Biomechanics and plantar ulcers in diabetes

Abstract

Patients with diabetes are at risk of developing plantar ulceration. To study the frequency of abnormal biomechanics and its possible influence on the location and distribution of lesions, patients presenting with active or recently healed forefoot plantar ulcers were investigated. 28 feet were assessed. Heel bisection angles were measured with the foot in subtalar joint neutral calcaneal stance and in relaxed calcaneal stance positions. The location of the lesion was mapped. In all cases abnormal function was demonstrated, expressed as abnormal positions in neutral and/or relaxed stance, and quantified by compensatory pronation. In relaxed stance for metatarsal ulcers there was a strong correlation between heel angles and metatarsal ulcer sites. Inverted heels were associated with lateral ulcers and everted heels with medial ulcers (r=0.8696: P < 0.001). In subtalar joint neutral stance position, large heel angles (> +8.0°) were associated with lateral ulcers, and smaller angles (< +6.0°) were associated with medial ulcers (r=0.7962: P<0.001). A significant difference was found between the compensatory pronation for metatarsal lesions, and that for toe lesions ( P < 0.05). Biomechanical assessment of patients may help in the identification of those at risk of ulceration and in the fabrication of functional orthoses or pressure relieving insoles.