Transmenopausal changes in the trabecular bone structure

Introduction: Post-menopausal osteoporosis is a disorder of excess skeletal fragility, due partly to changes in bone microstructure. Menopause is known to result in bone loss and reduction in bone mechanical strength. However, the mechanism and nature of microstructural changes at menopause need more detailed description and analyses. The overall hypothesis for this analysis is that the variables describing trabecular bone micro-architecture will be affected by changes in the hormonal status of women just prior to, and early after, last menses, and that volumetric bone density, and trabecular structure will decline significantly. The study was designed to capture true longitudinal transmenopausal changes in three-dimensional (3-D) trabecular bone architecture. Currently, minimal data exist regarding these features. Materials and methods: Transilial biopsies specimens were obtained from healthy pre-menopausal women (age > 46), and repeated at 12 months after the last menstrual period. Bone architecture was quantified in 38 paired specimens using micro-computed tomography (micro-CT-40, Scanco) techniques. Bone biopsies were embedded for histomorphomteric analyses and parts of the analyses have been published elsewhere. Embedded bone biopsies were scanned at 30-mu m resolution such that the region of interest was similar to that in the two-dimensional (2-D) histomorphometric analyses. Paired t-tests were used to compare the pre- and post-menopausal bone structural data from each technique. Results: There was good correlation between standard histomorphometric (2-D) and micro-CT (3-D) measurements. Most of the variables characterizing bone structure in post-menopausal women (from micro-CT) significantly decreased (BV/TV, trabecular number, apparent and tissue density). In addition, both trabecular spacing (Tb.S) and the structure model index (SMI) increased in the post-menopausal women suggesting transformation of trabecular bone from plate- to rod-like structure. The 3-D trabecular connectivity density (Conn.D) was negatively correlated with activation frequency (Ac.f). Conclusions: These data suggest that 3-D micro-CT measurements (longitudinal) are comparable to those of standard histomorphometry, and that most of the bone structural measurements are sensitive to changes in women's hormonal status across menopause. (c) 2007 Elsevier Inc. All rights reserved.