Astronauts have stated increased incidence of back pain during spaceflight and herniated intervertebral discs (IVD) have been diagnosed after the return of Skylab and Shuttle spaceflight participants.
These conditions and symptoms may stem from previous back injuries, but evidence of IVD injuries raises concerns that astronauts are at increased risk of intervertebral disk damage during scenario loading experienced during exploration missions (reentering the gravitational field and activities on the surface planet). To date, flight data related to potential back injury has focused on spinal extension and the steady-state effect of mechanical disassembly on intervertebral discs.
Video Intervertebral disc damage and spaceflight
Causes and recent studies
Sixty-eight percent of early astronauts, by 1991, who flew in space had reported general back pain. Pain is considered the most painful during early flight and decreases as the flight progresses.
Possible causes of back pain in flight may be associated with:
- vertebral column elongation due to the inherited gravity force
- Weakness of core and back muscles includes space-induced atrophy of the spine
- increase of proximal facet joint stretch capsule
- final vertebrate bone initialized
- disk degeneration
- herniation of annulus fibrosus
Regardless of the cause, astronauts may have a higher risk of intervertebral disc injury or damage when swollen discs are subjected to excessive force or torque while working on the planet's surface. Mission exploration on the surface of the planet can also introduce feasibility issues that can lead to excessive torsional stress, a risk factor set for the herniation of the annulus fibrosus.
Currently, there is minimal inner and post-flight data that will characterize changes in intervertebral disks in crewmembers to assess how these changes will affect disks for injuries under re-loading. Herniated nucleus pulposus is known to occur in aviators that are exposed to high G-force environments and have occurred in astronauts after the mission.
The relative risk level of recent intervertebral disk damage has been investigated, but currently there is no evidence linking the origin of intervertebral disk damage with disc changes as a result of spaceflight.
Based on uneven weighted intervertebral disk network analysis, biochemical changes to the nucleus pulposus during spaceflight will affect the ability of osmotic pressure and pulposus nuclear elasticity to withstand compressive loads. Biochemical changes in intervertebral discs of crew members after flight have not been identified, but there is in vitro study with cow cartilage explants to use magnetic resonance technology to correlate changes in intervertebral proteoglycan disc content with T 1 rho proton relaxation. This biomarker will allow non-invasive monitoring of proteoglycan content as a method for assessing the biochemical impact of weights.
Computer-based simulation information
The study of applying Finite Element Modeling (FEM) to IVDs under osmotic pressure under the spatial environment suggests that the emergence of a gap in IVD experiencing lower osmotic pressure will increase the risk of IVD for injury. FEM is also used to indicate that static loading alone will not promote fluid extrusion from swollen IVD at rest or lack of weight. The fluid expulsion will increase as the loading frequency increases.
Future work in this simulation capability needs to be pursued.
Risk in the context of operational exploratory scenarios
Defines the cause of back pain and IVD injury because spaceflight is still an open problem. Assumptions and presumptions considered include:
- the absence of axial and force loading due to atrophy of the back muscles affecting the crew to IVD injury
- the risk of destructive change to return and the structure of IVD and biochemistry will increase with increasing periods that are not loaded in terms of weightlessness
- the risk of back injury and IVD damage will be greater with greater G power experienced during reentry, landing and surface activity
Maps Intervertebral disc damage and spaceflight
Evidence Spaceflight
During a 4 84 day Skylab mission, the elongation of an astronaut's spine is measured and recorded to 1/16 inch (Thornton, 1987). This study illustrates the asymptomatic height increase during a stable flight at 29 days. The total increase in total is 1.5 inches, measured at the end of the mission. This elongation is thought to be due to the expansion of intervertebral discs during unweighted (axial unloading). Astronauts also reported back pain on the landing day associated with a herniated intervertebral disk.
Astronaut chart review
A retrospective chart review to evaluate the incidence of intervertebral disc damage after some astronauts develop cervical or lumbar cervical pulmus nuclei in the immediate post-light period. This study specifically compares the incidence of intervertebral disk damage to astronauts with control populations adapted to the age of people who have never flown in space. This review should also clarify whether there is an increased risk of intervertebral disk damage because:
- exposed to high and low G environments
- a long time in abnormal posture
- changes in intervertebral disk structure due to expansion in the absence of axial loading
It is unclear whether changes due to spaceflight increase the risk of intervertebral disk damage because there is evidence that many of the previously wounded astronauts had some exposure to excessive G-forces such as high-performance pilot jets (6-20 G) or the vibrations of troops as helicopter pilots.
Pathophysiology of intervertebral disc injury after spaceflight has not been clearly identified. The expansion of the documented disk volume after the spaceflight, along with the intervertebral disc injury after reloading in Earth's gravity, suggests that the adaptive change of the intervertebral disc in the imbalance disrupts the balance between the osmotic pressure of the nucleus pulposus and the resistive collagen structure of the anuli. fibroxy, thereby reducing the ability of the intervertebral disk structure to retain exposure back to strength G. Repeated, previous exposure to excessive G strength in high performance jets may also weaken the intervertebral disk structure, especially in the cervical vertebra, increasing the vulnerability of this disc to damage. The relative risk of spatial induced spaceflight-induced intervertebral injury should be illustrated by comparing the absolute risk of astronaut populations with populations of terrestrial control groups with similar aviation histories.
Ground-based evidence
The change in the volume of the intervertebral disk is quantified by magnetic resonance imaging in response to various axial unloading scenarios. The cross-sectional area and the relaxation constant of transverse protons (T2) from IVD are the indices used to monitor adaptive changes of intervertebral discs to overnight breaks (greater than 5 weeks and 17 weeks) and after 8 days of spaceflight. The average expansion of IVD with bed rest seems to achieve a balance anywhere between 9 hours and 4 days of unloading with expansion ranging from 10-40% of baseline, pre-bed rest (average = 22%). There is a slight increase in T2 relaxation time relative to the increase in disk area. Recovery of IVD volume after disassembly is not systematically evaluated but Table 1 provides a relative comparison of the elapsed time in 1 G at which the measured IVD volume does not differ from the baseline measurement; the relative period of recovery appears to extend over the period of IVD adaptation to lower the load.
See also
- disc herniation
References
This article incorporates public domain material from the National Aeronautics and Space Administration document "Health and Human Performance Risk from Space Exploration Mission" (NASA SP-2009-3405).
External links
- Sonographic Astronaut Vertebral Examination (Spinal Ultrasound)
- NASA tapped a USF spinal injury expert. John Mayer
Source of the article : Wikipedia
0 Comments