Abstract
Introduction: Conflicting opinions exist as to whether bone healing is affected by the administration of bisphosphonates for osteoporosis. In an animal model, we assessed the effect of bisphosphonates on osteoporotic fracture healing and whether the timing of administration made a difference.
Methods: 36 female Wistar rats underwent a mid-diaphyseal femoral osteotomy six weeks after ovariectomy. They were then divided into 3 groups:
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no treatment (control);
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administration of alendronate (ALN) from 14 days after osteotomy;
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ALN from the time of osteotomy. Fracture repair was assessed weekly with the use of standardised radiography, DEXA scan and in vitro peripheral quantative computed tomography (pQCT). The rats were sacrificed 42 days post-osteotomy and the femora underwent mechanical testing.
Results: Of the 36 rats, 8 were unable to complete the study. Group 3 differed from control in three respects: higher bone mineral content (BMC) and density (BMD); larger callus; lower torsional stiffness. Group 2 did not differ significantly from control. There was a significant positive correlation between stiffness and change in BMC in group 1 (r=0.85, p< 0.001) but not so for group 2 (r=0.2, p> 0.05) and group 3 (r=0.04, p> 0.05). A similar trend existed for all radiographic parameters in the three groups.
Conclusion: The results suggest that, with early bisphosphonate treatment, although there is an increase in the size of the callus, that callus is biomechanically inferior. Furthermore, administration of bisphosphonates at either stage destroys the relationship between radiographic and mechanical parameters used to assess fracture healing.
The abstracts were prepared by Mr Matt Costa and Mr Ben Ollivere. Correspondence should be addressed to Mr Costa at Clinical Sciences Research Institute, University of Warwick, Clifford Bridge Road, Coventry CV2 2DX, UK.
