Understanding The Recovery Of The Intervertebral Disc

Picture from Wikipedia

I came across a recent paper (Feki et al, 2024) about the positions which help our intervertebral discs recover and heal when we sleep. I have written at least 5 articles on intervertebral discs. This is definitely still a topic that I get questions from most often among my friends and patients alike. Almost every single one of my friends and patients are fearful of having a 'slipped intervertebral disc' whenever they have low back pain (LBP). The intervertebral discs (IVD) have a really bad reputation for causing significant pain and disability in many people.

Here's a quick review if you did not read those 5 articles.

The IVD consists of a very tough outer layer called the annulus fibrosis (AF). It is made of of several layers of fibrocartilage consisting of Type I and II collagen fibers. The AF protects the soft, gel-like substance in the middle known as the nucleus pulposus (NP). The NP helps distribute pressure evenly across the IVD and prevent excessive forces on the spine.

See how thick the AF is from the picture above? Here's something else you need to know. There is a cartilaginous endplate between the AF and the vertebra (the spine). The endplates hold the IVD in place. It allows load to be spread evenly and to provide attachment to the IVD. This creates a super strong connection to the AF making it impossible for the IVD to 'slip' out of position.

Yes, our discs are actually very strong and hardy. How strong are our IVD's? In a published study on thoracic discs in the young (28 years old plus minus 8 years) , it took about 740 pounds of force to compress the disc height 1 mm. For the older subjects (70 years young plus minus 7 years), it took almost 460 pounds of force. Note that these are on cadavers with the muscles and bones cut away (Stemper et al, 2010).

The IVD's withstand a whole variety of complex forces in our daily activities and also when we exercise. This can lead to significant structural changes in terms of volume, area and height of the intervertebral disc. It can lead to an increase in disc stiffness and a decrease in interdiscal pressure.

In order for your discs to remain healthy and strong, it is dependent on a recovery phase which serves to prevent premature disc degeneration. This happens during a period of nocturnal rest i.e. when you sleep at night.

This phenomenon of disc recovery has been documented extensively through many studies using MRI and intradiscal pressure measurement. Fluid dynamics (water content) within the disc are considered a primary factor in recovery, while it's intricate multiscale structure and viscoelastic (behaving with both liquid-like and solid-like) properties also play key roles.

Feki et al (2024) in their review collated, analyzed and evaluated the existing in vivo (human) and in vitro (in controlled environments) on this topic to provide a comprehensive understanding of this recovery process to enable future advancements in medical treatment and biomedical enginerring solutions to enhance the natural recovery processes of intervertebral discs.

As it is a very long (and complex) review article (Feki et al, 2024), I am simply highlighting the optimal recovery positions (pictured below) for intervertebral disc rehydration. 

Picture from Feki et al, 2024

(a) prone (b) modified press up/ push up position (c) supine with under knee and back support

(d) and (e) side lying with lumbar flexion with pillows between legs

(f) and (g) side lying with and without manual distraction

(h) 50 degrees gravity assisted position (i) 110 degrees supported sitting

(j) inclined sitting with lumbar support

So, you see from the pictures that some of the supposedly 'poor' posture/ positions you were told, are actually good for your intervertebral discs.

References

Feki F, Zairi F, Tamoud A et al (2024). Understanding The Recovery Of The Intervertebral Disc: A Comprehensive Review Of In Vivo And In Vitro Studies. J Bionic Eng. DOI: 10.1007/s42235-024-00542-2

Fournier DE, Kiser PK, Shoemaker JK et al (2020). Vascularization Of The Human Intervertebral Disc: A Scoping Review. JOR Spine. 15: 3(4): e1123. DOI: 10.1002/jsp2.1123.

Stemper BD, Board D et al (2010). Biomechanical Properties Of Human Thoracic Spine Disc Segments. J Craniovert Junct Sp. 1(1): 18-22. DOI: 10.4103/09774-8237.65477