|Title:||Development of a computational foot model for biomechanical evaluation of high-heeled shoe designs|
|Subject:||Hong Kong Polytechnic University -- Dissertations.|
Shoes -- Design -- Data processing.
Footwear -- Design -- Data processing.
Biomechanics -- Data processing.
|Department:||Department of Health Technology and Informatics|
|Pages:||xxii, 192 leaves : ill. (some col.) ; 30 cm.|
|Abstract:||Foot problems such as corn, callus, ulceration, bunion and bone fracture may result from improperly or incorrectly fitted footwear. Wearing high-heeled shoes (HHS) may cause discomfort and eventually lead to foot problems such as hallux valgus, metatarsalgia, knee osteoarthritis and lower back pain. Many experimental techniques were developed and employed to quantify the biomechanical interactions of foot and footwear, such as in-shoe pressure measurement, motion analysis, in-shoe thermal measurement and skin blood flow measurement. However, direct biomechanical measurement of internal stress and strain on bony, ligamentous and intramuscular structures of the foot remains unavailable or highly invasive. Our understanding and quantification of HHS design from biomechanical aspects are still far from complete. In this study, a comprehensive finite element (FE) model of a female foot with HHS was developed. The model used real three-dimensional foot geometry, and incorporated nonlinear material properties, large deformations and interfacial slip/friction conditions. The results of the computational model were validated by comparison of pressure distributions, shape deformations and cadaveric experiments. In general, the FE predictions were in good agreement with experimental measurements. For the parametric study on heel height from 0-inch to 3-inch, an increase in heel height resulted in a decrease in arch deformation from 8.8 mm to 1.1 mm, which was consistent with measured deformations. It was found that wearing HHS may help to reduce arch deformation of the weight-bearing feet. There was a general increase in predicted maximum von Mises stress of foot bones with increasing heel height of foot supports from 0-inch to 3-inch. In the forefoot region, relatively high von Mises stresses concentrated at the second to the fourth metatarsals. With 2-inch high-heeled foot support, the strain and total tension force in the plantar fascia was minimum in all calculated cases. Moderate heel elevation may help to reduce the strain of in plantar fascia. This finding copes with existing conservative treatment strategy for plantar fasciitis. Comparing the FE predictions of static standing on flat support and HHS, no noticeable rotation movement in transverse plane of the first metatarsophalangeal (MTP) segment was found, which was consistent with cadaveric experiment. A pronounced increase in peak von Mises stress in the first MTP joint was predicted in HHS condition compared to flat support. Therefore, heel elevation was not found to be a direct biomechanical risk factor for hallux valgus deformity. However, combined effects with tight toe box may impose risk of hallux valgus deformity. Heel elevation could be a triggering factor and should be confirmed in further study. For the parametric study on outsole stiffness, comparison of von Mises stress in outsole with and without shankpiece suggested that embedded steel shankpiece is an important component of HHS, which sustains most of the loading of outsole and prevents outsole from collapsing and distorting. For the parametric study on coefficient of friction, the model predicted that reduction of coefficient of friction will result in reduction in peak shear stress, whereas the peak plantar pressures remain approximately the same. The ground reaction force (GRF) in anterior-posterior direction increased by 55.5% with the reduction of coefficient of friction from 0.6 to 0.2. Comparing mid-stance phase to standing from the FE predictions, arch deformation increased 98.3% from 5.9 mm to 11.7 mm. Tension and peak strain of plantar fascia increased 243.6% and 250.5%, respectively. While comparing walking with 2-inch HHS to balanced standing on flat support, tension force of plantar fascia increased by 31.1%. Results from gait analysis showed that increasing heel height from 0-inch to 4-inch increased the peak pressure and pressure-time integral in the forefoot region by 33% and 54%, respectively, whereas corresponding values in the heel region decreased. Moreover, for the GRF, the maximal propulsive force and maximal braking force with HHS was larger than those of the flat condition. The results imply that wearing HHS may be a possible risk factor of metatarsalgia. It should be noted that current FE predictions were carried out with HHS without the shoe upper structures such as toe box and heel counter. In addition, high loading-bearing stance phases such heel strike and push off were not simulated in this study. Therefore, further investigations and simulations should be conducted before a solid conclusion about the biomechanical effects of wearing HHS can be made. The biomechanical effects of different parameters, such as heel height, material properties and friction of HHS obtained from this study will be useful for better understanding HHS related foot problems and designing proper HHS. Meanwhile, much work still needs to be done to change footwear selection habits and public health cognition.|
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