Hockey injuries across the lifespan: a descriptive, population-based study.INTRODUCTION
As a sport, ice hockey is a dynamic and demanding activity. The pace at which hockey is played stresses the development of motor coordination, speed and strength among its players.  As characterized by Sim and Chao (1978), hockey is a sport which is played on knives (skates), with clubs (sticks) and bullets (pucks). [16,21] Contact with the bladed edge of a skate, hockey stick, or puck can result in significant trauma to players.
At the elite levels, physical play is also seen as a fundamental part of the game.  Used primarily as a defensive tactic, "body checking" is defined by Hockey Canada as a technique whereby a player may legally separate a player from the puck through forceful body contact. Contact can come from the side, front or diagonally, but contact from behind is prohibited.  Body checking has been cited by several researchers as a primary cause of hockey related injury. [9, 15, 16]
A meta-analysis of hockey injury literature conducted by Benson and Meeuwisse (2005), found that the most common types of injuries among competitive hockey players [less than or equal to] 20 years old were: contusions, sprains/strains, lacerations, concussions and fractures.  In adult recreational leagues (i.e. [greater than or equal to] 18 years old) where player contact is not allowed, it was found that players in the Adult Male Recreational Leagues and Old-Timers Leagues reported injuries to the lower extremity as being the most common site of injury; accounting for 34% of all injuries. 
Previous Hockey injury investigations have focused primarily on fairly small samples of hockey players within a definable age range [6,7,9,13], sex [3,20], or ability level [22-24], or a combination thereof. What is lacking are large scale, population based analyses detailing the risk factors associated with hockey injuries.
The primary objective of this investigation is to describe the epidemiology of hockey injury in Ontario Canada from 2004-2006. This includes an analysis by age group, sex, body part injured, and mechanism of injury.
All hospitals in Ontario report Emergency Department visit and hospitalization data to the Ontario Ministry of Health and Long Term Care. The National Ambulatory Care and Reporting System (NACRS) and Discharge Abstract Database (DAD) are two routinely collected administrative databases, directed by the Canadian Institute for Health Information (CIHI).
The NACRS database includes data submitted by all emergency departments in the province, as well as day surgery and outpatient clinics. The DAD contains similar health care data for patients who were admitted to hospital. Access to anonymized records within NACRS and the DAD was granted by CIHI. Research ethics approval was granted by York University, Toronto, Canada.
The definition of a hockey injury was according to the Canadian edition of the International Classification of Disease Codes; tenth revision (ICD-10 CA), published by the World Health Organization.  Four codes encompass all broad mechanisms of hockey injury (Table 1).
Patient data submitted to the Ontario Ministry of Health and Long Term Care is processed and standardized to according to ministry guidelines; thereby minimizing variation in coding methodologies. The data sets (NACRS and the DAD) contain demographic information including the patient's age, sex, body part injured, and mechanism of injury. With respect to the type of injury sustained, classification proceeded according to ICD injury codes (e.g. S82.300 = distal fracture of the Tibia). 
Frequency distributions for age, sex, mechanism of injury and body region injured were tabulated. Age cohorts were defined by 5 year intervals. However, the youngest ([less than or equal to] 9 years old) and oldest patients ([greater than or equal to] 55 years old) were collapsed into wider ranges because of low numbers at either end of the age spectrum. The division of body regions were made according to accepted anatomical principles. For instance, the upper extremity was divided into two sections: structures proximal to the elbow (i.e. the shoulder, arm and elbow) and structures distal to the elbow (i.e. the forearm, wrist and hand). The distribution of all variables by mechanism of injury was also examined. All data were analyzed using SPSS 15.0.
There were 53,843 emergency department visits and 928 hospitalizations for hockey injuries over the two year period (2004 to 2006) in Ontario resulting in an average annual incidence rate of 489.4 per 100,000 population for ED visits and 8.13 per 100,000 population for hospitalizations.
Frequency distributions for sex and age of patients in the DAD (inpatient) and NACRS (outpatient) are presented in Table 2. Most hockey injuries are incurred by males, representing over 90% cases among both NACRS and the DAD. With respect to age group and hockey injury, over 50% of patients admitted to hospital, and approximately 60% of injuries among outpatients were [less than or equal to] 19 years old.
The distribution of hockey injury by mechanism of injury is presented in Table 3. With respect to the DAD, approximately 84% of injuries requiring admission to hospital resulted from contact injury mechanisms. Among outpatients, the corresponding number is 61%.
Table 4 illustrates the frequencies of hockey injury by body region. Hockey injuries to the head and face among outpatients totalled 18,246 (33.89%) cases, representing the most frequent body region injured among outpatients. With respect to inpatients, Knee/Leg/Ankle/Foot injuries represent the greatest proportion of injuries by body region, with 280 (30.17%) of injuries.
Findings from the analyses of mechanism of injury and the other variables are presented in Tables 5 and 6 (representing outpatients and inpatients respectively). Covariates such as sex, age and injury location were cross-referenced by their injury mechanism to yield the number of injuries within each variable. For example, the number of males incurring hockey puck impact injuries in NACRS totalled 8,377; representing 17.1% of all male hockey outpatient injuries.
Patients [greater than or equal to] 50 years of age display more from a hockey puck impact injuries, than players in other age groups. Among outpatients, of the 1476 injured players 50 years and older, 516 (35%) sustained hockey puck impact injuries.
The findings of this investigation provide a unique examination of ice hockey injuries across the lifespan. Previous investigations studying the epidemiology of hockey injury, tended to examine injury incidence and prevalence among specific hockey playing populations (e.g. hockey teams or leagues). [6,9,24] While these studies have provided important information about risk factors they are limited by the scope of their study population. Hockey injuries occurring outside structured competitive play are often not captured or studied. This investigation, using standardized hospital injury surveillance records, has captured all incidents of hockey injury presenting to Ontario hospitals occurring in both organized and recreational play.
Many of our findings are consistent with previous research. The majority of hockey injuries among both outpatients and hospital admissions are incurred by males. This observation coincides with findings published by Hostetler et al. who reported that female hockey injuries represented approximately 10% of the total number of hockey injuries observed.  Additionally, Ontario hockey injury hospitalizations in 2002/2003 saw 453 males compared to 34 females hospitalized for hockey injury.  The large disparity of hockey injury occurring between males and females may be attributed to several factors. Most notably, more males play hockey than females. Hockey Canada reports that for the 2004/2005 hockey season, of the total 209,978 players registered in the Ontario Hockey Federation, 182,028 (87%) players were male.  Further, there is no contact play allowed within women's leagues, which makes them less likely to suffer a contact injury.
The proportions of hockey injuries occurring across age groups indicate that the majority of hockey injuries are being incurred by players [less than or equal to] 19 years old. Among outpatients, players 10-19 years old account for the majority of hockey injuries. This may be attributed to the more intense level of play and inclusion of contact play among players within this age group. It may also reflect a population that plays hockey more frequently. Previous research [2,6,24] has also noted that exposure time to hockey and physical play is greatest within this age range. Additionally, recognizing that the adolescent growth spurt among boys and girls attains peak velocity at age 10-14 , disparities in anthropometric measures among players are apparent. For instance, in Bantam league hockey players (i.e. 14 years old), the differences in height and weight between the largest and smallest players were reported as being 55cm and 53 kg respectively.  This in turn can translate into differences of skating speeds of 2.3 m/s and impact force generation differences in excess of 357%. 
The effects of the substantial variations in body stature among players in this age cohort, may be echoed in the results of the analysis examining the injury characteristics surrounding contact with another player (i.e. W51.02). Players 10-19 years old display the highest proportions of injury resulting from contact with other players. Further, a large proportion of injuries requiring inpatient treatment resulted from contact.
Of the other mechanisms of injury studied in this investigation, those resulting from stick and puck impacts presented clear age-associated influences. Specifically with reference to injuries resulting from stick impacts, it was found that players [less than or equal to] 9 years old have the highest percentage of stick injuries. This may be because younger players are relatively unskilled, and may have difficulty controlling their sticks or adhering to the no "high-sticking" rule in hockey. Thus, coaches and parents should encourage the development of strong stick handling skills as a means of reducing injuries resulting from wayward sticks.
Contrary to the risk profile for injuries due to hockey sticks, the risk of sustaining a hockey puck impact injury increases as players' age. With respect to puck injuries by body region, the Head/Face demonstrated the second highest frequency for injury. Relating this observation back to age and ability level, it may be that as age increases, skill increases. This increase in skill can manifest itself in terms of increasing puck velocities from shooting actions. Playing in leagues where players are not required to wear mandatory facial protection (i.e. [greater than or equal to] 18 years old), this lack of protection, combined with faster puck velocities may account for the increasing risk of injury from puck impacts to older players.
Hockey is a challenging sport which emphasizes speed, agility and strength. As a result of the dynamics of the game and the implements used, the potential for injury must be recognized. Some injuries (e.g. puck impacts) may be hard to prevent. Proper instruction and use of proper protective equipment may represent a method which can reduce the occurrence of these types of injuries.
The prevention of contact injuries in hockey is much more controversial. It has been argued that physical play is a fundamental and inseparable part of hockey. This contention certainly holds at the elite levels of performance. What can be re-evaluated is the minimum age at which physical play is introduced to players. The majority of Canadian leagues permit body checking among players 11-12 years old. However, the province of Quebec, does not allow body checking until the age 14. [13,17] After this age level, anthropometric differences between players are reduced.  Therefore, players may be better able to absorb and tolerate impact forces sustained as a result of physical play. It can also be hypothesized that delaying the introduction of physical play among youth players, can reduce the exposure time to contact injury, while allowing for a prolonged focus on technical skill development (e.g. stick handling). Future research is needed to explore these hypotheses.
Other injury prevention strategies which can be effective are education programs aimed at increased safety conscious behaviours among players. Past programs such as the "Smart Hockey" program instituted by The ThinkFirst Foundation of Canada, was effective in increasing safety conscious behaviours among its participants.  Adult players may benefit from an increased awareness of the consequences of ocular or facial injuries resulting from hockey. This in turn may promote the inclusion of a facemask as a standard protective device.
As this study was an investigation into hockey injuries within Ontario, the results may not be generalizable to other populations. Further, no information was available regarding the context of injuries sustained by patients (e.g. organized versus unorganized hockey). This study only included hockey injuries which presented to hospital. As such, hockey injuries which were treated by a patient's doctor or those which never sought medical attention were not captured.
Hockey is a popular sport; it is played for fun and physical activity. Injuries sustained by players can be prevented by the amendment of rules, usage of proper equipment, or proficient execution of skills. However recognizing that hockey is a contact sport, there is an element of risk. A reduction in preventable injuries is a desirable outcome for players, regulatory bodies and the medical community.
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Jonathan Michael Josse
4700 Keele Street
Toronto, Ontario, Canada
Fax: (416) 736-5774
Phone: 1 (416) 736-2100 x.77216
Jonathan M. Josse, MSc (1), Joseph R. Baker, PhD (1), and Alison K. Macpherson, PhD (1,2)
(1) School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada, and (2) Institute for Clinical Evaluative Sciences, Toronto, ON
Table 1: Hockey ICD-10-CA External Causes of Injury Codes for Hockey Injury ICD-10 CA Code Injury Description W21.02 Striking against or struck by hockey stick W21.03 Striking against or struck by hockey puck W22.02 Striking against or struck by/playing hockey W51.02 Striking against or bumped into by another person in hockey Table 2: Frequency Distributions of Inpatient and Outpatient Hockey Injuries in Ontario from 2004 -2006 Inpatient (DAD) Outpatient (NACRS) Sex Count (%) Sex Count (%) Male 870 (93.75) Male 48922 (90.86) Female 58 (6.25) Female 4921 (9.14) Age Group Count (%) Age Group Count (%) 5-14 years 239(25.75) [less than or 2539 (4.71) equal to] 9 years 15-19 years 249 (26.83) 10-14 years 14454 (26.85) 20 years-24 years 78 (8.41) 15-19 years 15269 (28.36) 25 years-29 years 44 (4.74) 20 years-24 years 4953 (9.20) 30 years-34 years 73 (7.87) 25 years-29 years 3874 (7.19) 35 years-39 years 66 (7.11) 30 years-34 years 3523 (6.54) 40 years-44 years 83 (8.94) 35 years-39 years 3112 (5.78) [greater than or equal to] 45 years 96 (10.35) 40 years-44 years 2873 (5.34) 45 years-49 years 1770 (3.29) 50 years-54 years 743 (1.38) [greater than or 733 (1.36) equal to] 55 years/ other Total 928 (100) Total 53843 (100) Table 3: Mechanism of Hockey Injury within Inpatient and Outpatient Databases from 2004 - 2006 Inpatient (DAD) Mechanism of Injury Count (%) Striking against or struck by hockey stick 84 (9.05) Striking against or struck by hockey puck 60 (6.47) Striking against or struck by/playing hockey 401 (43.21) Striking against or bumped into by another person in hockey 383 (41.27) Total 928 (100) Outpatient (NACRS) Mechanism of Injury Count (%) Striking against or struck by hockey stick 10719 (19.91) Striking against or struck by hockey puck 9132 (16.96) Striking against or struck by/playing hockey 17219 (31.98) Striking against or bumped into by another person in hockey 15682 (29.13) Missing 1091 (2.03) Total 53843 (100) Table 4: Frequency Distributions of Hockey Injuries by Body Region between Outpatients and Inpatients from 2004 - 2006 Inpatient (DAD) Outpatient (NACRS) Count (%) Count (%) Head/Face Injury 124 (13.36) 18246 (33.89) Neck Injury 49 (5.28) 1645 (3.06) Trunk/Pelvic Injury 114 (12.29) 3677 (6.83) Shoulder/Upper Arm Injury 81 (8.73) 8579 (15.93) Forearm/Wrist/Hand Injury 150 (16.16) 10692 (19.86) Hip/Thigh Injury 57 (6.14) 624 (1.16) Knee/Leg/Ankle/Foot Injury 280 (30.17) 8100 (15.04) Other Injuries 73 (7.87) 2280 (4.23) Total 928 (100) 53843 (100) Table 5: Mechanism of outpatient hockey injuries by demographic variables and body part injured Stick Impacts Puck Impacts (W21.02) n (%) (W21.03 n (%) Sex Male 9702 (19.8) 8377 (17.1) Female 1017 (20.7) 755 (15.3) Age Group [less than or equal to] 1166 (45.9) 234 (9.2) 9 years 10-14 years 2294 (15.9) 1370 (9.5) 15-19 years 2371 (15.5) 1615 (10.6) 20 years-24 years 1318 (26.6) 1078 (21.8) 25 years-29 years 1011 (26.1) 959 (24.8) 30 years-34 years 882 (25.0) 966 (27.4) 35 years-39 years 643 (20.7) 895 (28.8) 40 years-44 years 511 (17.8) 926 (32.2) 45 years-49 years 334 (18.9) 573 (32.4) 50 years-54 years 106 (14.3) 252 (33.9) [greater than or equal to] 83 (11.3) 264 (36.0) 55 years Body Region Head/Face 6483 (35.5) 4359 (23.9) Neck 228 (13.9) 114 (6.9) Trunk/Pelvic Injury 504 (13.7) 310 (8.4) Shoulder/Upper Arm 220 (2.6) 181 (2.1) Injury Forearm/Wrist/Hand 2339 (21.9) 1617 (15.1) Injury Hip/Thigh Injury 42 (6.7) 22 (3.5) Knee/Leg/Ankle/Foot 581 (7.2) 2293 (28.3) Injury Other 322 (14.1) 236 (10.4) Incidental Contact Player Contact (W22.02) n (%) (W51.02) n (%) Sex Male 15608 (31.9) 14344 (29.3) Female 1611 (32.7) 1338 (27.2) Age Group [less than or equal to] 639 (25.2) 443 (17.4) 9 years 10-14 years 5417 (37.5) 5068 (35.1) 15-19 years 5263 (34.5) 5757 (37.7) 20 years-24 years 1316 (26.6) 1159 (23.4) 25 years-29 years 1033 (26.7) 808 (20.9) 30 years-34 years 928 (26.3) 681 (19.3) 35 years-39 years 900 (28.9) 583 (18.7) 40 years-44 years 825 (28.7) 547 (19.0) 45 years-49 years 481 (27.2) 348 (19.7) 50 years-54 years 221 (29.7) 137 (18.4) [greater than or equal to] 196 (26.7) 151 (20.6) 55 years Body Region Head/Face 3486 (19.1) 3598 (19.7) Neck 512 (31.1) 729 (44.3) Trunk/Pelvic Injury 1246 (33.9) 1532 (41.7) Shoulder/Upper Arm 3793 (44.2) 4234 (49.4) Injury Forearm/Wrist/Hand 4007 (37.5) 2545 (23.8) Injury Hip/Thigh Injury 256 (41.0) 292 (46.8) Knee/Leg/Ankle/Foot 3065 (37.8) 2014 (24.9) Injury Other 854 (37.5) 738 (32.4) Table 6: Mechanism of inpatient hockey injuries by demographic variables and body part injured Stick impacts Puck Impacts (W21.02) n (%) (W21.03) n (%) Sex Male 78 (9.0) 59 (6.8) Female 6 (10.3) * (1.7) Age Group 5-14 years 21 (8.8) 5 (2.1) 15-19 years 20 (8.0) 11 (4.4) 20 years-24 years 9 (11.5) 10 (12.8) 25 years-29 years 8 (18.2) 5 (11.4) 30 years-34 years 10 (13.7) 7 (9.6) 35 years-39 years * (6.1) * (3.0) 40 years-44 years 9 (10.8) 5 (6.0) [greater than or equal to] * (3.1) 15 (15.6) 45 years Body Region Head/Face 20 (16.1) 37 (29.8) Neck 13 (26.5) * (6.1) Trunk/Pelvic Injury 14 (12.3) 8 (7.0) Shoulder/Upper Arm Injury * (2.5) * (1.2) Forearm/Wrist/Hand Injury 18 (12.0) * (1.3) Hip/Thigh Injury * (1.8) 0 (0.0) Knee/Leg/Ankle/Foot Injury 10 (3.6) * (0.7) Other 6 (8.2) 7 (9.6) Incidental Contact Player Contact (W22.02) n (%) (W51.02) n (%) Sex Male 375 (43.1) 358 (41.1) Female 26 (44.8) 25 (43.1) Age Group 5-14 years 105 (43.9) 108 (45.2) 15-19 years 99 (39.8) 119 (47.8) 20 years-24 years 20 (25.6) 39 (50.0) 25 years-29 years 21 (47.7) 10 (22.7) 30 years-34 years 36 (49.3) 20 (27.4) 35 years-39 years 31 (47.0) 29 (43.9) 40 years-44 years 41 (49.4) 28 (33.7) [greater than or equal to] 48 (50.0) 30 (31.3) 45 years Body Region Head/Face 28 (22.6) 39 (31.5) Neck 19 (38.8) 14 (28.6) Trunk/Pelvic Injury 38 (33.3) 54 (47.4) Shoulder/Upper Arm Injury 40 (49.4) 38 (46.9) Forearm/Wrist/Hand Injury 61 (40.7) 69 (46.0) Hip/Thigh Injury 30 (52.6) 26 (45.6) Knee/Leg/Ankle/Foot Injury 157 (65.1) 111 (39.6) Other 28 (38.4) 32 (43.8) * = cell size <5