Biomechanic and biosignal based modeling of sagittal spine disorders and rehabilitation focused evaluation

Sagittal plane deformities can be defined as deviations from the normal curvature of the spine in the sagittal plane. These deformities can disrupt the natural shape of the spine and cause postural problems. In recent years, effects such as reduced activity in daily life, increased time spent in front of computers and mobile phones, and inactivity during the recent pandemic period have led to a significant increase in sagittal plane deformities. The main objective of this study is to evaluate the biomechanical and biosignal based modelling and rehabilitation oriented evaluation of subjects with sagittal plane deformities and healthy subjects. In this context, detailed analyses should reveal the differences in muscle activation between subjects with sagittal plane deformities and healthy subjects, detailed analyses of tomography images should be performed and biomechanical models should be successfully created. Subjects with thoracic kyphosis and lumbar lordosis, which are common in subjects with sagittal plane deformity (SPD), were included in the study. To provide surface EMG (sEMG) data, 16 healthy adolescents with similar demographic and physical characteristics and 16 adolescents with sagittal plane deformity were included in the study. To assess the activation of different muscle groups, 15 movements were defined. SEMG recordings were made during these movements. Raw sEMG data were analysed after filtering. Energy values corresponding to low and high frequency components were calculated. These analyses provided muscle activation distributions of subjects in each movement. These energy values were also statistically analysed using the Mann-Whitney U test to determine muscle differences between SPD subjects and healthy subjects. This statistical analysis identified channels with significant differences between SPD subjects and healthy subjects. The physical characteristics and biomedical images of the subjects were used to create the biomechanical models. A healthy biomedical model was created to represent healthy subjects, a kyphosis biomedical model was created to represent kyphosis subjects, and a lordosis biomedical model was created to represent lordosis subjects. Analyses of the subjects' MRI and tomography images were used to form the main structure of the model. The muscle definitions of the biomedical model were modelled by considering the muscle groups recorded in the study. To determine the accuracy of the model, each movement was performed by developing an algorithm and analysing the distribution of muscle forces. When the muscle activation of the channels was compared, higher activation was found in SPD subjects, while in some movements activation was found in different channels in SPD subjects and healthy subjects. As a result of the analyses, significant differences in muscle activation were found in individuals with sagittal plane deformities. Statistical analysis using the Mann-Whitney U test identified the channels in which there were significant differences between subjects with sagittal plane deformities and healthy subjects. Subjects with SPD showed more muscle activity than healthy subjects and expended more energy to improve the quality of movements and to perform them with correct muscle dynamics. It was observed that subjects with SPD developed compensations from different muscle regions in order to perform movements correctly due to postural changes. In healthy subjects it was observed that the movements were performed in accordance with the kinematics of the movement and that the maximum movement quality was achieved with less energy. The results obtained show that the biomechanical models were correctly constructed and in agreement with the data obtained with sEMG. The biomechanical models were successfully used to simulate the effects of sagittal plane deformities on muscle activation. In conclusion, this thesis provides a comprehensive review to understand the effects of sagittal plane deformities on muscle activations and biomechanical models. The findings provide an important contribution to the development of rehabilitation strategies for spinal health and postural problems.