Research Papers

Comparison of linear, rotational and finite element thresholds of brain injury for impacts at multiple locations to the head

Filename Good.pdf
Filesize 518 KB
Version 1
Date added June 6, 2010
Downloaded 1 time/fois
Category 2010 CMRSC XX Niagara
Tags Session 5A
Author/Auteur Craig Good, Steve Thannhauser

Abstract

Traumatic head injuries are a serious problem in modern society. Those affected suffer from long term disability or death. In 2003 - 2004, there were 16,800 hospitalizations and 1400 deaths due to head injuries in Canada. The largest causes of traumatic brain injury in Canada and the US are falls, motor vehicle collisions and assault. There is significant debate in the research community regarding the biomechanical mechanism responsible for brain injury. As early as the 1940s, researchers proposed brain injury mechanisms from both linear and rotational impact acceleration. There have been a significant number of studies identifying rotational impact acceleration as the mechanism of traumatic brain injury. This is in contrast to the historical reduction in head injury from standards and criteria based on linear acceleration (i.e., Head Injury Criteria or HIC). Recently, researchers have developed finite element models (FEM) of the brain. The FEM research has led to proposals for tissue level injury measures. This investigation compares head injury measures based on linear acceleration, rotational acceleration and injury criteria derived from finite element models. Various impact head impact directions and locations are used. The interactions between kinematic and FEM injury criteria are investigated. The head injury measures were calculated using a computational approach. Head kinematics were determined using Madymo 7.1 (TASS Safe, The Netherlands). The Hybrid III, 50th percentile, Q dummy, head and neck model was used. A 2 kg impactor was used to strike the head at 20 m/s (impact energy 400 J) at various locations and directions. Linear acceleration, rotational velocity, rotational acceleration and HIC-15 were calculated. The head kinematics were input to the improved SIMON 3.07 (NHTSA, Washington, DC) finite element brain injury model. Cumulative Strain Damage Measure (CSDM 15%) and maximum principle strain was calculated with the FEM as injury criteria for diffuse axonal injury (DAI). There was considerable variability in all head injury measures for longitudinal and lateral impacts using constant impact energy. Several impacts were glancing blows. HIC-15 varied from 157 - 1409. Peak rotational acceleration ranged from 8782 – 18342 s^-2 and peak rotational velocity ranged from 17 - 49 s^-1. The CSDM (15%) ranged from 6% to 90% of total brain tissue. Linear regression models were calculated for each pairing of head injury measures. As expected, HIC-15 correlated well with linear acceleration (R²=0.96). HIC-15 was also found to be weakly correlated with CSDM (15%) (R²=0.34). This correlation may explain the effectiveness of linear acceleration based brain injury criteria such as HIC to keep head injuries in check. Several correlations were observed for peak rotational velocity or change in rotational velocity. Peak rotational velocity was correlated with CSDM (15%) (R²=0.84), HIC-15 (R²=0.59), linear acceleration (R²=0.50) and peak principal strain (R²=0.48). Correlations between linear or rotational acceleration and FEM injury criteria were not observed. The results are relevant to not just a single impact point but head impacts at multiple impact locations and in different directions. These results support further research and refinement of the biomechanical head injury measures commonly used to evaluate brain injury.

Craig Good and Steve Thannhauser