Information for medical professionals 2018: Part 7 - More on atlantoaxial rotational instability

We would like to express our gratitude for the great interest in the articles we have published on our webpage. It is delightful to see that there are so many readers from around the world. We also thank you for the praise we have received for our English version. The honor for that belongs to our two translators from USA and England.

We received a particularly great response from both patients and medical professionals after publishing part 5.

Important points that we have received feedback on from that article are:

  1. Use of T2 and STIR weighted MRI 3T sequences in functional neck and head positions must be based on the guidance from prior precise clinical examination.
  2. We at Firda Physical Medicine Centre consider it crucial that there is a prior clinical diagnosis BEFORE the MRI 3T examination. Without accurate and concrete diagnostics with precise questions, targeted MRI 3T will be very difficult.
  3. MRI 3T sequences: To clarify, we at Firda Physical Medicine Centre do not claim credit for combining these two types of sequences in MRI 3T (T2-STIR). These are very common MRI sequences.
  4. Is it is important to perform diagnostics with this degree of accuracy? Yes, we believe so. The way we envision clinical and MRI diagnostics for those with neck injuries is only the starting point for a development in diagnostics where the level and quality of cervical radiological diagnostics will improve faster than has been done previously. This will aid us in initiating more targeted and effective measures.
  5. We will write more about rehabilitation measures in the future.
  6. We have received requests for more CT images that show the consequences of tissue damages in the upper neck region that have been detected using MRI 3T. We will show a few annotated images here that visualize atlantoaxial rotational instability, subluxation, and full dislocation.

Image 1

Image 1 shows a substantial rotational instability. In our work at Firda Physical Medicine Centre, we see patient cases like this almost daily. This patient had rotational instability both to the left and to the right.

I will try to further illustrate atlantoaxial rotational and sideways rotational instability. The first image is meant to illustrate the anatomy to familiarize ourselves with the area.

The view is from above looking down - an axial cross section.

We see the atlas (the uppermost vertebra, blue arrows) and axis (the second vertebra, red arrows). The red cross shows the center of dens axis on the C2 vertebra.

Image 2 (identical to image 1)

Now we will see what happens to a person with rotational instability atlas-axis. This person has (as shown in the image) a subluxation (the atlas joint surface has almost no contact with the axis joint surface, see blue double arrow). However, the patient can keep rotating so far that the atlas surface moves completely out from the underlying axis joint surface, creating a complete dislocation. We call this habitual luxation.

  1. The first thing we notice is that there is complete sideways instability. Atlas is hanging on dens axis on one side. (See the blue lines).
  2. Long red lines: One line goes through the axis joint surfaces from right to left. The other red line goes through the atlas joint surfaces. The rotational angle between these two lines is 61 degrees. Normal rotation is at most 45 degrees. It is important to note that this patient could have rotated further, but stopped due to symptoms.
  3. If the rotation had been stable, the place where these lines should have crossed would have been in the center of dens axis. The green line shows the deviation.
  4. The purple arrows demonstrates how atlas is moving into the channel. In this image the channel is constricted by about 50%. Had the person kept rotating his head, the constriction would have been even greater. The consequence of atlas moving this far into the channel is pressure on the spinal cord, membranes and local circulation and nerve supply. This creates debilitating local symptomatology, and a source of radiating pain both upwards and downwards. In this case the patient can rotate the head equally far in both directions, leading to alternating constriction with pressure from both the right and left side.

Image 3.

MRI 3T. Axial cross section in the level of atlas-axis. The focus is on the spinal cord and surrounding soft tissue.

Patient 1, 21 years old. Rotation to the left side (seen from below and upwards, hence mirrored).

The blue arrows show the compression area between damaged fibrous tissue and the medulla.

Image 4.

Patient 1. Rotation to the right side.

Image 3 and 4 shows that the spinal cord is compressed when rotating to either the left or right side. See blue arrows.

Image 5.

Patient 2, 43 years old.

A new example of medulla compression. See blue arrow.

Image 6

Patient 3, 56 years old.

Another example of medulla compression in the C1-2 level from rotation.

Image 7

When returning to CT imaging, we can see that patient 4 (52 years old) suffers from significant rotational instability. It requires very little force before the atlas joint surface completely slides out from the underlying axis surface. See the blue arrow.

Image 8:

The same patient as in image 7 as seen from above. Marginal remaining contact between atlas and axis. There must be significant tissue damage in the surrounding area for such a large range of motion to be possible. See blue arrows. The blue LINE shows UNCOVERED axis joint surface.

When it comes to atlantoaxial rotational and sideways instability, it is crucial to produce an expeditious and precise diagnosis for the following reasons:

  1. To avoid temporary or permanent ailments or deteriorating injuries from erroneous treatments and training, incorrect neck movement, stretches or joint manipulation.
  2. Better knowledge about the injury allows us to initiate the most efficient treatment and rehabilitation.
  3. Expeditious diagnostics means targeted treatment can start early. Time is of the essence! We cannot wait and see who doesn't heal by themselves, and then treat those who end up with chronic pain. Valuable time can be lost with the wrong approach!


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