Templates for pressure relief under the ischial tuberosities in special seating

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Templates for pressure relief under the ischial tuberosities in special seating


Author: Chung, Ka-wai David
Title: Templates for pressure relief under the ischial tuberosities in special seating
Year: 2000
Subject: Bedsores -- Prevention
Cushioning materials
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Jockey Club Rehabilitation Engineering Centre
Pages: xii, 68 leaves : ill. (some col.) ; 30 cm
Language: English
OneSearch: https://www.lib.polyu.edu.hk/bib/b1541816
URI: http://theses.lib.polyu.edu.hk/handle/200/1282
Abstract: The development of pressure sores can lead to very serious medical consequences for nonambulatory people who have impaired sensation. Associated medical treatment can be extremely expensive. Pressure has been recognized as the primary causative factor in pressure sore formation. This study attempted to obtain better pressure distribution under the ischial tuberosities (IT) of a given user using a "cut-out" based on the anatomy and locations of the ischial tuberosities of the appropriate sex. The morphology of the pelvis and ischial tuberosities of male and female skeletons was captured using the MicroScribe 3D Scanner, a 3D digitizer. 3D shapes of two templates, one for each sex, were obtained from IT data using AutoCAD, a drafting program. To determine placement of the templates, IT locations of subjects were identified as the centres of the two highest pressure regions of pressure maps obtained when the subjects sat on a firm hard surface. Pressure maps were obtained using the Tekscan Pressure Analyser. To determine how deep a template should be cut, downward IT displacements of subjects were obtained by measuring how deep the ITs sank when each subject sat on a 50 mm foam slab with 50 mm diameter holes under the ITs. Since the area of a template was not the same as the 50 mm diameter holes, two foam slabs were cut with a male template at two different depths with IT locations of the author. The depth found to be better in terms of pressure distribution and comfort was used as the depth of cut for both male and female templates. To evaluate if the template cut-out was a good solution for a range of adults, twelve subjects were recruited to sit on three surfaces, viz. a 50 mm flat foam cushion, a 50 mm flat foam cushion with 50 mm diameter holes and a foam cushion with the template based cut-out (tbco) of the appropriate sex. All cushions were made of 50 mm polyurethane foam slabs from the same batch. The tbco cushions provided an average ischial pressure and peak ischial pressure reduction of 51% and 43% as compared with the flat foam cushion. Cushions with 50 mm diameter holes did provide better pressure relief relative to the flat foam but results were difficult to interpret because hammocking effect of the Tekscan pressure mat might contribute significantly to interfacial pressure readings. A questionnaire was also used to provide subjective evaluations of the three seating surfaces. Results indicated that the tbco cushion and the cushion with 50 mm diameter holes provided equal comfort from the subjects' standpoint. However, 33% of subjects reported that the edges of the 50mm holes were uncomfortable. In general, a template cut-out did provide comfort and pressure relief Since this benefit resulted from only one template for each sex for all six subjects (of each sex), this approach could be a general solution in special seating when extra pressure relief is required in pressure sore prompt areas, such as the ischium and sacrum. A possible application will be applying a template in custom contoured cushions to provide extra pressure relief under the ischial tuberosities. It must be noted that the template cannot be applied by itself in isolation because it only tackles one of the pressure prompt regions and does not optimize pressure distribution under the whole buttock.

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