Low speed collisions are not equivalent to normal daily activities.

The last podcast covered how injuries occur with no damage to vehicles and patients in collisions with no damage often go through more treatment than patients with damage to the vehicle.  I would like to spend some time today going over the chances of being hurt in a low speed and minimal to no damage collision and how this compares to normal activities of daily living. 

Today’s study was published in 2021 in the International Journal of Environmental Research and Public Health by Paul nolet, larry Nordhoff, Vicki Kristman, Arthur Croft, Maurice Zeegers and Michael Freeman.  The article is titled Is Acceleration a Valid Proxy for Injury Risk in Minimal Damage Traffic Crashes? A Comparative Review of Volunteer, ADL and Real-World Studies . 

The article starts by stating that minimal damage crashes make up a substantial portion of civil litigation.  They showed that minimal damage crashes often litigate on causation.  They reported that insurer defendants often rely on an engineering or Biomechanical approach to show no possible causation.   These biomechanical analyses often reconstruct delta V or change in velocity and then assign g forces to the collision.  They then compare g forces for normal activities of daily living and conclude that the risk of being injured in the collision is the same as normal activities of daily living. 

They often compare a minimal damage crash as no more likely to cause a medically observed injury than forces encountered when walking, running, sitting down in a chair, head nodding or sneezing.  Todays study looks into the claims of minimal damage collisions having similar forces as the ADLs. 

They start by showing that a 1999 study showed that minimal and no damage crashed have an injury rate of 20% and a 2020 study showed several hundred thousand injuries were diagnosed in the U.S. emergency departments from minimal and no damage crashes.  These 2 studies alone are at odds with a biomechanical analysis that always shows the same conclusion that minimal damage and no damage collisions have the same potential to injure someone as normal activities.   

For this study they went to the literature and looked up studies that had rear impact crash tests of human volunteers that reported the delta V or change in velocity and showed the acceleration in g’s or gradational force.    

Next they found a study showing linear and angular head acceleration recorded for various activities of daily living including walking, sitting, head nod, running, chair plopping, jumping down from a stair and leaping. 

Next they found literature showing information regarding real world impact collisions that were reconstructed for speed change.  Only papers with airbag sensor data were included.  These studies had the average peak vehicle acceleration in g’s and duration of the crash impulse in msecs and delta V in km/h. 

The activities of daily living studies showed that walking and sitting produced less than 1 g and the highest ADL g forces came with jumping from a stair and leaping which were around 4 g’s.  The g forces involved in an 11 km/h or 6.8 mph collision is around 12 g’s.  This is 3 times higher than the g’s involved in ADLs.  During the 11 km/h or 6.8 mph collision there is an angular acceleration of 1150 rad/s² and this is 13 times greater than angular acceleration for any of the ADLs. 

This study went on to show that no literature was found showing injury risk for ADLs.  They reported that this is “Likely because ordinary ADLs do not cause injury in healthy people, and thus the topic has previously carried no research interest”.  They reported that it is reasonable to assume that ordinary ADLs such as walking or sitting down would likely be less than 1 injury per 1 million steps or 1 injury per 3,650 acts of sitting.  This study showed that you are 2000 times more likely to be injured in the 11 km/h or 6.8 mph collision than sitting or walking. 

They compare these biomechanical analysis to walking down the stairs and falling down the stairs.   They report that walking and falling down stairs do share similar attributes, but a comparison of risks of being injured by walking and falling down stairs should not be made.  Similarly traffic crashes and some ADLs share similar attributes ADLs should not be used to compare risks for a traffic crash. 

They concluded that injury risk of a minimal to no damage rear impact crash is at least three orders of magnitude greater than the injury risk of any ADL. 

This study went on to show that the defense community has published studies showing comparisons of crashes and ADLs.  These studies have all been funded by insurance companies. 

The conclusion showed that “there is enormous disparity between the risk of injury from ADLs and minimal damage crashes, and that the former cannot be used as a proxy for the latter”.  The risk of injury in minimal to no damage crashes is at least 20% and this is thousands of times greater than any ADLs.  “  These results demonstrate that the biomechanical approach utilized in the legal defense of injury claims, in which the injury risk of a minimal damage rear impact crash is deemed comparable to the injury risk of ADLs, is an invalid method for evaluating injury causation. The approach should be discontinued, or in the alternative, ruled inadmissible by courts as its use results in unreliable expert testimony”.

This is a classic example of trying to show what can or cannot happen in a collision and not what did happen.  The defense in litigation is trying to show that injuries can not occur any more frequent in these collisions than normal activities.  While other studies have shown that even low speed collisions with minimal or no damage cause injury 20% of the time.  I am interested to know that yes injuries can occur and the risk of being injured is thousands of times greater than normal activities.  With that being said it is most important to use all available information and means to show an injury did occur and it is related to the collision or it did not. 

Real World:

I did a deposition for a patient in a low-speed collision.   I spent a lot of time discussing the patient’s injuries as seen with objective evidence on imaging.  There was a lumbar disc herniation seen on MRI seen right after the MVC.  The MRI did not show type 1 modic changes or any modic changes.  The MRI did show no signs of osseous degeneration and no disc space height loss.  The herniation was focal and not circumferential.  The herniation was abutting a nerve root with no compression.  The patient had no history of back pain, but developed back pain and radiculopathy right after the MVC. 

All evidence in this case shows a new disc herniation likely caused by trauma and correlated perfectly with the patient’s MVC.  The defense hired an expert to help with this case after my deposition.  The defense expert had an approach similar to the study we went over today. 

The defense expert had no opinion on the images.  He had no opinion on why there is a new focal herniation with no osseous degenerative changes and no loss of disc space height.  He had no opinion on no prior history of back pain and onset of back pain and radiculopathy right after a traumatic event.  There was no disputing the facts of the case as I explained in my deposition. 

The entire defense report suggested that a low speed collision could in no way cause injuries to the lumbar spine.  It was his opinion that the forces in the MVC would be similar to most normal daily activities.  He even reported that the change in velocity would be high with every step we take and similar to the forces in the MVC. 

He didn’t dispute the actual injury or even comment on the new or old nature of the injuries.  It was just that his injuries were more likely from normal activities and would have had nothing to do with his MVC.  I was asked to write a rebuttal on the defense experts report.  I started by reporting that this expert gave no opinion of the patients images and actual injuries.  There was no rebuttal of all the evidence showing he had a new injury.  I challenged him to spend some time looking at the images and the facts of the case and offer an opinion on this. 

Then I was able to use the study we went over today to show that his opinion is not based in science and has been proven wrong.  I showed that today’s study showed that you are 2,000 times more likely to be injured in a low speed meaning 11 km/h or 6.8mph collision than normal daily activities.  I also showed that today’s study showed that these low speed collisions can create up to 12 g’s of force while most normal ADLs produce less than 4 g’s.  I reported that studies have shown that in fact 20% of people in low speed MVCs have injuries and that his particular case showed that he was one of these 20%. 

I was not surprised to see that the defense expert was unwilling to rebut my rebuttal and that the insurance company pushed to settle the case.   I see it too often that the actual facts of a case are discarded and rhetoric is used.  This drives me crazy.  I think working an injury case is a lot of fun and I get to be a detective and look at all available evidence and see what type of story is told.  This is so much more important than stating what can and cannot happen in a collision it is more fun to state what did happen.  Although research like today’s study help us understand that yes injuries can occur and the mechanisms of a MVC are very different that normal ADLs. 

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