Limb amputation in diabetic patients
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v10n2p37 Limb amputation in diabetic patients Ann Millward MA, MSc, MD, MRCP, is Clinical Senior Lecturer in Medicine, Ply-mouth Postgraduate Medical School, Jona-than Roberts BSc (Hons) is a research stud-ent, Graham Bruce, DPodM SRCh, is Deputy Head of Podiatry, Plymouth health district. T he main complications associated with diabetes are microvascular and macrovascular. The microvascular problems affecting the small blood vessels include neuropathy, nephropathy and retino-pathy. Macrovascular disease is associated with the large arteries supplying the heart, brain, legs and feet. Blockage or reduced circulation in these areas results in angina, myocardial infarction, cerebovascular events and peripheral vascular disease, resulting in claudication or lower limb amputation, disease affecting the brain or peripheral vascular disease affecting the limbs (Edmonds and Watkins, 1997). It is estimated that the treatment of diabetic complications consumes 10% of the annual NHS budget, with £12.9 million of the £1 billion devoted to the care of people with diabetes attributed to treatment of its complications (Edmonds and Watkins, 1997). In 1983 it was reported that the rate of lower limb amputation is 15 times higher in diabetic patients compared with nondiabetics (Most and Sinnock, 1983). With data such as this, the representatives of government health departments and diabetic experts met at the offices of the WHO in St Vincent, Italy in October 1989. The resulting report, known as the 'St Vincent declaration' set a number of goals for both patients and health services in relation to management, education and care of people with diabetes in Europe. One of these recommendations was to reduce by 50% the rate of lower limb amputation for diabetic gangrene over a five year period (WHO/International Diabetes Federation, 1990). Foot ulceration is the leading cause of hospital admission for patients with diabetes (Edmonds and Watkins, 1997). The feet are the major site of both peripheral neuropathy, which leads to sensory deficit and autonomic dysfunction, and of ischaemia, due to arteriosclerosis of the leg vessels. Infection can complicate these factors and cause necrosis of the foot. There are two main types of 'diabetic foot', the neuropathic and the neuroischaemic. The neuropathic foot is warm, dry, numb and usually painless. Pulses are palpable and three complications are found: * neuropathic ulcers * neuropathic (charcot) foot * neuropathic oedema. The neuroischaemic foot is cool and pulses are diminished or absent. It is complicated by rest pain, ulceration and possible gangrene. Diagnosis depends on the palpation of foot pulses either by hand or by use of Doppler ultrasound. Neurological status can be assessed clinically, by using a neurothesiometer and by assessing ankle and knee jerks. According to the British Diabetic Association in 1988 the estimated cost of major amputation in diabetic patients was £15 million per year, approximately £9400 per amputation. The estimated cost of amputation in 1996 was £38.06 million (Connor, 1997). The national data for England indicated a 45% increase in amputation rates between 1989/90 and 1993/94 (Hewitt, 1997). We audited the number of patients with diabetes in our large district general hospital who underwent any form of lower limb amputation between 1 January 1996 and 31 December 1996. Derriford Hospital subserves a population of 430000, covering the Plymouth health district and east Cornwall. The hospital has two specialist vascular surgeons, two diabetologists and a chiropody team serving all diabetes clinics. Methods A search was made of the hospital's patient administration system (PAS) for all patients who had had any amputation affecting the lower limb. The PAS was also used to identify all those with diabetes. With the consent of all the consultants caring for these patients, case notes were examined and clinical data extracted. This included patient details such as age, gender, ethnic group, diabetes type, current treatment, duration of diabetes and any complications. Specific foot pathology such as rest pain and claudication was also recorded as well as full details about the amputation. Glycated haemoglobin (HBA1C) data was obtained from the laboratory computer file. Results Number of amputations There were a total of 138 patients ( Table 1 ) who received any form of lower limb aputation in 1996, of whom 49 (35%) had diabetes. There were 53 amputations of any form carried out in these 49 patients, whose mean age was 70 (±12.9) years. Five (10%) had type 1 diabetes, 26 (53%) were treated with diet/tablets and 18 (37%) had type 2 diabetes but were treated with insulin. In 91% of those without diabetes, trauma was the main cause. Type of amputations in diabetic patients Table 1 shows the breakdown of all the types of amputation occurring. In the diabetic group a greater proportion received above knee amputations (AKA) and below knee amputations (BKA) and there were significantly more amputations of digits in the nondiabetic group. In addition, 15 out of the 49 (30.6%) patients with diabetes had more than one amputation in the year on the same limb, in which case the final level has been recorded. In 4 out of the 49 the amputations were bilateral (three AKA and one BKA). Reasons for amputation in diabetic patients The primary reasons for amputation in diabetic patients can be neuroischaemia or neuropathy. In 49 out of 53 (86.8%) cases the primary problem was neuroischaemia, 2 out of 53 (3.8%) due to neuropathy alone and in a further 5 of 53 (9.4%) amputation was for nonhealing ulcers, presumably (though not documented) due to a neuroischaemic problem. In 9 of the 53 (17%) a degree of osteomyelitis was present clinically and was included in the reason for amputation. Additional clinical details on diabetic patients * Smoking. Of the 49 patients, 25 were current or recent past smokers. * Metabolic control. In 1996 the method for measuring HBA1C in our laboratories changed the upper limit of the normal before April was 7.2% and 5.6 % after this. The mean HBA1C of the 49 patients was 10.8% before and 9.8% after April, suggesting relatively poor control, at least around the time of the operation. * Creatinine. Creatinine results were found in 47 patients with a mean reading of 109 µmol/l. Only 2 patients (4.1%) had established renal failure with creatinines >= 150 µmol/l. * Age. The vast majority of amputations occurred after the age of 61 (86%) and, therefore, in patients with type 2 diabetes. Discussion In the Plymouth health district in 1996, 138 people needed an amputation of part of their lower limb or limbs and 142 amputations were carried out. Around 57% of these were due to trauma, but 37% were in patients with diabetes. If traumatic amputations are excluded, amputations were 6.6 times more common in the diabetic compared to nondiabetic population, contrasting favourably with a decade ago (Most and Sinnock, 1983.) The typical diabetic patient who receives an amputation is most likely to be a man or woman over 60 years old with type 2 diabetes. He, or she, is likely still to be smoking, have indifferent diabetic control and to need an amputation above or below the knee for neuroischaemic problems. This was the main problem in up to 96% of those receiving amputation. Fortunately, a very low proportion lost a digit or limb from neuropathy alone, though coexistent neuropathy complicates simple ischaemic problems. Prevention remains better than care so how can such problems be prevented in our diabetc population? One should focus on improving diabetic contol, reducing vascular risk factors such as dyslipidaemia, making careful choices regarding other medication particularly antihypertensive treatment and advising patients to give up smoking. Regular examination of the feet by the diabetes team, GP or practice nurse remains extremely important. Large reductions in amputation rates have been shown in some areas where specialist clinics are in operation (Connor, 1997). Investment in space and people is necessary to provide this service and it is important to target 'at risk' groups, particularly those with an ulcer. Prompt referral to a vascular surgeon should result in early assessment, with the possibility of reconstuctive surgery (Cheshire et al, 1992). In our population 19 out of 49 (39%) received previous angioplasty or femoro politeal bypass grafting. Prompt treatment of infection of foot ulcers remains vital. Assuming the diabetic population to be approximately 10000 in the Plymouth health district, then 4.9 patients per thousand lost at least one limb in 1996. Other UK studies have shown amputations for all causes to be 3 per 10000 general population with 1 per 10000 attributable to diabetes (Anon, 1997). The estimated cost of a major amputation in 1996 was £12686 and £3172 for a minor amputation (Connor, 1997). If a BKA/AKA is considered major and digits or forefoot minor, then there were 39 major and 14 minor amputations in 1 year. This equates to £539162 though this is probably an underestimate as only the higher levels of amputation were recorded in the 15 patients who had more than one amputation in the year. A 50% reduction would save £269581. Conclusion The Plymouth health district has a specialist diabetic team serving an estimated diabetic population of 10000. In 1996, 53 were amputations undertaken at Derriford Hosp-ital. The data collected serves as a baseline for that collected in subsequent years to establish how successfully the recommended 50% reduction is achieved. Reduction in amputation rates has been recorded in areas where specialist care for diabetic patients is in place, despite the recorded 45% increase in incidence for the UK as a whole. Many factors contribute to the prevalence of amputation, including re-sources, population size, availability of specialist care and ethnicity. Further resourcing of the educational and preventative side should result in reduction of amputation costs to the NHS. * Acknowledgement Completion of this project has been dependent on the cooperation of staff at Derriford Hospital, to whom we give our thanks. References Anon (1997) An audit of amputations in a rural health district. Pract Diabetes Int (14) 6: 1524 Cheshire, NJW, Wolfe JHN (1992) Critical leg ischaemia, amputation or reconstruction. Br Med J 304 :312 Connor H (1997) The St Vincent amputationtarget: the cost of achieving it and the cost of failure. Pract Diabetes Int (14) 6: 1524 Edmonds ME, Watkins PJ (1997) The Diabetic Foot. In: Alberti KGMM et al, eds. The International Textbook of Diabetes Mellitus. John Wiley & Sons, Chichester. Hewitt D (1997) Data currently available to the Department of Health on diabetes. Pract Diabetes Int 14 ( 6):152-4 Most RS, Sinnock P (1983) The epidemiology of lower extremity amputations in diabetic individuals. Diabetes Care 6 : 8791 WHO/International Diabetes Federation (1990) Diabetes care and research in Europe: the St Vincent declaration. Diabetes Med 7 : 360