Normal Functional Local Alignment and Segmental Motion at the Thoracolumbar Junction: A Cross-Sectional Study of Healthy Subjects

Several studies have investigated the mechanical behavior of the thoracolumbar spine. However, finding an accurate reference for the normal functional local alignment and segmental motion (SM) at the thoracolumbar junction (TLJ) is challenging. Therefore, this study aimed to assess age- and sex-related changes and differences in local alignment and SM at the TLJ. The study recruited healthy subjects aged 20 to 79 without complaints of back pain. Healthy subjects (60 males and 60 females) with appropriate imaging results were enrolled in the study. The subjects were divided into age groups (20–29, 30–39, 40–49, 50–59, 60–69, and 70–79 years); each group included 10 subjects of each sex. The SM at the TLJ was small but noticeable, and the motion gradually increased toward the lower level of the TLJ, closer to the lumbar region. No significant differences were observed between male and female subjects in any SM measurements at the TLJ. The SM at the TLJ gradually decreased with age, while local kyphosis of TLJ progressed. The results also showed that the thoracolumbar slope value did not change with age and remained at a mean of −12.8 ± 7.2° (P = 0.893). This study's results provide valuable guidance for appropriate surgical planning and rehabilitation of patients with spinal diseases or trauma. Furthermore, the results can be the basis for categorizing accurate criteria to evaluate the degree of disability after treatment.