title: 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.
authors.affiliation: Department of Clinical and Experimental Medicine, Orthopedics, Faculty of Health Science, Linköping University, 581 85, Linköping, Sweden, per.aspenberg@liu.se.
authors.forename: Per
authors.initials: P
authors.lastname: Aspenberg
authors.forename: Jörg
authors.initials: J
authors.lastname: Schilcher
mesh_terms: D050071:Bone Density Conservation Agents / Q000009:adverse effects*; D004164:Diphosphonates / Q000009:adverse effects*; D005264:Femoral Fractures / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D006801:Humans; D011859:Radiography; D013314:Stress, Mechanical
chemical_list: D050071:Bone Density Conservation Agents; D004164:Diphosphonates