The prognosis for foot ulceration is often poor. At best, the patient can expect a stringent regime of ulcer management until healing is achieved; at worst, indolent or recurrent ulceration, often with infection, may result in gangrene and amputation of a limb (Figure 2). Incidence data show that 84% of all non-traumatic lower-limb amputations performed on those with diabetes are preceded by ulceration 5 . Diabetic foot disease is also costly for society6 . Foot and lower-limb complications are the most common reason for hospital admission for those with diabetes, at estimated costs of between £12.9 and 13.5 million a year7 •8. With regard to amputation specifically, the economic burden is suggested to amount to £8500 per patient for an amputation and limb fitting 7 •9 .
Neuropathy and ulceration The exact pathway to tissue breakdown and ulceration in those with diabetes is unknown 10. However, many studies have identified markers or risk factors that are associated with the likelihood of developing ulceration in those with diabetes 2•11 •12 :
Figure 1 A patient with diabetic peripheral neuropathy presenting with ulceration over the lateral aspect of the mid-foot region.
22
Journal of Tissue Viability 2000 Vol lO No l
down the legs and may also report hyperaesthesia (excess sensitivity) and sensations of cold or warmth or of overtight skin 15 . The pain history may allow differential diagnosis from other possible causes of pain and the practitioner can subsequently arrange for appropriate pain relief. Topical analgesics such as capsaicin or application of Opsite film dressing (Smith & Nephew) over the affected area have proved effective15.16. Systemic preparations used successfully in the treatment of painful neuropathy include tricyclic anti-depressants, anti-epileptics and anti-arrhythmics, although none are licensed for this purpose 15 .
Figure 2 A patient presenting with gangrene of the second digit as a result of infection of a neuropathic ulcer.
• • • • • • •
history of previous ulceration limited joint mobility diabetic nephropathy elevated foot pressures presence of plantar callus visual impairment living alone
As many as 30% of people with diabetes have peripheral neuropathy, and of all known risk factors, neuropathy (with or without vascular insufficiency) has been confirmed as one of the most important factors in the development of ulceration3·11·13. The relevance of neuropathy is emphasized by Young et al who demonstrated that patients with diabetic peripheral neuropathy are seven times more likely to develop ulceration than those without 14. Furthermore, the majority of secondary and tertiary referrals to specialist diabetic foot clinics are as a result of neuropathic ulceration15.
Observations of the foot may indicate to the clinician that a patient has neuropathy. Typically the patient will present with clawing of the toes and prominent metatarsalphalangeal joints on the plantar surface of the foot. The veins on the foot may be distended and there are often areas of circumscribed callus formation 15 (Figure 3). Whilst history taking may determine those with painful neuropathy, and observations of the foot can provide clues as to whether neuropathy is present, both are subjective measures and neither are reliable in determining the extent and severity of neuropathy. A reliable measure of neuropathy will identify those individuals who will ulcerate, and will therefore allow preventive management strategies to be employed such as the use of casting techniques, custommade footwear, orthoses and orthotic walkers 17 •18 . Research has shown that determination of nerve conduction velocities is the gold standard method of measuring nerve damage and these are an excellent indicator of the severity of neuropathy 19 . However, the time and cost of determining
Assessment of neuropathy - the evidence The evidence for the association of neuropathy and lowerlimb complications reiterates the on-going need for regular, accurate and reliable methods for assessing neuropathy 2 • In practice, however, if neuropathy screening exists at all, there doesn't appear to be a standard or accepted method for assessing it, irrespective of the healthcare profession responsible for performing the assessment 15 . Reasons for this disparity may be numerous, but clearly the research in the field that should inform practice has not been integrated into assessment protocols. History taking should not be ignored in the assessment process, as it will provide information on any pain associated with nerve deterioration. Painful neuropathy is thought to occur in only 10% of those with diabetic neuropathy; typically the patient will complain of shooting or lancinating pain
Figure 3 The feet of a patient with diabetic peripheral neuropathy. Note the prominent distention of the veins on the dorsum of the feet, and the third and fourth digits of the patient's right foot beginning to claw.
Journal of Tissue Viability 2000 Vol 10 No 1 23
age-adjusted VPTs were over four times more sensitive at predicting those individuals at risk of ulcerating than raw VPT values. On the strength of these results, Coppini et al advocated that age-corrected VPT measurements should form part of everyday practice in the assessment of neuropathy21. Again, this work demonstrates the potential for achieving objective and reliable clinical assessment to identify those most at risk of complications. A patient's inability to detect pressure using monofilaments has also been shown to identify those who are at risk of lower-limb complications 17·20 . Monofilaments are nylon filaments that buckle under a known pressure. Research has shown that patients who can detect fewer than eight applications of a 10 g monofilament, when applied to five selected sites on each foot, are ten times more likely to ulcerate than those who are able to detect eight or more applications 17 . This research suggests that the sites that should be tested are as illustrated in Figure 6. The testing sites are thought to be appropriate as incidence data has shown that these areas of the foot are prime sites for neuropathic ulceration. Other authors have also suggested monofilament testing over the styloid process of the fifth metatarsal and on the heel for the same reason, these areas of the foot also being cited as being prone to ulceration 15 .
Figure 4 A neurothesiometer in use to detect and quantify vibration perception by the patient (Scientific Laboratory Supplies)
nerve conduction velocities preclude their use in the clinical environment 15 ·19 . Objective, quantifiable measures of neuropathy that are used clinically in the assessment of neuropathy include the patient's ability to detect vibration as measured using a neurothesiometer (Scientific Laboratory Supplies) and the patient's ability to detect pressure using one or a range of monofilaments (Bailey Instruments) 14·17 ·20·21 (Figures 4 and 5). Studies have shown that patients who cannot detect the vibration of the probe of a neurothesiometer at a reading of 25 V (the vibration perception threshold, VPT), when applied to the apex of the big toe are seven times more likely to ulcerate than those who can detect vibration at 15 V or less 14. The relevance of this finding is that clinicians are able to categorize patients immediately as high risk if they have VPTs at or above 25 V. Previous work on VPTs demonstrated that one's ability to detect vibration diminishes with advancing age in a 'normal' population 22·23 . Coppini et al demonstrated that VPT values obtained using a neurothesiometer could be adjusted through use of a simple statistical formula to accommodate normal age-related changes in vibration perception21 . When applied to the diabetic population, the results showed that
Figure 5 An example of a monofilament that is used to ascertain whether a patient is able to detect 10 g of pressure at a selected site. The monofilament shown is calibrated to ensure reliability (Bailey Instruments).
24
Journal of Tissue Viability 2000 VollO No 1
Assessment findings and intervention The information obtained from objective assessment of neuropathy can be used specifically to influence and organize patient treatments, and can be used in organizing patient access to diabetic foot care services. A limitation of the subjective 'traditional' approaches to assessing neuropathy in the diabetic foot (such as whether the patient can detect cotton wool, 'neurotips' (Owen Mumford UK), or hot and cold instruments, for example) is that the results only give an indication of whether neuropathy is present or not and therefore do not provide the clinician with a basis for tailored management plans or organization of care for at-risk patients.
Figure 6 A monofilament in use. The five suggested sites for testing each foot are the apex of the big toe, and the first, second, third and fifth plantar metatarso-phalangeal joints. These are marked with an X.
The literature also provides clinicians with protocols on how, specifically, monofilament testing should be performed 15 (Table 1). It should be stressed that areas of callus are to be avoided or removed when using monofilaments. Callus or any other hyperkeratosis of the epidermis forms a barrier to the detection of pressure and thus when left intact could give false-negative results. Clinicians are also warned that recent research has identified that the quality of monofilaments can vary greatly. For example, monofilaments of the same grade from the same manufacturer have been found to have differences in moisture content, or length of filament, both of which have been found to affect the filament's buckling pressure, and making any testing with the filaments less reliable 15 •24.
Table 1 How to perform monofilament testing 15
Stage
2 3 4 5
*
Procedure Apply the monofilament to the palm of the tester two or three times before applying it to the patient, to allow any extra stiffness to be removed Apply it to the test site on the patient, perpendicular to the surface to be tested Keep it applied until the monofilament bends by around lcm Remove the monofilament pressure Allow a couple of seconds to pass before applying the monofilament to the next test site
Reproduced with the kind permission of SB Communications
Research shows that if the methods of using neurothesiometers and monofilaments are standardized, then the results of assessing neuropathy are repeatable and reliable 14·20· 22•23. As previously mentioned, the results from neurothesiometer and monofilament testing allow the practitioner to assign patients into categories which reliably identify those who are at greatest risk. The process of categorizing and targeting at-risk patients is deemed to be a necessary measure in the endeavour to reduce lower-limb complications such as amputation 17 . Once categorized, the practitioner can tailor education and treatment programmes for individuals in a category, and arrange return times and access to services according to their risk status. Whilst this concept may appear obvious, current evidence suggests that many patients with diabetes are receiving foot screening and other podiatry services more frequently than is necessary, at the expense of those that need more frequent attention, treatment and on-going education25 . Standardization and objective assessment of neuropathy may go some way to rectifying the problems with accessing services and inequality of care. However, it should be emphasized that assessment and screening programmes should also provide clarity as to who is responsible for carrying out assessments and the education and treatment plans that follow for those in identified risk categories. Without this, the relationship and referral routes between primary care and hospital centres may be obscure, again resulting in inequality of care and ultimately poor outcomes for patients. Of equal importance is the consideration of an appropriate method of recording assessment findings. Preferably neuropathy assessment data should be included as part of centralized diabetes databases whereby other interested practitioners can access the information when required.
Conclusion The main aim for those involved in the care of the diabetic foot is to prevent complications such as ulceration and amputation, and subsequently to diminish the impact that diabetic foot disease has on individuals and society as a whole. Objective assessment of neuropathy has been used successfully in strategies to prevent complications, through identifying and improving services for those at risk. The
Journal of Tissue Viability 2000 VollO No 1
challenge is for practitioners to standardize and revise existing protocols for the assessment of neuropathy based on research evidence, in the ever-continuing attempt to fulfil this aim. With the implementation of clinical governance, the forthcoming quality initiative from the Department of Health, this challenge may become a reality, with the government providing the framework to assist in identifying training needs and resources required to implement the necessary changes in practice.
Address for correspondence J Booth, Podiatry Department, School of Health Professions and Rehabilitation Sciences, University of Southampton, Highfield, Southampton SO 17 lBU.
References 1 Reiber GE. The epidemiology of diabetic foot problems. Diabetic Medicine 1996; 13 (Suppll): S6-Sll. 2 Edmonds M, Boulton A, Buckenham T, Every N, Foster A, Freeman D, eta!. Report of the diabetic foot and amputation group. Diabetic Medicine 1996; 13 (9 Suppl4): S27-S42. 3 Sims DS, Cavanagh PR, Ulbrecht JS. Risk factors in the diabetic foot. Physical Therapy 1988; 68: 1887-1902. 4 Currie CJ, Morgan CL, Peters JB. The epidemiology and cost of inpatient care for peripheral vascular disease, infection, neuropathy and ulceration in diabetes. Diabetes Care 1998; 21: 42-46. 5 Pecoraro RE, Reiber GE, Burgeis EM. Pathways to diabetic limb amputation: basis for prevention. Diabetes Care 1990; 13: 513-521. 6 Boulton AJM. The diabetic foot. Surgery 1996; 14: 37-39. 7 Connor H. The ecomonic impact of diabetic foot disease. In: Connor H, Boulton AJM, Ward JD, editors. The foot in diabetes. Chichester: Wiley, 1987: 145-149. 8 Williams DRR. The size of the problem: epidemiological and economic aspects of foot problems in diabetes. In: Boulton AJM, Connor H, Cavanagh P, editors. The foot in diabetes, 2nd ed. Chichester: Wiley, 1994: 15-24. 9 Hart WM, Guest JF. Critical limb ischaemia: the burden of illness in the UK. British Journal of Medical Economics 1995; 8: 211-221. 10 Cavanagh PR. Foot pressure measurement in the diabetic foot clinic. Presented at the 6th Footpressure Interest Group Conference, 30 May-1 June 1999, Leeds. 11 Veves A, Uccioli L, Manes C, Van Acker K, Komninou H, Philippi des P et a!. Comparison of risk factors for foot problems in diabetic patients attending teaching hospital outpatient clinics in four different European states. Diabetic Medicine 1994; 11: 709-713. 12 Murray H, Young MJ, Veves A, Boulton AJM. The association between callus formation, high pressures and neuropathy in diabetic foot ulceration. Diabetic Medicine 1996; 13: 979-982. 13 Boulton AJM, Gries FA, Jervell JA. Guidelines for the diagnosis and management of diabetic peripheral neuropailiy. Diabetic Medicine 1998; 15: 508-514. 14 Young M, Breddy JL, Veves A, Boulton AJM. The prediction of diabetic peripheral neuropathy using vibration perception thresholds: a prospective study. Diabetes Care 1994; 117: 557-560. 15 Young M, Matthews C. Neuropathy screening: can we achieve our ideals? Diabetic Foot 1998; 1: 22-25. 16 Foster AVM, Eaton C, McConville DO, Edmonds M. Application of Opsite film: a new and effective treatment of painful diabetic neuropathy. Diabetic Medicine 1994; 11: 768-772. 17 Rith-Najarian SJ, Stolusky T, Gohdes DM. Identifying diabetic patients at high risk for lower extremity amputation in a primary health care setting. Diabetes Care 1992; 15: 1386-1389.
25
18 Knowles A. The role of pressure relief in diabetic foot problems. Diabetic Foot 1998; 1: 55-63. 19 Dyck PJ, Karnes J, O'Brien PC. Diagnosis, staging and classification of diabetic neuropathy and associations with other complications. In: Dyck PJ, Thomas PK, Asbury A, Winegrad A, Porte D, editors. Diabetic neuropathy. Philadelphia: WB Saunders, 1987: 36-44. 20 Kumar S, Femanso DJS, Veves A, Knowles EA, Young MJ, BoultonAJM. Semmes-Weinstein monofilaments: a simple, effective and inexpensive screening device for identifying diabetic patients at risk of ulceration. Diabetes Research and Clinical Practice 1991; 13: 63--68. 21 Coppini DV, Young PJ, Weng C, Macleod AF, Sonksen PH. Outcome on diabetic foot complications in relation to clinical examination and quantitative sensory testing: a case-control study. Diabetic Medicine 1998; 15: 765-771. 22 Bloom S, Till S, Sonksen P, Smith S. Use of a biothesiometer to measure individual vibration thresholds and their variation in 519 non-diabetic subjects. British Medical Journal 1984; 288: 1793-1795. 23 Wiles PG, Pearce SM, Rice PJS, Mitchell JMO. Vibration perception threshold: influence of age, height, sex, and smoking, and calculation of accurate centile values. Diabetic Medicine 1991; 8: 157-161. 24 McGill M, Molyneaux L, Yue DK. Use of the Semmes-Weinstein 5.07110 gram monofilament: the long and the short of it. Diabetic Medicine 1998; 15: 615--617. 25 Donohue M. The Exeter Integrated Footcare Project. Presented at the 7th National Diabetic Foot Conference, May 1998, Malvern.
Assessment of peripheral neuropathy in the diabetic foot Jodi Booth Podiatry Department, School of Health Professions and Rehabilitation Sciences, University of Southampton Peripheral neuropathy is associated with major morbidity in the diabetic population. The detection of whether peripheral neuropathy is simply present or not in patients with diabetes is insufficient. What is required is a reliable measure of both the extent and severity of neuropathy, as this enables the appropriate allocation of resources and improves the quality of care for the patients who need it most. Standardized approaches involving the use of a neurothesiometer and a 10 g monofilament can provide a reliable and objective measure of the extent and severity of neuropathy, and should therefore be adopted into protocols for best practice in the assessment of neuropathy.
Introduction Of the estimated 110 million people worldwide who have diabetes mellitus 1, many will experience one or a number of syndromes affecting the foot, in which neuropathy, ischaemia and infection can result in major morbidity 2 . Foot ulceration remains one of the most prevalent and serious complications associated with diabetes 3•4 (Figure 1). A suggested 15% of the diabetic population are afflicted by ulceration during their lifetimes, and 6-20% of these require in-patient treatment for their ulcer management 1.
• • • •
peripheral neuropathy peripheral vascular disease poor glycaemic control bony deformity
The prognosis for foot ulceration is often poor. At best, the patient can expect a stringent regime of ulcer management until healing is achieved; at worst, indolent or recurrent ulceration, often with infection, may result in gangrene and amputation of a limb (Figure 2). Incidence data show that 84% of all non-traumatic lower-limb amputations performed on those with diabetes are preceded by ulceration 5 . Diabetic foot disease is also costly for society6 . Foot and lower-limb complications are the most common reason for hospital admission for those with diabetes, at estimated costs of between £12.9 and 13.5 million a year7 •8. With regard to amputation specifically, the economic burden is suggested to amount to £8500 per patient for an amputation and limb fitting 7 •9 .
Neuropathy and ulceration The exact pathway to tissue breakdown and ulceration in those with diabetes is unknown 10. However, many studies have identified markers or risk factors that are associated with the likelihood of developing ulceration in those with diabetes 2•11 •12 :
Figure 1 A patient with diabetic peripheral neuropathy presenting with ulceration over the lateral aspect of the mid-foot region.
22
Journal of Tissue Viability 2000 Vol lO No l
down the legs and may also report hyperaesthesia (excess sensitivity) and sensations of cold or warmth or of overtight skin 15 . The pain history may allow differential diagnosis from other possible causes of pain and the practitioner can subsequently arrange for appropriate pain relief. Topical analgesics such as capsaicin or application of Opsite film dressing (Smith & Nephew) over the affected area have proved effective15.16. Systemic preparations used successfully in the treatment of painful neuropathy include tricyclic anti-depressants, anti-epileptics and anti-arrhythmics, although none are licensed for this purpose 15 .
Figure 2 A patient presenting with gangrene of the second digit as a result of infection of a neuropathic ulcer.
• • • • • • •
history of previous ulceration limited joint mobility diabetic nephropathy elevated foot pressures presence of plantar callus visual impairment living alone
As many as 30% of people with diabetes have peripheral neuropathy, and of all known risk factors, neuropathy (with or without vascular insufficiency) has been confirmed as one of the most important factors in the development of ulceration3·11·13. The relevance of neuropathy is emphasized by Young et al who demonstrated that patients with diabetic peripheral neuropathy are seven times more likely to develop ulceration than those without 14. Furthermore, the majority of secondary and tertiary referrals to specialist diabetic foot clinics are as a result of neuropathic ulceration15.
Observations of the foot may indicate to the clinician that a patient has neuropathy. Typically the patient will present with clawing of the toes and prominent metatarsalphalangeal joints on the plantar surface of the foot. The veins on the foot may be distended and there are often areas of circumscribed callus formation 15 (Figure 3). Whilst history taking may determine those with painful neuropathy, and observations of the foot can provide clues as to whether neuropathy is present, both are subjective measures and neither are reliable in determining the extent and severity of neuropathy. A reliable measure of neuropathy will identify those individuals who will ulcerate, and will therefore allow preventive management strategies to be employed such as the use of casting techniques, custommade footwear, orthoses and orthotic walkers 17 •18 . Research has shown that determination of nerve conduction velocities is the gold standard method of measuring nerve damage and these are an excellent indicator of the severity of neuropathy 19 . However, the time and cost of determining
Assessment of neuropathy - the evidence The evidence for the association of neuropathy and lowerlimb complications reiterates the on-going need for regular, accurate and reliable methods for assessing neuropathy 2 • In practice, however, if neuropathy screening exists at all, there doesn't appear to be a standard or accepted method for assessing it, irrespective of the healthcare profession responsible for performing the assessment 15 . Reasons for this disparity may be numerous, but clearly the research in the field that should inform practice has not been integrated into assessment protocols. History taking should not be ignored in the assessment process, as it will provide information on any pain associated with nerve deterioration. Painful neuropathy is thought to occur in only 10% of those with diabetic neuropathy; typically the patient will complain of shooting or lancinating pain
Figure 3 The feet of a patient with diabetic peripheral neuropathy. Note the prominent distention of the veins on the dorsum of the feet, and the third and fourth digits of the patient's right foot beginning to claw.
Journal of Tissue Viability 2000 Vol 10 No 1 23
age-adjusted VPTs were over four times more sensitive at predicting those individuals at risk of ulcerating than raw VPT values. On the strength of these results, Coppini et al advocated that age-corrected VPT measurements should form part of everyday practice in the assessment of neuropathy21. Again, this work demonstrates the potential for achieving objective and reliable clinical assessment to identify those most at risk of complications. A patient's inability to detect pressure using monofilaments has also been shown to identify those who are at risk of lower-limb complications 17·20 . Monofilaments are nylon filaments that buckle under a known pressure. Research has shown that patients who can detect fewer than eight applications of a 10 g monofilament, when applied to five selected sites on each foot, are ten times more likely to ulcerate than those who are able to detect eight or more applications 17 . This research suggests that the sites that should be tested are as illustrated in Figure 6. The testing sites are thought to be appropriate as incidence data has shown that these areas of the foot are prime sites for neuropathic ulceration. Other authors have also suggested monofilament testing over the styloid process of the fifth metatarsal and on the heel for the same reason, these areas of the foot also being cited as being prone to ulceration 15 .
Figure 4 A neurothesiometer in use to detect and quantify vibration perception by the patient (Scientific Laboratory Supplies)
nerve conduction velocities preclude their use in the clinical environment 15 ·19 . Objective, quantifiable measures of neuropathy that are used clinically in the assessment of neuropathy include the patient's ability to detect vibration as measured using a neurothesiometer (Scientific Laboratory Supplies) and the patient's ability to detect pressure using one or a range of monofilaments (Bailey Instruments) 14·17 ·20·21 (Figures 4 and 5). Studies have shown that patients who cannot detect the vibration of the probe of a neurothesiometer at a reading of 25 V (the vibration perception threshold, VPT), when applied to the apex of the big toe are seven times more likely to ulcerate than those who can detect vibration at 15 V or less 14. The relevance of this finding is that clinicians are able to categorize patients immediately as high risk if they have VPTs at or above 25 V. Previous work on VPTs demonstrated that one's ability to detect vibration diminishes with advancing age in a 'normal' population 22·23 . Coppini et al demonstrated that VPT values obtained using a neurothesiometer could be adjusted through use of a simple statistical formula to accommodate normal age-related changes in vibration perception21 . When applied to the diabetic population, the results showed that
Figure 5 An example of a monofilament that is used to ascertain whether a patient is able to detect 10 g of pressure at a selected site. The monofilament shown is calibrated to ensure reliability (Bailey Instruments).
24
Journal of Tissue Viability 2000 VollO No 1
Assessment findings and intervention The information obtained from objective assessment of neuropathy can be used specifically to influence and organize patient treatments, and can be used in organizing patient access to diabetic foot care services. A limitation of the subjective 'traditional' approaches to assessing neuropathy in the diabetic foot (such as whether the patient can detect cotton wool, 'neurotips' (Owen Mumford UK), or hot and cold instruments, for example) is that the results only give an indication of whether neuropathy is present or not and therefore do not provide the clinician with a basis for tailored management plans or organization of care for at-risk patients.
Figure 6 A monofilament in use. The five suggested sites for testing each foot are the apex of the big toe, and the first, second, third and fifth plantar metatarso-phalangeal joints. These are marked with an X.
The literature also provides clinicians with protocols on how, specifically, monofilament testing should be performed 15 (Table 1). It should be stressed that areas of callus are to be avoided or removed when using monofilaments. Callus or any other hyperkeratosis of the epidermis forms a barrier to the detection of pressure and thus when left intact could give false-negative results. Clinicians are also warned that recent research has identified that the quality of monofilaments can vary greatly. For example, monofilaments of the same grade from the same manufacturer have been found to have differences in moisture content, or length of filament, both of which have been found to affect the filament's buckling pressure, and making any testing with the filaments less reliable 15 •24.
Table 1 How to perform monofilament testing 15
Stage
2 3 4 5
*
Procedure Apply the monofilament to the palm of the tester two or three times before applying it to the patient, to allow any extra stiffness to be removed Apply it to the test site on the patient, perpendicular to the surface to be tested Keep it applied until the monofilament bends by around lcm Remove the monofilament pressure Allow a couple of seconds to pass before applying the monofilament to the next test site
Reproduced with the kind permission of SB Communications
Research shows that if the methods of using neurothesiometers and monofilaments are standardized, then the results of assessing neuropathy are repeatable and reliable 14·20· 22•23. As previously mentioned, the results from neurothesiometer and monofilament testing allow the practitioner to assign patients into categories which reliably identify those who are at greatest risk. The process of categorizing and targeting at-risk patients is deemed to be a necessary measure in the endeavour to reduce lower-limb complications such as amputation 17 . Once categorized, the practitioner can tailor education and treatment programmes for individuals in a category, and arrange return times and access to services according to their risk status. Whilst this concept may appear obvious, current evidence suggests that many patients with diabetes are receiving foot screening and other podiatry services more frequently than is necessary, at the expense of those that need more frequent attention, treatment and on-going education25 . Standardization and objective assessment of neuropathy may go some way to rectifying the problems with accessing services and inequality of care. However, it should be emphasized that assessment and screening programmes should also provide clarity as to who is responsible for carrying out assessments and the education and treatment plans that follow for those in identified risk categories. Without this, the relationship and referral routes between primary care and hospital centres may be obscure, again resulting in inequality of care and ultimately poor outcomes for patients. Of equal importance is the consideration of an appropriate method of recording assessment findings. Preferably neuropathy assessment data should be included as part of centralized diabetes databases whereby other interested practitioners can access the information when required.
Conclusion The main aim for those involved in the care of the diabetic foot is to prevent complications such as ulceration and amputation, and subsequently to diminish the impact that diabetic foot disease has on individuals and society as a whole. Objective assessment of neuropathy has been used successfully in strategies to prevent complications, through identifying and improving services for those at risk. The
Journal of Tissue Viability 2000 VollO No 1
challenge is for practitioners to standardize and revise existing protocols for the assessment of neuropathy based on research evidence, in the ever-continuing attempt to fulfil this aim. With the implementation of clinical governance, the forthcoming quality initiative from the Department of Health, this challenge may become a reality, with the government providing the framework to assist in identifying training needs and resources required to implement the necessary changes in practice.
Address for correspondence J Booth, Podiatry Department, School of Health Professions and Rehabilitation Sciences, University of Southampton, Highfield, Southampton SO 17 lBU.
References 1 Reiber GE. The epidemiology of diabetic foot problems. Diabetic Medicine 1996; 13 (Suppll): S6-Sll. 2 Edmonds M, Boulton A, Buckenham T, Every N, Foster A, Freeman D, eta!. Report of the diabetic foot and amputation group. Diabetic Medicine 1996; 13 (9 Suppl4): S27-S42. 3 Sims DS, Cavanagh PR, Ulbrecht JS. Risk factors in the diabetic foot. Physical Therapy 1988; 68: 1887-1902. 4 Currie CJ, Morgan CL, Peters JB. The epidemiology and cost of inpatient care for peripheral vascular disease, infection, neuropathy and ulceration in diabetes. Diabetes Care 1998; 21: 42-46. 5 Pecoraro RE, Reiber GE, Burgeis EM. Pathways to diabetic limb amputation: basis for prevention. Diabetes Care 1990; 13: 513-521. 6 Boulton AJM. The diabetic foot. Surgery 1996; 14: 37-39. 7 Connor H. The ecomonic impact of diabetic foot disease. In: Connor H, Boulton AJM, Ward JD, editors. The foot in diabetes. Chichester: Wiley, 1987: 145-149. 8 Williams DRR. The size of the problem: epidemiological and economic aspects of foot problems in diabetes. In: Boulton AJM, Connor H, Cavanagh P, editors. The foot in diabetes, 2nd ed. Chichester: Wiley, 1994: 15-24. 9 Hart WM, Guest JF. Critical limb ischaemia: the burden of illness in the UK. British Journal of Medical Economics 1995; 8: 211-221. 10 Cavanagh PR. Foot pressure measurement in the diabetic foot clinic. Presented at the 6th Footpressure Interest Group Conference, 30 May-1 June 1999, Leeds. 11 Veves A, Uccioli L, Manes C, Van Acker K, Komninou H, Philippi des P et a!. Comparison of risk factors for foot problems in diabetic patients attending teaching hospital outpatient clinics in four different European states. Diabetic Medicine 1994; 11: 709-713. 12 Murray H, Young MJ, Veves A, Boulton AJM. The association between callus formation, high pressures and neuropathy in diabetic foot ulceration. Diabetic Medicine 1996; 13: 979-982. 13 Boulton AJM, Gries FA, Jervell JA. Guidelines for the diagnosis and management of diabetic peripheral neuropailiy. Diabetic Medicine 1998; 15: 508-514. 14 Young M, Breddy JL, Veves A, Boulton AJM. The prediction of diabetic peripheral neuropathy using vibration perception thresholds: a prospective study. Diabetes Care 1994; 117: 557-560. 15 Young M, Matthews C. Neuropathy screening: can we achieve our ideals? Diabetic Foot 1998; 1: 22-25. 16 Foster AVM, Eaton C, McConville DO, Edmonds M. Application of Opsite film: a new and effective treatment of painful diabetic neuropathy. Diabetic Medicine 1994; 11: 768-772. 17 Rith-Najarian SJ, Stolusky T, Gohdes DM. Identifying diabetic patients at high risk for lower extremity amputation in a primary health care setting. Diabetes Care 1992; 15: 1386-1389.
25
18 Knowles A. The role of pressure relief in diabetic foot problems. Diabetic Foot 1998; 1: 55-63. 19 Dyck PJ, Karnes J, O'Brien PC. Diagnosis, staging and classification of diabetic neuropathy and associations with other complications. In: Dyck PJ, Thomas PK, Asbury A, Winegrad A, Porte D, editors. Diabetic neuropathy. Philadelphia: WB Saunders, 1987: 36-44. 20 Kumar S, Femanso DJS, Veves A, Knowles EA, Young MJ, BoultonAJM. Semmes-Weinstein monofilaments: a simple, effective and inexpensive screening device for identifying diabetic patients at risk of ulceration. Diabetes Research and Clinical Practice 1991; 13: 63--68. 21 Coppini DV, Young PJ, Weng C, Macleod AF, Sonksen PH. Outcome on diabetic foot complications in relation to clinical examination and quantitative sensory testing: a case-control study. Diabetic Medicine 1998; 15: 765-771. 22 Bloom S, Till S, Sonksen P, Smith S. Use of a biothesiometer to measure individual vibration thresholds and their variation in 519 non-diabetic subjects. British Medical Journal 1984; 288: 1793-1795. 23 Wiles PG, Pearce SM, Rice PJS, Mitchell JMO. Vibration perception threshold: influence of age, height, sex, and smoking, and calculation of accurate centile values. Diabetic Medicine 1991; 8: 157-161. 24 McGill M, Molyneaux L, Yue DK. Use of the Semmes-Weinstein 5.07110 gram monofilament: the long and the short of it. Diabetic Medicine 1998; 15: 615--617. 25 Donohue M. The Exeter Integrated Footcare Project. Presented at the 7th National Diabetic Foot Conference, May 1998, Malvern.