A review of the biomechanics, data acquisition, and head trauma

By Josh Wu. This article was initially published in our Concussion Update newsletter; please consider subscribing.

Gregory Tierney published a review on concussion biomechanics, head acceleration events (HAE), and brain injury criteria in Taylor & Francis Online. Tierney pooled data from past studies to understand the relationship between the kinematic magnitude and rotational nature of HAE and damage to the brain. 

This study provided three common mechanisms of concussions. The first is when the mechanical load is beyond the tolerable limit of the brain. The second is cumulative concussion exposure. The third is increased risk after previous concussions.

When they compared linear to rotational forces of impact, the study found that linear motion leads to more localized damage. In contrast, the main source of brain injury risk seems to be rotational motion due to the brain’s increased sensitivity to rotational forces. The structure of the brain allows greater spreading of rotational shear forces than linear forces. However, both linear and rotational forces need to be considered when assessing concussion risk.

There are many methods to attain head acceleration exposure and biomechanics data. One method is video analysis, which provides one or two-dimensional estimates. Another method is Model-Based Image-Matching technology that uses speed and location to measure linear and rotation velocity changes in three dimensions using video footage. A third method is multibody simulations to simulate the impact of two people colliding by using multiple parameters for the human body for head translations (every point on the head moving an equal distance), head impact duration, and head impact velocity. A fourth method is to use test dummies to do controlled impact experiments, but these models are limited in many ways. There are also instrumented mouthguards that can track head movement/collisions in real-time. Lastly, subject-specific finite element (FE) brain models are an up-and-coming technology that computes the location and magnitude of brain deformation due to impact.

There is still room for growth in this area of sports. Our available technologies are still estimates, and athlete removal or injuries are still heavily reliant on medical personnel on the sidelines. More studies need to be done on existing methodologies to attain biomechanical data to ensure that the data is accurate and can accurately identify brain trauma.