RF30#095
Rapid Fire
Lumbar-dominant Adult Spinal Deformity Is Associated with Sagittal
Keiji Nagata1, Hashizume H1, Murata S1, Asai Y1, Teraguchi M1, Iidaka T2, Yoshimura N2, Yamada H1
1Dept.of orthopedics, Wakayama Medical University, Wakayama, Japan 2Dept. of Preventive Medicine for Locomotive Organ Disorders, 22nd Century Medical and Research Center, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
Background: Adult spinal deformity (ASD), often referred to as age-related kyphotic deformity, is common in aging Asian populations. Although ASD involves both thoracic kyphosis and lumbar lordosis loss, it remains unclear whether clinical characteristics differ according to the primary location of deformity. This population-based study aimed to clarify phenotype-specific radiographic and clinical differences in kyphotic ASD.
Methods: This study analyzed data from the Wakayama Spine Study, a population-based cohort of community-dwelling adults in Japan. Among 1,575 participants, individuals with kyphotic deformity were classified into thoracic-dominant (TD) and lumbar-dominant (LD) phenotypes. TD was defined as thoracic kyphosis ≥50°, and LD as pelvic incidence–lumbar lordosis (PI–LL) mismatch ≥20°. Mixed-type deformities were excluded. A total of 52 TD and 159 LD participants were included. Radiographic parameters—including C7 sagittal vertical axis (C7-SVA), pelvic tilt (PT), sacral slope (SS), cervical (C2–7) angle, and thoracic (T2–12) angle—were evaluated. Body mass index (BMI) and the presence of low back pain were assessed. Group comparisons and multivariate analyses were performed.
Results: The LD group demonstrated significantly greater sagittal imbalance, with a larger C7-SVA compared with the TD group (68.4 mm vs. 37.8 mm, p<0.001), as well as higher PT (32.4° vs. 22.3°, p<0.001). The T2–12 angle was significantly larger in the TD group (65.9° vs. 28.4°, p<0.001), indicating thoracic-predominant deformity without marked global imbalance. BMI was significantly higher in the LD group (p=0.021). The prevalence of low back pain was significantly greater in the LD group than in the TD group (56.0% vs. 36.5%, p=0.015), and lumbar-dominant deformity remained independently associated with low back pain in multivariate analysis (p=0.033).
Conclusions Thoracic-dominant and lumbar-dominant kyphotic ASD represent distinct phenotypes with different sagittal alignment patterns and compensatory mechanisms. Lumbar-dominant deformity is associated with greater sagittal imbalance and a higher risk of low back pain in a community-dwelling Asian population. Early identification of this high-risk phenotype may facilitate timely conservative intervention and prevention of functional decline.