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.

Evidence For Using Floss Bands

showing how Flossing is done

Remember the floss band courses we used to teach? We often had participants asking what is the evidence behind increasing joint range of motion (ROM), sporting performances, helping with recovery and decreasing pain. In short, they all wanted to know how it works. 

I wrote previously that you've got to try it to believe it, well there is now a published *scoping review article for floss bands (Konrad et al, 2021), referenced below.

The review paper summarizes the existing evidence for the effect of floss band treatment on range of motion (ROM), sporting performance (strength or jump performance), recovery (due to DOMS) and pain (due to disease or injuries).

In all, 24 studies met the inclusion criteria with a total of 513 subjects. 15 of the 24 studies investigated the effects of a single floss band application on the ROM of several joints. On the ankle joint, flossing was found to have a significant change of 11.17% in the dorsiflexion ROM.  

4 studies investigated the effects of calf flossing on the ankle, showing a very large increase of 19.95% in dorsiflexion of the ankle.

Similarly 4 studies measured thigh flossing and found a significant increase in knee bending (3.61%), and knee straightening (7.38%). However, another study showed no improvement in hip ROM after flossing the thigh. None of studies showed any decrease in range after flossing.

Of the two studies that investigated the effects of flossing on DOMS, one study reported significantly reduced DOMS 24 and 48 hours post exercise in the study group (in the upper arms) compared to the control group. The other study (on leg muscles) found no difference in the intervention versus control group following 12, 24, 36, 48 60 and 72 hours post exercise.

When comparing flossing to other treatment like dynamic stretching, flossing had a more noticeable effect in increasing hip range of motion and maximal eccentric knee extension (Kaneda et al, 2020b). With regards to static stretching and flossing, rate of force development was more pronounced in the flossing group compared to the static stretching group (Kaneda et al 2020a). Kaneda and colleagues concluded in both studies that flossing should be applied as a warm up rather than as a stretching exercise. This is exactly what my patients who do CrossFit tell me. They normally use a floss band for warm up before they start their easier routines, before the heavy lifting.

I know all athletes are after improved performances. Results from the individual studies showed that 11 of of the 44 performance measures showed a significant improvement (comparing pre and post floss band application, Table 3 in article). There is some evidence that joint flossing (ankle and knee) can increase jump height, although sprint performance (5 to 20 m sprints) seems to be unaffected after ankle flossing. (Personally, I would floss the quads and hamstrings and calf muscles if I wanted to improve sprint times rather than the ankle). 

One study showed improvement in maximal voluntary contraction (strength) in the quadriceps muscle and hamstrings after thigh flossing.

The researchers suggest this is possibly due to hormonal responses related to the flossing. Similar to other occlusion (or blood flow restriction methods), enhanced growth hormone and norepinephrine levels increase may be responsible for increase in performance reported. More importantly, the review concluded that from the involved studies there was no detrimental effects on performance from a single floss band treatment.

Evidence also show that a single floss band treatment is able to increase ROM of the related joint and can positively affect jumping and strength performance. Possible mechanism is suggested to be changed neuromuscular function rather than changed mechanical properties.

after surgery in 2016

After Ronald Susilo (above) ruptured his patella tendon and tore his anterior cruciate ligament at the same time, he came to see me after the surgeon reattached his patella tendon. He did not have the range to even pedal one round on the stationary bike. I definitely increased his knee ROM with a single floss band treatment. He could pedal immediately after a single floss band application. 

Yes, back then it was only one subject (or n=1), however it was a definite improvement. Those of you reading then may be critical and probably not even believe it, but I have since replicated it many times in our clinic. Hence I feel that clinical evidence (what we see in the clinic) is just as good as published evidence (like this scoping review).

There will probably be long term studies about the effects of flossing treatment on joint ROM, sporting performance, whether it helps with recovery and decreasing pain. I am sure there also will be studies that say there are no benefits to it. The question is does it work for you?

Reference

Konrad A, Mocnik R and Nakamura M (2021). Effects Of Tissue Flossing On The Healthy And Impaired Musculoskeletal System: A Scoping Review. Front. Physiol. 21 May 2021. DOI: 10.3389/fphys.2021.666129

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

Let's do the twist