• Weipeng Qiu, Zhuoran Sun, Siyu Zhou, Zimu Chen, Gengyu Han, Da Zou, Yi Zhao, Ze Chen, Qiang Qi, and Weishi Li.
• Department of Orthopaedics, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191, China.
• Spine. 2024 Oct 15.

Study DesignA cross-sectional cohort study.ObjectiveTo present a normative value reference of spinal segmental inclination stratified by age and pelvic incidence (PI), and to clarify the impact of segmental inclination on spinal sagittal morphology.Summary Of Background DataThoracolumbar segmental inclination has been shown to correlate with the clinical outcomes of adult spinal deformity surgery. However, there currently exists no normative value reference in a large sample of asymptomatic population.MethodsAsymptomatic adult volunteers were enrolled from the community. All volunteers underwent a standing full-spine anteroposterior and lateral radiograph. Lumbar tilt (LT) and thoracic tilt (TT) were measured to quantify the segmental inclination of the lumbar and thoracic spine. Regional curvature, global balance and thoracolumbar apex were analyzed across different age and PI groups. The correlation between sagittal parameters and age was analyzed using Pearson correlation tests.ResultsA total of 618 volunteers were included with a mean age of 38.7 ± 17.1 years (range 18 to 82 y). As age increased, the LT and TT significantly increased (P<0.001). The LT was significantly correlated with PI (r=0.410, P<0.001), with the low PI group exhibiting a greater negative LT. The TT remained constant across different PI groups. Compared to the young and middle-age groups, the thoracic apex and lumbar apex were located more caudally in the elderly group (P<0.001). Subjects with a more caudal lumbar apex exhibited a greater negative LT, and those with a more caudal thoracic apex exhibited a greater positive TT.ConclusionThe thoracic spine naturally adapts to a relatively neutral position, yet it tends to tilt forward with aging. The physiological lumbar inclination is predominantly determined by the PI value with a slight backward tilt, and tends to counteract the anterior truncal inclination with advanced age. Physiological segmental inclination should be considered in spinal surgical planning.Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.

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