Recurrence of Vertebral Fracture with Cyclical Etidronate Therapy in Osteoporosis: Histomorphometry and X-Ray Microanalysis Evaluation

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Abstract
In an open prospective study, we evaluated differences between patients with (wRVF group) and without recurrence of vertebral fracture (woRVF group) during cyclical etidronate therapy for osteoporosis. Thirty-two patients (age 64 +/- 1.8 years) characterized by at least one osteoporotic VF were treated during 1 year. At baseline, body mass index was significantly lower (23.3 +/- 0.6 vs. 26.9 +/- 1.0 kg/m2, p< 0.05), the number of previous VFs was higher (4.0 +/- 0. 4 vs. 2.4 +/- 0.4, NS), and patients were older in the wRVF group as compared with the woRVF group (67.8 +/- 3 vs. 62.6+/- 2.2 year, NS). Trabecular bone volume (11.6 +/- 1.2 vs. 15 +/- 0.9%, p< 0.05) and trabecular number (1.06 +/- 0.08 vs. 1.27 +/- 0.05, p < 0.05) were significantly lower in the wRVF group. None of the baseline resorptive variables differed, whereas the bone formation rate (BFR) was 2-fold lower in the wRVF group (p< 0. 05). After 1 year of treatment, osteoclast number, active eroded surfaces, and resorption depth dramatically decreased in both groups (p< 0. 01). To a lesser extent, the mineral apposition rate and serum alkaline phosphatase level were significantly reduced (p< 0.05). No impaired mineralization was observed. Using X-ray microanalysis, we found no abnormality in bone mineral but a significant increase of the calcium/phosphorus ratio during treatment in the wRVF group. Our results demonstrate that recurrence of VFs within the first year of cyclical etidronate therapy was related neither to a lack of histologic response to the treatment nor induction of an abnormality of mineralization. VFs were more likely in the presence of a decreased BFR and lower trabecular connectivity, providing support for treating osteoporotic patients with etidronate early in the course of the disease.

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