title: The fracture sites of atypical femoral fractures are associated with the weight-bearing lower limb alignment.
abstract: Atypical femoral fractures (AFFs) are stress-related fractures that are speculated to associate with long-term treatment with bisphosphonates for osteoporosis. A history of AFF is a high risk factor for the development of a subsequent AFF in the same location of the contralateral femur, suggesting that a patient's individual anatomical factor(s) are related to the fracture site of AFFs. In this study, we investigated the radiographs of fourteen AFFs (four bilateral fractures among ten patients) treated at six hospitals associated with our university between 2005 and 2010. The fracture site and standing femorotibial angle (FTA), which reflects the mechanical axis of the lower limb, were measured on weight-bearing lower limb radiographs. The fracture site and FTA of patients with typical femoral fractures (TFF) were compared to those of patients with AFFs. The correlations were examined using Spearman's rank correlation coefficients. The fracture locations in the femora were almost the same in the patients with bilateral AFFs. There was a positive correlation between the fracture site and the standing FTA in the patients with AFFs (r=0.82, 95% confidence interval; 0.49 to 0.94), indicating that the larger the standing FTA (varus alignment), the more distal the site of the fracture in the femur. The FTA of the patients with atypical diaphyseal femoral fracture were significantly larger compared to that of those with not only atypical subtrochanteric fractures but also TFFs. In conclusion, the fracture sites of AFFs are associated with the standing lower limb alignment, while those of TFFs are not.
authors.affiliation: Department of Orthopaedics, Juntendo University Faculty of Medicine, Tokyo, Japan.
authors.forename: Yoshitomo
authors.initials: Y
authors.lastname: Saita
authors.affiliation: Department of Orthopaedics, Juntendo University Faculty of Medicine, Tokyo, Japan. Electronic address: ishijima@juntendo.ac.jp.
authors.forename: Muneaki
authors.initials: M
authors.lastname: Ishijima
authors.affiliation: Department of Orthopaedic Surgery, Juntendo Shizuoka Hospital, Shizuoka, Japan.
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Mogami
authors.affiliation: Department of Orthopaedics, Juntendo University Faculty of Medicine, Tokyo, Japan.
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Kubota
authors.affiliation: Department of Orthopaedic Surgery, Juntendo Urayasu Hospital, Chiba, Japan.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Baba
authors.affiliation: Department of Orthopaedics, Juntendo University Faculty of Medicine, Tokyo, Japan.
authors.forename: Takefumi
authors.initials: T
authors.lastname: Kaketa
authors.affiliation: Department of Orthopaedic Surgery, Juntendo Nerima Hospital, Tokyo, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Nagao
authors.affiliation: Department of Orthopaedic Surgery, Juntendo Nerima Hospital, Tokyo, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Sakamoto
authors.affiliation: Department of Orthopaedic Surgery, Juntendo Nerima Hospital, Tokyo, Japan.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Sakai
authors.affiliation: Department of Orthopaedic Surgery, Koto Hospital, Tokyo, Japan.
authors.forename: Rui
authors.initials: R
authors.lastname: Kato
authors.affiliation: Department of Orthopaedic Surgery, Juntendo Shizuoka Hospital, Shizuoka, Japan.
authors.forename: Nana
authors.initials: N
authors.lastname: Nagura
authors.affiliation: Department of Orthopaedic Surgery, Chiba Central Medical Center, Chiba, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Miyagawa
authors.affiliation: Department of Orthopaedic Surgery, Juntendo Shizuoka Hospital, Shizuoka, Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Wada
authors.affiliation: Department of Orthopaedics, Juntendo University Faculty of Medicine, Tokyo, Japan.
authors.forename: Lizu
authors.initials: L
authors.lastname: Liu
authors.affiliation: Department of Orthopaedic Surgery, Juntendo Shizuoka Hospital, Shizuoka, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Obayashi
authors.affiliation: Department of Orthopaedic Surgery, Juntendo Urayasu Hospital, Chiba, Japan.
authors.forename: Katsuo
authors.initials: K
authors.lastname: Shitoto
authors.affiliation: Department of Orthopaedic Surgery, Juntendo Nerima Hospital, Tokyo, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Nozawa
authors.affiliation: Department of Orthopaedic Surgery, Koto Hospital, Tokyo, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Kajihara
authors.affiliation: Department of Orthopaedic Surgery, Chiba Central Medical Center, Chiba, Japan.
authors.forename: Hogaku
authors.initials: H
authors.lastname: Gen
authors.affiliation: Department of Orthopaedics, Juntendo University Faculty of Medicine, Tokyo, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kaneko
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D018483:Diaphyses / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D005260:Female; D005264:Femoral Fractures / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005269:Femur / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D035002:Lower Extremity / Q000503:physiopathology*; D008875:Middle Aged; D011859:Radiography; D016474:Weight-Bearing
keywords: Atypical femoral fracture (AFF); Bisphosphonate; Femorotibial angle (FTA); Lower limb alignment; Osteoporosis