Full-contact orthopedic insole design for plantar pressure optimization

doi:10.11996/JG.j.2095-302X.2024040868

Abstract

Abstract:

In order to optimize the plantar pressure distribution and reduce the peak plantar pressure, a parametric design method for full-contact orthopedic insoles based on a three-dimensional foot model was proposed. Based on the plantar pressure data and combined with the 3D lattice structure analysis, the offloading structure of the insole was optimized. First of all, in order to realize the personalized design of the full-contact insole, the foot 3D scanning model was employed to develop the parametric design process of the full-contact insole model through the Grasshopper plug-in platform. Subsequently, the energy absorption efficiency of six common 3D cubic lattice structures made of TPU was analyzed under the Abaqus environment, and the effective elastic modulus of diamond lattice structures was calculated under different filling rates. The performance of different lattice structures in absorbing plantar pressure was evaluated to provide a scientific basis for the selection of pressure-reducing structures. In the next part, the image sampling algorithm was used to extract the areas with higher plantar pressure, and the corresponding effective modulus of elasticity was chosen to fill different parts, completing the optimization design of the full-contact orthopedic insole. Additionally, the pressure reduction performance of the orthopedic insole before and after the optimization was compared through simulation analysis. Finally, static and dynamic plantar pressure measurement experiments demonstrated that personalized orthopedic insoles based on foot shape and three-dimensional pressure-reducing structures can effectively optimize the distribution of plantar pressure, offload the peak value of plantar pressure, and improve foot stability.

Key words: plantar pressure optimization, orthopedic insoles, parameterization design, three-dimensional lattice structure

CLC Number:

TP391
TS943

HUANG Yuzhe, WANG Xupeng, CHEN Wenhui, ZHOU Zhongze, ZHAO Jiaxin, WANG Yunqian. Full-contact orthopedic insole design for plantar pressure optimization[J]. Journal of Graphics, 2024, 45(4): 868-878.

Figures/Tables 32

Fig. 1 Get a 3D foot model ((a) Semi-weight-bearing standing foot scan; (b) Foot STL file)

Fig. 2 Parametric automatic modeling program

Fig. 3 Global coordinate system

Fig. 4 Extract the 3/4 foot section contour line

Fig. 5 Schematic diagram of the inner and outer cross-sectional lines

Fig. 6 NURBS curve fitting

Fig. 7 The curve deviation of the feature line 5 when the number of type value points is 30

Fig. 8 The relationship between the deviation value of the NURBS curve and the number of value points

Fig. 9 Forefoot contour line extraction

Fig. 10 Insole model generation

Fig. 11 Lattice structure generation

Fig. 12 Insole surface deviation analysis

Fig. 13 Three-dimensional cubic unit cell structure ((a) Simple cubic; (b) Body-centered cubic; (c) Face-centered cubic; (d) Diamond; (e) Fluorite; (f) Kelvin)

Fig. 14 Finite element model construction ((a) Simulation model of the seismic lattice structure; (b) Applied loads and conditions)

Fig. 15 The amount of deformation displacement for different unit cell structures ((a) Simple cubic; (b) Body-centered cubic; (c) Face-centered cubic; (d) Diamond; (e) Fluorite; (f) Kelvin)

Fig. 16 Force displacement curves of each lattice structure

Fig. 17 The amount of deformation displacement for different combinations of arrays ((a) 2×2×1; (b) 2×2×2; (c) 4×4×1; (d) 4×4×2)

Fig. 18 Energy absorption effect with different fill rates ((a) 30%; (b) 35%; (c) 40%; (d) 45%; (e) 50%)

Fig. 19 Trends in compression set for different filling rates

Table 1 Unit cell diameter and effective elastic modulus of structures with different filling rates

填充率/%	晶胞管直径/mm	E/MPa
30	2.40	0.53
35	2.65	0.64
40	2.90	0.92
45	3.20	1.36
50	3.50	1.88

Table 2 The effective modulus of elasticity of the lattice structure is used in each zone of the insole [10]

鞋垫区域	E/MPa
足趾区	0.47
跖骨区	0.95
足弓区	2.47
足跟区	1.39

Fig. 20 Optimized rear insole model

Fig. 21 Foot-insoles-ground model

Table 3 Insole parameter definition table

鞋垫类型	形态	结构	材料	鞋垫厚度/mm
平板鞋垫	二维平板	均质无减压结构	TPU	7
优化前矫形鞋垫	三维全接触	均质无减压结构	TPU	7
优化后矫形鞋垫	三维全接触	有减压结构	TPU+ 乳胶	5+ 2

Table 4 Maximum, minimum, and average plantar stress

裸足状态	S.Max/kPa	S.Min/kPa	S.Ave/kPa
裸足	88.5	24.80×10^-4	18.2
平板鞋垫	58.6	23.35×10^-4	16.4
优化前矫形鞋垫	53.7	19.39×10^-4	15.1
优化后矫形鞋垫	41.6	13.68×10^-4	13.3

Fig. 22 Optimized the simulation comparison of the front and rear insole models ((a) Bare feet; (b) Flat insole; (c) Optimized anterior orthopedic insole; (d) Optimized posterior orthopedic insoles)

Fig. 23 Static plantar stress test ((a) Bare feet; (b) Orthopedic insoles before wearing optimization; (c) Wearing orthopedic insoles after wearing optimization)

Fig. 24 Insole fabrication ((a) Optimized anterior orthopedic insoles; (b) Optimized posterior orthopedic insole)

Fig. 25 Static plantar pressure distribution contour of subjects with three foot types ((a) Bare feet; (b) Wearing optimized anterior orthopedic insole; (c) Wearing optimized posterior orthopedic insole; P.Max: peak pressure；Ave.P: average pressure)

Fig. 26 Dynamic foot pressure distribution contour and foot pressure center trajectory map of high arched feet ((a) Bare feet; (b) Wearing optimized anterior orthopedic insole; (c) Wearing optimized posterior orthopedic insole)

Fig. 27 Dynamic plantar peak pressure before and after wearing orthopedic insoles in subjects with three foot types ((a) Flat feet; (b) Normal feet; (c) High arched feet)

Fig. 28 Plantar mean pressure curve ((a) Flat foot; (b) Normal foot; (c) High arched foot)

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