What will happen if an astronaut falls during a
spacewalk on the moon? Is a bone fracture likely to occur? Can this
injury be treated effectively? What if the same event occurs on Mars?
What will be the consequences?
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Astronauts
traveling and working in hypo-gravity environments
experience unique risks to their skeletal structures
(Credit: NASA). |
In addition to the bone fracture and renal
stone simulations, Glenn is also developing a module predicting
the likelihood that an astronaut will need a sleep aid due
to sleep schedule disruptions. Glenn is also beginning a
model quantifying the likelihood and severity of a head injury,
and will conduct additional analyses quantifying the expected
incidence rate of glaucoma, stroke, and seizure. The IMM
is an ongoing effort to quantify risks to astronauts, guide
mission planners in improving safety, and helping improve
fitness for duty standards.
Bone Fracture
Treating medical conditions in space can
be especially challenging. The absence of gravity can make
stabilizing an injured body very difficult. The limited space
within the spacecraft does not allow for excess equipment
to be stored for possible medical treatment if the risk of
injury is low. Decisions must be made quickly using the available
resources to preserve an astronaut’s life.
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Falling
during extravehicular activity results in a unique
risk of leg (Femoral Neck) fracture (Credit: NASA). |
Glenn is using clinical and biomechanical
analyses of bone fractures that occur on Earth to develop
a bone fracture risk module. Using this computer model, the
data from the analyses on Earth will then be translated to
conditions on the moon and Mars.
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Ex
vivo test of Femoral Neck bone fracture strength in
a bone exhibiting reduced levels of bone mineral density
(Credit: Bonnaire, et al, INJURY, 2002). |
A significant effect of microgravity is
the reduction of an astronaut’s bone mineral density
and bone strength, which can make his/her bones more susceptible
to fracture. Though gravity is reduced in space, an astronaut
could still fall and injure him/her self during a space walk
on the moon or Mars. Space suits used for extra-vehicular
activity (outside the spacecraft) are very heavy and dramatically
increase the overall mass of the astronaut.
Glenn is using clinical and biomechanical
analyses of bone fractures that occur on Earth to develop
a bone fracture risk module. Based on current flight experience
and the best Earth-based clinical evidence, this model is
designed to estimate the likelihood and health impact of
fractures during exploration missions. Using this computer
model, the data from the analyses on Earth will then be translated
to conditions on the moon and Mars.
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The
IMM bone fracture risk module predicts the skeletal
loading potential during regular astronaut activities
(graph1) and estimates the probability that these will
result in a fracture (graph2). (Data shown represents
a Mars mission with 6 month travel to Mars and 500
days on the surface.) |
Glenn recently extended this module to quantify
the probability of wrist fractures on the International Space
Station (ISS). Additionally, Glenn used a space suit simulator
to quantify the attenuation likely to be provided to the
hip by the suit in the case of a fall to the side.
Kidney Stones
As another part of the Integrated Medical
Model, Glenn is also developing a model to assess the risk
of renal (kidney) stone formation during long duration exploration
missions as well as after an astronaut has returned to Earth.
This condition can occur due to an increase of calcium in
the blood, which is a result of bone loss during space flight.
As an additional complication, astronauts become dehydrated
in microgravity, which may also increase the risk for kidney
stone formation.
As part of the integrated model, the
bone fracture wrist and renal stone models will help NASA predict
the likelihood of occurrence as well as the outcome of treatment.
In the future, Glenn plans to create a simulation model to
help predict behavioral health changes in astronauts during
and after a mission. The complete integrated model will establish
improved safety guidelines and fitness for duty standards for
astronauts.
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