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IMM

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?

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.

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.

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.

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.