Although the incidence of IVD injury is higher in astronauts compared to a matched control group not involved in spaceflight, the risk for IVD injury due to spaceflight still requires evidence. The 2009 NASA Research Announcement was utilized to solicit and select proposals to gather data to increase understanding as to the etiology of IVD injury due to spaceflight. Once data are collected to describe spaceflight effects on IVD morphology and the contribution from risk factors, the data will be presented to the Human System Risk Forum to decide if countermeasures need to be developed.
Present state of knowledge
There is an increased incidence of back pain expressed by crewmembers in space. In addition, herniated IVDs have been diagnosed in returning astronauts (both short-duration and long-duration) on landing day, and after varying periods of time in the postflight period. Such injuries in astronauts, however, may be related to their careers as aviators (either high performance jet pilots and/or helicopter pilots), although a recent probability assessment for disc herniation in astronauts, presented at a Human Research Program Investigator Workshop (2015) revealed that demographics (gender, height, weight) or previous career as a high performance jet pilot influenced the risk., The evidence of IVD injuries, however, raises the concern that astronauts may be at increased risk during exploration missions following a prolonged sojourn.
Mechanical unloading with space flight is associated with distortions in IVD morphology, with alterations in biochemistry (proteoglycan and collagen content) and with reduced biomechanical forces of muscles. Collectively, reports in the literature suggest that adaptation to the space environment can directly or indirectly induce back pain and may increase the risk for injury when crewmembers are re-subjected to gravity enhanced mechanical forces and torques. Back pain is commonly reported by crewmembers during spaceflight and a chart review of 321 astronauts revealed an increased risk for IVD injury in astronauts following spaceflight, when compared to age-matched control subjects. This review suggests that astronauts may be at increased risk for injury during exploration missions. Space-adapted IVDs might be at risk for injury when reloaded during the performance of mission tasks or when subjected to high G forces with entry and landing; this in-mission risk, however, has not been well defined due to limited descriptions of spaceflight-induced changes to the intervertebral unit.
Integration/Unique Aspects: Data share with Spinal Ultrasound (Dulchavsky PI) study.
1. Determine the accuracy of musculoskeletal (MSK) ultrasound in characterizing the normal and microgravity associated changes in the vertebral unit.
2. Investigate the human factors, level of experience, and training necessary to perform focused cervical and lumbar vertebral MSK ultrasound in microgravity with inexperienced ultrasound operators in parallel with expert operators.
3. Determine the anatomic changes in the vertebral unit during long duration spaceflight with astronaut performed vertebral ultrasound.
Integration/Unique Aspects: Data share with IVD post-spaceflight study (Hargens PI).
The Disk Damage Countermeasure study will validate the intervention (TBD) identified in the Disk Damage Assessment study as part of the HHC Integrated Countermeasure Suite.
Integration/Unique Aspects: This study will be integrated with other HHC studies as part of the HHC Integrated CM Suite and will follow the Disk Damage Assessment study.
Integration/Unique Aspects: Obtain data from LSDA/LSAH.