Purpose/Hypothesis : Diabetes mellitus can result in deformity of the medial column of the foot. The plantar fascia functions to help create a stable medial column during walking via toe extension (windlass mechanism). Individuals with diabetes mellitus and peripheral neuropathy (DMPN) are known to have plantar fascia tissue changes, however it is unclear how the function of the plantar fascia is affected. The purpose of this study was to measure change in radiographic alignment between toe flat and extended position in subjects with DMPN and medial column deformity, and age- and weight-matched controls. We hypothesized that subjects with DMPN and medial column deformity would have impaired plantar fascia function resulting in less change in radiographic alignment from toe flat to toe extension.
Number of Subjects : 22 subjects; 12 with DMPN+deformity (7 male/5 female; age: 59±13yrs, weight: 110±24kg) and 10 controls (6 male/4 female; age: 59±15 yrs, weight: 104±32kg).
Materials/Methods : Subjects had weightbearing, lateral radiographs in a toe flat and 60 degree toe extended position. Forefoot and midfoot alignment (Meary’s angle, navicular height) and hindfoot alignment (calcaneal pitch, talar declination) were measured by a blinded rater using iSite PACS software. Within group and within position data were analyzed with a repeated measures ANOVA. Group comparison of change in alignment was analyzed with a t-test.
Results : The DMPN+deformity group demonstrated greater deformity in toe flat position compared to controls as evidenced by a more negative Meary’s angle (-20±11° versus -10±6°, p<.01), lower navicular height (28±9mm versus 40±7mm, p<.01), decreased calcaneal pitch (10±7° versus 21±6°, p≤.01) and larger talar declination (35±11° versus 21±5°, p<.01).
Amount of change in alignment between toe flat and extended conditions was significant in Meary’s angle (4±6° versus 10±3°, p≤.01), navicular height (6±4° versus 10±4°, p<.01) and calcaneal pitch (3±1° versus 2±2°, p<.01) in the DMPN+deformity and control groups. Talar declination changed between toe flat and extended conditions for control group (-5±4°, p<.01) but not the DMPN+deformity group (-1±5°, p=.32). In the DMPN+deformity group, the amount of change between conditions was smaller for Meary’s angle and navicular height compared to the control group (p<.03).
Conclusions : This study provides evidence of impaired plantar fascia function in individuals with DMPN+deformity. From toe flat to extended position, the DMPN+deformity demonstrated decreased navicular rise and forefoot plantarflexion compared to controls.
Clinical Relevance : Individuals with DMPN+deformity have impaired plantar fascia function when engaging the windlass mechanism that may contribute to progressive neuropathic foot deformity. Additional research is needed to determine if screening for plantar fascia function may assist in identifying individuals at-risk for onset or progression of neuropathic foot deformity.
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