The average pressure distribution of the diabetic foot: can it be used as a clinical diagnostic aid?
INTRODUCTION:: The aim of this study was to investigate whether averaged data obtained from pressure distribution measurements could be used to distinguish differences between diabetic feet with normal and no sensation. The calculated parameters most sensitive to any differences were established, and the potential of the averaged maximum pressure picture as a quick recognition pattern of a neuropathic diabetic foot was assessed for clinical use. METHODS:: Dynamic pressure distribution data was collected from 56 diabetics using an emed SF2 platform. The first step method was used, and only one step per subject was recorded for this set of data. Each subject completed a questionnaire which included a grading of the sensitivity to vibration on the plantar surface of the foot evaluated by a clinician. The subjects were subsequently divided into four groups depending on this sensitivity, but only data from the two groups with normal (n=16) and no sensation (n=12) were evaluated in this study. Control data were obtained from two separate sources: for adults (n=40) using an emed SF4 platform and for teenagers (n=73) using a mini-emed platform. The groupmask evaluation program from the novel-win software and the average program from the novel-ortho software were used to evaluate the data. Each dynamic pressure distribution was automatically masked using the foot recognition algorithms of the 'novel' mask, which divided the foot into ten areas: the heel, midfoot, first, second, third, fourth and fifth metatarsal heads (MTH), hallux, second toe, and remaining toes. The parameters analysed for each of these masks included: the mean peak pressure, maximum force, contact time, beginning of contact time, pressure-time integral and force-time integral. RESULTS AND DISCUSSION:: The results showed clearly that both pressure and contact time are important parameters in differentiating a neuropathic from a non-neuropathic diabetic foot. Values of the maximum force in each area of the foot showed no difference between the two groups. Owing to the small sample sizes for the two diabetic groups the 95% confidence limits were relatively large, however, clear differences existed between the two sets of data for the mean peak pressure and the mean pressure-time integral for the total foot and the forefoot. Based upon this data, peak pressure values above 56 N/cm(2) for the 1st MTH, 46 N/cm(2) for the 3rd MTH, 35 N/cm(2) for the 4th MTH and 26 N/cm(2) for the 5th MTH, and pressure-time integrals above 31 Ns/cm(2) for the 1st MTH, 21 Ns/cm(2) for the 2nd MTH, 24 Ns/cm(2) for the 3rd MTH, 19 Ns/cm(2) for the 4th MTH and 12 Ns/cm(2) for the 5th MTH would suggest the possibility of a neuropathic diabetic foot. The averaged maximum pressure distribution picture for each group showed some differences between diabetic feet with normal sensation and those with no sensation. However, owing to the small size of the groups, it was felt that the averaged pressure pictures were, at the moment, limited in their use as a quick recognition pattern for the clinician. Although further data has already been collected and will be added to the databank in the near future. CONCLUSIONS:: These data show that averaged maximum pressure pictures alone do not provide sufficient information to differentiate clearly between a non-neuropathic and a neuropathic diabetic foot. Parameters obtained from the dynamic process, in particular, the pressure-time integral, must also be taken into account. It is anticipated that this work will be continued in order to investigate differences between other dynamic processes of potential importance, such as the location and speed of the gait line. ACKNOWLEDGEMENTS:: The authors would like to thank Dr M Morlock and Dr T Tsvetkova for the control data.
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Novel GmbH, Beichstrasse 8, 80802 Munich, Germany.
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