Do nerves get stuck? Part 2. How to consider the evidence.

"There is no evidence for that so I don't use it."























"A common error is to use 'lack of evidence' to justify that something doesn't exist."
Consider the statement "There is no evidence for that so I don't use it".

If you think this, it may mean that you are reluctant to believe. Such skepticism should be encouraged because it helps prevent misconceptions, misinformation, infocultures, physiotribes and religions in our profession.  It is also a key means of connecting our intellect to the facts and health professionals are obliged to apply science rigorously.

However, a common practice (and error) is to overplay 'lack of evidence' by using it to support that something is incorrect.  Unfortunately 'lack of evidence' is NOT proof that something does not exist or work. It is very different from 'evidence that something does not exist', which is 'negating evidence'.  Both supportive and negating evidence are very important clinically and must have applied to them the same rigour that would usually be applied to 'supporting evidence' alone.​
If there is a lack of information about a topic, the ERRONEOUS conclusion is that this constitutes negating evidence, unless there is general knowledge that defies the idea. 

For instance, for discussion purposes:  "It has never been proven that the tibia moves anteriorly under the femur during the knee extension phase of walking." If it has not been studied, we could, on technical grounds, conclude 'there is no evidence' that the tibia does this.  However, the natural experience and common sense show that it must happen this way, so to use only 'available research evidence' could produce the erroneous conclusion that the tibia does NOT move anteriorly.  So, even though there is no research evidence, it does NOT mean it doesn't happen.  If it were proven by research that the tibia does NOT move anteriorly, it could be concluded that there exists 'negating evidence' and this would justify believing that the tibia does not move forward.
In relation to stuck nerves, we could easily think "I have never seen a study showing that nerves get stuck so this means nerves don't get stuck".

If nerve stuckness has not been studied, or the individual has not done an adequate literature search, the individual also has NO evidence that nerves DON'T get stuck and to conclude that they don't would be to also base any negative conclusion on lack of evidence. So it goes both ways and often opinionists don't consider the matter in this way.

​This is a cardinal scientific error and unfortunately is commonly applied.

Take home points:
1. lack of evidence is NOT negating evidence.
2. a common error is to use 'lack of evidence' to justify that something doesn't exist.

Black holes were originally thought to have nothing in them.
Here is a real life example:

"Darling, where is the ......?"
"It's in the ....."
"No, it's not there ...."
"Yes it is, I put it there yesterday ..."
"I didn't see you do that ..."
"I did it when you were out ..."
"OK, but really, it's not here ..."
"Well it should be. Did you look behind the ...."
"Ohhhh, you didn't tell me that.  Here it is."

The person doing the searching repeatedly makes the same error - "I couldn't find it so it doesn't exist" and this is a perfect case of NOT LOOKING PROPERLY.  In science, this is such a common and important problem that it is classified as a type II error - not finding something means it doesn't exist.  It is effectively a false negative.
Two common errors in interpreting scientific research:

1. The opinionist makes the mistake of thinking that, if they haven't seen it, it doesn't exist or it's not worth worrying about.  
2. If a study doesn't show an effect then it doesn't work.  All manner of factors must be taken into account before any conclusions can be drawn, particularly the study methods.  It must be certain that the methods were sufficiently sensitive and reproduced the correct events for us to be sure that the effect is disproven.  Disproving something scientifically is actually very difficult, and rare.

Black holes were originally thought to have nothing in them.  What a mistake that was!
TAKE HOME POINTS










​
"If you haven't considered evidence that challenges your beliefs, you are biasing your intellectual development and may never arrive at a factual basis for your thoughts."
​ If you think there is a LACK OF EVIDENCE:
- have you looked properly?

- have you read the relevant literature in detail and critically?

- do you know the difference between a high quality study, low quality study or one that is patently erroneous that gives the wrong conclusions?

- have you consulted an expert in the area who has done research and published in peer-reviewed literature before coming to any firm conclusions?

If you think there IS evidence:
- have you read your supporting evidence critically, as you would for a study that challenges your opinion or personal philosophy.

If not, you are biasing your intellectual development and you may never arrive at a factual basis for your thoughts.
​
PART 3 - Integrate the evidence.

Watch the video on lumbar disc function - not what you think!
The intervertebral disc does NOT bulge more in flexion.