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Abstract
Background We report the incidence, type, mechanism and severity of ice hockey injuries in women's international ice hockey championships.
Methods All injuries in the International Ice Hockey Federation World Women's Championship, World Women's under-18 Championship and Olympic Winter Games tournaments were analysed over an 8-year period using a strict injury definition, standardised reporting and team physician diagnosis.
Results 168 injuries were recorded in 637 games over an 8-year period resulting in an injury rate (IR) of 6.4 per 1000 player-games and 22.0/1000 player-game hours. The IRs were 2.7/1000 player-games for the lower body, 1.4 for the upper body, 1.3 for the head and face and 0.9 for the spine and trunk. Contusion was the most common injury followed by a sprain. The most commonly injured site was the knee (48.6% of lower body injuries; IR 1.3/1000 player-games). The Medial collateral ligament sprain occurred in 37.1% and ACL rupture in 11.4% of knee injuries. A concussion (74.3%; IR 1.0/1000 player-games) was the most common head injury.
Conclusions and recommendations The risk of injury to female ice hockey players at World Championship and Olympic tournaments was about half of that observed in the men's Championships. Full facial protection decreases the risk of lacerations and should be continued in all future female tournaments. More effective prevention strategies for knee, ankle and shoulder injuries are needed in women's ice hockey. Improved concussion education is necessary to promote more consistent diagnosis and return to play protocols.
- Ice hockey
- Epidemiology
- Female
- Injuries
- Concussion
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Introduction
Twenty-eight countries competed in the 2014 International Ice Hockey Federation (IIHF) World Women's Championship (WWC) programme and 19 in the World Women under-18 Championships (WWC U18) category. The IIHF, in collaboration with the local organising committee, runs WWC in the five different divisions and WWC U18 in three different divisions. The teams were qualified to the divisions and its subgroups according to IIHF World ranking. Women's ice hockey has been part of the Olympic Winter Games (OWG) since 1998.
Each ice hockey team typically consists of 20–22 players (depending of the level and age group of the tournament), including two wingers, one centre, two defencemen and a goalkeeper, who are usually on the ice at the same time. The active playing time is three periods of 20 min each. Despite the fact that body checking is not permitted in women's ice hockey at any level, ice hockey is associated with many potential risks, such as unintended collisions, high velocity, rapid changes in direction and traumas from the boards, stick or puck.1 Concussions, contusions, sprains and strains occur in female ice hockey.2 ,3 However, the risk, type, mechanism and severity of women's ice hockey injuries at the international elite level have not been well studied.
We aimed to report the incidence, nature, causes, severity and time-trend of injuries in women's international ice hockey, using standardised epidemiological methods.4 Our larger goal is to promote athlete's health and reduce the risk of injuries.5
Methods
During the eight ice hockey seasons between 2006–2007 and 2013–2014 (from 1 July 2006 to 30 June 2014) we registered, with the permission from the IIHF, all ice hockey injuries from the 39 female ice hockey tournaments. Twenty-five of them were WWC, including 2010 and 2014 OWG, and 14 were WWC U18 (table 1). A total of 637 games were played in the 39 tournaments by 259 teams (5344 players). WWC competitions consisted of 393 games in the 25 tournaments played by 163 teams (3376 players), and WWC U18 competitions consisted of 14 tournaments played by 96 teams (1968 players).
Investigated tournaments in World Women's Championship (WWC) and World Women's under-18 Championship (WWC U18)
A team medical personnel meeting before each tournament allowed the IIHF medical supervisor (MS) to review the definition of the injury, game injury report (GIR) form and the injury report system (IRS) form with the individual team physicians (figure 1). The definition of an injury was made in accordance with accepted international ice hockey norms. An IRS form was completed when one of the following criteria was observed:
Any injury sustained in a practice or a game that prevented the player from returning to the same practice or game;
Any injury sustained in a practice or a game that caused the player to miss a subsequent practice or game;
A laceration that required medical attention;
All dental injuries;
All concussions;
All fractures.
Injury report system form of the International Ice Hockey Federation.
The team physician followed all the players on the team and reported all injuries to the MS using the GIR form. GIR was obtained from each team physician after every game to verify the number of injuries that satisfied the definition (figure 2). Each injury also required completion of a more detailed IRS form by the team physician. The GIR and IRS forms were both anonymous. The IIHF MS assigned to each championship was responsible for data collection. The IRS form was filled only once for each injury and included detailed information on the period, location on ice, mechanism, anatomic location, severity and specific injury diagnosis. The anonymous forms were returned to the IIHF Medical Committee for insertion into a computer-based IRS for ice hockey injuries (Medhockey, Medisport Ltd, Finland).
Game injury report form of the International Ice Hockey Federation.
Injury rate (IR) was expressed as the number of injuries per 1000 ice hockey player-games and per 1000 player-game hours. These two different IR definitions were used to allow comparison with other IIHF championships, hockey leagues and sports (handball, soccer).6–10
The population-at-risk or player exposure to injury was determined by an estimation of collective playing time. The number of player-games was based on 20–22 players competing for each team in a game, depending on the specific level and year of a given tournament. Only the participating athletes were included in the denominator when calculating incidence of injury.
The player-game IR was an average risk of one individual player per 1000 games (number of injuries/number of players (2 teams)/number of games×1000= number of injuries per 1000 player-games). The IR for 1000 player-game hours was based on a 60-min active game with five players and a goalie per team on the ice at the same time (number of injuries/number of players on ice same time (2 teams)/number of games×1000= number of injuries per 1000 player-game hours).
Practice injuries were excluded because there were few documented injuries (n=10); therefore, the given IRs refer to game injuries only. Time loss was used as a proxy for severity of an injury. Risk ratios (RRs) and 95% CIs for player position-wise concussion were calculated by comparing concussions at one position to concussions at all others positions.
Results
Incidence of injury
During the study period, 168 injuries were reported in 637 games. The IR per 1000 ice hockey player-games was 6.4 for all female tournaments (WWC U18, WWC and OWG). The annual IR ranged between 4.5 (2014) and 11.2 (2010). For WWC U18 tournaments, the IR was 7.5/1000 player-games, and the annual IR ranged between 4.2 (2012) and 11.2 (2013). For WWC tournaments, the IR was 5.7/1000 player-games and the annual IR ranged between 3.6 (2011) and 11.3 (2010; figure 3). IR per 1000 player-game hours was 22.0 for all female tournaments, 25.6 for WWC U18 tournaments, 19.7 for WWC tournaments and 29.8 for OWG.
Annual ice hockey injury rates per 1000 player-games for all female tournaments, WWC and WWC U18 (OWG, Olympic Winter Games; WWC, World Women's Championship; WWC U18, World Women's under-18 Championship).
Injuries by anatomic region
Injuries involved were the head and face in 35 cases (20.8% of game injuries), the lower body in 72 cases (42.9%), the upper body in 37 cases (22%) and spine or trunk in 24 cases (14.3%). The IR for head and face injuries was 1.3/1000 player-games, for lower body 2.7, for upper body 1.4, and for spine and trunk 0.9, respectively. In WWC U18 tournaments, the IR for head and face injuries was 1.9/1000 player-games, for lower body 3.1, for upper body 1.5, and for spine and trunk 1, respectively. In WWC tournaments, the IR for head and face injuries was 1.0/1000 player-games, for lower body 2.5, for upper body 1.3, and for spine and trunk 0.9, respectively (table 2 and figure 4).
Head and face injuries: Concussion was the most common head injury (74.3%; IR 1.0/1000 player-games). There were 8.6% lacerations and 5.7% dental injuries (IR 0.1). There were no eye injuries. In all female tournaments, 17.1% of the head and face injuries were facial injuries, with an IR of 0.2/1000 player-games (WWC U18 21.1%; IR 0.4; WWC 13.3%; IR 0.1).
Lower body injuries: The knee was the most frequent site of lower body injury (48.6%). The knee IR was 1.3/1000 player-games. Medial collateral ligament (MCL) sprain (37.1%) and knee contusion (28.6%) were the most common knee injuries. ACL rupture occurred in 11.4% of all knee injuries. Ankle (27.8%; IR 0.8) and thigh injuries (8.3%; IR 0.2) were the second and third common lower body injuries.
Upper body injuries: The shoulder was the most common location for an upper body injury (32.4%). The shoulder IR was 0.5/1000 player-games. Acromioclavicular joint sprain (50%) was the most frequent diagnosis. Wrist (18.9%) and elbow (18.9%) injuries were the second and third most common upper body injuries.
Ice hockey injuries by anatomic region in all female tournaments, WWC and WWC U18
Injury rate by anatomic region per 1000 player-games in World Women's Championship and World Women's under-18 Championship.
Injury types by diagnosis
The vast majority of injuries (80.8%) were acute in nature and this trend was consistent over the 8-year study period. A contusion was the most common type of injury (28.0%), followed by a sprain (20.8%), concussion (15.5%), strain (11.9%) and laceration (5.4%; figure 5).
Injury distribution by diagnosis in all female tournaments, WWC and WWC U18 (OWG, Olympic Winter Games; WWC, World Women's Championship; WWC U18, World Women's under-18 Championship).
Concussion
Concussions accounted for a small yet clinically important number (n=26, 15.5%) of injuries in the championships. The concussion IR was 1.0/1000 player-games in all female tournaments, 1.4 in WWC U18 tournaments and 0.7 in WWC tournaments. The two most common causes for concussion were unintended collision (34.6%) and body check (30.8%). A penalty was called in only 25.0% of the events when a concussion was caused by body check. For those players diagnosed with a concussion, 11.5% returned to play in the same game. The majority of concussions occurred before the 2012 Zurich Consensus Guidelines, which do not allow return to play in the same game. The centre position (IR 1.6/1000 player-game hours) had the highest risk of concussion, followed by defence position (IR 0.5) and wing (IR 0.4). RR for concussion on centre position versus all other positions was 4.29 (95% CI 1.99 to 9.24). The majority of concussions occurred during the second (30.8%) and third (34.6%) periods.
Contact with the boards
The majority of injuries occurred away from the boards (61.1%). This trend was apparent in all championships and was similar over the 8-year study period. Head and knee injuries resulting from contact with the boards were the most common (18.6%, respectively). The majority of concussions occurred without board contact (65.4%).
Causes of injury
Injuries were caused by unintended collision (26.3%), body checking (24.6%) and puck contact (12.0%). The majority of the injuries caused by stick were lower body injuries (70.0%). Penalties were assessed in 24.4% of body check injuries, 40.0% in checking to the head and 50.0% in hitting from behind injuries.
Injury severity
The majority of players who were injured returned to play within 1-week (58.1%); however, 9.6% of the injured players did not return for at least 3 weeks. The most severe injuries were wrist and hand fractures and knee sprains.
Player position, period and zone
Injuries were equally distributed according to player position: wing 37.7% (2 wings per team), centre 24.0% (1 centre per team) and defence 30.5% (2 defences per team). The goalkeeper was the least injured of all positions (6.6%). In the women's tournaments, the proportion of concussions sustained by centre was about four times higher than that of other positions (RR 4.29, (95% CI 1.99 to 9.24)). There were no significant differences between player positions concerning other injuries. The second and third period had the highest percentages of injured players (35.3%; 37.1%) during the game. There were only a few injuries sustained during warm up (2.3%) and overtime (1.7%). Only 5.6% of the injury situations occurred during the practices. Players sustained injuries at the home zone (39.5%), visitor zone (31.7%) and neutral zone (19.8%).
Discussion
This observational study followed 39 women's Ice Hockey World Championship tournaments over an 8-year period, to determine the incidence, type, mechanism and severity of injuries. During the study period, 5344 players sustained 168 injuries in 637 games. The total IR was 22.0/1000 player-game hours for all female tournaments. Contusion was the most common type of injury followed by ligament sprain. The lower body was injured most frequently (42.9% of game injuries). In all female tournaments, 74.3% of the head and face injuries were concussions, which were the most common diagnoses in female ice hockey, followed by knee and ankle sprains.
Quality of the data
The strengths of this study include the large number of players competing at the highest level of international competition over an 8-year period. The number of events was determined with a strict injury definition that incorporated time lost and specific diagnosis, standardised nomenclature and a reliable data collection instrument.4 Detailed information was collected with the two structured questionnaires.11
Data collection was reliable and accurate because team physicians diagnosed the injuries. Coverage of all injuries was ascertained by the MSs who collected study forms after each game. They followed all the games during a tournament, and enquired about possible injuries and players who were missing from the team roster. Injury incidence rates were estimated by collective playing time since individual on-ice exposure could not be measured. We assumed that six players were on the ice for each team during a 60 min game. This method does not take penalties or overtime into consideration.
In a similar study of men's international ice hockey, the total men's IR was 52.1/1000 player-game hours for all World Championships (WC) and 59.6 for WC A-pool tournaments.12 In men, the most commonly injured sites were the head and face (39.8% of game injuries; IR 5.7/1000 player-games). Laceration, especially facial laceration, was the most common injury type (26.1% of all injuries). In the present study, a laceration was diagnosed only in 5.4% of all injuries due to the fact that full facial protection is mandatory at all levels of female ice hockey.13 In men's tournaments, the most common lower body injury involved the knee (46.9%; IR 2.0/1000 player-games), with the MCL (56.6% of all knee injuries) being the most frequently injured anatomic structure. ACL injury was documented in 10.5% of all knee cases. The knee IR for women during games was 1.3 (WWC U18 IR 1.8; WWC IR 1.0) and 28.6% of knee injuries were contusions. In the present study, the shoulder IR for women (IR 0.5) was clearly lower than the rate in men's tournaments (IR 1.5). In contrast, the ankle IR for women (IR 0.8) was higher than that for men (IR 0.6). The risk of concussion for women during international competition was lower than that in men's tournaments but was similar, in the WWC U18 level, to men's tournaments: 1.4/1000 player-games in all men's WC and 1.9 in men's A-pool tournaments compared with 1.0/1000 player-games in all female tournaments, 1.4 in WWC U18 tournaments and 0.7 in WWC tournaments.
Comparison with women's hockey data in National Collegiate Athletic Association (NCAA) and elsewhere
Agel and Harvey reported an IR of 12.1/1000 athlete-exposure (AE) in women's National Collegiate Athletic Association ice hockey games. The AE was determined by the number of athletes participating in a game or practice regardless of duration or type of exposure. Concussions were the most common type of injury followed by the hip/groin and ankle. The average rate of concussion over a 7-year period was 0.82/1000 AEs. Body checking and unintentional collision with an opponent were the common mechanisms of injury.14 Schick and Meeuwisse reported that the IR for female players was 7.77 per 1000 AEs. Ninety-six per cent of injuries were related to contact mechanisms. Concussions were the most common injury, followed by ankle sprains and adductor muscle strains.2
Injury risk in ice hockey can be compared with other sports. In the present study, the IR was 22.0/1000 player-game hours in women's ice hockey World Championships. In contrast, the IRs have been reported to be 103/1000 player-game hours in female handball,6 and 67.4/1000 player-game hours in female soccer.7 In women's World Football tournaments from 1998 to 2012, the IR was 65.4/1000 player-game hours.8 IRs for the different women's team sports during the 2004 Olympic Games were: soccer 70/1000 player hours, handball 145/1000 player hours and basketball 100/1000 player hours.9 Pasanen et al10 reported that the injury incidence in Finnish woman's floorball was 40.3/1000 player-game hours. However, the comparison between sports with respect to injury risk is difficult because of the different study methodology, differences in definition of injury and estimation of exposure.
In summary, this 8-year study showed that the risk of injury during women's international ice hockey tournaments was substantially lower than the risk in men's games. Moreover, the IR in female ice hockey appears to be lower than that in other women's team sports. The knee, head, ankle and shoulder are the most vulnerable body sites. Improved knowledge on the risk factors and mechanisms of ice hockey injuries are needed for initiation of effective preventive strategies.
What are the new findings?
The overall injury rate in women's World Championships and Olympic Winter Games was 22.0 per 1000 player-game hours.
The risk of injury in female ice hockey is about half of that reported in men's ice hockey.
Lower body injuries are most common. The knee, head and ankle are the three most common injured anatomic sites. ACL disruption comprised 11.4% of all knee injury cases.
Concussion was the most common head and face injury. The centre position has fourfold the risk ratio for concussion compared with wing or defence.
One of 10 players diagnosed with a concussion returned to play during the same game.
A laceration occurred in only 8.6% of the head and face injuries; all players wear full facial protection.
How might it impact on clinical practice?
Continued use of a full face mask is recommended.
More effective prevention strategies for knee, ankle and shoulder injuries are needed in female ice-hockey, including neuromuscular exercises.15
Improved concussion education will promote more consistent diagnosis, treatment and return to play protocols. Further research is necessary to determine if improved skills and physical performance of the players can reduce the risk of concussion.
Body checking is not allowed in women's hockey and this rule should not be changed in the future.
Acknowledgments
This study was financially supported by The International Ice Hockey Federation and the Finnish Ministry of Education and Culture. The authors highly appreciate the cooperation of all team physicians, physiotherapists and IIHF Medical Supervisors who volunteered their time to collect the data for this project. The authors would like to thank the International Ice Hockey Federation Medical Committee for all practical support.
References
Footnotes
Contributors MT, MJS, MA, PK, KT and JP contributed to study conception and design. MT carried out the literature search and coordinated and managed all parts of the study. MT, MJS and MA conducted data collection and performed preliminary data preparations. MT and KT conducted data analyses and all the authors contributed to the interpretation of data. MT and JP wrote the first draft of the paper and all the authors provided substantive feedback on the paper and contributed to the final manuscript. All the authors have approved the submitted version of the manuscript. MT is the guarantor.
Funding This study was financially supported by The International Ice Hockey Federation and the Finnish Ministry of Education and Culture.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.