Variations in vertebral body dimensions in women measured by 3D-XA: a longitudinal in vivo study.

Bone size and shape play an important role in bone strength, as shown by biomechanical testing and clinical studies. Vertebral body dimensions determine vertebral body strength even after adjustment for bone mineral density. We have recently proposed an in vivo method for 3D reconstruction of vertebral bodies using the whole spine imaging on a standard DXA device (3D-XA). The aim of our study was to measure in vivo vertebral body dimension changes by 3D-XA in women over a 6 year period. A total of 174 women were included in this study. They were divided into 3 groups: premenopausal (20-40 years; N=53), postmenopausal women (55-60 years; N=65) and elderly women (70-80 years; N=56). Thoracic and lumbar spine (T4-L4) were reconstructed using the 3D-XA method at baseline and 6 years later. Biochemical markers of bone remodeling were measured at baseline. In premenopausal women, there was an increase in minimal cross-sectional area (minCSA), vertebral body volume as well as end plate width of the lumbar vertebrae, without statistically significant change of these parameters at the thoracic spine; there was no change in anterior heights. In postmenopausal women, there was a decrease in vertebral body anterior height and depth, driven by results in the elderly group at both the thoracic and lumbar spine. Vertebral body width decreased at the thoracic spine but increased at the lumbar spine. MinCSA and volume decreased at the thoracic spine, in contrast with an increase of these 2 parameters at the lumbar spine in early postmenopausal women (55-60 years). In elderly women (70-80 years), the change in minCSA and volume of the lumbar spine was not statistically significant over 6 years. In postmenopausal women, there was no correlation between changes in vertebral dimensions and baseline biochemical markers of bone remodeling except for NTX/Cr and anterior height decrease. Our study confirms that an increase in geometric dimensions of lumbar vertebrae occurs through adult life. This could be related to a compensation for bone loss, aiming to maintain bone strength through increase in size. However, this phenomenon is not observed at all levels in the spine; since we do not confirm this increase at the thoracic spine. This might be one of the determinants of the higher risk of fractures in this part of the spine.

Spinal deformity index (SDI) is a good predictor of incident vertebral fractures.

UNLABELLED: The spinal deformity index is a convenient tool to quantify the number and the severity of prevalent vertebral fractures. It is a predictor of the risk of sustaining incident vertebral fracture. This quantification must be taken into account to improve management of patients. INTRODUCTION: Prevalent fractures are strong risk factors for subsequent fractures. METHODS: The study subjects were women from the placebo groups of two studies of strontium ranelate in postmenopausal osteoporosis (N = 723 and 637 patients, respectively). Three lateral radiographs of the spine were obtained at baseline and annually over 3 years, according to standardized procedures. The semiquantitative visual assessment of each vertebra from T4 to L4 was performed by the same reader throughout the study. A spinal deformity index (SDI) was calculated by summing for each patient the grade of each vertebra from T4 to L4. RESULTS: There was a linear relationship between baseline SDI and the 3-year incidence of vertebral fracture (adjusted R(2) = 0.76). The 3-year incidence of vertebral fractures was different among the tertiles of baseline SDI: 17.3 +/- 3.6%, 25.4 +/- 2.6%, and 47.6 +/- 3.1% from the lowest to the highest, respectively. There was no relationship between SDI and non-vertebral fractures incidence. CONCLUSION: SDI is a good predictor of incident vertebral fractures. Patients with highest SDI should receive highest priority to treatment.