Bone microdamage: a clinical perspective

Microdamage accumulation due to fatigue loading may lead to fracture. In addition, several studies using animal models have suggested in recent years that bisphosphonates might increase microdamage accumulation. We have reviewed the literature after a PubMed search, to examine the techniques to look for microcracks, the relationship between microdamage and bone strength, and the influence of anti-osteoporosis agents. Currently, the search for microcracks relies on bulk staining of bone samples, which are then examined on optic microscopy and fluorescence or confocal microscopy. The accumulation of microdamage is associated with fatigue loading and is likely to trigger targeted bone remodeling, especially in cortical bone. Several studies examining beagle dogs receiving bisphosphonates have shown a dose-dependent accumulation of microdamage in bone, with conflicting results regarding the consequences on bone mechanical properties. In living humans, obtaining data is limited to the iliac crest bone. The potential association between long-term bisphosphonate use and microcrack accumulation at the iliac crest bone has not been established unequivocally. Bone microdamage is critical in the understanding of bone quality. Assessment of microdamage is technically difficult, especially in humans. The clinical impact of microdamage potentially induced by bone drugs has not been established in humans.