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Fracture Healing in Haversian Bone under Conditions of Simulated Microgravity (NNX11AQ81G)
Principal Investigator
Research Area:
Biomedical countermeasures
Species Studied
Scientific Name: Ovis aries Species: Sheep

There is a need for information regarding hard and soft tissue healing in microgravity environments, and if impaired healing exists, what countermeasures can be called upon to enhance healing. Research on fracture healing using the rodent hindlimb suspension model shows healing is impaired in simulated microgravity, while clinical research shows that moderate, early mechanical loading caused by weight bearing induces osteogenesis and aids in repair of bone fracture. Further research is needed to determine what loads, if any, should be applied during space flight to promote fracture healing.

Most ground-based microgravity models utilize rodent hindlimb suspension to simulate how reduced loading affects isolated physiologic systems. Unfortunately, results derived from these studies are difficult to directly translate to the human condition due to major anatomic and physiologic differences between rodents and humans. Specifically, the differences in rodent and human bone structures become increasingly important when studying orthopaedic issues such as bone maintenance and healing during space flight. For example, the basic microstructure of rodent bone, known as "plexiform" bone, lacks the osteons (Haversion systems) that are the main micro-architectural feature of human cortical bone. Furthermore, it is known that the osteogenic and healing potential of rodent bone far exceeds that of adult human tissue.

Due to these limitations in current ground-based microgravity models, there exists a need to develop a ground-based, large animal model of fracture healing in simulated weightlessness that more closely approximates the human condition as has been done in the first year of this study. This animal model should be capable of simulating a wide spectrum of microgravities and able to investigate exercise protocols that may aid in the optimization of the fracture healing cascade.

Four specific aims were defined to meet these goals:

  1. Develop a ground-based large animal model of bone unloading in order to simulate full weightlessness;
  2. Interrogate the effects of a simulated microgravity environment on bone fracture healing in a large animal model;
  3. Develop a computational model of weightbearing in ovine bone under different experimental conditions in order to characterize the loads experienced by the fracture site; and
  4. Develop treadmill protocols that enhance bone fracture healing in the presence of simulated microgravity.

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Gadomski BC, McGilvray KC, Easley JT, Palmer RH, Ehrhart EJ, Haussler KK, Browning RC, Santoni BG, and Puttlitz CM. An in vivo ovine model of bone tissue alterations in simulated microgravity conditions. Journal of Biomechanical Engineering. 2014. February; 136(2):021020. [DOI]

Gadomski BC, McGilvray KC, Easley JT, Palmer RH, Santoni BG, and Puttlitz CM. Partial gravity unloading inhibits bone healing responses in a large animal model. Journal of Biomechanics. 2014. September 22; 47(12):2836-42. [DOI]

Lerner ZF, Gadomski BC, Ipson AK, Haussler KK, Puttlitz CM, and Browning RC. Modulating tibiofemoral contact force in the sheep hind limb via treadmill walking: Predictions from an OpenSim musculoskeletal model. Journal of Orthopaedic Research. 2015. August; 33(8):1128-33 [DOI]

Gadomski BC, McGilvray KC, Easley JT, Palmer RH, Jiao J, Li X, Qin Y-X, and Puttlitz CM. An investigation of shock wave therapy and low-intensity pulsed ultrasound on fracture healing under reduced loading conditions in an ovine model. Journal of Orthopaedic Research. 2018. March; 36(3):921-9. [DOI]

Gadomski BC, Lerner ZF, Browning RC, Easley JT, Palmer RH, and Puttlitz CM. Computational characterization of fracture healing under reduced gravity loading conditions. Journal of Orthopaedic Research. 2016. July; 34(7):1206-15. [DOI]

Adaptation, physiological
Bone density
Cell count
Exercise test

Data Information
Data Availability
Archive is complete. Data sets are not publicly available but can be requested.
Data Sets+ Request data

Bone formation rate
Bone volume
Fracture gap, hydrostatic stress
Fracture gap, principal strain
Fracture healing cascade
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Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
Ground 05/01/2009 In Progress

Human Research Program (HRP) Human Research Roadmap (HRR) Information
Crew health and performance is critical to successful human exploration beyond low Earth orbit. The Human Research Program (HRP) investigates and mitigates the highest risks to human health and performance, providing essential countermeasures and technologies for human space exploration. Risks include physiological and performance effects from hazards such as radiation, altered gravity, and hostile environments, as well as unique challenges in medical support, human factors, and behavioral health support. The HRP utilizes an Integrated Research Plan (IRP) to identify the approach and research activities planned to address these risks, which are assigned to specific Elements within the program. The Human Research Roadmap is the web-based tool for communicating the IRP content.

The Human Research Roadmap is located at:

+ Click here for information of how this experiment is contributing to the HRP's path for risk reduction.

Additional Information
Managing NASA Center
Johnson Space Center (JSC)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Pamela A. Bieri
Institutional Support
National Aeronautics and Space Administration (NASA)
Proposal Date
Proposal Source
2010 Crew Health NNJ10ZSA003N