Elsevier

Journal of Biomechanics

Volume 38, Issue 7, July 2005, Pages 1469-1481
Journal of Biomechanics

Verification of biomechanical methods employed in a comprehensive study of mild traumatic brain injury and the effectiveness of American football helmets

https://doi.org/10.1016/j.jbiomech.2004.06.025Get rights and content

Abstract

Concussion, or mild traumatic brain injury, occurs in many activities, mostly as a result of the head being accelerated. A comprehensive study has been conducted to understand better the mechanics of the impacts associated with concussion in American football. This study involves a sequence of techniques to analyse and reconstruct many different head impact scenarios. It is important to understand the validity and accuracy of these techniques in order to be able to use the results of the study to improve helmets and helmet standards.

Two major categories of potential errors have been investigated. The first category concerns error sources specific to the use of crash test dummy instrumentation (accelerometers) and associated data processing techniques. These are relied upon to establish both linear and angular head acceleration responses. The second category concerns the use of broadcast video data and crash test dummy head–neck–torso systems. These are used to replicate the complex head impact scenarios of whole body collisions that occur on the football field between two living human beings.

All acceleration measurement and processing techniques were based on well-established practices and standards. These proved to be reliable and reproducible. Potential errors in the linear accelerations due to electrical or mechanical noise did not exceed 2% for the three different noise sources investigated. Potential errors in the angular accelerations due to noise could be as high as 6.7%, due to error accumulation of multiple linear acceleration measurements. The potential error in the relative impact velocity between colliding heads could be as high as 11%, and was found to be the largest error source in the sequence of techniques to reconstruct the game impacts. Full-scale experiments with complete crash test dummies in staged head impacts showed maximum errors of 17% for resultant linear accelerations and 25% for resultant angular accelerations.

Introduction

The concussion can be regarded as a form of mild traumatic brain injury (MTBI), which can be induced mechanically as a result of the head being accelerated (Gennarelli, 1983; Newman, 1982). It is generally regarded that the motion of the brain lags that of the skull and the brain distorts. If this distortion is excessive, neurological dysfunction will subsequently be observed. Protective headgear, i.e,. a helmet, reduces the potential for brain injury by reducing the extent to which the brain experiences mechanical loading within the skull. It accomplishes this by reducing the acceleration of the head upon impact.

The criteria by which one might develop human concussion tolerance limits and thereby assess the effectiveness of various helmet design features have generally been based upon various measures of head acceleration (Newman, 1998). To be completely general, both linear and angular accelerations are taken into account.

Most of what is known in this regard has been established from experiments with various surrogates including animals, volunteers, cadavers and occasionally from reconstructing motor vehicle accidents. The limitations of these methods are well known (Newman, 1993; Viano et al., 1989).

Traumatically induced brain injury has not been studied extensively for the obvious reason that one cannot willingly expose a live human being to a potentially injurious blow to the head. However, there is an untapped database of information where such blows do occur unwillingly: professional American-style football. In this game, head impacts occur frequently and, though standardized helmets are always worn, athletes do occasionally sustain a concussion.

From 1997 to 2002, a database of 182 head impacts was generated, both with and without MTBI (see Table 1). Several categories of impact have been distinguished, including head-to-head, head-to-ground, and head-to-body part. The injury data were obtained through the National Football League (NFL) Injury Surveillance System. Of these 182 cases, 31 were selected for full-scale laboratory reconstruction.

The objective of the research, as identified by the NFL subcommittee on MTBI, is “to gain a better understanding of how and why concussion occurs, and to devise better means to measure concussion, such that ultimately improved protection can be offered.” The work presented herein deals primarily with the means of measuring concussion, or more specifically the kinematic analysis of on-field incidents and the methods of re-enacting them in the laboratory. Recently, Pellman, 2003a, Pellman, 2003b, Pellman, 2004 have published detailed analyses of this mild traumatic brain injury database.

Section snippets

Helmet design features

A typical helmet worn by professional American football players is shown in Fig. 1. The helmet includes a tough thermoplastic shell covering a series of interlocking pads made of slow recovery polymer foam. This interior padding is supplemented by a series of air inflation chambers for fit adjustment. A faceguard, usually made of coated and welded steel wire, attaches to the shell. The helmet is retained on the head by a Y-type chinstrap. Football helmets must meet specific performance

Experimental procedures

Detailed photogrammetric analyses (Newman et al., 1999) yielded the impact sites on, and the relative impact velocity of, the players’ helmeted heads. Impact velocity, contact points and orientation of the players were then carefully used to reconstruct the incident, using automotive crash test dummies to represent the players. The laboratory setting employs elements of two Hybrid-III adult male anthropomorphic test devices (ATDs or crash test dummies) (Backaitis and Mertz, 1994). A helmeted

Discussion of error sources in the reconstruction process

Six potentially important sources of error are identified. The first three are associated with data acquisition and processing, the latter three with assumptions and simplifications made relative to the ATD representation of actual incidents involving living human beings.

The former include:

  • Data anomalies due to transducer and data processing noise.

  • Headform system response anomalies associated with signal-frequency content and the effects of analog and digital filtering of raw and processed data.

Conclusions

Many issues surrounding the prevention, management, and treatment of MTBI (concussion) remain under study. The biomechanics research on concussion occurring in professional American football that has continued for the past 5 years, provides a new foundation for understanding the biomechanical conditions for concussion, and hence for improving the effectiveness of football helmets. Through a comprehensive analysis and reconstruction of head impacts sustained by football athletes with and without

Acknowledgements

Biokinetics would like to thank the NFL and NFL Charities who made this research possible. The NFL Subcommittee on MTBI, chaired by Dr. E. Pellman, is thanked for their direction and support. Mr. D. Blandino is thanked for providing the video data. Dr. J. Powell is thanked for providing injury confirmation from the NFL injury surveillance system. Dr. D. Viano is thanked for his continued guidance. Ms. D. Mitchell is thanked for her enthusiasm and support for this research.

References (24)

  • D.C. Viano et al.

    Injury biomechanics researchan essential element in the prevention of trauma

    Journal of Biomechanics

    (1989)
  • Backaitis, S.H., Mertz, H.J. (Eds.), 1994. Hybrid-III: The First Human-like Crash Test Dummy. Society of Automotive...
  • Beusenberg, M., Shewchenko, N., Newman, J., de Lange, R., Cappon, H., 2001. Head, neck and body coupling in...
  • De Jager, M., Sauren, A., Thunnissen, J., Wismans, J., 1996. A global and detailed mathematical model for head–neck...
  • DiMasi, F.P., 1995. Transformation of nine-accelerometer-package (NAP) data for replicating headpart kinematics and...
  • Federal Motor Vehicle Safety Standard (FMVSS) 208, 1999. Occupant Crash Protection. US Code of Federal Regulations,...
  • Gadd, C.W., 1966. Use of weighted-impulse criterion for establishing injury hazard. In: Proceedings of the 10th Stapp...
  • Gennarelli, T.A., 1983. Mechanistic approach to the head injuries: clinical and experimental studies of the important...
  • Johnson, A.K., Hu, A.S., 1977. Review of head rotational measurements during biomechanical impact tests. Technical...
  • J.P. Kelly et al.

    Diagnosis and management of concussion in sports

    Neurology

    (1997)
  • National Operating Committee on Standards for Athletic Equipment (NOCSAE), 1996. Standard Drop Test Method and...
  • Newman, J.A., 1982. Temporal characteristics of translational acceleration in the prediction of helmeted head injury....
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