Design and development of anisotropic textile brace for adolescent idiopathic scoliosis (AIS)

Abstract

Adolescent idiopathic scoliosis (AIS) is a complex three-dimensional (3D) deformation of the spine, affect 2%-4% of children during their puberty. To date, there is still no clear etiology of this condition. Three possible risk factors for the progression of spinal curvature is pointed out by researchers that are immature skeleton, female gender and large curve magnitude. AIS not only leads to posture and appearance problems for patients including uneven shoulders, scapular asymmetry, abnormal shape of the spine, and pelvis obliquity, but also causes other psychological and health issues for severely affected patients, such as back pain, leg numbness, as well as cardiopulmonary diseases. More importantly, spinal progression is found in scoliotic cases, especially the one before skeletal maturity. Proper treatment is therefore the key for all patients with AIS. For patients with Cobb's angle above 20°, bracing treatment, rigid bracing in particular, is recommended by doctors, which is a common non-invasive treatment for AIS. It aims to control the progression of spinal curvature or even correct the curve. Even if the corrective performance of rigid braces has been proven, its physical and psychological consequences like low self-esteem and low patient compliance due to discomfort, bulkiness of the brace, inconvenience and even the stigma of wearing a hard brace cannot be neglected as they may result in failure of bracing. To cope with these shortcomings, non-rigid braces are developed, for instance SpineCor, TriaC, and functional intimate apparel. However, there are other problems caused by such orthoses, including ambiguous bracing effect, insufficient corrective forces provided by the braces, skin irritation and so forth. Thus, the aim of this study is to design and develop a non-rigid brace for AIS patients to anticipate an alternative choice or even a more comfortable and better option for bracing treatment, and halt the progression of spinal deformity as well as enhance body image. This study consists of three main goals to (1) contribute to the knowledge gap in non-rigid brace designs and provide a comfortable yet effective option for bracing treatment for AIS patients, (2) conduct a series of physical tests to select the most appropriate materials for developing this new brace, and more importantly, (3) conduct a systematic clinical trial that periodically monitors the compliance rate and situation of human subjects during bracing treatment with the newly designed brace, including changes in their spinal curvature, body contours, sitting posture, and Health-Related Quality of Life (HRQOL) items. Apart from low compliance rate of treatment with existing braces and ambiguity in the non-rigid bracing effectiveness, few studies and little research effort on the use of non-rigid braces was also found in another literature review which was done by using citation network analysis (CNA) in this study to thoroughly understand the background and the potential study areas in the field of nonsurgical treatments. Moreover, the findings also highlighted the importance of patient compliance with the brace treatment and the tightness of the brace in a bracing treatment. In response to the research gaps found in the background study, an anisotropic textile brace for AIS was designed in this study. Due to the satisfactory in-brace correction of functional intimate apparel, the proposed brace design was inspired by it. This newly brace design adopted the same mechanism on spinal correction and similar design concepts as functional intimate apparel with the aim to maintain the bracing effectiveness of previous brace, meanwhile, minimize its design limitations like fit, comfort and durability. During this process of design and development, a design framework, a modified functional, expressive and aesthetic (FEA) model for designing a medical textile or scoliosis brace, was adopted. At last, the final anisotropic textile brace was designed as a one-piece garment with a hinged artificial backbone, corrective bands with pads, and pelvis belt. Besides, a series of physical tests were carried out to select the most appropriate materials for brace fabrication. More importantly, a preliminary 2-hour wear trial and 3-6 month clinical trial were conducted respectively to investigate the initial bracing outcomes and a short-term effect of proposed brace. Changes in Cobb's angle, body contours, interface pressure measurement, quality of life, and user comments were focused on in the preliminary trial. It was indicated that almost all recruited subjects achieved 5 or more degrees in their initial in-brace reduction of spinal curvature, in which the average correction was 29.6%. Although the rate of initial spinal improvement was still lower than the functional intimate apparel, it is comparable to some types of existing braces in the market. As for the initial changes in body contours, it was found a severer shoulder oblique problem in most of cases in this study whereas most cases shown a better improvement on shoulder rotation. Even if the value of posterior trunk symmetry index (POTSI) obviously reduced up to 60%, no correlation had been detected between all changes above and spinal correction. Furthermore, in considering the corrective forces in interface pressure value, there was no significant difference between the prior functional intimate apparel and the newly developed brace that implied the proposed brace could still contribute a similar performance on spinal correction. In terms of health-related test, no significant correlation was found between initial changes in Cobb's angle and any item of questionnaires. Surprisingly, significant better patient acceptance towards proposed brace was found compared with the functional intimate apparel. Only with 5 degrees or above initial in-brace correction, subjects were invited in the 3-6 month clinical trial to examine the short-term effectiveness of anisotropic textile brace in terms of the correction of spinal curvature, body contours, sitting posture, quality of life, compliance rate, and user feedback of wear experience. Follow-up session was carried out as periodical monitoring for each subject every month. It was found that the spinal deformity of all recruited subjects was under control, and even one of them got 32% spinal improvement after 3 months of bracing. Such improvement had no positive correlation with the changes of body contours. With regard to their changes in their sitting posture, prior study stated the assumption that more even pressure distribution between left and right buttock regions represents a better sitting posture. Even if there is no significant difference shown in the changes in their body alignment, their pressure distribution significantly shown much more even in the buttock regions after 2nd month of intervention that was considered as improved sitting posture after bracing. Besides, no obvious changes were found in health-relative tests after 3rd month of intervention but a significant improvement in an aspect of physical functioning in the Brace Questionnaire that showed the proposed bracing treatment did not affect their quality of life. In addition, most subjects had a good brace compliance and their bracing effectiveness of spinal correction relied on the brace compliance, for instance the rate of the best compliant subject was up to 98.3% who also achieved the most pleasing reduction in Cobb's angle after 3-month bracing. Overall, no negative effect was found that affected quality of life of subjects during bracing and they were all satisfied with the proposed brace treatment, even if there was still room for improvement on the durability and fitting problems of hinge bone.