The effect of alendronate on bone mass after distal forearm fracture.

Fracture and immobilization of an extremity lead to bone loss at the fracture and at adjacent sites. We conducted a 1-year, single-center, prospective, randomized, double-blind study to determine whether bone loss would occur in the distal radius after a Colles' fracture and whether this loss could be prevented using an antiresorptive drug (alendronate). Thirty-seven women with a recent fracture of the distal forearm and low bone mineral density (BMD) of the lumbar spine were randomized to receive either 10 mg alendronate daily or placebo. BMD of both forearms was measured at baseline and after 3, 6, and 12 months. The results of four women who developed reflex sympathetic dystrophy were not included in the analysis. In the placebo group, there was a significant reduction at 3 months and 6 months in BMD of total radius (p < 0.01), one-third distal radius (p < 0.01), middistal radius (p < 0.05), and ultradistal radius (p < 0.01) on the fractured side. The loss in BMD at one-third distal radius remained significant at month 12 (p < or = 0.001). In the alendronate group BMD of total distal radius, one-third distal radius, and middistal radius at the fractured side remained unchanged. BMD of ultradistal radius increased significantly at months 3, 6, and 12, compared with baseline (p < 0.05). The difference between the two treatment groups was significant at 3 months and 6 months and borderline significant (p = 0.054) after 1 year in total distal radius. In ultradistal radius the differences were significant at all time points. We conclude that BMD of the distal radius of a recently fractured forearm decreases significantly in the 6 months after fracture and the resulting deficit remains evident at least 1 year after fracture. This bone loss can be prevented by alendronate.