Plantar pressures are elevated in the neuroischemic and the neuropathic diabetic foot

OBJECTIVE - Clinical observation has noted that diabetic neuropathic ulcers occur frequently on the plantar surface, whereas neuroischemic ulcers seem to occur often on the foot margins. The reason for this difference in the site of ulceration is unknown, but it may be related to differences in pres sure loading. The aim of the study was to compare vertical in-shoe foot pre ssures measured during walking (using the F-SCAN system) in four groups of patients whose degree of neuropathy was measured by vibration perception th reshold (VPT). RESEARCH DESIGN AND METHODS - Subjects included 14 neuroischemic diabetic p atients (VPT 29.3 +/- 13.5 V) with history of ulceration on the margins of the foot, 18 patients with neuropathy alone (VPT 38.7 +/- 12.7 V) and previ ous history of ulceration on the plantar surface, 10 diabetic control patie nts (VPT 9.9 +/- 2.7 V), and 15 nondiabetic control subjects (VPT 7.0 +/- 0 .5 V). RESULTS - When compared with the other three groups, neuroischemic patients had higher foot pressures when measured as mean peak pressures and highest peak pressures under four areas of the foot: medial and lateral forefoot, hallux, and heel. Furthermore, when measuring the maximum pressures develop ed at any point under the plantar surface, the neuroischemic patients also had the most elevated pressures (757.6 +/- 135.9 kPa), significantly higher than those found in the neuropathic group (482.8 +/- 68.6 kPa, P = 0.04) a nd in both diabetic control patients (310.2 +/- 34.7 kPa, P = 0.008) and no ndiabetic control subjects (365.1 +/- 49.8 kPa, P = 0.007), CONCLUSIONS - Despite having increased plantar pressures and a comparable d egree of neuroischemic the neuroischemic patients did not have a history of ulceration oil the plantar surface. These observations may have relevance to different mechanisms of ulcer formation in the neuroischemic and neuropa thic foot.