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    ASBMR 2012 Annual Meeting

    Association between the Fracture Site and the Mechanical Axis of Lower Extremities in Patients with Atypical Femoral Fracture

    Category: Bone Biomechanics and Quality (Basic)

    Poster Sessions, Presentation Number: SU0076
    Session: Poster Session II and Poster Tours
    Sunday, October 14, 2012 11:30 AM - 1:30 PM, Minneapolis Convention Center, Discovery Hall-Hall B

    * Yoshitomo Saita, Department of Orthopaedics, Juntendo University School of Medicine, JAPAN, Muneaki Ishijima, Juntendo University Graduate School of Medicine, JAPAN, Atsuhiko Mogami, Department of Orthopaedic Surgery, Juntendo Shizuoka Hospital, Japan, Mitsuaki Kubota, Department of Orthopaedics, Juntendo University School of Medicine, Japan, Takefumi Kaketa, Department of Orthopaedics, Juntendo University School of Medicine, Japan, Kei Miyagawa, Department of Orthopaedic Surgery, Chiba Central Medical Center, Japan, Nana Nagura, Department of Orthopaedic Surgery, Juntendo Shizuoka Hospital, Japan, Tomoki Wada, Department of Orthopaedic Surgery, Juntendo Shizuoka Hospital, Japan, Taisuke Sato, Department of Orthopaedic Surgery, Kitanarashino Hanawa Hospital, Japan, Susumu Fukasaku, Department of Orthopaedic Surgery, Kitanarashino Hanawa Hospital, Japan, Hogaku Gen, Department of Orthopaedic Surgery, Chiba Central Medical Center, Japan, Osamu Obayashi, Department of Orthopaedic Surgery, Juntendo Shizuoka Hospital, Japan, Masayuki Nemoto, Department of Orthopaedic Surgery, Kitanarashino Hanawa Hospital, Japan, Kazuo Kaneko, Department of Orthopaedics, Juntendo University School of Medicine, Japan

       The ASBMR task force defined the major features of atypical femoral fracture (AFF) in which AFF occurs at the subtrochanteric region or diaphysis of femoral shaft. Although there were several case series reporting the clinical features of AFF, it is still remained unclear what determines the fracture site of AFF. Based on our hypothesis that anatomical and/or biomechanical factors of lower limbs would affect the fracture site, the weight-bearing full length radiographs of lower limbs in patients with AFF were analyzed to examine whether there are relationships between the fracture site and the mechanical axis of the lower limbs.

       The 8 patients with AFF (avr. 65.8 y) were analyzed. They were all female. The half of them (4 pts.) fractured at subtrochanteric region and the remaining half (4 pts.) fractured at diaphyseal region of femoral shaft. Five of 8 patients fractured their both femora. Interestingly, the bilateral AFFs were occurred almost the same region of their femoral shaft, suggesting that the individual factor(s) could affect the AFF site. We found that while the patients with subtrochanteric fracture (6 fractures in 4 pts.) tended to show genu valgus, those with diaphyseal fracture (7 fractures in 4 pts.) showed varus deformity of their lower limbs. There were significant correlations between the AFF site and the femorotibial angle (FTA) (r=0.80, p=0.001). The FTA in patients with diaphyseal fracture (avr. 182.7°) was significantly increased in comparison to that in those with subtrochanteric fracture (FTA; avr.171.5°) (p=0.009). On the other hand, there were no significant difference between the fracture site and the angle of anatomical axis and mechanical axis of femora.

       Although there were some reports mentioned about the shape of femora, such as lateral bowing, could be one of the risk factors of atypical diaphyseal femoral fracture, there were no report focused on the relationships between the alignment of lower limbs and AFF site. These findings suggested that fracture site of AFFs were affected by the mechanical axis of lower limbs rather than by the mechanical axis of femora per se. Within our knowledge, this is the first report to reveal the correlation between the biomechanical factor of lower limbs and AFF site. Our data could help physicians where to check the radiographs of patient with the risk of AFF when they complain thigh pain, and can also provide a clue to elucidate the unknown aspects of AFF.

    Disclosures: None

    * Presenting Authors(s): Yoshitomo Saita, Department of Orthopaedics, Juntendo University School of Medicine, JAPAN