Development of an adaptive corset for children with spinal deformities

Abstract

Orthotic bracewear, commonly used to treat patients with spinal deformities, mechanically controls and modifies abnormal curvature and rotation of the spine. The bracewear is normally custom-engineered and made of rigid thermoplastic materials to exert adequate pressure onto the spine. However, associated problems, such as discomfort, activity limitations and bulkiness, induce a low rate of patient compliance, and thus the curve may progress to the point of significant physical deformity and even cardiopulmonary problems. The "ideal" pressure exerted by current bracewear is somewhat unreliable. The defining of the geometric shape of the torso and fitting of the bracewear, and even the prescription of the amount of corrective forces and type of pressure paddings for the 3D design and development of bracewear are highly complex and generally determined based on the experience of individual orthotists. As early management of spinal deformity is crucial, the novelty of this project is to fill the knowledge gap in determining the torso geometry and evaluating the corrective pressure, which not only will improve the fit to the torso, thus enhancing the performance of bracewear, but also provide the option of a less intrusive orthotic treatment for children with a small and simple curvature, as opposed to observation, bracing and surgery. Therefore, a thorough scientific basis was established in this study, for understanding the physiological mechanisms, responses and behaviours of children with spinal deformities in relation to various clinical situations, and the current design and development processes of making orthotic bracewear to control curve progression. The result of participant questionnaire indicate that the patients have a negative perception towards the brace. The compliance of the 6 subjects is generally low. The average time spent in the brace ranges from 9.3 to 10.8 hours a day. Amongst the 6 subjects, only 3 are considered to have moderate treatment compliance. The use of the brace caused a substantial increase in the humidity underneath the brace (increase from an average of 43% under clothing versus 67.9% underneath the brace amongst the 3 patients), thus adversely affecting the thermal comfort of the wearers and most likely, the compliance of the orthotic treatment. Moreover, the magnitude of the skin-brace interfacial pressure was found to be considerably reduced in the second visit (after 3 months). The anthropometric measurements, morphologies and asymmetry of the body of 6 recruited patients with spinal deformities were analyzed, which were in relation to pressure requirements in order to create adequate corrective forces in a corset design for spine support and the halting of the progression of the curvature. When the torso models with no brace worn were compared, major body deviations (up to a maximum of 2.4 cm) were found in the thorax, lumbar spine, pelvis and the front of the abdomen. The symmetry of the cross-sectional profiles between the left and the right sides of the torso was reduced in the second and third visits when the rigid brace is not worn. The intervention of the brace and duration of treatment have resulted in significant profile changes to most of the body cross-sections. An additional 6 teenage subjects (the minor spine curvatures were somewhat normal in most teenagers) were further recruited and their body symmetry was further analyzed. Compared to traditional studies on the mechanical assessments of fiber composite materials, the physical, thermal and mechanical properties of composite materials were systematically investigated in this study in considering the great potential of the reduction in weight, increase in strength and decrease in bulkiness. Based on the evaluation of the mechanical properties and physical properties, three composites, that is, CF2-1 (1 layer composite of carbon fiber 2) CF2-2 (2 layers composite of carbon fiber 2) and C2G1 (hybrid composite of carbon fiber 2 and fiberglass 1), were selected for the spinal brace prototyping in which the brace-model interface pressures were measured and compared with a traditional custom-fit spinal brace made of PE(Polyethylene) The brace prototype made of C2G1 delivered the highest levels of pressure to the trunk model. The number of composite layers in the brace had considerable effects on the magnitude of the brace-trunk interfacial pressures. The potential use of fiber composites was evaluated and proved as the major means of support in retaining the corrective properties of orthoses for reducing cumbersomeness and improving ventilation so as to facilitate their practical use in normal activities of daily life and increase patient compliance. A biomechanical pressure prediction model for scoliosis which may provide an improved idea of the interaction between the torso of the patient and the brace was formulated by using the finite element method (FEM). The model allows the interface pressure and internal stress and strain on the torso to be simulated without the prerequisite of replicating subject trials and experimental tests which can also be used to design. On the basis of clinical and textile science analyses in this study, an optimally fitting adaptive corset for spine support was designed and developed. Fabrics are the main parts of the corset which increase the wearing comfort while composite materials are adopted as the supportive components to exert the adequate pressure to avoid the progression of the spinal deformation.