Shoulder Injury and Surgery Patterns Among Astronauts Across Spaceflight Phases and Mission Operations: An Analysis of 677 Injuries from 1981 to 2024.

Abstract

Shoulder injuries are the most frequently reported musculoskeletal condition among astronauts, occurring across all spaceflight mission phases. With rising extravehicular activity (EVA) demands, a detailed understanding of injury patterns is critical. Prior studies have linked prolonged microgravity exposure to post-flight shoulder pathology but have not comprehensively characterized large-scale epidemiologic trends, phase-specific timing, or the influence of cumulative training exposures. Therefore, this study aimed to: (1) characterize overall prevalence, identify the top 20 diagnoses, and report the 5 most common surgical procedures; (2) compare injury distributions across spaceflight phases, including a post-flight sub-analysis stratified by <6 versus ≥6 months of microgravity exposure; and (3) determine associations between Neutral Buoyancy Laboratory (NBL) and EVA exposure durations and injury timing. A retrospective review of the Lifetime Surveillance of Astronaut Health database identified musculoskeletal shoulder injuries and surgeries between 1981 and 2024 among NASA astronauts. Inclusion criteria required injuries to occur ≤5-years of a mission and be related to operational duties. Temporal mapping used days relative to mission timelines. Astronaut demographics, diagnoses, surgical procedures, and cumulative NBL and EVA exposure durations were collected. Chi-square tests assessed phase-specific injury distributions. Wilcoxon rank-sum tests compared post-flight injury timing in astronauts with <6 versus ≥6 months of microgravity exposure. Linear regression models evaluated associations between cumulative NBL and EVA hours and injury timing. A total of 677 shoulder injuries and 25 surgical interventions were identified. The post-flight phase accounted for most injuries (64.8%), followed by pre-flight (33.6%) and in-flight (1.6%). The top diagnoses included tendinopathy (8.9%), osteoarthritis (7.8%), and rotator cuff injury (7.8%), with rotator cuff repair (32.0%) and arthroscopic debridement (28.0%) as the most common surgeries. Astronauts with ≥6 months of microgravity exposure experienced significantly earlier post-flight injury onset (P=0.040). Greater cumulative NBL exposure was associated with earlier pre-flight (R²=0.233; P=0.007) and post-flight injury timing (R²=0.119; P=0.009). Over 43 years, astronauts sustained 677 shoulder injuries and 25 surgeries, with post-flight injuries significantly more frequent, and those exposed to ≥6 months of microgravity experiencing earlier onset. Increasing NBL exposure was also associated with accelerated post-flight injury timing, suggesting cumulative training stress as a key driver, an effect EVA exposure may mirror as lunar missions extend duration and frequency. These findings reinforce the need for targeted pre-flight conditioning, exposure-calibrated training thresholds, and post-flight surveillance models to preserve shoulder function and maintain mission readiness in next-generation spaceflight.