Posture Differences Between the Right and Left Sides in High School Boys with Sway-Back: A Comprehensive Approach

Background and Aims: The sway-back posture is very common among different societies. It is characterized by a faulty alignment in which the pelvis moves forward and the upper body shifts backward in the sagittal plane. In these individuals, in the standing position and from the side view, the line of gravity passes behind the hip joint. This body position can be associated with an increase in thoracic kyphosis, forward head and shoulders, a decrease in lumbar lordosis, posterior or anterior pelvic tilt and hyperextension of the hip and knee joints. In this passive position many anti-gravity muscles do not support the body, and the person is completely surrendered to the force of gravity, with most of the passive structures, like ligaments and joint capsules, providing stability. Studies and clinical observations have reported numerous neuromuscular, morphological, and biomechanical complications associated with this posture, which has many consequences, especially for teenage boys. In previous studies, photogrammetry has been utilized as a reliable method for assessing posture in normal standing, particularly for measuring angles in the sagittal plane. Therefore, in most of the previous studies, researchers have employed this method to quantitatively assess the sway-back posture in the sagittal plane. However, with a traditional approach and a reductionist perspective, it has been assumed that there is no difference between the postures on the right side compared to the left in the sagittal plane for individuals with sway-back. In a comprehensive approach, researchers believe that it is necessary to measure the posture of these individuals in the sagittal plane on both sides of the body to lead to problem-solving with a higher degree of confidence. Thus, the primary aim of this study was to investigate the difference in posture between the right and left sides in the sagittal plane in high school boys with sway-back and anterior pelvic tilt.

Materials and Methods: The study involved 45 high school boys with sway-back posture and anterior pelvic tilt who were randomly selected. The mean age of the participants is 16.33 years. The mean BMI is 21.33 kg/m². The mean sway-back angle is 15.49 degrees on the right side and 15.29 degrees on the left side. Additionally, the mean pelvic tilt is 16.96 degrees on the right side and 15.27 degrees on the left side. 15 reflective markers were used for each person. The markers were placed on the tragus, acromion process, superior anterior iliac spine, superior posterior iliac spine, greater trochanter of the femur, lateral epicondyle of the femur, lateral malleolus (all on both sides of the body), and the seventh cervical vertebra. The sway angle as the main characteristic of this posture and forward head, forward shoulder, Trunk lean, Pelvic displacement, and pelvic tilt and hip angles as its connected details were calculated using photogrammetry method on both sides of the body. thoracic hyper-kyphosis was measured using by flexible ruler. Having a sway angle greater than or equal to 10 degrees, and an anterior pelvic tilt greater than or equal to10 degrees on the right side, thoracic kyphosis angle greater than46 degrees, along with a body mass index ranging from 18 to 25, were the inclusion criteria for entering the study. A history of bone and joint problems and diseases, such as rheumatoid arthritis and fractures, as well as previous surgeries in the spine, pelvis, shoulder girdle, and lower limbs, and a history of diseases that require special considerations, such as cardiovascular diseases, spinal canal stenosis, spondylolisthesis, epilepsy, severe anemia, and metabolic and endocrine diseases, based on questions asked of the parents of the participants (self-reported), and tibia vara, antiversion or retroversion of the femoral head and neck, pes cavus, genu varum, and scoliosis greater than10 degrees in different parts of the spine, were exclusion criteria for this study. Descriptive statistics and inferential statistics were utilized to examine and analyze the research data, with the analysis conducted using SPSS version 27 software. To compare the posture on the right side to the left in the sagittal plane, the means of the variables were compared. In this context, to assess the differences in means, considering there were multiple dependent variables, a one-Way Multivariate Repeated Measures Analysis of Variance (MANOVA) test was employed. Additionally, the degree of correlation between the corresponding dependent variables on the right and left sides was examined.

Results: The results of the One-way repeated measures MANOVA test showed that there is a significant difference between the posture on the right side compared to the left in high school boys with sway-back with a large effect size (p=0.001 and ɳp²=0.593). Additionally, the results of the one-way repeated measures ANOVA test indicated that this difference is significant for the forward head, forward shoulder, pelvic displacement, and pelvic tilt angles. The difference between the means on the two sides for forward head, pelvic displacement, and pelvic tilt angles exhibited a large effect size, while for forward shoulder, the effect size was close to large. Furthermore, there was no strong correlation between the data obtained from posture measurements on the right side compared to the left side. The Pearson correlation results revealed a weak correlation between the two sides of the body for sway and trunk lean angles despite no significant difference in their means. This indicates a slight similarity between these variables on both sides of the body.

Conclusion: In conclusion the results of the current research indicate that, contrary to the assumptions of past studies based on a traditional reductionist approach, it is necessary to measure the posture of individuals with sway-back on both sides of the body using a comprehensive approach grounded in a systemic perspective.

The data obtained from one side of the body, whether from the variables that did not show a significant difference in their means between the two sides of the body, or from the variables that had a significant difference in their means between the two sides of the body, cannot be representative of the opposite side of the body.