title: Bone loss patterns in cortical, subcortical, and trabecular compartments during simulated microgravity.
abstract: Disuse studies provide a useful model for bone adaptation. A direct comparison of these studies is, however, complicated by the different settings used for bone analysis. Through pooling and reanalysis of bone data from previous disuse studies, we determined bone loss and recovery in cortical, subcortical, and trabecular compartments and evaluated whether the study design modulated skeletal adaptation. Peripheral quantitative tomographic (pQCT) images from control groups of four disuse studies with a duration of 24, 35, 56, and 90 days were reanalyzed using a robust threshold-free segmentation algorithm. The pQCT data were available from 27 young healthy men at baseline, and at specified intervals over disuse and reambulation phases. The mean maximum absolute bone loss (mean ± 95% CI) was 6.1 ± 4.5 mg/mm in cortical, 2.4 ± 1.6 mg/mm in subcortical, and 9.8 ± 9.1 mg/mm in trabecular compartments, after 90 days of bed rest. The percentage changes in all bone compartments were, however, similar. During the first few weeks after onset of reambulation, the bone loss rate was systematically greater in the cortical than in the trabecular compartment (P < 0.002), and this was observed in all studies except for the longest study. We conclude that disuse-induced bone losses follow similar patterns irrespective of study design, and the largest mean absolute bone loss occurs in the cortical compartment, but apparently only during the first 60 days. With longer study duration, trabecular loss may become more prominent.
authors.affiliation: Department of Electronics and Communications Engineering, Tampere University of Technology, Tampere, Finland; Institute of Bioscience and Medical Technology, Tampere, Finland; tomas.cervinka@tut.fi.
authors.forename: Tomas
authors.initials: T
authors.lastname: Cervinka
authors.affiliation: Bone Research Group, UKK Institute, Tampere, Finland;
authors.forename: Harri
authors.initials: H
authors.lastname: Sievänen
authors.affiliation: Department of Electronics and Communications Engineering, Tampere University of Technology, Tampere, Finland; Institute of Bioscience and Medical Technology, Tampere, Finland;
authors.forename: Jari
authors.initials: J
authors.lastname: Hyttinen
authors.affiliation: Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany; and Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, Manchester, United Kingdom.
authors.forename: Jörn
authors.initials: J
authors.lastname: Rittweger
mesh_terms: D000328:Adult; D000465:Algorithms; D001510:Bed Rest / Q000379:methods; D015519:Bone Density / Q000502:physiology; D001851:Bone Diseases, Metabolic / Q000503:physiopathology*; D001842:Bone and Bones / Q000503:physiopathology*; D006801:Humans; D008297:Male; D014057:Tomography, X-Ray Computed / Q000379:methods; D018474:Weightlessness Simulation; D055815:Young Adult
keywords: bed rest; image processing; immobilization; osteoporosis; pQCT