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Summary - Bone in Microgravity Environments: "Houston, we have a problem"
| Content Provider | Semantic Scholar |
|---|---|
| Author | Chair, Session Bloomfield, Susan A. |
| Copyright Year | 2006 |
| Abstract | With the recent change in leadership at NASA, a sea change in research priorities at the agency has occurred. Monies once dedicated to life science research have been dramatically reduced in order to provide resources for development of a new Crew Exploration Vehicle, designed to replace the aging shuttle vehicles. Bone loss during spaceflight, once considered a "show-stopper" when long duration exploration missions were more central to NASA planning, no longer commands center stage. The prevailing sentiment appears to be that changes in bone with short-term missions to the International Space Station (ISS) or to the lunar surface will be too small to impact on mission outcomes and will be successfully mitigated with current exercise countermeasures, perhaps in combination with bisphosphonate therapy. Strategies to minimize bone loss with long-term spaceflight (e.g., 2-3 years’ duration) may not be necessary 10 years from now some speculate, given projections of improved pharmacological treatments or even the integration of artificial gravity on board exploration vehicles. It behooves bone biologists to carefully define the specific challenges to bone integrity incurred during (or following) the shorter 3- to 6-month Lunar or ISS missions planned for the next 10 years. Data presented during this session illustrate well that, with reference to microgravity effects on bone integrity, there is too much of "we don’t know what we don’t know". The key health risk to working astronauts associated with the reduced bone mineral density (BMD) and altered bone geometry is bony fracture. A hip fracture could be devastating to astronaut health as well as mission objectives, and difficult to treat. Data recently published by speaker Thomas Lang 1 demonstrated significant decrements in BMD of femoral neck cancellous bone and dramatic thinning of the cortical shell in ISS astronauts; estimates are that 90% of the bone loss observed resulted from endocortical resorption. Using a patient-specific finite element modeling approach 2 , Lang and colleague Joyce Keyack have performed safety factor analyses to predict the risk of fracture given these carefully quantified changes in astronaut crew members. The challenge of these analyses, of course, lies in the many assumptions that must be made to perform the modeling, introducing increasing levels of uncertainty. Although these analyses predict no increase in fracture risk for a fall to the side while on the Mars surface (3/8 g), they do reveal a significant increase in fracture risk in more than half of the astronauts on whom CT data were collected for a fall to the side upon return to the 1 g of Earth. In fact, the average factor of risk for all crew members studied (presuming a fall to the side in 1 g) matched that estimated for 70- to 80-year-old postmenopausal women. Given the documented perturbations in dynamic postural stability post-spaceflight, falling risk is presumably increased in the first days or weeks upon return to Earth, further increasing risk of fracture in the postflight period. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.ismni.org/jmni/pdf/26/08BLOOMFIELD_summary.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
