Group-Wise Evaluation and Comparison of White Matter Fiber Strain and Maximum Principal Strain in Sports-Related Concussion

Address correspondence to: Songbai Ji, MS, ScD, Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755, E-mail: [email protected]

Introduction

Sports-related concussion is a major public health problem in the United States that is estimated to occur in 1.6-3.8 million persons annually and is particularly common in football and ice hockey.¹ Despite the significance and growing concerns about the potential long-term consequences of concussion, its biomechanical mechanisms remain elusive.

On-field brain injury studies measuring head impact exposure (frequency, location, and kinematics of head impact) using the Head Impact Telemetry (HIT) System (Simbex, Lebanon NH) have provided important insight on head impact characteristics in contact sports.^2-8 Kinematic measures such as peak linear and rotational acceleration alone, however, lack specificity in identifying athletes with diagnosed concussions, and no consensus has been reached on an injury tolerance threshold at the kinematics level.^2,5,6,9 In parallel, studies of neuronal and cellular responses to deformation at the microscale demonstrate that mechanical forces in the brain during traumatic brain injury (TBI) are capable of triggering both acute and chronic changes in function.¹⁰

Injury thresholds for stretching have also been established in terms of magnitudes of axonal strain and/or strain rate required for nerve fibers, single axons, neural cell cultures, and organotypic brain slice cultures.¹¹ These in vivo animal and in vitro studies indicate the mechanical conditions under which functional deficits appear or cell death results in the brain, and provide...