title: The contribution of trabecular bone to the stiffness and strength of rat lumbar vertebrae.
abstract: METHODS
  In vitro compressive load-displacement experiments on intact rat lumbar vertebrae and on the same vertebrae after part of their trabecular bone was removed.
  
  
  OBJECTIVE
  To determine the contribution of the trabecular bone component to the stiffness and strength of rat lumbar vertebrae.
  
  
  BACKGROUND
  Vertebral fractures are common in the aging population, possibly resulting from the deterioration of the mechanical properties of vertebral bone. Studies of the contribution of trabecular bone to the mechanical behavior of whole vertebra were published, but yielded mixed results. Here, we propose a novel optical metrology approach to address this important question.
  
  
  METHODS
  The bodies of intact rat lumbar vertebrae and the bodies of the same vertebrae after part of their trabecular bone was removed were loaded within their elastic region in a wet environment. The amount of trabecular bone removed was determined by micro-computer tomography scanning. Deformation maps of the dorsal vertebral surface of the intact and manipulated vertebrae were obtained using an optical metrology method, and compared. Intact and manipulated vertebrae were also loaded to failure in compression and their strengths and stiffness were compared.
  
  
  RESULTS
  The preferred trabecular orientation was found to be along the anterior-posterior axis, which is similar to humans. Removal of up to 42% of the trabecular tissue in the intact vertebrae did not significantly affect lumbar vertebral stiffness. However, removal of even smaller amounts of the intact trabecular tissue significantly reduced vertebral strength.
  
  
  CONCLUSIONS
  Trabeculae in rat lumbar vertebrae fulfill an important role in failure resistance (strength), but have little or no effect on the deformational behavior (stiffness) of the bone. These results differ from previous results we reported for rat femora, where removal of trabecular bone surprisingly increased the stiffness of the whole bone, and suggest that trabecular tissue may have different functions depending on anatomic location, bone function and morphology, and mode of loading.
authors.affiliation: Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel. mbarak@fas.harvard.edu
authors.forename: Meir Max
authors.initials: MM
authors.lastname: Barak
authors.forename: Steve
authors.initials: S
authors.lastname: Weiner
authors.forename: Ron
authors.initials: R
authors.lastname: Shahar
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology; D019245:Compressive Strength / Q000502:physiology; D004548:Elasticity / Q000502:physiology; D005260:Female; D008159:Lumbar Vertebrae / Q000502:physiology*; D023421:Models, Animal; D009068:Movement / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013131:Spine / Q000502:physiology*; D014129:Trabecular Meshwork / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology; D055114:X-Ray Microtomography / Q000379:methods