Author: Lee, Ka Po
Title: Development of pressure monitoring undergarment for scoliotic brace treatment
Advisors: Yip, Joanne (SFT)
Yick, Kit-lun (SFT)
Degree: Ph.D.
Year: 2024
Subject: Scoliosis -- Patients -- Rehabilitation
Scoliosis -- Treatment
Electronic textiles
Hong Kong Polytechnic University -- Dissertations
Department: School of Fashion and Textiles
Pages: xxiv, 205 pages : color illustrations
Language: English
Abstract: Monitoring force and pressure are critical for effective compression therapy, such as bracing, which is the most prevalent type of treatment for adolescent idiopathic scoliosis (AIS) patients with a Cobb’s angle greater than 25°. The goal of this treatment is to passively correct spinal abnormalities by exerting pressure. However, because of ambiguous brace effectiveness, the applied pressure depends on the judgment of the orthotist. Not only can result in physical injury, excessive pressure also negatively impacts compliance and quality of life. A variety of sensors is available to measure the force and pressure exerted by braces, but they have some limitations, including inflexibility, small measuring ranges, time delays, and difficulty in application. To prevent these issues, a a pressure monitoring undergarment is developed by inserting 14 fibre bragg gratings (FBG) sensors into a knitted undergarment. The primary objective of this pressure monitoring undergarment is to deliver reliable sensor readings while placing a paramount emphasis on optimizing wearer comfort.
This study consists of four main components including (a) a review of the development of textile-based fibre optic sensors (TFOSs) for health monitoring, in regard of their features, applications, and integration methods, (b) an examination of the main factors affecting the wear comfort of undergarments, (c) the design and development of a flexible pressure monitoring undergarment, (d) the formulation of a simulation model to examine the how the spine response to brace pressure.
TFOSs is one of the most appropriate means of obtaining close-to-body measurements because they are very flexible and lightweight and have electromagnetic immunity while maintaining high strain sensitivity. Although they have gained increasing receptivity in health monitoring, there is a lack of comprehensive understanding of the knowledge structure and research trends in this field. This study stands out by providing an objective and systematic literature review on TFOSs for health monitoring, coupled with a citation network analysis (CNA). The study brings attention to the largest research cluster, "Flexible sensors for vital signs monitoring," with a specific emphasis on respiratory monitoring. This insight has the potential to shape future research directions and contribute to advancements in health monitoring technologies. Additionally, one of the most popular methods was to embed fibre Bragg grating (FBG) sensors into a flexible silicone with a curvilinear shape, which enhanced the fibre flexibility, robustness, and compatibility of the sensor with the skin's surface. Therefore, the pressure monitoring undergarment is also developed by using this method.
To create an undergarment with high comfort, it is necessary to investigate the main factors that affect wear comfort in terms of tactile and thermal sensations. A series of experiments including physical experiments, KES-FB measurements, and a wear trial were conducted on seven conventional undergarments. The results indicated that lighter, thinner, and low stitch density fabrics constructed with uniform filaments increased breathability and enhanced moisture wicking. Additionally, lighter and thinner materials with a higher percentage of elastane, finer yarn, and uniform and long fibres offered a softer, smoother, and cooler hand feel. Moreover, the pure cotton material appeared to more regulate body temperature as the resultant undergarment facilitated a higher rate of perspiration despite clinging. These results serve as a useful reference for developing the pressure-monitoring undergarment.
To investigate the relationship between normal force and strain sensed by using FBG sensors, the protocol of pressure-monitoring undergarment was developed by inserting four silicone-embedded FBG sensors into a knitted undergarment via the inlay method. The proposed design offers several advantages over existing methods, including ease of use and adaptability to adolescents with different body shapes, without requiring any additional procedures prior to treatment. Additionally, the instant data acquisition and overall pressure distribution allow the tightness to be adjusted and monitored during the fitting process. After conducting a bracing stimulation on artificial skin, the experimental results showed that the sensors embedded in the silicone membranes achieved enhanced sensitivity to force, as well as flexibility and softness. Additionally, by assessing the degree of FBG response to a range of standardised forces, the linearity (R2) between the shift in the Bragg wavelength and force was found to be above 0.95, with an ICC of 0.97, when tested on a soft surface. The implications of this study are particularly relevant in healthcare, specifically in the fitting processes for bracing treatment in AIS patients because it offers a more objective approach to determine the optimal bracing pressure.
The formulation of a biomechanical model that simulates the forces exerted by a brace can aid in the examination of how the spine responds to brace pressure. Therefore, a FE model based on Fok (2020)’s FE model was constructed, which consisted of a body torso, ribs, a spine, and a sternum that corresponded to the X-rays of the recruited subject. Unlike Fok (2020)’s FE model, the loading condition was increased from 2 to 14 to study how the overall pressure distribution affects the spinal corrective effect. Since it is impossible to recruit the same AIS subject to do the brace pressure measurement, a validated soft mannequin was employed to the pressure test by using the pressure monitoring undergarment with 14 FBG sensing points. To validate the model, the in-brace vertebrae position and Cobb’s angle on the FE model were compared to that on X-rays. Their correlation coefficient is found to be 0.90, which is highly correlated. In addition, both the X-ray image and the FE model show a reduction in the Cobb's angles in the thoracic (T5 to T11) and lumbar (T11 to L3) regions. These results are comparable to the clinical study that conducted by Fok (2020). Therefore, it is believed that the implementation of the biomechanical model in this study effectively overcomes the challenges associated with conducting human wear trials to assess the efficacy of bracing.
The research results in this study provided valuable insights into the research domains and trends in TFOSs for health monitoring purposes. This understanding is crucial for researchers and practitioners to navigate the existing knowledge and identify areas for further investigation. Additionally, the study suggests desired properties of summer undergarment. The identified relationships between fabric specifications offer insights for developing summer underwear that prioritizes breathability, moisture-wicking, and a cooler feel. Moreover, the study stands out for its originality and novelty in developing a pressure monitoring undergarment using silicone-embedded FBG sensors and warp-inlay method. It overcomes the limitations of existing sensors, such as lack of elasticity and inconvenience, absence of instant and overall pressure distribution. In addition, the simulation model could be used to examine how the spine responds to the exerted brace pressure and predict the degree of in-brace correction. The research output could be further extended to determine ideal bracing pressure levels, thus preventing AIS patients from having to endure excessive pressure, while maintaining an appropriate amount of bracing force in order to halt curve progression and reduce the risk of pressure-related injuries.
Rights: All rights reserved
Access: open access

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