Atypical Femoral Fractures, Bisphosphonates, and Mechanical Stress
ABSTRACT Atypical fractures are stress fractures occurring in the femoral shaft and closely related to bisphosphonate use. We here discuss their radiographic definition and different putative etiologies, apart from mechanical stress. Long time reduction of skeletal remodeling because of bisphosphonate use is thought to allow time for the bone to deteriorate mechanically, resulting in reduced toughness. However, the risk of atypical fracture diminishes rapidly after cessation of treatment, which suggests more acute effects of bisphosphonate use. Microdamage normally accumulates at areas of high stress. Possibly, ongoing bisphosphonate use reduces the ability to resorb and replace areas of microdamage by targeted remodeling. This could lead to crack propagation beyond a point of no return, ending in macroscopic stress fracture.
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ABSTRACT: The causal relationship between chronic use of bisphosphonates and occurrences of atypical femoral fractures has not yet been established. Nonetheless, it is known that their chronic use is more related to fractures with a pattern differing from that of classical osteoporotic fractures. Atypical fractures are still rare events and the benefit from using bisphosphonates remains greater for prevention and treatment of osteoporosis. There are few studies guiding the diagnosis and management of these fractures, thus making it difficult to achieve better results. In this report, we present the case of an elderly patient with an atypical femoral fracture that was managed in accordance with guidance from the American Society for Bone and Mineral Research.Revista Brasileira de Ortopedia 01/2015; 12. DOI:10.1016/j.rbo.2014.08.007
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ABSTRACT: Osteoporosis leads to increased bone fragility, thus effective approaches enhancing bone strength are needed. Hence, this study investigated the effect of single or combined application of high-frequency (HF) loading through whole body vibration (WBV) and alendronate (ALN) on the mechanical competence of ovariectomy-induced osteoporotic bone. Thirty-four female Wistar rats were ovariectomized (OVX) or sham-operated (shOVX) and divided into five groups: shOVX, OVX-shWBV, OVX-WBV, ALN-shWBV and ALN-WBV. (Sham)WBV loading was applied for 10 min/day (130 to 150 Hz at 0.3g) for 14 days and ALN at 2 mg/kg/dose was administered 3x/week. Finite element analysis based on micro-CT was employed to assess bone biomechanical properties, relative to bone micro-structural parameters. HF loading application to OVX resulted in an enlarged cortex, but it was not able to improve the biomechanical properties. ALN prevented trabecular bone deterioration and increased bone stiffness and bone strength of OVX bone. Finally, the combination of ALN with HF resulted in an increased cortical thickness in OVX rats when compared to single treatments. Compared to HF loading, ALN treatment is preferred for improving the compromised mechanical competence of OVX bone. In addition, the association of ALN with HF loading results in an additive effect on the cortical thickness.Scientific Reports 06/2015; 5:10795. DOI:10.1038/srep10795 · 5.58 Impact Factor