Ice hockey is an inherently physical sport and as such creates situations where injury is possible and often likely. With the influence that injuries can have on a team’s success, research has started to focus on our ability to assess injury risk and prevent injuries before they occur. However, these strategies cannot be effectively laid out until we first understand who gets hurt, when they get hurt, and how they get hurt.
Who gets hurt?
According to a prospective cohort study performed by Flik et al., there is a significant disparity in injury incidence depending upon player position in NCAA Division 1 ice hockey. Only 6.2% of injuries were sustained by goaltenders, whereas 32.7% were defensemen and 61.1% were forwards. In agreement with this distribution, Agel et al found 9.6% of injuries effected goaltenders, 40.8% were defensemen, and 48.3% were forwards. This information also correlated with a recent study investigating injury incidence during the World Championship and Olympic tournaments, where goaltenders were once again the least injured followed by defensemen and forwards. However, when evaluating injuries in the National Hockey League (NHL), the only significant difference found was a higher likelihood of defensemen missing game time due to injury in comparison to forwards. This study also found that a significant predictor of missing at least 5 games due to injury included being a goaltender (odds ratio = 1.68). So, while goaltenders do not get injured as often, their return to play is often more extended in comparison to other players. These numbers are likely not as drastically position dependent due to the disparity of position players on the ice at one time (3 forwards, 2 defensemen, and 1 goaltender), which may account for a significant amount of the variance reported in the literature at the collegiate, international, and professional levels.
When do they get hurt?
Understanding when injuries occur during the course of an individual game and throughout the course of the season allows us to understand when an athlete is at an increased risk of injury. With regards to the collegiate level, 65.5% of injuries occur during games and 35.5% during practice. Additionally, preseason practice rates were more than twice as high as in season injury rates. Two studies looked into the distribution of injuries during gameplay and found drastically different results. Agel and colleagues found that most injuries occurred in the 2nd and 3rd periods, which is likely due to athlete fatigue and intensity of gameplay increasing as the game progresses. In contrast to this report, amongst NHL regular season injuries, the vast majority occur in the first period (48.1%). Intuitively, as the NHL season progresses, the likelihood of injury also increases. This increase in injury rate is likely due to player fatigue and increased intensity of play as teams are fighting for a playoff spot.
How do they get hurt?
Due to the physical nature of ice hockey, the vast majority of injuries are contact-related, however non-contact injuries tend to make up a higher proportion of practice injuries. According to Agel and colleagues, non-contact injuries make up 9.7% of injuries during games, whereas they make up 32% of injuries during practice. During games, approximately 50% of injuries are due to contact with another player and 39.6% are due to contact with another object (boards, puck, etc.). In agreement with these trends, in the NHL body checking made up 28.6% of injuries, while incidental contact (14.3%), hit by puck (13.5%), contact with the environment (9.4%), and other intentional player contact (7.4%) made up the bulk of injuries incurred. Aside from these mechanisms, non-contact injuries made up 14.8% of all injuries and accounted for 11.7% of man games lost due to injury (1,921 games) between 2009 and 2012. This gives good insight into the general cause of injury, but what types of injury are most common amongst ice hockey players?
Over a 16 season timeframe, injures most often sustained during gameplay included internal derangement of the knee (13.5%), concussion (9.0%), acromioclavicular joint injury (8.9%), upper leg contusion (6.2%), and musculotendinous strain of the hip/groin region (4.5%). However, distribution of injuries during practice shows a slightly different distribution. The most common injuries during practice were musculotendinous strain of the hip/groin region (13.1%), internal derangement of the knee (10.1%), ankle ligament sprain (5.5%), concussion (5.3%), and acromioclavicular joint injury (4.4%). Looking further at this data, during games, the highest prevalence of severe injuries was knee internal derangement and the most common mechanism of injury was due to player contact. Of the most common severe injuries reported, musculotendinous injuries of the pelvis/hip was the only pathology (6.2%) that had a non-contact mechanism as the most common cause. In agreement with these findings, amongst NHL players, the most common sites of injury include the head (17%), thigh (14%), knee (13%), and shoulder (12%). Additionally, with regards to man games lost, these regions also comprised the largest impact on their respective teams. Unfortunately, this study did not break the body regions into specific injuries/pathologies.
Given the fairly vague description of the injuries reported in these large epidemiological studies, it is also important to look more in depth to determine which specific injuries are actually reported in the literature. With regards to knee ligamentous injuries, Sikka and colleagues found that between 2006 and 2010, only 47 players sustained an anterior cruciate ligament tear in the NHL, which is significantly lower than most professional contact team sports. These injuries included 3 goaltenders, 8 defensemen, and 36 forwards. Of these 47 injuries, the reported mechanism for all but one injury was contact with another player and/or with the boards. In addition to the primary ACL rupture, 68% of injuries reported a concomitant meniscal or medical collateral ligament injury as well. Looking at the more commonly injured MCL, from 2003-04 to 2010-11, 13 MCL injuries were reported within one collegiate ice hockey program. This resulted in ten different players being injured (12.7%) and an incident rate of 0.44 per 1,000 athlete exposures. Of these injuries, 77% were contact related and an acute non-contact injury was reported in 15% of cases.
Looking at the most common non-contact injury, hip/pelvic pathology has also been investigated in the literature for this population. Over a four year span, 890 hip or groin injuries were reported in the NHL. Of those reported, 10.6% were found to be intra-articular in nature. There was a very small difference between injury occurring during games (44.6%) and during practice (41.4%), but the vast majority occurred during the regular season (71.2%). The most frequent intra-articular hip diagnosis made in this cohort was hip labral tear (69.1%), followed by hip osteoarthritis (13.8%), hip loose body (6.3%), femoroactebular impingement (5.3%), other hip injury (3.1%), and hip chondromalacia (2.12%). With regards to player position, injuries per 1000 player-game appearances were significantly higher in goaltenders compared with all other players.
Why does it matter?
Having a successful team depends on multiple factors, but regardless of coaching or talent, injuries can have a significant impact on a team’s ability to win. Unfortunately, the NHL does not readily provide injury data to the general public, however ManGamesLost.com has provided data supporting the negative impact of injuries on a team’s success. Over the past five seasons, the Stanley Cup champion has been among the top five least injured teams throughout the regular season. Along those same lines, this season’s President’s Trophy (best regular season record) winning Washington Capitals also had the least man games lost due to injury. Additionally, with the exception of the Pittsburgh Penguins, none of the top five most injured teams have had consistent success over the past five years. In fact, two of those included in the top five most injured also had the two of the worst overall records over this timeframe (Columbus Blue Jackets and Edmonton Oilers).
In addition to the obvious impact on team performance, when a player returns from a significant injury, their productivity and durability has the potential to decline in the seasons following their return to play. The presence of a meniscal injury was associated with a decreased length of career for all positions. Furthermore, for wings and centers, the number of games played decreased in the first full season after ACL injury from 71.2 to 58.2 and in the second full season to 59.29. With regard to offensive production, there was a 31% reduction in goals scored per season, 60% reduction in assists, and 42% reduction in total points compared with an uninjured control group. Only 37.5% of players who were previously selected as All-Stars were able to regain this honor upon their return to play.
Finally, there is also a financial impact as well. According to Donaldson and colleagues, between the 2009-10 and 2011-12 seasons, 50.9% of NHL players missed at least one game, which translated to a total salary cost of $218 million per year.
With the substantial impact on team performance and the associated financial implications, understanding how to identify those at risk and develop programs to lessen the likelihood of injury is paramount to a successful organization. Part 2 of this series will delve into the evidence regarding injury risk assessment and prevention in this population of athletes.