title: Bone cross-sectional geometry is not associated with atypical femoral fractures in Asian female chronic bisphosphonate users.
abstract: BACKGROUND
  Atypical femoral fractures (AFF) tend to occur in Asian women with prolonged bisphosphonate exposure. Hip geometry is thought to contribute to the risk of AFF formation. We examined the hip structural geometry parameters in Asian female chronic bisphosphonate users who sustained an AFF and compared them to chronic bisphosphonate users who did not sustain any femoral fracture (NFF) and bisphosphonate-naïve patients who sustained an osteoporotic femoral fracture (OFF).
  
  
  METHODS
  Thirty-one patients with AFFs were gender and age-matched to 31 patients with NFFs and 49 patients with OFFs. The Hip Structural Analysis parameters analyzed were bone mineral density (BMD), cross-sectional area (CSA; a metric of resistance to axial compression), section modulus (SM; a metric of resistance to tensile loads), average cortical thickness (ACT; mean thickness of the femoral cortices), buckling ratio (BR; an index of likelihood of local buckling), and neck shaft angle (NSA; the angle between the neck and shaft axes). The regions analyzed were three cross-sections measured at the narrowest femoral neck diameter, the intertrochanteric area, and the proximal femoral shaft. One-way ANOVA with Bonferroni adjustment for multiple comparisons was used to compare parameters between the three patient groups, with statistical significance defined as p<0.05.
  
  
  RESULTS
  There were no statistical differences in parameters between patients with AFFs and patients with NFFs at all measured regions. Patients with AFFs and NFFs had statistically higher BMD, CSA, ACT, SM values and lower BR values at the NN and IT regions than patients with OFFs. Additionally, patients with NFFs had statistically higher SM values at the IT region than patients with OFFs, while patients with AFFs had statistically higher BMD, CSA, and ACT values at the FS region. All other measured parameters were not statistically different between the groups.
  
  
  CONCLUSIONS
  Chronic bisphosphonate users with and without AFFs had similar femoral structural geometries. Unlike in other populations, varus neck shaft angles were not found to be associated with AFFs in Asian female chronic bisphosphonate users. Thus, bone cross-sectional geometry is not likely to be associated with AFFs in Asian female chronic bisphosphonate users. Hip Structural Analysis does not show an increased predilection for tensile failure in AFFs.
authors.affiliation: Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Republic of Singapore. Electronic address: andrew.chou@alumni.stanford.edu.
authors.forename: Andrew Chia Chen
authors.initials: AC
authors.lastname: Chou
authors.affiliation: Department of Endocrinology, Singapore General Hospital, Outram Road, Singapore 169608, Republic of Singapore. Electronic address: alvinngcm@gmail.com.
authors.forename: Alvin Choong Meng
authors.initials: AC
authors.lastname: Ng
authors.affiliation: Department of Diagnostic Radiology, Singapore General Hospital, Outram Road, Singapore 169608, Republic of Singapore. Electronic address: gdrpma@gmail.com.
authors.forename: Meng Ai
authors.initials: MA
authors.lastname: Png
authors.affiliation: Department of Orthopaedic Surgery, Changi General Hospital, 2 Simei Street 3, 529889, Republic of Singapore. Electronic address: david.chua@cgh.com.sg.
authors.forename: David Thai Chong
authors.initials: DT
authors.lastname: Chua
authors.affiliation: Department of Nuclear Medicine and PET, Singapore General Hospital, Outram Road, Singapore 169608, Republic of Singapore. Electronic address: david.ng.c.e@sgh.com.sg.
authors.forename: David Chee Eng
authors.initials: DC
authors.lastname: Ng
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Outram Road, Singapore 169608, Republic of Singapore. Electronic address: howe.tet.sen@sgh.com.sg.
authors.forename: Tet Sen
authors.initials: TS
authors.lastname: Howe
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Outram Road, Singapore 169608, Republic of Singapore. Electronic address: joyce.koh.s.b@sgh.com.sg.
authors.forename: Joyce Suang Bee
authors.initials: JS
authors.lastname: Koh
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D044466:Asian People; D015519:Bone Density / Q000502:physiology; D050071:Bone Density Conservation Agents / Q000009:adverse effects*; D019245:Compressive Strength; D004164:Diphosphonates / Q000009:adverse effects*; D005260:Female; D005264:Femoral Fractures / Q000473:pathology* / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D013718:Tensile Strength
chemical_list: D050071:Bone Density Conservation Agents; D004164:Diphosphonates
keywords: Atypical femoral fracture; Bisphosphonates; Hip morphology; Hip structural geometry; Neck shaft angle; Osteoporosis