Bone Abstracts

Introduction: Adolescent idiopathic scoliosis (AIS) is associated with osteopenia, which was found to be a significant prognostic factor for curve progression. However, in-depth quantitative assessment of bone quality was previously hampered by invasive nature of the investigations. The recently available high-resolution pQCT (HR-pQCT) allows a three-dimensional assessment of the bone quality in-vivo. This study aimed to evaluate and compare the bone quality in AIS girls and controls.

Methods: 234 untreated AIS and 211 non-AIS healthy girls between 11 and 13 years old were recruited. Bone quality, including bone morphometry, vBMD, and trabecular bone micro-architecture were measured at the non-dominant distal radius using HR-pQCT. To consolidate our understanding on the trabecular bone micro-architecture, Structural model index (SMI), which measures the degree of rod/plate-like configuration of trabeculae, was further determined in 73 AIS and 48 controls.

Results: Bone quality is altered in both cortical bone and trabecular bone in AIS. With multivariate linear regression analysis, after adjusted for age, arm span and sexual maturity, AIS was significantly associated with lower cortical area, cortical thickness, cortical bone vBMD, trabecular bone vBMD, BV/TV, trabecular number and greater trabecular separation, and SMI.

Conclusion: The abnormal profile in bone quality suggested the presence of disturbed endocortical modeling, trabecular bone formation and bone mineralization and could contribute to a better understanding of the role of abnormal bone quality in the etiopathogenesis of AIS. Furthermore, cortical area, an important parameter in bone strength index associated with cross-sectional moment of inertial (CSMI), could be an important potential clinical parameter for further longitudinal studies on the prognostication of curve progression in AIS.

This study was supported by Research Grants Council of the Hong Kong S.A.R., China (project nos: 468809 and 468411).