Head-Impact Mechanisms in Men's and Women's Collegiate Ice Hockey

Context:

Concussion injury rates in men''s and women''s ice hockey are reported to be among the highest of all collegiate sports. Quantification of the frequency of head impacts and the magnitude of head acceleration as a function of the different impact mechanisms (eg, head contact with the ice) that occur in ice hockey could provide a better understanding of this high injury rate.

Objective:

To quantify and compare the per-game frequency and magnitude of head impacts associated with various impact mechanisms in men''s and women''s collegiate ice hockey players.

Design:

Cohort study.

Setting:

Collegiate ice hockey rink.

Patients or Other Participants:

Twenty-three men and 31 women from 2 National Collegiate Athletic Association Division I ice hockey teams.

Main Outcome Measure(s):

We analyzed magnitude and frequency (per game) of head impacts per player among impact mechanisms and between sexes using generalized mixed linear models and generalized estimating equations to account for repeated measures within players.

Intervention(s):

Participants wore helmets instrumented with accelerometers to allow us to collect biomechanical measures of head impacts sustained during play. Video footage from 53 games was synchronized with the biomechanical data. Head impacts were classified into 8 categories: contact with another player; the ice, boards or glass, stick, puck, or goal; indirect contact; and contact from celebrating.

Results:

For men and women, contact with another player was the most frequent impact mechanism, and contact with the ice generated the greatest-magnitude head accelerations. The men had higher per-game frequencies of head impacts from contact with another player and contact with the boards than did the women (P < .001), and these impacts were greater in peak rotational acceleration (P = .027).

Conclusions:

Identifying the impact mechanisms in collegiate ice hockey that result in frequent and high-magnitude head impacts will provide us with data that may improve our understanding of the high rate of concussion in the sport and inform injury-prevention strategies.Key Words: impact biomechanics, sport, concussion, sex

Key Points

• The most frequent head-impact mechanism in both men''s and women''s collegiate ice hockey was contact with another player. Contact with the ice was the mechanism that resulted in head impacts with the greatest magnitude.
• Male collegiate ice hockey players experienced head impacts from contact with another player and contact with the boards more frequently than did female players, and these impacts were generally of greater magnitude.

Ice hockey is a high-intensity, high-speed collision sport in which most injuries are caused by blunt trauma or direct contact with another player or object as opposed to overuse injuries.¹ High rates of injury have been reported in both men''s and women''s collegiate ice hockey (5.95/1000 and 5.12/1000 athlete-exposures AEs], respectively), and the most common injury in both populations is concussion.² The rate of concussion has been reported to be higher in women''s ice hockey (0.82/1000 AEs) than in men''s (0.72/1000 AEs), but the reasons for this are not well understood.² Concussions are usually attributed to a direct impact to the head but can also be caused by an impact to the body that results in an acceleration of the head.³ The high rate of injury, including concussions, in ice hockey can be attributed to the unique factors of the game: the playing area is made of solid ice and enveloped by rigid boards, players manipulate pucks that, when shot, can exceed speeds of 80 mph (117 kph), and players travel at speeds of up to 30 mph (44 kph) and purposefully collide with opponents.^4,5 These factors allow for a number of different head-impact mechanisms, or circumstances in which a head impact occurs (head contact with ice, boards, etc), in ice hockey.Currently, data quantifying the biomechanics of head impacts as a function of the different impact mechanisms that occur in ice hockey are lacking. Previous authors^6,7 have quantified the frequency and magnitude of head impacts in cohorts of male and female hockey players at different levels of play using the Head Impact Telemetry (HIT) System (Simbex, Lebanon, NH). The HIT System measures and records biomechanical data from head impacts, including the linear and rotational acceleration of the head, impact duration, and impact location on the helmet.^5–19 These studies have provided valuable information on individual players'' exposure to head impacts but did not identify or examine the relationship with mechanisms of impact. Other researchers^2,4,20–22 have reported injury epidemiology, including diagnosed concussions, by specific injury mechanisms in collegiate ice hockey. Agel et al^20,21 used the National Collegiate Athletic Association (NCAA) Injury Surveillance System to report concussion mechanisms in collegiate men and women. Diagnosed concussions were classified into 1 of 7 mechanisms: contact with another player, contact with the ice surface, contact with the boards or glass, contact with the goal, contact with the stick, contact with the puck, or no apparent contact. Another author²³ classified injury mechanisms in National Hockey League players by reviewing video footage from games in which diagnosed concussions occurred. The most common mechanism that resulted in diagnosed concussions for both studies was player-to-player contact.^20,21,23 Although these assessments provided important information on injury and concussion mechanisms in ice hockey, the collection and analysis of the impact biomechanics that resulted from these mechanisms were beyond the scope of the study designs. Synchronizing video with the biomechanics of head impacts would provide a quantitative approach to evaluating head impact mechanisms and biomechanics.The aim of our study was to quantify and compare the frequency and magnitude of head impacts associated with various impact mechanisms in men''s and women''s collegiate ice hockey players. We accomplished this by synchronizing video footage from games with biomechanical data from the HIT System. We hypothesized that the frequency and magnitude of head impacts would differ among the various head-impact mechanisms and that sex would be a significant factor in both frequency and magnitude.