Poster E2 - Impact of Microgravity on Astronauts' Vertebral Bone and Muscle Health

Friday, October 25, 2024

10:00 AM - 11:00 AM EST

Location: Exhibit Hall E, F & G

Presenting Author(s)

Kyle A. Thrush

Student
Liberty University and Department of Biomedical Engineering at Wake Forest University School of Medicine
Leacock-Leola-Bareville, Pennsylvania, United States

Co-Author(s)

Muzammil Mumtaz, PhD

Postdoctoral Research Fellow
Wake Forest University School of Medicine, United States
TJ

Thomas Jeong

Graduate Research Associate
Wake Forest School of Medicine, United States
Luis Poveda, MS (he/him/his)

Graduate Research Associate
Wake Forest School of Medicine, United States
Diana A. Madrid, MS (she/her/hers)

PhD Student
Wake Forest University School of Medicine, North Carolina, United States
KD

Karan Devane, PhD

Research Assistant Professor
Wake Forest University School of Medicine, United States

Primary Investigator(s)

AW

Ashley Weaver, PhD

Associate Professor
Wake Forest School of Medicine, United States

Introduction: Spaceflight introduces unique forces and stresses on the body not only during takeoff and reentry but also while in space. Because of the microgravity experienced in space, bones, and muscles require different workloads compared to those on Earth. A decrease in musculoskeletal strength during a mission can result in injuries upon reentry or over time. Computed tomography (CT) and magnetic resonance imaging (MRI) scans were taken before and after 9 astronauts’ missions to the International Space Station. To determine the significance of spaceflight on the vertebral bone and muscle health of astronauts, these scans were utilized to model and test the vertebral body strength of the C3 and L1 vertebrae through finite element (FE) computational modeling. Muscle cross-sectional area (CSA) in the lumbar and cervical regions was used to additionally correlate bone strength increases or decreases before and after spaceflight.

Materials and

Methods: CT scans with a bone calibration phantom were acquired pre-flight and post-flight. Subject specific segmentations were created from the CT scans to generate 3D models of each L1 and C3 vertebra after which a voxel-based mesh was created using an in-house Python script to perform FE analysis. Each mesh element was assigned material property based on the bone mineral density calibrated from each CT scan voxel. Subject specific segmentations were also used to create form-fitting impactors on the superior surface of each vertebral body. A local coordinate system was defined to dictate the directional displacement of the impactor to be normal to the superior endplate of the vertebra. The bottom surface of the vertebra was constrained, and the impactor compressed the vertebral body at 0.15 mm/s. The load was applied until a 2% decrease in the vertebral body height was achieved, indicative of failure. The resultant force was measured at the time taken to reach failure to determine the vertebral strength. Lumbar and cervical muscle segmentation of MRI scans were conducted at the mid-intervertebral disc level which maximized the CSA of each muscle. Descriptive statistics were computed for the pre-to-postflight changes in vertebral strength and muscle CSA using a t-test with a significance level of 0.05. Associations between the pre- and post-flight vertebral strength and CSA of the lumbar and cervical muscles were also made.

Results, Conclusions, and Discussions: Changes in L1 and C3 vertebral strength as well as lumbar and cervical muscle CSA varied from subject to subject. The average±SD normalized percentage change in L1 vertebral strength per month was 0.26±1.11% with the greatest increase of 2.89% and a decrease of –1.07%. The average normalized percentage change in C3 vertebral strength per month was 0.10±0.47% with the greatest increase of 0.84% and a decrease of –0.42%. The average normalized percentage change in lumbar muscle CSA per month was –1.81±2.92% and cervical muscle CSA per month was 16.94±26.03%. No statistical significance was found between pre- and post-flight vertebral bone strength or lumbar and cervical muscle CSA (all p>0.05). No significant linear trend or Pearson correlation was found between the changes in L1 vertebral strength and lumbar muscle CSA (r=-0.052; p=0.087). Additionally, no significant linear trend or Pearson correlation was found between the changes in C3 vertebral strength and cervical muscle CSA (r=-0.32; p=0.090). When applying a voxel-based mesh FE analysis on the L1 and C3 vertebrae, no significant correlation between vertebral strength before and after spaceflight was found. MRI muscle CSA measurements indicated no statistical significance from pre-to-postflight. Comparing vertebral strength and muscle CSA indicated an insignificant negative correlation between L1 vertebral strength and lumbar muscle CSA and between C3 vertebral strength and cervical muscle CSA. Astronauts are trained to exercise while in space to reduce the effects of microgravity on their musculoskeletal health. Depending on a given astronaut’s level of training before, during and after spaceflight, musculoskeletal health may change over time or remain relatively constant.

Acknowledgements (Optional): This study was funded by a NASA Human Research Program grant (NNX16AP89G) and NSF REU Site award #1950281.
This project was supported in part by the Wake Forest Summer Research Internship Program in the Department of Biomedical Engineering at Wake Forest University School of Medicine.