About Intervertebral Discs

Picture from M.A. Adams et al, 2010

Having learnt in anatomy class (when I was a physiotherapy student) that our intervertebral discs (IVD) are avascular (has no blood supply), I was instantly surprised when recent research showed that it may not be totally true.

picture from springer link

A little anatomy lesson before I tell you more. Our IVD's are fibrocartilaginous joints that are thought to be the largest avascular structures in the human body. They are made up of three distinct and interdependent tissues. The outer most cartilage endplates are thin layers of hyaline cartilage that anchor the IVD to the adjacent vertebral bones. The vertebral end plates have plenty of blood supply and this allows for diffusion of nutrients into the IVD through the cartilage end plate.

The annulus fibrosus (AF) is a series of super strong well organized concentric lamellae of fibrocartilage that surround and protect the nucleus pulposus (NP) of the IVD. 

The NP is the innermost jelly like substance made up mainly of water and proteoglycans. The NP helps distribute pressure evenly across the IVD and prevent excessive forces loading the spine. This is what can herniate through the AF, causing what is commonly know as a 'slipped disc' or prolapsed intervertebral disc (PID).

A group of researchers performed a comprehensive *scoping review on peer-review publications on the blood supply of human IVD's excluding disc herniations. 22 out of 3122 articles found met the inclusion criteria of fetal to > 90 years old, various health status and both sexes using gross dissection, histology or medical imaging to assess if there is blood supply.

Consistent observations from this review were that there is no blood supply in the NP of the IVD throughout life. 

Both the cartilage endplates and AF have considerable blood supply during fetal development and in infants, but decreases over our lifespan. A common feature of the cartilage endplate was the presence of channels throughout the tissue, likely from the well vascularized vertebral endplate from the adjacent vertebrae. Between birth and ten years of age, there is a drastic decrease in blood vessels within these channels; which are not seen at all in adults.

However, there are blood vessels growing into the endplates and inner layers of the AF especially when there is damaged or disrupted tissue regardless of age. This is more common in older adults. Location of blood vessels are variable. 

It is thought that annular fissures or tears associated with degenerated discs are perhaps more conducive to the ingrowth of blood vessels since there is a loss of proteoglycans (a protein compound found in connective tissue) due to the healing process. Interestingly, there are also nerves found together with the blood vessels suggesting some patients may get more pain than others with such conditions.

Through this scoping review, we now know that the IVD is not entirely avascular as often thought and cited. This is great news for patients. We always knew that you can heal from a "slipped disc", but the discs having a blood supply means a better chance that it can heal from an injury.

Reference

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.

*A scoping review has a broader scope compared to traditional systematic reviews with correspondingly more expansive inclusion criteria.

* you can read more about slipped discs and how slipped discs can heal here.

Is Good Posture Just A Myth?

If 295 physiotherapists (from four countries) cannot even agree on which is the best sitting posture, then how can the average person know what is? 

Other than having the physiotherapists do a back beliefs questionnaire (BBQ), the above mentioned study had a range of nine sitting options ranging from slumped to upright sitting. 85 percent of the physiotherapists surveyed selected one of two postures as 'best', with one posture being selected more significantly than the other. 

However, those two frequently selected postures were very different to say the least. The physiotherapists who selected the more upright posture had more negative low back pain beliefs in the BBQ. The main differences were what constitutes what a 'neutral' spine is and what is the best sitting posture is.

If you are slouching at your desk, almost everyone will tell you to sit up straight and watch your back. This is especially so when bending forward or while lifting. Back in 2019, I first suggested that slouching while sitting is not necessarily bad for you, challenging society beliefs about posture and back pain. 

So many companies have spent money on ergonomic programs to prevent back pain. This would usually involve a health professional/ physiotherapist (trained in ergonomics) checking your office chair/ desk height, screen height/ position with respect to your keyboard/ mouse to ensure everything is lined up in a straight line.

However, there is very little evidence linking back pain to poor posture. Oops, this basically means a huge profitable industry on work place/ home office ergonomics has very little sound evidence. 

All the published research to date has shown that there is no relationship between any postural factors causing back pain. This includes the shape and curves of the back, asymmetries and how we use our backs.

Yes, if you already suffer from back pain, you may feel it more while sitting, especially for long periods. But sitting is not the cause of the back pain.

One of my patients told me that she just bought a two thousand dollar Herman Miller chair due to working from home 'causing' her back pain. It definitely helps with sitting up straight, however, it did not seem to help her back pain. That's why she still came to see me yesterday.

So, if you currently do not have neck/ back pain, you do not need to worry about your posture. If you do have pain, then your posture may affect it. Sitting for a sustained period is best avoided. The best ergonomic chair/ table will still give you pain. It is better to move more. Take breaks. Get advice and/or treatment to move with confidence and less pain.

References

O'Sullivan K, O'Sullivan P et al (2012). What Do Physiotherapists Consider To Be The Best Sitting Spinal Posture? Manual Therapy. 17(5): 432-437. DOI: 10.1016/jmanth.2012.04.007

Slater D, Korakakakis V et al (2019). "Sit Up Straight" : Time To Re-evaluate. JOSPT. 49(8): 562-564. DOI: 10.2519/jospt.2019.0610

Our spines have natural curves. It is not totally straight at all. You can see from the picture above that the neck is slightly concave, the chest area is convex while the lumbar (low back) region is again concave. In an ergonomic assessment, a 'good' posture usually refers to eliminating/ straightening out these curves.

Here are some common myths and facts about low back pain, slipped discs and your core muscles if you're interested in reading more.

Back Pain? Check The Psoas

See the how the Psoas attaches to the spine

Here's a patient who came to our clinic this past week complaining of perpetual low back pain. He seemed more frustrated because he had not been able to do his "normal" exercise for over two weeks. The patient is young medical doctor in his mid thirties and among other things does a thousand sit ups a day (2 sets of 500 each).

At Physio and Sports Solutions, our challenge is always to find out the cause of the patient's problem. (and not just treat the pain). It's quite similar to detective work. We look for clues from the moment they walk into the clinic/ treatment room, how they sit/ stand when we are talking to them.

Next is asking the patient many questions about their condition, their exercise routine (if they have one) and their daily routine followed by a physical assessment.

When he told me about his 1000 sit ups a day routine (in addition to his 12-14 hours of desk bound job), I knew that this was a key component to his pain.

Physical assessment revealed exquisite discomfort to his Psoas and Illiacus muscles among other things. Now the Psoas muscle has been described as "the most important and vital skeletal muscle" in the human body for it connects the spine to the legs.

It is structurally the deepest muscle we have in the core/ tummy. They start at the thigh bone (see picture above) and finish at the 12th thoracic vertebrae and all five lumbar vertebrae. That's how it can cause your back pain!

Any force on the Psoas muscle (muscular contractions) is also thought to support our internal organs and work like hydraulic pumps allowing blood and lymph to pushed in and out of the area. Organs stimulated include the intestines, kidneys, liver, spleen, pancreas, bladder, stomach and the reproductive organs. This is why after my accident, every time my stomach hurts (usually from eating something that my stomach doesn't like), my back hurts too.

These deep organs are often referred to as viscera, and communication from theses organs to the brain is called visceral messaging. (Aized can do visceral manipulation if you need).

Connection between the diaphragm and psoas

Here's another remarkable fact. Your diaphragm (main breathing muscle) is connected to the spine where the Psoas muscle attaches. The diaphragm's medial arcuate ligament also wraps around the top of the Psoas along with fascia that connects to the other hip muscles.

These connections connect your ability to walk, run and breathe and also how you respond to fear and excitement - a direct influence on your fight or flight response.

So I addressed my patient's Psoas problem and got rid of his back pain without even touching his back.  As a medical doctor he and his previous physio had been attempting to treat his back for over a month with no real improvement. He was totally amazed as everyone else had told him it was his back that gave him problem.

Having back pain and not better after your back is treated? Make sure you get your physiotherapist/ healthcare practitioner to check your psoas and your internal organs/ viscera (although your healthcare practitioner may think you're nuts if they're not trained in that area).