title: Cancellous bone structure of iliac crest biopsies following 370 days of head-down bed rest.
abstract: BACKGROUND
  Static bone histomorphometry was applied to existing iliac bone sections originating from a 370-d 5 degrees head-down bed rest experiment. This bed rest experiment is the longest ever to have been conducted. We hypothesized that bed rest would decrease cancellous bone volume fraction and that this effect would be reversed by countermeasures.
  
  
  METHODS
  Eight healthy male subjects underwent 370 d of 5 degrees head-down bed rest. Three subjects were treated with bisphosphonate (Xidifon, potassium salt of ethane-1-hydroxy-1-disphosphonate, EHDP) combined with an exercise regimen (1-2 h x d(-1)) for the entire study period. Five subjects underwent 120 d of bed rest without countermeasures followed by 250 d of bed rest with the exercise regimen. Transiliac bone biopsies were obtained either at baseline and day 366, or at baseline, day 116, and day 366 at alternating sides of the ileum. Static histomorphometry was performed using a computerized method.
  
  
  RESULTS
  The 120 d of head-down bed rest without countermeasures resulted in decreased bone volume fraction BV/TV (-6.3%, p = 0.046) and trabecular number (Tb.N; -10.2%, p = 0.080) and increased trabecular separation (Tb.Sp; 14.7%, p = 0.020), whereas the 250 d of subsequent head-down bed rest with exercise treatment prevented further significant deterioration of the histomorphometric measures.
  
  
  CONCLUSIONS
  The 120 d of 5 degrees head-down bed rest without countermeasures induced significant deterioration of iliac crest cancellous bone histomorphometric properties. On average, the countermeasures consisting of either bisphosphonate and exercise, or exercise alone were able to either prevent or stop immobilization-induced changes of the iliac cancellous bone structure.
authors.affiliation: Department of Connective Tissue Biology, Institute of Anatomy, University of Aarhus, Arhus, Denmark. jesper@jst.ana.au.dk
authors.forename: Jesper S
authors.initials: JS
authors.lastname: Thomsen
authors.forename: Boris V
authors.initials: BV
authors.lastname: Morukov
authors.forename: Laurence
authors.initials: L
authors.lastname: Vico
authors.forename: Christian
authors.initials: C
authors.lastname: Alexandre
authors.forename: Peter I
authors.initials: PI
authors.lastname: Saparin
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Gowin
mesh_terms: D000328:Adult; D001510:Bed Rest; D001706:Biopsy; D004164:Diphosphonates / Q000627:therapeutic use; D018475:Head-Down Tilt / Q000009:adverse effects*; D006801:Humans; D017543:Iliac Aneurysm; D007085:Ilium / Q000033:anatomy & histology* / Q000166:cytology*; D008297:Male; D010024:Osteoporosis / Q000503:physiopathology*; D013026:Space Flight
chemical_list: D004164:Diphosphonates