Snowsport Helmets: The Good and Bad Irving Scher, PhD, PE Jasper Shealy, PhD
Inherent Risks in Snow Sports
Head Injuries in Snow Sports 4% to 12% of all injuries Potential outcomes: minor to severe Death or devastating permanent cognitive issues ⅔ of fatalities involve a head injury 3
Wear a Helmet Shell Foam liner Energy attenuating Comfort Chin strap
Outline for Talk Helmet Use and Head Injury Statistics Helmet Capabilities & Limitations Influence of Helmets on Fatality Risk 5
Takeaway Points 1. Ski helmets reduced minor and potentially serious head injuries 2. Ski helmets have not reduced (and cannot reduce) fatal injuries
Percent Utilization 0 20 40 60 80 100 U.S. Helmet Use on the Rise Overall Helmet Utilization 02/03 03/04 04/05 05/06 06/07 07/08 08/09 09/10 10/11 11/12 12/13 Season 7
Percent Utilization 0 20 40 60 80 100 U.S. Helmet Use: 02/03 12/13 Season 02/03 12/13 <10 10-14 15-17 18-24 25-34 35-44 45-54 55-64 >64 Age Group 8
Percent Utilization 0 20 40 60 80 100 U.S. Helmet Use by Age Season 11/12 10/11 09/10 08/09 07/08 06/07 05/06 04/05 03/04 02/03 <10 10-14 15-17 18-24 25-34 35-44 45-54 55-64 >64 Age Group 9
Percent Utilization 0 20 40 60 80 100 Canadian Helmet Use: 2012-2013 <10 10-14 15-17 18-24 25-34 35-44 45-54 55-64 65-74 >74 Age Group 10
% Helmet Utilization Sugarbush - Helmet Use Trend 90 80 70 60 50 40 30 20 10 0 95/96 96/97 97/98 98/99 99/00 00/01 01/02 02/03 03/04 04/05 05/06 06/07 07/08 08/09 09/10 10/11 11/12 Season
Mean Days Between Injuries Sugarbush - Head Injuries 100000 PSHI MDBI CPSC MDBI Better Better Better Better R² = 0.3551 10000 R² = 0.4874 1000 Worse Worse Worse Worse 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Helmets Capabilities and Limitations 13
Limitations Helmets only protect the head Limited amount of impact mitigation capability Does not protect against all types of head injuries 14
Head Motion for TBI Linear Acceleration Angular Acceleration
Linear Acceleration Injuries Skull fracture Coup brain injuries At the site of impact Linear Acceleration Contrecoup brain injuries On the side opposite of impact Localized injuries
Angular Acceleration Shearing injuries Diffuse Axonal Injury Bridging vein rupture (subdural hematoma) Angular Acceleration Injury not necessarily at or opposite to site of impact Diffuse injury 17
Common Head Injury Mechanism Opposite-edge phenomenon Nakaguchi et al. (2002) Usually:
When Can a Helmet Help? Conducted testing to find out Back edge catch (snowboarding) Impact with a fixed object
Methods On-slope speed measurements Average speed = 18 mph Indoor Test Facility Falls onto a snow surface Obstacle strike Crash Test Dummy Instrumented head Helmeted Unhelmeted 20
Helmet Testing Equipment Helmets Various makes/models Fit to the dummy head Snow Surface Soft, spring snow Hard packed and icy snow Fixed obstacle 11-inch diameter wooden pole 21
Helmet Testing Procedure Slope of 20 ~19 mph impact speed
Results - Five phases of a fall
Ave Max Head Acceleration (Gs) Results Head Accelerations 750 Helmet No Helmet 500 250 0 Soft Snow Icy Snow Obstacle (tree) 24
Average 15ms HIC Score 12, 000 Results HIC 15 3500 3000 2500 2000 1500 1000 500 Helmet No Helmet 0 Soft Snow Icy Snow Obstacle 25
Probability of Severe Brain Injury (%) Results Probability of Brain Injury 100 Helmet No Helmet 75 50 25 0 Soft Snow Icy Snow Obstacle (tree) 26
Testing Conclusions Hard, icy snow: Helmets likely help Soft snow: Helmet may not be needed Still a good idea Hit a tree or lift tower Not likely to make a difference 27
Has Increased Helmet Use Decreased Fatalities?
Do Helmets Reduce Fatalities? Most fatal ski accidents involve an enormous amount of energy Energy attenuating capability of a helmet Hypothesis: A helmet may alter the pattern of death, but not the ultimate outcome. 29
Skiing Fatalities Following analysis based on publicly available media reports (not death certificates) 2000-2001 to 2004-2005 seasons Found 215 fatalities 58 had data on helmet use AND primary cause of death 30
Primary Cause of Death Head injury as primary cause of death 2.3 times more likely for nonhelmeted fatalities Wearing a helmet had no overall effect on fatalities Pattern in leading cause of death changed 31
Rate (Fatal per Million; Helmet Per Cent) Helmet Use and Fatality Rates 1.2 1 0.8 SB Rate Ski Rate Per Cent Utilization Linear (SB Rate) Linear (Ski Rate) R 2 = 0.0009 0.6 0.4 R 2 = 0.0001 0.2 0 91/92 92/93 93/94 94/95 95/96 96/97 97/98 98/99 99/00 00/01 01/02 02/03 03/04 04/05 05/06 06/07 07/08 08/09 Season 32
Conclusion Use of helmet will alter primary body part No data to support increased helmet use will decrease fatality rate For incident scenarios associated with fatality, more than a helmet is needed to avoid death 33
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