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Title:Bone loss in the lower leg during 35 days of bed rest is predominantly from the cortical compartment
Authors:Rittweger, Joern (Author)
Šimunič, Boštjan (Author)
Bilancio, Giancarlo (Author)
De Santo, Natale Gaspare (Author)
Cirillo, Massimo (Author)
Biolo, Gianni (Author)
Pišot, Rado (Author)
Eiken, Ola (Author)
Mekjavić, Igor B. (Author)
Narici, Marco (Author)
Files:URL http://www.sciencedirect.com
 
Language:English
Work type:Not categorized
Tipology:1.01 - Original Scientific Article
Organization:UPR - University of Primorska
Abstract:Immobilization-induced bone loss is usually greater in the epiphyses than in the diaphyses. The larger fraction of trabecular bone in the epiphyses than in the diaphyses offers an intuitive explanation to account for this phenomenon. However, recent evidence contradicts this notion and suggests that immobilization-induced bone loss from the distal tibia epiphysis is mainly from the cortical compartment. The aim of this study was to establish whether this pattern of bone loss was a general rule during immobilization. Wemonitored various skeletal sites with different tissue composition during 5 weeks of immobilization. Ten healthy male volunteers with mean age of 24.3 years (SD 2.6 years) underwent strict horizontal bed rest. Bone scans were obtained during baseline data collection, at the end of bed rest and after 14 days of recovery by peripheral Quantitative Computed Tomography (pQCT). Sectional images were obtained from the distal tibia epiphysis (at 4% of the tibia's length), from the diaphysis (at 38%), from the proximal metaphysis (at 93%) and from the proximal epiphysis (at 98%), as well as from the distal femur epiphysis (at 4% of the femur's length) and from the patella. Relative bone losses were largest at the patella, where they amounted to - 3.2% (SD 1.8%, p < 0.001) of the baseline values, and smallest at the tibia diaphysis, where they amounted to - 0.7% (SD 1.0%, p = 0.019). The relative losses were generally larger from cortical than from trabecular compartments (p = 0.004), and whilst all skeletal sites depicted such cortical losses, substantial trabecular losses were found only from the proximal tibia epiphysis. Results confirm that the differential losses from the various skeletal sites cannot be explained on the basis of trabecular vs. cortical tissue composition differences, but that endocortical circumference can account for the different amounts of bone loss in the tibia. The present study therefore supports the suggestion of the subendocortical layer as a transitional zone, which can readily be transformed into trabecular bone in response to immobilization. The latter will lead to cortical thinning, a factor that has been associated with the risk of fracture and with osteoarthritis.
Keywords:space flight, simulated microgravity, osteoporosis, exercise, pQCT
Year of publishing:2009
Number of pages:str. 612-618
Numbering:Vol. 44, no. 4
ISSN:8756-3282
UDC:616.71:612.766
COBISS_ID:1559763 Link is opened in a new window
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Downloads:52
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