Background: Diabetic foot disease is characterized by progressive foot deformities that lead to amputation and disabling morbidity. The purpose is to investigate the classification of two distinct phenotypes of mid foot structural polymorphism in individuals using plantar kinetic and pressure distribution and tarsal bone density assessments.
Methods: Twenty-two individuals (26 ft) with diabetes mellitus, peripheral neuropathy and at least one mid foot deformity were compared to 29 age-, gender- and race-matched healthy controls (58 ft). Eleven subjects with diabetes mellitus and peripheral neuropathy (11 ft) had lateral deformity; 11 subjects (15 ft) had medial deformity. Each subject had calcaneal bone mineral density and plantar force and pressure assessments walking barefoot over an EMED-ST P-2 platform.
Findings: Control subjects had lower mid foot vertical forces and pressures despite significantly higher preferred walking speed. In subjects with diabetes and neuropathy, maximum vertical force was 6-fold greater, force-time integral 9.5-fold greater, peak pressure 6.7-fold higher, pressure-time integral was 9.7-fold greater, contact area 2-fold greater and contact time 1.9-fold higher than controls. Pressure values were larger in involved vs uninvolved (P0.05). During stance in the mid foot, subjects with medial column phenotype showed greater pressure in the medial mask; subjects with lateral column phenotype had greater pressures in the lateral mask (P<0.05). Calcaneal bone density was lower for the deformity foot vs the non-deformity foot; bone mineral density was lower in medial column phenotype vs lateral column phenotype (P=0.02).
Interpretation: Diabetic foot disease can be classified as stereotypical, structurally-distinct phenotypes of deformities of the medial and lateral columns of the mid foot. Assessments of pedal bone density and plantar mid foot force and pressure during barefoot walking can characterize the structural polymorphic phenotypes and may assist the foot care specialist in clinical decision making.