Acquired midfoot deformity and function in individuals with diabetes and peripheral neuropathy

BACKGROUND: Diabetes mellitus related medial column foot deformity is a major contributor to ulceration and amputation. However, little is known about the relationship between medial column alignment and function and the integrity of the soft tissues that support and move the medial column. The purposes of this study were to determine the predictors of medial column alignment and function in people with diabetes and peripheral neuropathy.

METHODS: 23 participants with diabetes and neuropathy had radiographs, heel rise kinematics, magnetic resonance imaging and isokinetic muscle testing to measure: 1) medial column alignment (Meary's angle--the angle between the 1st metatarsal longitudinal axis and the talar head and neck), 2) medial column function (forefoot relative to hindfoot plantarflexion during heel rise), 3) intrinsic foot muscle and fat volume, ratio of posterior tibialis to flexor digitorum tendon volume, 4) plantar fascia function (Meary's angle change from toes flat to extended) and 5) plantarflexor peak torque. Predictors of medial column alignment and function were determined using simultaneous entry multiple regression.

FINDINGS: Posterior tibialis to flexor digitorum tendon volume ratio and intrinsic foot muscle volume were significant predictors of medial column alignment (P<.05), accounting for 44% of the variance. Intrinsic foot fat volume and plantarflexor peak torque were significant predictors of medial column function (P<.05), accounting for 37% of the variance.

INTERPRETATION: Deterioration of medial column supporting structures predicted alignment and function. Prospective research is required to monitor alignment, structure, and function over time to inform early intervention strategies to prevent deformity, ulceration, and amputation.