Design of plantar fasciitis orthotic using finite element modelling

NewsBot · May 16, 2008

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Using an Optimization Approach to Design an Insole for Lowering Plantar Fascia Stress-A Finite Element Study.
Hsu YC, Gung YW, Shih SL, Feng CK, Wei SH, Yu CH, Chen CS.
Ann Biomed Eng. 2008 May 15. [Epub ahead of print]

Plantar heel pain is a commonly encountered orthopedic problem and is most often caused by plantar fasciitis. In recent years, different shapes of insole have been used to treat plantar fasciitis. However, little research has been focused on the junction stress between the plantar fascia and the calcaneus when wearing different shapes of insole. Therefore, this study aimed to employ a finite element (FE) method to investigate the relationship between different shapes of insole and the junction stress, and accordingly design an optimal insole to lower fascia stress.A detailed 3D foot FE model was created using ANSYS 9.0 software. The FE model calculation was compared to the Pedar device measurements to validate the FE model. After the FE model validation, this study conducted parametric analysis of six different insoles and used optimization analysis to determine the optimal insole which minimized the junction stress between plantar fascia and calcaneus.This FE analysis found that the plantar fascia stress and peak pressure when using the optimal insole were lower by 14% and 38.9%, respectively, than those when using the flat insole. In addition, the stress variation in plantar fascia was associated with the different shapes of insole.
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Admin2 · May 16, 2008

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NewsBot · Jul 17, 2008

Parametric design of pressure-relieving foot orthosis using statistics-based finite element method.
Cheung JT, Zhang M.
Med Eng Phys. 2008 Apr;30(3):269-77.

Custom-molded foot orthoses are frequently prescribed in routine clinical practice to prevent or treat plantar ulcers in diabetes by reducing the peak plantar pressure. However, the design and fabrication of foot orthosis vary among clinical practitioners and manufacturers. Moreover, little information about the parametric effect of different combinations of design factors is available. As an alternative to the experimental approach, therefore, computational models of the foot and footwear can provide efficient evaluations of different combinations of structural and material design factors on plantar pressure distribution. In this study, a combined finite element and Taguchi method was used to identify the sensitivity of five design factors (arch type, insole and midsole thickness, insole and midsole stiffness) of foot orthosis on peak plantar pressure relief. From the FE predictions, the custom-molded shape was found to be the most important design factor in reducing peak plantar pressure. Besides the use of an arch-conforming foot orthosis, the insole stiffness was found to be the second most important factor for peak pressure reduction. Other design factors, such as insole thickness, midsole stiffness and midsole thickness, contributed to less important roles in peak pressure reduction in the given order. The statistics-based FE method was found to be an effective approach in evaluating and optimizing the design of foot orthosis.
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NewsBot · Dec 31, 2014

Plantar pressure relief under the metatarsal heads - therapeutic insole design using three-dimensional finite element model of the foot
Wen-Ming Chen, Sung-Jae Lee, Peter Vee Sin Lee
Journal of Biomechanics; Article in Press

Therapeutic footwear with specially-made insoles are often used in people with diabetes and rheumatoid arthritis to relieve ulcer risks and pain due to high pressures from areas beneath bony prominences of the foot, in particular to the metatarsal heads (MTHs).

In a three-dimensional finite element study of the foot and footwear with sensitivity analysis, effects of geometrical variations of a therapeutic insole, in terms of insole thicknesses and metatarsal pad (MP) placements, on local peak plantar pressure under MTHs and stress/strain states within various forefoot tissues, were determined. A validated musculoskeletal finite element model of the human foot was employed. Analyses were performed in a simulated muscle-demanding instant in gait.

For many design combinations, increasing insole thicknesses consistently reduce peak pressures and internal tissue strain under MTHs, but the effects reach a plateau when insole becomes very thick (e.g., a value of 12.7 mm or greater). Altering MP placements, however, showed a proximally- and a distally-placed MP could result in reverse effects on MTH pressure-relief. The unsuccessful outcome due to a distally-placed MP may attribute to the way it interacts with plantar tissue (e.g., plantar fascia) adjacent to the MTH. A uniform pattern of tissue compression under metatarsal shaft is necessary for a most favourable pressure-relief under MTHs.

The designated functions of an insole design can best be achieved when the insole is very thick, and when the MP can achieve a uniform tissue compression pattern adjacent to the MTH.
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NewsBot · Apr 27, 2022

Computationally efficient model to predict the deformations of a cellular foot orthotic
MohammadrezaMoeini et al
Computers in Biology and Medicine; 21 April 2022, 105532

Highlights
•We introduced a computationally efficient FE model of a honeycomb lattice foot orthotic by numerical homogenization.
•The homogenized model's prediction is verified by the explicit model's prediction and validated by the experimental measurements.
•The homogenized model predicts the same displacement field as the explicit model, but it is 46 times faster.
•In a contact simulation, the homogenized model predicts the force-displacement curve 60 times faster than the explicit model. The relative difference between their predictions is less than 1.0%.
•Both models predict a contact force close to the experimental results with a relative difference smaller than 10%.
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Background
Foot orthotics (FOs) are frequently prescribed to provide comfortable walking for patients. Finite element (FE) simulation and 3D printing pave the way to analyse, optimize and fabricate functionally graded lattice FOs where the local stiffness can vary to meet the therapeutic needs of each individual patient. Explicit FE modelling of lattice FOs with converged 3D solid elements is computationally prohibitive. This paper presents a more computationally efficient FE model of cellular FOs.

Method
The presented FE model features shell elements whose mechanical properties were computed from the numerical homogenization technique. To verify the results, the predictions of the homogenized models were compared to the explicit model's predictions when the FO was under a static pressure distribution of a foot. To validate the results, the predictions were also compared with experimental measurements when the FO was under a vertical displacement at the medial longitudinal arch.

Results
The verification procedure showed that the homogenized model was 46 times faster than the explicit model, while their relative difference was less than 8% to predict the local minimum of out-of-plane displacement. The validation procedure showed that both models predicted the same contact force with a relative difference of less than 1%. The predicted force-displacement curves were also within a 90% confidence interval of the experimental measurements having a relative difference smaller than 10%. In this case, using the homogenized model reduced the computational time from 22 hours to 22 minutes.

Conclusion
The presented homogenized model can be therefore employed to speed up the FE simulation to predict the deformations of the cellular FOs.
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