Improvement of bone properties in children with osteogenesis imperfecta after pamidronate: a bone biopsy study

OI, or bone brittle disease, is characterized by increased mineralization of bone matrix independently of clinical severity. So, a beneficial effect of antiresorptive treatments such as bisphosphonates (BP) is questionable. We aim to compare the bone matrix characteristics before and after BP pamidronate (PAM). Fifty-eight children (9 ± 5 yr-old) with OI (Type I, III, IV, V, VI, XI, or unknown) received intravenous PAM for 2 yr and underwent transiliac bone biopsies before (<i>n</i> = 57) and after (<i>n</i> = 35) treatment. Compared with age-matched controls, untreated OI was characterized by cortical and cancellous rarefaction. Two years of PAM in OI patients significantly decreased bone remodeling activity, increased cortical thickness, improved the maturation of both organic and mineral matrix, and most of the nanomechanical properties, despite further increase in the degree of mineralization. Overall, in addition to a gain in bone mass, our results showed for the first time that PAM is able to increase the maturation of mineral crystals and collagen matrix contributing to its antifracture efficacy in OI patients.