Development of balance-enhancing geriatric indoor footwear

Abstract

Falling and instability in balance are prevalent public health issues among the elderly. Many fall incidents actually occur at home, when the elderly are engaged in their normal daily activities, such as walking or changing positions during locomotion. With increasing age, degenerative foot changes, foot deformities, as well as pain and deterioration of the neuromuscular system are commonly observed in the elderly. Deterioration of cutaneous touch and pressure sensation is also a pervasive observation in the elderly. These phenomena result in increased plantar pressure during walking, increased postural sway, poor balance control and ultimately high risks of falling. Poor fit and lack of fixation in current indoor footwear as well as poor foot thermal comfort inside the footwear also lead to various foot deformities, diseases and ulcers, and have adverse impacts on the balance control of the elderly. However, limited research has focused on determining the foot morphologies of older people and understanding the preferences and requirements as well as the fit and design features of indoor footwear for the elderly to achieve better fit and thermal comfort to prevent falling. Moreover, textured insoles with protrusions on the entire insole that are a low-cost means and passive in principle are proposed to improve balance control. However, their effects on enhancing body balance and plantar pressure distribution are uncertain. This ultimate goal of this research is to develop geriatric indoor footwear with specific types of protrusions on the textured insoles for site-specific stimulation and suitable footwear materials that are optimal in fit and design to enhance the body balance of older people and provide improved thermal comfort. To understand the needs of indoor footwear as well as the foot morphologies and foot problems of the elderly, face-to-face questionnaires, foot condition and mobility assessments and precise 3D foot scanning were first carried out at an elderly residential care centre with a total of 49 participants aged between 65 and 95 years (mean: 82 years). The results indicate that the older people prefer open-toed indoor footwear with no fasteners. The most common foot problems for the elderly are hallux valgus, bunionettes and flat foot. Lower foot sensitivity was found in the forefoot and rearfoot than in the midfoot. The characteristics of the deformed feet of the elderly were different from those of healthy feet, especially in terms of higher instep height for men and larger degree of hallux valgus deformity and increased ball width for women. Common predictors were also identified to differentiate deformed feet from healthy feet and can be used as indicators in footwear sizing systems for the elderly. These information and precise dimensions can then be used in designing well-fitting indoor footwear. To develop textured insoles which can improve balance control and plantar pressure distribution of the elderly, a specific type of protrusions (frusto-conical shape) was fabricated and their properties were evaluated through a series of physical and mechanical tests. The fabricated protrusions showed good performance in absorbing energy and reducing impact forces and could balance comfort, durability and hardness for sensation stimulation. Textured insoles with specific site stimulation were proposed by using eight tailored protrusions for each foot on the toe crest and at the boundaries of the metatarsal heads (five protrusions) as well as at the boundaries of the heel on lateral side (three protrusions). The performance of the designed textured insoles on the balance control, plantar pressure distribution and subjective perception of sensory comfort of the elderly was examined through a wear trial of 24 elderly women ageing between 60 and 73 years old (mean: 65 years) by using the in-shoe Pedar® system. In this examination, the participants were asked to perform both standing and walking tasks. Results showed that the wearing indoor footwear with designed textured insoles can significantly improve balance performance, particularly in the medial-lateral (ML) direction during walking. The center of pressure trajectory (COP) remained supported with less variance among steps, especially in the ML direction, when the designed textured indoor footwear was worn than when walking barefoot. The peak pressure in the forefoot and rearfoot regions was significantly reduced because the plantar pressure may be redistributed to the midfoot region. The overall subjective comfort of the textured indoor footwear is high with a mean score of 7.29. To further enhance the foot comfort sensation for balance control and prevention of foot diseases, the microclimate inside the footwear of the elderly due to the fit, design features and especially the materials of the footwear was studied by examining the changes and distribution of the foot skin temperature of 40 older people in barefoot and wearing four types of footwear in the sitting and walking tasks by using the FLIR Infrared camera. Results showed that the elderly had higher temperature elevations and distribution when wearing footwear made of synthetic leather and multi-layered fabrics with foams while lower temperature elevations and distribution when wearing mesh sports shoes with high perceived comfort. The gender difference in temperature change was only found at the instep of the dorsal foot and at the toes of the plantar foot. By integrating the key parameters that affect the thermal environment inside the footwear, including the gender, activity levels, types of footwear and their material properties, two numerical thermal equations was formulated with moderate R square to predict the in-shoe temperature of the dorsal and plantar foot of the elderly wearing various types of footwear. Apart from levels of activity, the water vapour transmission (permeability) property of the footwear was suggested by the equations to have certain important impacts on the foot skin temperature, thereby affecting the in-shoe comfort. Validation was also conducted to confirm the reliability of the thermal equations. On the basis of the established findings, optimisation was conducted on the first prototype of the balance-enhancing geriatric indoor footwear by changing the rigid heel counter to flexible one and the vamp material of terry fabrics to mesh fabrics as well as modifying the outsole and adding the cushioning material of Poron® to the midsole to further improve the thermal comfort, fit, plantar pressure distribution and balance performance of the indoor footwear for the elderly. A wear trial of 10 elderly women was carried out to confirm the effectiveness of these modifications by using the in-shoe Pedar® system. Results confirmed that the optimised geriatric indoor footwear significantly improved the plantar pressure distribution and balance control in both ML and AP directions during static standing and dynamic walking with satisfactory subjective perception in thermal comfort of a mean score of 8.48 (SD 0.57) and in overall comfort of a mean score of 7.67 (SD 0.82). This study enhanced our knowledge on the foot anthropometric measurements, morphologies and deformities of the elderly as well as their needs and preferences of footwear. These foot dimensions improve the fit and comfort of the footwear for the elderly. The thermal equations help to predict the in-shoe temperature of the elderly wearing different footwear and provide the basis to facilitate the design and development of geriatric footwear with improved in-shoe comfort. The development of geriatric indoor footwear with designed textured insoles and balance-enhancing features with suitable materials in this project improves the thermal comfort and balance control of the elderly in a cost-effective manner, thus preventing or reducing incidents of falls at home.