Space flight missions over 6 months significantly increase the risk of shoulder pathology and rotator cuff tears

Abstract

Background

The purpose of this study was to determine risk of shoulder injury in astronauts returning from space flight and highlight the need for further exploration of risk factors and preventative strategies.

Methods

Using The Lifetime Surveillance of Astronaut Health epidemiology database at National Aeronautics and Space Administration, a retrospective cohort study was conducted to assess the effect of space flight mission duration on rate of shoulder injury among astronauts. Inclusion criteria were all astronauts who participated in space flight regardless of age or space flight mission time. Exclusion criteria were all injuries occurring greater than 5 years following return to Earth. Patient demographics were compared between injured and noninjured cohorts with stratification by shoulder pathology.

Results

Of total 242 astronauts, 22 sustained a shoulder injury (9.09%) and 220 did not sustain a shoulder injury (90.91%). Average age of the noninjured cohort was 46 years and average age of the shoulder pathology cohort was 48 years. There were 8 rotator cuff tears, 5 cases of shoulder impingement, 5 shoulder contusions, and 4 rotator cuff sprains/strains. Compared to the noninjured cohort, incidence of all shoulder pathology was significantly associated with space flight missions greater than 6 months (P < .001). Rotator cuff tears in isolation, as well as rotator cuff and impingement pathology combined, were significantly associated with greater than 6 months in space flight (P < .001).

Conclusion

Space flight missions greater than 6 months were associated with increased risk of shoulder injury, especially rotator cuff tears. However, specific aspects of space flight that increase risk remain understudied. Shoulder injuries upon return to gravitational environments have the potential to negatively impact astronaut health and possibly jeopardize mission success, particularly as upper-extremity mobility is vital in the microgravity environment of space.