Recovery of bone microarchitecture and density four years after spaceflight: two case studies

Area of Science:

• Space medicine
• Skeletal physiology
• Human physiology

Background:

• Spaceflight poses significant risks to bone health.
• The long-term skeletal consequences of space missions require further investigation.

Purpose of the Study:

• To investigate bone microarchitecture, density, and remodeling up to 4 years post-spaceflight.
• To inform the development of countermeasures for bone loss during and after space missions.

Main Methods:

• Two case studies of astronauts undergoing long-duration spaceflight.
• High-resolution peripheral quantitative computed tomography (HR-pQCT) and dual X-ray absorptiometry (DXA) scans.
• Pre-flight and up to 48-month post-flight assessments.

Main Results:

• Both astronauts experienced significant tibial bone loss upon return.
• One astronaut showed radius bone loss, while the other did not.
• After 4 years, one astronaut fully recovered; the other had persistent trabecular deficits with cortical thickening.

Conclusions:

• Skeletal recovery from spaceflight is variable and can be prolonged.
• Tailored countermeasures and extended monitoring are crucial for optimizing astronaut skeletal health.
• Findings have implications for understanding mechanical unloading and reloading effects on bone.