Use of Liquid Crystal Thermography in the Evaluation of the Diabetic Foot

Liquid crystal thermography (LCT) was used to determine temperature variations on theplantar surface of feet. The purpose was to identify thermal emission patterns associated with diabetic foot ulcers. Three population groups were screened: group I, 16 nondiabetic controls; group II, 21 diabetic patients with no history of pedal ulcers; and group III, 28 diabetic patients with active pedal ulceration or history of foot ulcerations. The results demonstrate a generalized increase in plantar foot temperature in group III compared with groups I and II. Temperature readings under metatarsal heads 1–5, great toe, heel, and lateral band were significantly increased (P < .01) in group III. Additionally, the warm lateral surface displayed by group III patients was not significantly different in temperature from the medial arch of the foot. In groups I and II, the lateral band was significantly cooler (P < .01) than the medial arch. In group III patients with active ulceration on only one foot, no significant difference in temperature was found between the foot with active ulceration compared with the contralateral nonulcerated foot. When patients with active pedal ulceration were compared with patients with a history of foot ulcers, no significant difference in temperature was seen at five of seven sites tested. A warm concentric color band surrounding active plantar ulcers was identified in group III. This pattern extended from the center of the ulcer to a distance of 8 mm. A significant change in temperature (P < .01) was noted at 6- and 8-mm distances from the center of the ulcer. In addition, a mottled thermographic pattern was observed more frequently in group III patients than in groups I and II. In summary, group III demonstrated significantly increased skin temperatures and identifiable thermographic emission patterns, which distinguish them from normal. These findings suggest the need for prospective studies to evaluate LCT as a diagnostic modality in the prediction of foot ulceration in the diabetic population.