Intervertebral disc swelling demonstrated by 3D and water content magnetic resonance analyses after a 3-day dry immersion simulating microgravity
Résumé
Background Vertebral deconditioning is commonly experienced after space flight and
simulation studies. Disc herniation (DH) is quadrupled after space flight.
Purpose The main hypothesis formulated by the authors is that microgravity results in
intervertebral disc swelling.
Study Design The aim of the study was to identify the morphological changes of the spine and
their clinical consequences after simulated microgravity by 3-day dry immersion (DI).
The experimental protocol was performed on 12 male volunteers using magnetic resonance
imaging and spectroscopy before and after DI.
Methods All the experiment was financially supported by CNES (Centre national d’études
spatiales i.e. French Space Agency).
Results We observed an increase in rachis height of 1.5 ± 0.4 cm and a decrease in curvature,
particularly for the lumbar region with a decrease of -4 ± 2.5°. We found a significant
increase in intervertebral disc (IVD) volume of +8 ± 9% at T12-L1 and +11 ± 9% at L5-S1.
This phenomenon is likely associated with the increase in disc intervertebral water content
(IWC), 17 ± 27%. During the 3 days in DI, 92% of the subjects developed back pain in the
lumbar region below the diaphragmatic muscle. This clinical observation may be linked to the
morphological changes of the spine.
Conclusions The morphological changes observed and, specifically, the disc swelling caused
by increased IWC may contribute to understanding disc herniation after microgravity
exposure. Our results confirmed the efficiency of the 3-day DI model to reproduce quickly the
effects of microgravity on spine morphology. Our findings raise the question of the subject
selection in spatial studies, especially studies about spine morphology and reconditioning
programs after space flight. These results may contribute to a better understanding of the
mechanisms underlying disc herniation and may serve as the basis to develop
countermeasures for astronauts and to prevent IVD herniation and back pain on Earth.