Cervical and thoracic intervertebral disc hydration increases with recumbency. a study in 101 healthy volunteers

Publication date: Available online 9 June 2017
Source:The Spine Journal
Author(s): Daniel L. Belavy, Matthew Quittner, Yuan Ling, David Connell, Timo Rantalainen
Background contextVariation in water content and size of the lumbar intervertebral discs (IVDs) is known to occur due to recumbency and has been associated with lumbar IVD herniation risk through the impact of IVD hydration on tissue mechanical properties. It is not clear if similar changes in the cervical or thoracic IVDs occur with recumbency.PurposeDetermine whether increases in hydration of thoracic and cervical IVDs occur with short-duration recumbency.Study Design/SettingTest-retest design in a magnetic resonance imaging facilityMethodsWe examined expansion of all IVDs in the spine in 101 healthy individuals (54 females) aged 25-35 yrs on sagittal T2-weighted magnetic resonance images after a mean of 26.9 minutes lying in the scanner bore. All scans were performed after midday. To mitigate false positives, p-values were adjusted by the false discovery rate method. There was no external funding or potential conflicts of interest for this study.ResultsAt the end of lying, cervical spine IVD volume increased by mean(SD) 2.6(5.6)% (p<0.001). This compared to a 1.0(4.0)% (p=0.024) increase in upper thoracic spine IVD volume and a 2.0(3.2)% (p<0.001) increase at the lower thoracic spine. Lumbar IVD volume increased by 1.2(2.4)% (p<0.001). C2/3 IVD volume (+4.1[13.8]%, p=0.011) increased the most at the cervical spine, followed by C5/6 (+3.9[9.8]%, p<0.001) and C3/4 (+3.8[13.5]%, p=0.014). Lumbar IVDs with higher degeneration grades showed more expansion with lying (p=0.0031).ConclusionsWe established that cervical and thoracic IVD volume increases with recumbency. We expect diurnal variation in cervical and thoracic IVD hydration will occur in the general population, with greater cervical and thoracic IVD hydration and size upon rising in the morning.



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