Evaluating Plantar Fascia Strain in Hyperpronating Cadaveric Feet

What is it about?

The primary goal of this investigation was to quantify strain on the medial band of the plantar fascia in feet exhibiting talotarsal instability, before and after an extra-osseous talotarsal stabilization (EOTTS) procedure. It was hypothesized that the excessive strain placed on the plantar fascia in hyperpronating cadaveric feet would be reduced significantly after the insertion of the HyProCure® EOTTS device.

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Why is it important?

The plantar fascia functions to stabilize the plantar arch(s) of the foot. Instability of the talotarsal mechanism (i.e., hyperpronation) results in the partial displacement of the talus on the tarsal mechanism and results in excessive strain acting on the medial band of the plantar fascia. Eventually, the critical threshold is reached igniting a painful stimulus. Methods A miniature differential variable reluctance strain gauge was used to quantify the plantar fascia strain in 6 fresh-frozen cadaver foot specimens exhibiting flexible instability of the talotarsal joint complex.  The blinded sub-investigator was instructed to maximally pronate the talotarsal mechanism by applying maximum force to the 4th & 5th metatarsal heads. A pressure sensor was placed under the 4th & 5th metatarsal heads ensuring that the same maximum pressure was applied for each reading.  The strain was measured as the foot was moved from its neutral to maximally pronated position, before and after intervention using the HyProCure® EOTTS device. Results The mean plantar fascia elongation was 0.83 ± 0.27 mm (strain 3.62% ± 1.17%) prior to EOTTS and 0.56 ± 0.2 mm (strain 2.42% ± 0.88%) after insertion of HyProCure®, (N = 18, variation reported is ± 1 SD).  The average plantar fascia strain decreased by 33%, and the difference was statistically significant with p < .001.

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