Effects of backpack on balance for subjects with adolescent idiopathic scoliosis with and without bracing

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Effects of backpack on balance for subjects with adolescent idiopathic scoliosis with and without bracing


Author: Leung, Sin-shan Dawn
Title: Effects of backpack on balance for subjects with adolescent idiopathic scoliosis with and without bracing
Degree: M.Sc.
Year: 2005
Subject: Hong Kong Polytechnic University -- Dissertations
Backpacking -- Physiological aspects
Backpacking injuries
Spine -- Wounds and injuries -- Prevention
Musculoskeletal system -- Wounds and injuries -- Prevention
Department: Jockey Club Rehabilitation Engineering Centre
Pages: 119 leaves : ill. ; 30 cm.
InnoPac Record: http://library.polyu.edu.hk/record=b1968125
URI: http://theses.lib.polyu.edu.hk/handle/200/5591
Abstract: Adolescent idiopathic scoliosis (AIS) is the most common type of scoliosis and typically affects adolescents between the ages of 10 and 16. Although the etiology of scoliosis is still unclear, it was found that abnormal external loading is one of the possible factors that may affect growth of the spine and exacerbate the deformity. In Hong Kong, most students between the ages of 10 and 16 are required to carry heavy schoolbags which may affect their gait and balance. It is known that bracing can effectively prevent the progression of scoliosis, but only a few studies have investigated the balance of AIS patients with brace. The aims of this study are to investigate the influences of bracing and different weights of backpack on balance performance in AIS patients. It was hoped to investigate the difference of the recommended backpack weight for the AIS patients and normal children. Twenty children (age between 10 to 16 years old) with AIS of moderate curvature requiring brace treatment were recruited for this study. Ten of them were asked to stand on a solid base support while the other ten were asked to stand on a foam base support. The balance performance of each subject was measured using a force platform (Kistler, Switerland) when carrying no backpack or a backpack loaded at different weights (7.5%, 10%, 125%, and 15% of the subject's body weight), both with and without using a brace. The order of testing conditions was randomized and the center of pressure motion was recorded and characterized by the following parameters, namely antero-posterior (AP) sway, medio-lateral (ML) sway, path length per second, average radial displacement, area per second, mean frequency, short-term diffusion coefficient and scaling exponent. The results were documented and compared using 2-way repeated measures Analysis of Variance (ANOVA) to evaluate the effects of the weight and the brace on the subject's balance.
The results showed that there was no significant interaction between loading and brace effects. A backpack load of 15% BW induced a significant increase in antero-posterior and medio-lateral sway. Path length was significantly increased when the subjects carried 12.5% and 15% BW and area per second was significantly increased when backpacks of 10%, 12.5% and 15% BW of were carried. It was observed that when the carrying load was increased, the subjects tried to balance this external load by shifting their trunks forward. The short-term diffusion coefficient was significantly increased when the subjects were carrying backpacks of 7.5%, 10%, 12.5% and 15% BW compared with the no load condition. The increase in short-term diffusion coefficient was also found to be significant between backpack loads of 15% BW and 7.5% BW. As the short-term diffusion coefficient is an indicator of the stochastic activity of the control system, this finding suggests that the stochastic activity increases with increasing load. Carrying a backpack of 15% BW appeared to induce a substantial challenge to the subjects in maintaining their standing balance. A backpack of 7.5% BW was preferred as it does not induce significant changes in sway displacement and velocity compared with the no load condition. Bracing induced larger sway as shown by the significant increase in ML sway, path length and average radial displacement when subjects stood on a foam base. It suggested that immobilization of the flexible spine using a brace can result in poorer balance performance when both the visual and somatosensory inputs are challenged. As brace and load carrying were both found to have adverse effects on the balance, this means that subjects with AIS will be in a distinctly disadvantaged condition. A longitudinal study is necessary to investigate the long-term effect of these two factors on the progression and severity of AIS.

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