Bone Abstracts

Objectives: Multiple studies have documented the presence of systemic osteopenia in adolescent idiopathic scoliosis and in simulated animal models. Osteopenia was also found to be associated with severe curves and as one of the prognostic factor in predicting curve progression in AIS. The objective of this study was to compare the bone quality and its association with osteopenia between AIS and normal controls.

Methods: AIS (n=234) and non-AIS girls (n=211) between 11–13 years old were recruited. aBMD of bilateral femoral necks was measured by DXA. Subjects were classified into the osteopenic (Z-score≤−1) and non-osteopenic (Z-score >−1) subgroup. Trabecular Bone Micro-architecture and Structural Model Index (SMI), which measures the degree of rod/plate-like configuration of trabeculae, were measured using HR-pQCT.

Results: In AIS, osteopenic group showed a lower trabecular thickness, greater trabecular separation and SMI, reflecting more rod-like trabeculae when compared to the normal BMD AIS subjects. In contrast, among the controls, only lower BV/TV and trabecular thickness were found between the osteopenic and normal BMD subgroups. Two-way ANOVA showed a significant interaction between AIS and osteopenia on Trabecular Thickness.

Conclusions: We revealed a unique alteration of trabecular bone micro-architecture in osteopenic AIS. Besides, there is an interaction between osteopenia and AIS on trabecular thickness, which indicates an important role of trabecular bone micro-architecture in the etiopathogensis of AIS. The % difference in SMI between osteopenic and non-osteopenic AIS (15.6%) was highest among all the parameters. One of the clinical significance was the call for developing a composite prognostic factor incorporating both BMD and SMI for more accurate prediction of curve occurrence and progression in AIS in clinical practice.

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