Vertebral Fracture

Vertebral Fracture

Why is the corresponding spinal segment not injured in the case of a vertebral fracture following a road traffic accident?

Did you ever read a book and realize that the answer given at the end of the book was also hidden between the lines at the very beginning of the same book?
Consider this hypothesis: The answer to every question in life - lies either within, or at the very beginning.

Tell me what you feel about this and let me know if you have any views on this matter.

Now, having come across loads of patients with spine injuries following road traffic accidents (RTAs), I am sure you are familiar with the fact that, in case of a vertebral fracture, the corresponding spinal segment is not involved.

To understand this, we need to go to the very beginning - the embryonic development of the spinal cord.

I request you to take a close look at the image given below:

Author: DrV


From the image, we can arrive at the following conclusions:

  1. The spinal nerves of the cervical region leave the vertebral column via the intervertebral foramen above the corresponding vertebra.
    Take the C1 spinal nerve; for example - it leaves the vertebral column between the base of the skull and the C1 vertebra (atlas).
     
  2. All the other spinal nerves (thoracic, lumbar, sacral, and coccygeal) exit the vertebral column via the intervertebral foramen below the corresponding vertebra.
     
  3. While the spinal nerves arise in the above fashion, the spinal segments, however, are not at the same level as the corresponding vertebrae. 
    Take the L1 spinal segment, for instance. While the L1 nerve exits from the intervertebral foramen below the L1 vertebra, it actually originates from the spinal cord at a much higher level!

So why is the spinal cord placed in such a manner within the spinal cord? Like I said before, to understand life, we must look into the past. To understand the alignment of the adult spinal cord, we must look into the embryo.

 

The Mysterious Alignment of the Vertebra and Spinal Segments

Until the 12th week (3rd month) of the intrauterine life (IUL), the spinal cord extends along the whole length of the vertebral column. The spinal nerves, at this stage, pass through the intervertebral foramina at their level of origin. As shown below:

Author: DrV

With increasing age, the vertebral column and the dura increase more rapidly compared to the developing spinal cord. 


The terminal end of the spinal cord shifts to a higher level, leaving behind a thread-like structure called the filum terminale (nervus impar). 
The lowermost part of the filum terminale attaches to the back of the first coccygeal vertebra as the coccygeal ligament.

This disproportionate growth is not limited to the intrauterine life. At birth, the spinal cord terminates at the upper border of the L3 vertebra. By the time the child becomes an adult, the spinal cord terminates at the L1 - L2 level.

The dura mater, however, extends up to the S2 level. This is why we perform the lumbar puncture (spinal tap) at the L3 - L4 level.

Author: DrV

Connecting all the dots ...

Okay, Sherlock. Let’s connect the dots now, shall we?

This disproportionate growth of the spinal cord is the answer to the problem at hand. 
Let’s say there’s a vertebra fracture at the level of L1, thanks to the disproportionate growth of the spinal cord, the actual spinal segment involved will be much lower than the L1 spinal segment.

Thus, the corresponding spinal segment is not injured in the case of a vertebral fracture.

References:

  1. Atlas of Functional Neuroanatomy 2nd edition - Page no: 8
  2. Langman’s Medical Embryology 14th edition - Page no: 320 - 321
  3. https://www.who.int/news-room/fact-sheets/detail/the-top-10-causes-of-death
  4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3963058/
  5. https://www.ncbi.nlm.nih.gov/books/NBK545206/
  6. https://www.ncbi.nlm.nih.gov/books/NBK544267/

Author’s footnote

In medicine, if you see a phenomenon for which the reason doesn’t stare at your face immediately, nine out of ten times, the reason is embryological. 

Anything that cannot be explained by anatomy, physiology, and biochemistry, can be explained by embryology. Cool, right?

Feel free to click on the references for a more in-depth reading if you so desire.

If you feel any information can be added or that there are any inadvertent errors, feel free to let us know in the comments below or bring it to our notice via support@medicalwizardry.com.

Ever otherwise, feel free to use the comments section for discussion. 

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Pop Quiz

The WHO places RTAs as one of the top 10 causes of death - globally. What do you think makes the top of this list?

  1. Ischemic heart disease
  2. Stroke
  3. RTA
  4. COPD

Answer:

Ischemic heart disease is said to be the leading cause of death globally. 

Reference:

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