Six Degree-of-Freedom Measurements of Human Mild Traumatic Brain Injury

Area of Science:

• Biomechanics
• Neuroscience
• Sports Medicine

Background:

• Current mild traumatic brain injury (mTBI) prediction relies on 3 degree-of-freedom (3DOF) translation-only criteria.
• Head rotation is implicated in mTBI, but direct 6DOF measurements were previously unavailable for validation.
• Existing safety standards do not fully capture the biomechanics of head impacts.

Purpose of the Study:

• To investigate if direct 6DOF head rotation measurements enhance mTBI prediction.
• To compare the efficacy of 6DOF criteria against existing 3DOF criteria.
• To evaluate the role of rotational kinematics in predicting head injuries.

Main Methods:

• Instrumented mouthguards measured 6DOF head impacts in American football, boxing, and MMA.
• Clinician-diagnosed mTBI was predicted using 12 kinematic and 6 finite element (FE) criteria.
• The study collected the first 6DOF data for clinically diagnosed mTBI.

Main Results:

• 6DOF criteria demonstrated superior prediction of mTBI compared to 3DOF translation-only or rotation-only criteria.
• Peak principal strain in the corpus callosum (a 6DOF FE criterion) was the most potent predictor.
• Rotational metrics like peak rotational acceleration and Head Impact Power (HIP) also showed strong predictive value.

Conclusions:

• Direct head rotation measurements appear to improve mTBI prediction accuracy.
• Further 6DOF data is necessary to validate these findings and develop new injury criteria.
• Incorporating rotational sensitivity into injury prediction models is recommended.