Abstract

Objective: Given recent concern about long-term safety of bisphosphonate therapy, the effects of long-term alendronate therapy on intrinsic bone properties were studied among postmenopausal osteoporotic women (PMOP).

Design & Methods: Transiliac bone biopsies were obtained from 32 outpatient clinic PMOP women treated with oral alendronate (ALN) for 6.4 ± 2.0 years. Variables reflecting bone mineralization were assessed at both tissue level using quantitative microradiography and crystal level by Fourier transform infrared microspectroscopy. Bone microhardness was investigated by Vickers indentation tests. Results were compared with those from 22 age-matched untreated PMOP women.

Results: Long-term treatment with alendronate was associated with a 84% (p<0.001) lower remodeling activity compared to untreated PMOP women, leading to an increased degree of mineralization in both cortical and trabecular bone (+9% and +6%, p<0.05, respectively). Despite a more mature and more mineralized bone matrix, after treatment, cortical and trabecular microhardness and crystallinity were lower than measured in untreated patients. None of the variables reflecting material properties was significantly correlated to the duration of the treatment.

Conclusion: Increased degree of mineralization associated with lower crystallinity and microhardness in ALN long-term-treated PMOP women suggests that ALN could alter the quality of bone matrix. The study also suggested that after three years of treatment, the changes in material properties are not dependent of the treatment duration. Further studies are requested to assess the short-term (< 3 years) effects of bisphosphonates on bone intrinsic properties.