Asymmetric distribution of vertebral bone microstructure in coronal adult spinal deformity: a cross-sectional study based on quantitative CT.

Abstract

This study aimed to investigate the asymmetric distribution of vertebral bone microstructure in adult spinal deformity (ASD) patients with coronal plane deformities using phantom-less quantitative CT (PL-QCT). Specifically, we sought to quantify vertebral 'bone void' (BMD < 40 mg/cm³) to analyze spatial heterogeneity of bone mass and structure, and examine its correlation with deformity characteristics, gender, age, and BMD. A retrospective cross-sectional study included 167 ASD patients (49 males, 118 females) with ASD. Vertebral BMD and bone void volume were measured using PL-QCT. The apex vertebra and its adjacent levels (Apex-1, Apex, Apex + 1) were analyzed. Each vertebra was divided into 8 regional sections (convex vs. concave sides) to assess bone void distribution. The key findings revealed significant spatial heterogeneity and asymmetry in bone void distribution. Bone voids were predominantly concentrated in the posterior-inferior region of the concave side (CC). Normalized bone void volume was significantly higher on the CC side compared to the convex side (CV) at all vertebral levels. Notably, female patients had significantly higher normalized bone void volume than males. PL-QCT revealed significant asymmetric spatial heterogeneity in vertebral bone microstructure in ASD, characterized by preferential 'bone void' accumulation on the concave side, particularly in posterior-inferior regions. This asymmetry, influenced by vertebral level, female gender, and advancing age, likely reflects abnormal biomechanical loading and remodeling imbalances. Quantifying bone void distribution provides a crucial multidimensional assessment for understanding ASD progression and developing targeted interventions focused on reinforcing the biomechanically vulnerable concave side.