Gap Fracture 1: We don't understand how the space flight environment affects bone fracture healing in-flight.
Last Published:  07/30/21 01:05:31 PM (Central)
Responsible Element: Exploration Medical Capability (ExMC)
Status: Closed
Closure Rationale
Sufficient knowledge exists with respect to the impact that the spaceflight environment might have on bone fracture healing. There is no clear evidence that there is a substantial clinical impact on fracture healing in spaceflight. Given that the likelihood of fracture occurrence in space is very low, there are no plans for further research in this area.
Closure Documentation:
No Closure Documentation Available
Initial State:

Because it is not ethical to study fracture healing in humans there is a reliance on animal models. However, clinical data (albeit limited and indirect) suggest that spaceflight changes the activities of bone cells that could detrimentally affect fracture healing (e.g., bone turnover markers indicate that turnover is uncoupled thereby impacting the remodeling of a fracture callus). There are enough ground-based, preliminary data to suggest that fracture healing is impaired when a rat limb is un-weighted (Midura et al. J Musculoskeletal Neuronal Interaction, 2006; Kirchen et al, Clin Orthop Relat Res, 1995; Durnova et al, Kosm Bio Aviakosm Med, 1991; Kaplansky et al, Physiologist, 1991). The consequence of a fracture to an astronaut and impact on mission success is variable depending upon, e.g., fracture site, conditions and complications. Evidence describing the impact of space fight on bone cells will inform Medical Operations as to the requirement for treatment options that could enhance fracture healing by directly influencing cell activities.

Interim Stages (Sequential):
  1. Characterize cellular and tissue hallmarks (bone histomorphometry and imaging data) of fracture healing in 0g versus 1g in animal models as influenced by spaceflight risk factors. (30%)
  2. Quantify time course of fracture healing 0g versus 1g in animals. (20%)
  3. Estimate/Quantify strength of healed bone by modeling and correlate to strength quantified by mechanical strength testing in animals. (30%)
  4. Seek interpretation/translation of effect humans for recommended Clinical Practice Guidelines (CPGs) by Research and Clinical Advisory Panel (RCAP). (15%)
  5. Submit recommendation to Medical Operations and Digital Astronaut for possible clinical validation. (5%)


Design animal studies to evaluate the impact of skeletal unloading on fracture healing to determine the target questions and treatment options, e.g., with mechanical loading, with pharmaceutical agents etc.
Target for Closure
Identification & quantification of cellular and tissue hallmarks/outcomes in fracture healing in 0g and 1g.
Risk Risk of Bone Fracture due to Spaceflight-induced Changes to Bone
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Multi-Disciplinary Research Plans

No Documentation Available