| Author: | Chow, Lung |
| Title: | Finite element model for design of pressure therapy gloves for hypertrophic scars |
| Degree: | M.Phil. |
| Year: | 2022 |
| Subject: | Hypertrophic scars -- Physical therapy Physical therapy -- Equipment and supplies Gloves -- Design Hong Kong Polytechnic University -- Dissertations |
| Department: | Institute of Textiles and Clothing |
| Pages: | xvii, 155 pages : color illustrations |
| Language: | English |
| Abstract: | Hypertrophic scars (HS) is one of the most cutaneous complications in wound and burn rehabilitation. In China, over 350,00 burn injuries require hospitalisation every year. Due to the dark red, raised and high vascularity appearance of HS, it can be differentiated from healthy skin obviously. The unique appearance may affect self-esteem and quality of life of the patients or even cause psychological complications. Apart from the aesthetic aspect, HS may also associate with pain, itchiness, pruritus and erythema. If rigid HS is close to a joint, it may result in joint contracture, affecting the range of motion of body. As a result, the normal daily life of the patients can be affected tremendously. Pressure therapy is a mainstay of therapy to prevent the growth and speed up the maturity of the HS from the 1970s. It becomes the standard first-line therapy for HS. The principle of pressure therapy is applying a tight circular garment to induce a certain amount of pressure to HS to reduce the oxygen and nutrient supply to the scar tissue. However, the garment itself has its inherent limitation that the pressure cannot be evenly exerted on the HS because of the organic shape of human body. More importantly, this problem may be exaggerated during the movement of body. Custom-made Polyethylene (PE) inserts are regularly used to strategically redistribute the pressure to the designated location in consideration of the shape geometry and maturity of the HS. Inappropriate garment pressure given to the healthy skin next to the HS and the associated discomfort, bruises and even ischemia can be minimised. Since the interactions between the insert and garment, as well as the geometry of the human body during movement are highly complex, a more in-depth understanding of the effects of body movement and material properties on pressure garments is therefore important to improve the efficiency of the HS treatment. This study starts with an investigation on impact of postural variation on hand measurement. In this part, various measurements of hand during 3 different postures (splayed, relaxed and gripped) are systematically evaluated. Results show that 40 out of 57 measurements of hand have statistically difference regarding to hand postures. The findings of this study provide valuable guidelines to enhance the anatomically engineered design for the pattern of pressure gloves which relates to the practical function of hand. Next, considering the problem of fluctuated pressure exertion during the hand movement, a series of 3D printed auxetic thermoplastic polyurethane (TPU) inserts were developed to substitute the conventional PE inserts. In this section, the phenomenal shape formability of auxetic structures is utilised as the foundation of design. Two widely discussed auxetic structures including re-entrant (RE) and double-arrowhead (DAH) were investigated regarding their shape formability, structural deformation and auextic response experimentally and numerically by finite element analysis (FEA). The result reveals DAH structure has superior shape formability verses that the RE and PE foam insert. A wear trial was conducted to further evaluate the effect of a more formable insert on the pressure delivery. Based on the result of wear trial, the application of DAH insert is able to maintain a stable pressure level at the centre part of the insert, even during the wrist flexion and extension. In consideration of HS in small dimensions and/or specific body regions, a new fabrication approach that combines a silicone insert and pressure garment has been developed. A medical grade silicone is directly three-dimensional (3D) printed on the knitted fabric. The geometry of silicone insert is based on the 3D scanned HS data, so that the customized insert can be securely placed onto the HS, fitting the needs and pressure dosage required of individual patients. The silicone insert attached pressure garment also facilitates the use of scars treating gel into the HS therapy that combines pressure, silicone sheet and scars treating gel. To increase the feasibility of the suggested therapy, a novel 3D multi-viscosity printing approach was developed for developing the silicone-fabric composite. By adopting the new approach that using a lower viscosity of print solution for the first layer of printing, the shearing strength between the silicone and fabric increased around 600% when comparing with the conventional 3D printing method. Apart from HS therapy, the proposed method can also be adopted at various types of 3D printed fabric reinforced composite development for customized clinical and healthcare products. To further evaluate the feasibility of the proposed pressure garment with silicone insert attachment, a wear trial has been conducted. A patient with HS on the right wrist was invited for the wear trial. Finite element models (FEMs) have been developed to investigate the parameter of garment size and thickness of insert to the pressure delivery for the patient. Satisfactory results were observed between the simulated and experimental data. Throughout the FEA, the parameters with optimal performance that provides suitable amount of pressure to the HS with minimal pressure exertion to the healthy skin was determined. The pressure garment was produced based on the best parameters with consideration of the needs of individual patient. After one year of wear, it can be observed that the HS has shown a significant reduction in thickness and pigmentation without creating any negative effect. The consolidated design framework of the proposed HS therapy demonstrates the application of various novel technologies into HS therapy and provides a new insight to advance the design of customised products. This whole study integrates the state-of-the-art technologies including 3D scanning, 3D printing and FEA to facilitate an effective therapy for HS. The suggested techniques for 3D printing of soft materials, applying auxetic structures for fitting human body not only contribute to the field of rehabilitation, but also make meritorious fundamental contributions for the development of human body monitoring wearables, flexible sensors, customised medical products. |
| Rights: | All rights reserved |
| Access: | open access |
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