Thoracolumbar Sagittal Shape Varies With Pelvic Morphology and Aging

Abstract

Study Design. Retrospective study of a multicenter prospective database. Objective. The objective of this study was to determine the organization and correlations between different spinal segments according to pelvic incidence (PI) and age. Summary of Background Data. When planning surgery for the correction of adult spinal deformities, considering lumbar lordosis (LL) as a uniform segment is an approximation that can lead to planning errors. Materials and Methods. Radiographs of 1540 subjects were analyzed and divided into three PI groups: low <45, intermediate 45 to 60, high >60, and stratified by age (<45, 45–70, and >70 yr). The different segments of L1–L4 proximal lumbar lordosis (PLL), L4–S1 distal lumbar lordosis (DLL), and T10–L1 thoracolumbar junction (TLJ) were analyzed. Results. The mean age was 53.5 years (SD=17, minimum=20, maximum=93). There was a significant correlation between thoracic kyphosis T5–T12 and TLJ segment T10–L1 (r=0.581, P<0.001). Only the L1–L4 PLL segment correlated with PI (r=0.47, P<0.001). The T10–L1 TLJ segment was constant regardless of age or PI groups considered (mean=−8, SD=9). PLL did not vary with aging but differed according to PI. The DLL showed significant differences between age and PI groups but without a significant correlation between PI and DLL. Conclusions. Pelvic morphology is known to determine the curvatures of the spine, however, the distribution of LL is not homogeneous. Our study provided a normative value reference and showed that T10–L1 is constant regardless of age or PI. Level of Evidence. III.