title: Association between femur size and a focal defect of the superior femoral neck.
abstract: Within each sex, there is an association between hip fracture risk and the size of the proximal femur, with larger femurs apparently more susceptible to fracture. Here, we investigate whether the thickness and density of the femoral cortex play a role in this association: might larger femurs harbour focal, cortical defects? To answer this question, we used cortical bone mapping to measure the distribution of cortical mass surface density (CMSD, mg/cm(2)) in cohorts of 308 males and 125 females. Principal component analysis of the various femoral surfaces led to a measure of size that is linearly independent from shape. After mapping the data onto a canonical femur surface, we used statistical parametric mapping to identify any regions where CMSD depends on size, allowing for other confounding covariates including shape. Our principal finding was a focal patch on the superior femoral neck, where CMSD is reduced by around 1% for each 1% increase in proximal-distal size (p<0.000005 in the males, p<0.001 in the females). This finding appears to be consistent with models of functional adaptation, and may help with the design of interventional strategies for reducing fracture risk.
authors.affiliation: University of Cambridge Department of Engineering, Trumpington Street, Cambridge CB2 1PZ, UK. Electronic address: ahg13@cam.ac.uk.
authors.forename: A H
authors.initials: AH
authors.lastname: Gee
authors.affiliation: University of Cambridge Department of Engineering, Trumpington Street, Cambridge CB2 1PZ, UK. Electronic address: gmt11@cam.ac.uk.
authors.forename: G M
authors.initials: GM
authors.lastname: Treece
authors.affiliation: University of Cambridge Department of Medicine, Level 5, Addenbrooke's Hospital (Box 157), Hills Road, Cambridge CB2 2QQ, UK. Electronic address: carol@zzob.com.
authors.forename: C J
authors.initials: CJ
authors.lastname: Tonkin
authors.affiliation: University of California, San Francisco, Department of Epidemiology and Biostatistics, 185 Berry Street, Lobby 5, Suite 5700, San Francisco, CA 94107, USA. Electronic address: dblack@psg.ucsf.edu.
authors.forename: D M
authors.initials: DM
authors.lastname: Black
authors.affiliation: University of Cambridge Department of Medicine, Level 5, Addenbrooke's Hospital (Box 157), Hills Road, Cambridge CB2 2QQ, UK. Electronic address: kenpoole@doctors.org.uk.
authors.forename: K E S
authors.initials: KES
authors.lastname: Poole
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density / Q000502:physiology; D005260:Female; D005265:Femoral Neck Fractures / Q000503:physiopathology; D005269:Femur / Q000000981:diagnostic imaging*; D005272:Femur Neck / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D012307:Risk Factors; D014057:Tomography, X-Ray Computed
keywords: Cortical bone mapping; Hip structure analysis; Osteoporotic fractures