Physical Properties of a New Orthopaedic Supporting Material for Posture Control in Chairs and Beds

Abstract

Abstract The prevalence of back discomfort has prompted the search for better orthopaedic supporting material in chairs and beds. A new warp-knit fabric has been developed to provide orthopaedic sleeping support without using traditional box-spring or spring-in-mattress devices. Described in an US patent [1] by one of the authors, J.K.L. Chang, the fabric is warp knitted with a lock-knit stitch with a laid-in yarn, using three guide bars with nylon and elastic yarns. As shown in Figure 1, if a pressure is exerted on any single loop which is only 0.5 mm2 in area, the pressure will be passed to the 11 neighbouring yarns, then further propagated via other adjacent yarns to a much larger area. This fabric has also been used in chairs. The fabric is stretched over the frame of a chair under different tensions along the length of the chair body so that it gives a contour fit to the person’s body, and put tension on the lumbar and raise the knee higher than the buttock to put the person in a good sitting posture. A clinic trial has been carried out involving three nursing homes, two institutions and eight individuals in USA. It has been observed that the fabric structure and this mechanism of “de-localising pressure” make people, sitting or sleeping on this supporting system, feel comfortable, with reduced pain and reduced chance of getting back sores. Experiments are being conducted in order to study relevant physical properties of the fabric related to the results of the clinical trial. Results from these tests will be presented including static and dynamic tensile properties, bending, shear, lateral compression and surface properties, air-permeability, thermal properties and flammability of the fabric. Comparison will be made between the supporting system made from the fabric and that from artificial leather/foam system. A prototype chair will be demonstrated during the conference.