Damage to bicycle helmets involved with crashes
Introduction
While bicycle helmet use has increased dramatically in the last decade, few data are available on the actual damage to helmets, the location of this damage and the correlation of damage to injuries which have occurred. Four prior studies have examined damaged helmets. Fisher and Stern (1994)examined 1 100 Bell helmets, using self-reported injury data. Williams (1991)evaluated 64 damaged bicycle helmets obtained from an emergency-department based study of 1 892 injured bicyclists. He found that serious injuries occurred if the helmet came off, or if the impact was below the level of the rim of the helmet. Smith et al. (1994)examined 72 helmets sent to manufacturers for replacement; they found that the most common site of impact was the left frontal region. Cameron et al. (1994)found that one third of impacts were below the helmet test line, and that the 1.5 m Australian drop test may be too low.
Data from epidemiological studies indicate that helmets are very protective against head and brain injury, although this protective effect is not 100% (Thompson et al., 1989; McDermott et al., 1993; Maimaris et al., 1994). The potential reasons for this lack of complete protection are many, and include poor fit, improper wearing because of style or fit, helmet failure, energy exceeding the helmet protective capabilities, and impact occurring outside the covered area of the head. Data available to date do not allow us to determine which of these mechanisms is most important.
The purpose of this study was to examine a large series of helmets involved in crashes in order to determine the location and type of damage to the helmet to gain a better understanding of why some helmeted cyclists sustain head injuries.
Section snippets
Design
This study was part of a larger case-control study of bicycle injuries and helmet effectiveness, based on the case-control design used in our previous investigation of bicycle helmet effectiveness (Thompson et al., 1989). Subjects were recruited from seven Seattle area hospitals: Central and Eastside Hospitals of Group Health Cooperative (GHC) of Puget Sound, a large staff-model HMO; Harborview Medical Center (HMC), a Level I Regional Trauma Center; University of Washington Medical Center, a
Results
During the study period, there were 3 849 eligible subjects treated in the emergency departments of the seven study hospitals. In addition, five subjects died from bicycle-related injuries prior to ER arrival, and were identified from medical examiner's records. We obtained completed questionnaires and injury data on 3 390 subjects for an overall response rate of 88.0%. There were 1 718 people (50.6% of the study subjects) who were helmeted at the time of the crash. Of these, 785 met the study
Discussion
This study provided important information on the events during a bicycle crash and the impacts to the head, face and helmet. The information should be of use to manufacturers and standards organizations, as well to groups conducting interventions to increase helmet use and decrease injuries.
The relatively large proportion (39%) of helmets which had damage to the liner indicates that the present policy of many manufacturers to offer free replacement for their helmets involved in crashes is very
Acknowledgements
This work was supported by a grant from the Snell Memorial Foundation, 6731 A 32nd St., North Highlands, CA 95660. The authors are indebted to Edward Becker and Frank Lin of the Snell Memorial Foundation for assisting with damaged helmet evaluation, to Alexandra Kaufman and Viviana Rebolledo (project coordinators), to Bob Soderberg for programming assistance, and to the emergency department and medical records personnel at our seven participating hospitals; Harborview Medical Center, Central
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