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Background Metatarsophalangeal joint deformity is associated with skin breakdown and amputation. The aims of this study were to compare intrinsic foot muscle deterioration ratios (ratio of adipose to muscle volume), and physical performance in subjects with diabetic neuropathy to controls, and determine their associations with 1) metatarsophalangeal joint angle and 2) history of foot ulcer. Methods 23 diabetic, neuropathic subjects [59 (SD 10) years] and 12 age-matched controls [57 (SD 14) years] were studied. Radiographs and MRI were used to measure metatarsophalangeal joint angle and intrinsic foot muscle deterioration through tissue segmentation by image signal intensity. The Foot and Ankle Ability Measure evaluated physical performance. Findings The diabetic, neuropathic group had a higher muscle deterioration ratio [1.6 (SD 1.2) vs. 0.3 (SD 0.2), P < 0.001], and lower Foot and Ankle Ability Measure scores [65.1 (SD 24.4) vs. 98.3 (SD 3.3) %, P < 0.01]. The correlation between muscle deterioration ratio and metatarsophalangeal joint angle was r = −0.51 (P = 0.01) for all diabetic, neuropathic subjects, but increased to r = −0.81 (P < 0.01) when only subjects with muscle deterioration ratios >1.0 were included. Muscle deterioration ratios in individuals with diabetic neuropathy were higher for those with a history of ulcers. Interpretation Individuals with diabetic neuropathy had increased intrinsic foot muscle deterioration, which was associated with second metatarsophalangeal joint angle and history of ulceration. Additional research is required to understand how foot muscle deterioration interacts with other impairments leading to forefoot deformity and skin breakdown.

Purpose To describe a semi-automated program that will segment subcutaneous fat, muscle, and adipose tissue in the foot using magnetic resonance (MR) imaging, determine the reliability of the program between and within raters, and determine the validity of the program using MR phantoms. Materials and Methods MR images were acquired from 19 subjects with and without diabetes and peripheral neuropathy. Two raters segmented and measured volumes from single MR slices at the forefoot, midfoot, and hindfoot at two different times. Intra and inter-rater correlation coefficients were determined. Muscle and fat MR phantoms of known volumes were measured by the program. Results Most ICC reliability values were over 0.950. Validity estimates comparing MR estimates and known volumes resulted in r2 values above 0.970 for all phantoms. The root mean square error was less than 5% for all phantoms. Conclusion Subcutaneous fat, lean muscle, and adipose tissue volumes in the foot can be quantified in a reliable and valid way. This program can be applied in future studies investigating the relationship of these foot structures to functions in important pathologies including the neuropathic foot or other musculoskeletal problems.

Background Diabetic forefoot joint deformities are a known risk factor for skin breakdown and amputation, but the causes of deformity are not well understood. The purposes of this study were to determine the effects of intrinsic foot muscle deterioration and limited ankle joint mobility on the severity of metatarsophalangeal joint (MTPJ) deformity, and determine the relationships between these potential contributing factors and indicators of diabetic complications (peripheral neuropathy and advanced glycation end products). Methods A total of 34 participants with diabetic neuropathy (average age, 59 years; range 41-73) were studied. MTPJ angle and intrinsic foot muscle deterioration were measured with computed tomography and magnetic resonance imaging, respectively. Maximum ankle dorsiflexion was measured using kinematics. Skin intrinsic fluorescence served as a proxy measure for advanced glycation end product accumulation. Results Total forefoot lean muscle volume (r = −0.52, P < .01) and maximum ankle dorsiflexion (r = −0.42, P < .05) were correlated with severity of MTPJ deformity. Together they explained 35% of the variance of MTPJ angle. Neuropathy was correlated with forefoot muscle deterioration (ρ = 0.53, P < .01). Skin intrinsic fluorescence was correlated to severity of neuropathy (r = 0.50, P < .01) but not maximum ankle dorsiflexion, or forefoot deterioration when controlling for neuropathy. Conclusion These results suggest that the interplay of intrinsic foot muscle deterioration and limited ankle mobility may be the primary contributor to the development of MTPJ deformity. Identifying these muscle and ankle motion impairments as risk factors for MTPJ deformity supports the need for targeted interventions early in the disease process to slow, or possibly stop the progression of deformity over time and reduce the risk of amputation. Level of Evidence Level IV, case series.

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.