Increases in BMD correlate with improvements in bone microarchitecture with teriparatide treatment in postmenopausal women with osteoporosis.

UNLABELLED: Increases in BMD are correlated with improvements in 2D and 3D trabecular microarchitecture indices with teriparatide treatment. Therefore, improvements in trabecular bone microarchitecture may be one of the mechanisms to explain how BMD increases improve bone strength during teriparatide treatment.

INTRODUCTION: Bone strength is determined by BMD and other elements of bone quality, including bone microarchitecture. Teriparatide treatment increases BMD and improves both cortical and trabecular bone microarchitecture. Increases in lumbar spine (LS) BMD account for approximately 30-41% of the vertebral fracture risk reduction with teriparatide treatment. The relationship between increases in BMD and improvements in cortical and trabecular microarchitecture has not yet been studied.

MATERIALS AND METHODS: The relationship between increases in BMD and improvements in cortical and trabecular microarchitecture after teriparatide treatment was assessed using data from a subset of patients who had areal BMD measurements and structural parameters from transiliac bone biopsies in the Fracture Prevention Trial. 2D histomorphometric and 3D microCT parameters were measured at baseline and 12 (n = 21) or 22 (n = 36) mo. LS BMD was assessed at baseline and 12 and 18 mo, and femoral neck (FN) BMD was measured at baseline and 12 mo. Pearson correlation was performed to assess the relationship between actual changes in BMD and actual changes in microarchitectural parameters.

RESULTS: Changes in LS BMD at 12 mo were significantly correlated with improvements in trabecular bone structure at 22 mo: 2D bone volume (r = 0.45, p = 0.02), 2D mean wall thickness (r = 0.41, p = 0.03), 3D bone volume (r = 0.48, p = 0.006), 3D trabecular thickness (r = 0.44, p = 0.01), 3D trabecular separation (r = -0.37, p = 0.04), 3D structural model index (r = -0.54, p = 0.001), and 3D connectivity density (r = 0.41, p = 0.02). Changes in LS BMD at 18 mo had similar correlations with improvements in bone structure at 22 mo. Changes in FN BMD at 12 mo were significantly correlated with changes in 2D mean wall thickness (r = 0.56, p = 0.002), 3D bone volume (r = 0.51, p = 0.004), 3D trabecular thickness (r = 0.44, p = 0.01), 3D trabecular separation (r = -0.46, p = 0.01), and 3D structural model index (r = -0.55, p = 0.001).

CONCLUSIONS: Increases in BMD are correlated with improvements in trabecular microarchitecture in iliac crest of patients with teriparatide treatment. Therefore, improvements in trabecular bone microarchitecture may be one of the mechanisms to explain how BMD increases improve bone strength during teriparatide treatment.