Part 6: Detection and Prevention of Foot Problems in Type 2 Diabetes

Background - Detection of Loss of Protective Foot SensationPeripheral neuropathy is common in people with Type 2 diabetes and was present in12.3% of people participating in the United Kingdom Prospective Diabetes Study atdiagnosis and in approximately 30% after 12 years (UKPDS 33, 1998). As reviewedin Section 1 peripheral neuropathy is a major risk factor for both foot ulceration andamputation. Therefore its clinical detection is important in identifying feet at risk ofulceration and is pivotal for effective strategies to prevent foot ulceration andamputation.One of the main objectives of the foot examination in the primary care setting is todetect a level of peripheral neuropathy which significantly increases the risk ofsustaining a foot wound, which is defined as ‘loss of protective sensation’. This is oneof the most important criteria in identifying people at high-risk of foot problems andis paramount in implementing a structured management plan to prevent lowerextremity complications (Armstrong et al, 1998). The detection of loss of protectivesensation is an important indicator to both the person with diabetes and the primarycarer that more frequent review and suitable preventative actions should be institutedand necessitates behavioural change in both the person with diabetes and the doctor.Several methods have been used to assess peripheral neuropathy in clinical studiesand include:• the 10g Semmes-Weinstein monofilament• vibration perception threshold (VPT) measured using a biothesiometer or 128Hztuning fork• calculation of a neuropathy score based on:− symptoms - the University of Texas Subjective Peripheral Neuropathyquestionnaire which relies on 4 questions of symptoms of neuropathy (Dyck,1988) or− clinical examination - the neuropathy disability score derived from acombination of testing for pain, temperature and vibration threshold with thepresence or absence of ankle reflexes (Young et al, 1993b)Symptoms alone are not considered reliable because a significant proportion of peoplewith diabetes who have neuropathy are asymptomatic (Young & Matthews, 1998).Similarly testing of ankle jerks alone is of little value since they are frequently absentin the elderly population, with or without diabetes (de Hens-van Putten et al, 1996)and has not been as successful as the more objective measures (eg VPT) in predictingulceration or amputation in people with diabetes.The primary care setting requires a simple, cheap and reliable means of identificationof the foot which has lost protective sensation (the insensate foot) and has led to theincreasing popularity of the 10g Semmes-Weinstein monofilament. The monofilamentconsists of a pressure sensitive nylon filament attached to a rod. The monofilamentbuckles at a reproducible pressure of 10g force which has been identified as the levelof sensation protective against foot ulceration, initially in leprosy (Birke & Sims,1986; Halar et al, 1987). The loss of this protective sensation at one site is taken asindicating an abnormal monofilament test. The test must be performed in areas free ofcallus which may impair the ability to feel the monofilament.41