Characteristics of sagittal spinal alignment in Japanese elementary school students in standing position: focusing on thoracic hyperkyphosis

Abstract

Several reports have raised concerns about poor posture in children worldwide. As Japan began to experience rapid economic growth toward the end of the 20th century, poor posture (hyperkyphosis) in children became a particular problem. However, little research has been conducted on hyperkyphosis among Japanese elementary school students, and sample sizes have been inadequate. This study aimed to determine the prevalence and characteristics of hyperkyphosis among Japanese elementary school students to help understand and prevent hyperkyphosis. A total of 403 Japanese elementary school students (208 boys and 195 girls) were enrolled in this study. The SpinalMouse system was used to measure thoracic kyphosis and upper thoracic, lower thoracic, lumbar lordosis, and sacral anteversion angles in the standing position. Hyperkyphosis was defined as a thoracic kyphosis angle of >40°. The participants were assigned to two groups: hyperkyphosis and non-hyperkyphosis. The prevalence of hyperkyphosis among Japanese elementary school students was approximately 25.0%. The upper and lower thoracic kyphosis angles were compared separately. The hyperkyphosis group had a significantly higher degree of kyphosis (upper and lower) than the non-hyperkyphosis group. The lumbar lordosis angle was significantly greater in the hyperkyphosis group than in the non-hyperkyphosis group. Additionally, the upper thoracic spine angle was significantly greater than the lower thoracic spine angle in the hyperkyphosis group. A strong negative correlation was found between the lumbar lordosis angle and sacral anteversion angles in both groups. The results of this study indicated a hyperkyphosis prevalence of approximately 25% and suggested that the upper thoracic spine may be characterized by a greater degree of kyphosis in Japanese elementary school students.