National injury prevention measures in team sports should focus on knee, head, and severe upper limb injuries

Floorball is played indoor, surrounded by 50 cm high boards. The players use a smaller and much lighter stick compared to ice hockey players and a light plastic ball. The ball can reach speeds of up to 200 km per hour. Only the goal keeper wears protective equipment. In the present study, knee, face (including eye injuries), and dental injuries were the most common injuries among floorball players, with PMI 1 + occurring particularly at the knee. There are a few studies on floorball, but those that exist have found the same injury patterns as in the present study [18, 21]. Foorball players had the highest proportion of eye injuries in the sports investigated in the present study (3–5% of total injuries), and this has also been reported in the other studies [4, 21]. These eye injuries have been found, in the earlier studies, to be caused by being hit by a ball or stick [4, 21]. One recent study has highlighted the importance of protective eyewear to prevent floorball-related eye injuries [4], and in 2015, it became mandatory for youth players (younger than 15 years) to wear eye protection in Sweden. Hopefully, this rule change for youth players will reduce eye injuries in floorball, but this needs further investigation.

The decrease in knee injuries after 2013 may, to some extent, be explained by gradual introduction of a neuromuscular training (NMT) program to Swedish floorball players. A similar program has led to a reduction in leg injuries in floorball players in Finland [19], but further research is warranted.

The more severe injuries in football were SR injuries to the knee and hand/finger fractures, for both sexes. Knee injury is a well-reported severe injury in football in all the ages [5, 10, 23]. In the present study, as in others, it is found that younger players experience more fractures and upper limb injuries than older ones [6]. Fractures require medical treatment, and there for medical costs for the player. Thus, it is more likely that this type of injury is reported to the insurance company than others. During the study period, football players had a decrease in lower limb injuries, particularly in the knee, as well as in dental injuries. The effect of the Swedish NMT “Knee control program” [26], structurally implemented nationwide in Sweden from 2010, to reduce knee and CL injuries, may explain the decrease in knee injuries, but further research is needed.

The most common injuries among handball players were to the knee, hand/finger, face, and dental. PMI injuries were most often an SR at the knee or a hand/finger fracture. This is in line with what has been reported for senior, U-18 and U-16 players in Denmark, except that they also reported high numbers of ankle injuries [14]. Handball is a physical sport with fast tempo, rapid changes of directions, and frequent contact and collisions between players [11]. Players do not use protective equipment, and mouth guards are rarely used [3]. Sidestep and landing manoeuvres are common injury mechanisms for knee injuries [16]. Since such manoeuvres are a necessary part of the sport, one needs to look at the methods of injury prevention, such as NMT. The implementation of such programs has had an injury preventive effect in different handball populations [15, 17]. The main injury mechanism for facial injuries is being hit by an arm or an elbow [18], and often caused by foul play, where only 60% of the events were sanctioned by the referee [12]. “Fair play”, attentive referees, and a mouth guard may prevent some of these injuries. In the present study, there was a decrease in knee and dental injuries after 2013. In 2014, there were rule-changes and clarifications of rules regarding offences and fair play that could impact the incidence of face and dental injuries. From 2013, there has been a gradual implementation of an NMT program to reduce injuries, especially knee injuries, nationwide in Sweden. This may have explained some of the reduction in knee injuries. In 2006, a rule change was introduced to reduce head injuries which may explain some of the reduction in dental injuries [2].

Ice hockey is a fast game on ice surrounded by rigid plastic and Plexiglas boards, where a player can reach speeds up to 48 km per hours and the puck over 160 km per hour. Due to high-speed collisions, the injury risk is proposed to be high [29]. The present study revealed that male ice hockey players had the highest incidence of injury in head/ neck body parts, and in most of the upper limb parts, compared to athletes in the other sports. PMI 1 + injuries occurred most often at the shoulder in males, and at the knee in females. The most common shoulder injury mechanism has been recognized to be body contact or body checking, which mainly affects the upper body and head/neck [1, 29]. Men are allowed to body-check the opponent, but not woman who are also required to wear full-face protection regardless of age. For men, the face protection rule terminates after the age of 18, when only a semi-covering protection, covering the eyes and nose, along with a gum-shield, is mandatory. It thus seems reasonable that males have a higher incidence of dental, facial, and shoulder injuries compared to female players, and other team players in the present study. It might also explain the increase in proportion of dental injuries in male hockey players after the age of 18 years. To reduce the frequency of head and upper limb impacts, player contact rules should be reconsidered, along with reinforcement of “fair play”. Helmet design could be revaluated to protect against high-magnitude head impacts caused by contact with the ice and boards [1, 13]. The use of flexible boards is shown to reduce concussions [29]. Female players, in agreement with a previous study, had a higher incidence of knee injuries and concussions [13]. They even had the highest incidence of concussion in all players in the present study. How these injuries should be prevented needs further investigations [13].

Different sports have different risk factors for injury. Team sports, like in this study, have opponents’ behaviour as one common risk factor. Contact with another player is one risk factor and also the manoeuvre to avoid contact is a risk factor, for example for a knee injury. In floorball, handball, and football, deliberately body contact is more or less prohibited and the avoidance of contact contributes to the high frequency of non-contact knee injuries in these sports [9, 10, 18]. Ice hockey players are allowed to have body contact which is the major injury mechanism during ice hockey matches [1, 24] involving high forces to the shoulder and accelerations to the head and neck. Handball players handle the ball with the hand which increases the risk for PMI injuries in the hand and fingers.

Advantages of using an insurance database in the present study are that it covered all licensed players at all the ages and levels of sports nationwide. Injury definition was the same, and the same systematic routines were used in all claims regardless of sport [30]. However, only those injuries reported to the insurance company were included in the study. The previous studies have shown that not all injuries are reported to insurance companies [7]. The health care system in Sweden is subsidized possibly reducing the need to report an injury claim. Dental health care, however, is less subsidized. This may have influenced the high incidence of a severe injuries and dental injuries. There was a decrease in dental injuries in all ball sports during the study period, especially after 2013. The cause for this is unknown, but severe dental injuries often take several years to treat and if the player reports the injury after the treatment is finished, then the injury will be reported late to the insurance company. Another consideration is the option to report an injury to the insurance company within 3 years (in rare cases up to 10 years) after it occurred. Injury data in the present study were exported from the insurance database at the end of 2016, 1 year after the end of the present study (year 2015). Approximately 80–90% of the injuries claims are reported to the insurance company within 1 year after occurrence, and thus, there is a risk that the injury incidences are somewhat underestimated for later years in the studied period. Moreover, the accuracy of the reported number of licensed players for each sport is dependent on the accuracy of the information from the different SFs, since the insurance company only records the injuries, not all licensed players within the SFs.

To the best of our knowledge, this is the first study to evaluate acute injury incidence over a 10-year period that includes all licensed players, both adolescent, amateur, and professional, in a whole nation. This makes this study unique and the results can guide coaches and medical staff as well as municipalities in their efforts to prevent acute sports injuries, at the local and national level.