Muscle, Joint and Movement Deterioration Contributing to Neuropathic Forefoot Deformity

The long term goal of this research is to reduce the incidence of lower extremity amputation in people with diabetes mellitus and peripheral neuropathy. It is hypothesized that muscle, joint, and movement deterioration associated with diabetes and peripheral neuropathy contribute to metatarsophalangeal joint (MTPJ) hyperextension deformity. MTPJ deformity results in excessive plantar stress on the insensitive forefoot, leading to ulceration and amputation. However, the specific cause of MTPJ deformity is not clear. The overall goal of this proposal is to identify the causes of MTPJ deformity and examine the ability of a targeted foot specific intervention to de-couple diabetes related mechanisms from MTPJ deformity and progression, following participants for 3 years. The investigators hypothesize that the cause of MTPJ deformity is an interaction of the accumulation of advanced glycation end products, muscle deterioration, limited joint mobility and compensatory movement strategies.

The specific aims are to determine:

1. relationships between advanced glycation end products, intrinsic foot muscle volume, limited ankle dorsiflexion joint mobility, MTPJ hyperextension movement pattern, and MTPJ alignment;
2. estimate the effect of a foot specific intervention on the MTPJ extension alignment and
3. determine progression of MTPJ deformity and the predictors of progression over three years.

The following will be collected on participants with diabetes mellitus and peripheral neuropathy and monitored over three years to understand the causes and progression of MTPJ deformity:

1. Skin intrinsic florescence to measure advanced glycation end product accumulation which increases collagen cross-linking and is associated with peripheral neuropathy, limited joint mobility, and muscle deterioration.
2. Magnetic resonance images to measure intrinsic foot muscle deterioration that precedes extrinsic foot muscle deterioration as a result of distal to proximal peripheral neuropathy. The muscle imbalance of weak intrinsic foot muscles, the only muscles able to flex the MTPJ, in the presence of relatively stronger extrinsic toe extensors, results in a force couple that hyperextends the MTPJ.
3. Kinematic and computed tomography measurement of foot and ankle joint positions to examine mobility and movement patterns that contribute to repeated and extreme MTPJ hyperextension during daily activities.