Bone histomorphometric evaluation of pamidronate treatment in clinically manifest osteoporosis

The effect of pamidronate therapy on bone histology was studied in patients with osteoporosis with at least one vertebral fracture in a randomized, do uble-masked, placebo-controlled, multi-center trial. Patients received pami dronate 150 mg/day or placebo in addition to calcium 500 mg/day and Vitamin D-3 400 IU/day. Transiliac bone biopsies were obtained before and after 1 or 2 years of treatment. Of these, 23 pairs of biopsies obtained from 14 wo men and 9 men (mean age +/- SD, 61.5 +/- 10 years) were of sufficient quali ty for histomorphometry. Histomorphometry was performed on sections stained with Goldner's trichrome, using a drawing tube and a digitizer. Urinary hy droxyproline excretion decreased significantly (p < 0.005) following pamidr onate treatment, indicating a decrease in bone resorption. Osteoid volume a nd osteoid surface also decreased significantly in the pamidronate group (p < 0.004 and p < 0.003 respectively), consistent with a secondary decrease in bone formation. Osteoid variables did not change in the placebo-treated patients. Cortical thickness, trabecular bone volume and trabecular thickne ss did not change after pamidronate or placebo treatment. Wall thickness, h owever, showed a borderline increase following pamidronate treatment. After pamidronate, eroded surface and mineral apposition rate did not change sig nificantly in the placebo and pamidronate groups. Mineralizing surface and activation frequency showed a borderline decrease in the placebo and pamidr onate groups. The decrease in mineralization lag time was of borderline sig nificance in the pamidronate group, corroborating the absence of any negati ve effect on mineralization. In conclusion, pamidronate treatment led to a decrease in bone turnover and did not interfere with bone mineralization.