David H. Janda, M.D., *David C. Viano, Ph.D., *Dennis V. Andrzejak, and +Robert N. Hensinger, M.D.
Institute for Preventative Sports Medicine, Ann Arbor, *General Motors Research Laboratories, Warren, and +Pediatric Orthopaedic Surgery Division, University of Michigan, Ann Arbor, Michigan, U.S.A.

ABSTRACT:
The purpose of this study was to evaluate a nonliving laboratory model for the low-mass, high-velocity chest impact scenario associated with baseball impact deaths in children. A second purpose was to evaluate current protective sports equipment that could favorably modify the incidence of chest impact fatalities that occur in baseball. We studied the effects of baseball impact to the chest of swine as well as in two modified crash dummies. The animal protocol was used initially in pilot tests of protective equipment, during which soft core baseballs and generic closed cell foam chest protection were studied. In the animal model, when chest protectors, utilized alone or in combination, were compared with the effects of hard ball impact on the unprotected chest, only minor reductions were found in the incidence of cardiac arrythmias. A child crash dummy and a fifth percentile female Hybrid III crash dummy were then utilized in the biomechanical testing of chest protectors. The internal deflection and viscous response values obtained from the Hybrid III dummy showed minimal reduction in response when chest protectors were used compared to the unprotected dummy. Using a generic dosed cell foam chest protector impacted by a standard hard baseball, the impact force in creased between 6 and 43%, and the momentum delivered increased between 10 and I5%. When a softer core baseball was used with generic closed cell foam protection, the force measured increased between IS and S8%, and the momentum delivered increased between 14 and 18%. Impact tests using the standard hardball and the softer core baseball on the unprotected chest showed minimal differences in the viscous response measured. Closed cell foam protectors, including ABS plastic hard shell-covered generic closed cell foam, had only a marginal effect in reducing levels of chest viscous response. We conclude that the different types of softer core baseballs utilized in this study have no appreciable protective effect and in some eases may exacerbate the impact force of a baseball to the chest. We also conclude that the chest protectors and the various types of chest protector materials studied have minimal protective effects and may also exacerbate the impact force to the chest. To date, no effective preventive approach has been developed to eliminate or reduce chest injuries from baseball impact in the pediatric population.

Key Words: Chest trauma - Baseball - Arrhythmia - Prevention - Protective equipment.

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