title: Assessment of femur geometrical parameters using EOS™ imaging technology in patients with atypical femur fractures; preliminary results.
abstract: Atypical femur fractures (AFF) arise in the subtrochanteric and diaphyseal regions. Because of this unique distribution, we hypothesized that patients with AFF demonstrate specific geometrical variations of their lower limb whereby baseline tensile forces applied to the lateral cortex are higher and might favor the appearance of these rare stress fractures, when exposed to bisphosphonates. Using the low irradiation 2D-3D X-ray scanner EOS™ imaging technology we aimed to characterize and compare femur geometric parameters between women who sustained bisphosphonate-associated AFF and those who had experienced similar duration of exposure to bisphosphonates but did not sustain fractures. Conditional logistic regression models were constructed to estimate the association between selected geometric parameters and the occurrence of AFF. We identified 16 Caucasian women with AFF and recruited 16 ethnicity-, sex-, age-, height- and cumulative bisphosphonate exposure-matched controls from local osteoporosis clinics. Compared to controls, those with AFF had more lateral femur bowing (-3.2° SD [3.4] versus -0.8° SD [1.9] p=0.02). In regression analysis, lateral femur bowing was associated with the risk of AFF (aOR 1.54; 95% CI 1.04-2.28, p=0.03). Women who sustained a subtrochanteric AFF demonstrated a lesser femoral neck shaft angle (varus geometry) than those with a fracture at a diaphyseal site (121.9 [3.6]° versus 127.6 [7.2]°, p=0.07), whereas femur bowing was more prominent in those with a diaphyseal fracture compared to those with a subtrochanteric fracture (-4.3 [3.2]° versus -0.9 [2.7]°, p=0.07). Our analyses support that subjects with AFF exhibit femoral geometry parameters that result in higher tensile mechanical load on the lateral femur. This may play a critical role in the pathogenesis of AFF and requires further evaluation in a larger size population.
authors.affiliation: McGill University, Montreal, Canada; McGill University Health Center Research Institute, Montreal, Canada. Electronic address: suzanne.morin@mcgill.ca.
authors.forename: Suzanne N
authors.initials: SN
authors.lastname: Morin
authors.affiliation: McGill University Health Center Research Institute, Montreal, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Wall
authors.affiliation: Laval University, Quebec City, Canada; CHU de Québec Research Centre, Quebec City, Canada.
authors.forename: Etienne L
authors.initials: EL
authors.lastname: Belzile
authors.affiliation: Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Canada.
authors.forename: Benoit
authors.initials: B
authors.lastname: Godbout
authors.affiliation: Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Canada; Université de Montréal, Montreal, Canada.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Moser
authors.affiliation: Laval University, Quebec City, Canada; CHU de Québec Research Centre, Quebec City, Canada.
authors.forename: Laëtitia
authors.initials: L
authors.lastname: Michou
authors.affiliation: Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Canada; Université de Montréal, Montreal, Canada.
authors.forename: Louis-Georges
authors.initials: LG
authors.lastname: Ste-Marie
authors.affiliation: Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Canada; Université de Montréal, Montreal, Canada.
authors.forename: Jacques A
authors.initials: JA
authors.lastname: de Guise
authors.affiliation: McGill University, Montreal, Canada; McGill University Health Center Research Institute, Montreal, Canada.
authors.forename: Elham
authors.initials: E
authors.lastname: Rahme
authors.affiliation: Laval University, Quebec City, Canada; CHU de Québec Research Centre, Quebec City, Canada.
authors.forename: Jacques P
authors.initials: JP
authors.lastname: Brown
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D005260:Female; D005264:Femoral Fractures / Q000000981:diagnostic imaging*; D005269:Femur / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D011859:Radiography
keywords: Atypical femur fracture; Bisphosphonates; Femur geometry; Imaging; Registry