title: Determinants of Transitional Zone Area and Porosity of the Proximal Femur Quantified In Vivo in Postmenopausal Women.
abstract: Bone architecture as well as size and shape is important for bone strength and risk of fracture. Most bone loss is cortical and occurs by trabecularization of the inner part of the cortex. We therefore wanted to identify determinants of the bone architecture, especially the area and porosity of the transitional zone, an inner cortical region with a large surface/matrix volume available for intracortical remodeling. In 211 postmenopausal women aged 54 to 94 years with nonvertebral fractures and 232 controls from the Tromsø Study, Norway, we quantified femoral subtrochanteric architecture in CT images using StrAx1.0 software, and serum levels of bone turnover markers (BTM, procollagen type I N-terminal propeptide and C-terminal cross-linking telopeptide of type I collagen). Multivariable linear and logistic regression analyses were used to quantify associations of age, weight, height, and bone size with bone architecture and BTM, and odds ratio (OR) for fracture. Increasing age, height, and larger total cross-sectional area (TCSA) were associated with larger transitional zone CSA and transitional zone CSA/TCSA (standardized coefficients [STB] = 0.11 to 0.80, p ≤ 0.05). Increasing weight was associated with larger TCSA, but smaller transitional zone CSA/TCSA and thicker cortices (STB = 0.15 to 0.22, p < 0.01). Increasing height and TCSA were associated with higher porosity of the transitional zone (STB = 0.12 to 0.46, p < 0.05). Increasing BTM were associated with larger TCSA, larger transitional zone CSA/TCSA, and higher porosity of each of the cortical compartments (p < 0.01). Fracture cases exhibited larger transitional zone CSA and higher porosity than controls (p < 0.001). Per SD increasing CSA and porosity of the transitional zone, OR for fracture was 1.71 (95% CI, 1.37 to 2.14) and 1.51 (95% CI, 1.23 to 1.85), respectively. Cortical bone architecture is determined mainly by bone size as built during growth and is modified by lifestyle factors throughout life through bone turnover. Fracture cases exhibited larger transitional zone area and porosity, highlighting the importance of cortical bone architecture for fracture propensity.
authors.affiliation: Department of Health and Care Sciences, UiT The Arctic University of Norway, Tromsø, Norway.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Shigdel
authors.affiliation: Department of Community Medicine, UiT The Arctic University of Norway, Tromsø, Norway.
authors.forename: Marit
authors.initials: M
authors.lastname: Osima
authors.affiliation: Department of Community Medicine, UiT The Arctic University of Norway, Tromsø, Norway.
authors.forename: Marko
authors.initials: M
authors.lastname: Lukic
authors.affiliation: Department of Health and Care Sciences, UiT The Arctic University of Norway, Tromsø, Norway.|Institute of Public Health, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates.
authors.forename: Luai A
authors.initials: LA
authors.lastname: Ahmed
authors.affiliation: Department of Clinical Medicine, UiT The Arctic University of Norway, Tromsø, Norway.|Department of Internal Medicine, University Hospital of North Norway, Tromsø, Norway.
authors.forename: Ragnar M
authors.initials: RM
authors.lastname: Joakimsen
authors.affiliation: Department of Clinical Endocrinology, Oslo University Hospital, Oslo, Norway.
authors.forename: Erik F
authors.initials: EF
authors.lastname: Eriksen
authors.affiliation: Department of Health and Care Sciences, UiT The Arctic University of Norway, Tromsø, Norway.
authors.forename: Åshild
authors.initials: Å
authors.lastname: Bjørnerem
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000378:metabolism; D005260:Female; D005269:Femur / Q000378:metabolism* / Q000473:pathology; D050723:Fractures, Bone / Q000453:epidemiology* / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D016062:Porosity; D017698:Postmenopause / Q000378:metabolism*
chemical_list: D015415:Biomarkers
keywords: AGING; BONE ARCHITECTURE; HEIGHT; POSTMENOPAUSAL WOMEN; TRANSITIONAL ZONE; WEIGHT