Abnormal bone quality versus low bone mineral density in adolescent idiopathic scoliosis: a case-control study with in vivo high-resolution peripheral quantitative computed tomography

Abstract

Background context: Adolescent idiopathic scoliosis (AIS) is associated with low bone mass that could persist into early adulthood and is an important prognostic factor for curve progression. Previous studies were confined to areal bone mineral density measurement that was a two-dimensional investigation for a three-dimensional structure. Evaluation of volumetric BMD (vBMD) and other bone quality parameters are important for gaining in-depth understanding of the etiopathogenesis of AIS.

Purpose: The objective of this study was to carry out direct in vivo measurement of bone quality in AIS using high-resolution peripheral quantitative computed tomography (HR-pQCT) and compare the correlation of bone quality with osteopenia between AIS and control subjects.

Study design/setting: A case-control study.

Patient sample: Newly diagnosed AIS girls (n=112) and non-AIS girls (n=115) between 11 and 13 years.

Outcome measures: Areal bone mineral density of bilateral femoral necks and HR-pQCT of the nondominant distal radius were performed.

Methods: Areal bone mineral density of femoral necks was measured by dual-energy X-ray absorptiometry. Subjects were classified into the osteopenic (Z score less than or equal to -1) and nonosteopenic (Z score more than -1) groups. Bone quality parameters, including bone morphometry, trabecular bone microarchitecture, and vBMD, were measured by HR-pQCT (XtremeCT; Scanco Medical, Zurich, Switzerland).

Results: In AIS, the osteopenic group had lower measurements in cortical area, cortical thickness, average vBMD, compact bone vBMD, trabecular vBMD, trabecular bone volume to tissue volume ratio, and trabecular thickness compared with nonosteopenic AIS subjects. In contrast, among the non-AIS controls, the osteopenic group had lower measurements only in bone morphometry, average vBMD, and compact bone vBMD but not in trabecular vBMD and all other trabecular bone microarchitecture parameters.

Conclusions: This is the first study using HR-pQCT to compare the correlation of bone quality with osteopenia in AIS and non-AIS subjects. It provides new insights and highlights the unique bone quality profile with predominant changes in the trabecular compartment in association with osteopenia being notably only detected in the AIS subjects. Further studies in this area are warranted for defining the metabolic nature and biomechanical sequelae of derangement in bone mass and bone quality and their roles in the etiopathogenesis of AIS.

Keywords: Abnormal bone quality; Adolescent idiopathic scoliosis; High-resolution peripheral quantitative computed tomography; Low bone mineral density; Osteopenia.