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Introduction and aim of the study
Definition of ice hockey
Canada was the first country which implemented ice hockey in the 19th century. Up to now, it belongs to one of the major sports worldwide. The National Hockey League (NHL) represents the largest all over the world. (rulesofsport)
Ice hockey is a dynamic sport between two teams, executed by ten outfield players, who skate with high speeds while shooting a puck between two goals, and two goal keepers in total. (Mosenthal) The game is located on an ice rink which is about 60m long and 30m wide. The players wear ice skates, a helmet, (full) face mask, optional a mouthguard, shoulder pads, arm guards, gloves, trousers which are padded, and use an ice hockey stick individually adjusted in length based on their height. (rulesofsport) One match takes more than 60 minutes, three times 20, with ten minutes break after the first two blocks on ice. The athletes play with a stretch, they change every 45-60 seconds on average with their substitutes. For each position the trainer can line up four players who can change frequently. (McKay) The aim of the match is to have the most goals, in case of tie, overtime is given. (rules of sport)
Epidemiology of ice hockey injuries and prognosis
Due to fast speeds, ice hockey bears a great risk to get injured. (Biasca) Researchers even named ice hockey the most violent sport worldwide. (Benson)
From all registered injuries of athletes, 13-35% affect ice hockey players. (LaPrade) The exact frequency of injuries in ice hockey varies in literature due to the heterogeneity of exposure, designs of studies and definitions of injury. One common terminology is used by LaPrade et. al: an injury is as a trauma which needs medical care and the affected person to be removed from the current game as well as subsequent session. (LaPrade) An injury occurs through the complex interaction between extrinsic and intrinsic risk factors which are modifiable and non-modifiable. The exposure to those is dynamic. (Benson/Mc) Minor trauma is often not reported but they happen four times as often in contact leagues than in non-contact sports as well as in ice hockey more often during games than practice. (Scanlan, McKay)
It is proven that men get injured more often than women probably due to the fact that body-checks in the male leagues are forbidden. (bfu1) Mc Kay et. al state in their study that 2.3-79.2 injuries / 1000 players occur in the men`s league. (McKay)
The most common injured body parts are head and shoulders. (McKay, Schmitt) Mc Kay et. al observed in the male professional NHL league between 2006-2007 and 2011-2012 that 16.8% of all injuries concerned the head, 14% the thigh and 13% were knee injuries. LaPrade et. al published the following numbers regarding affected body parts: 13.5% occurred in the knees, 8.9% acromioclavicular joint, 6.2% were contusions of the upper leg and lastly 4.5% hip and pelvis strains. (LaPrade) Concussions show the highest rates of all injuries in school and professional athletes playing ice hockey. This kind of injury lead to prolonged physical and mental health issues. (Todd) 56% of the concussions resulted from contact with boards. (Touminen)
But scientific information outline that the overall time-loss due to injuries and illnesses is decreasing. (McKay).
Causes and mechanism
The high speeds can result in collisions between players, according to Mosenthal et. al this is the main cause of athlete`s injury, as well as between players and boards. (Benson, Schmitt, Mosenthal). The incidence of injuries depends amongst others on the league, age and individual player (Scanlan) but body-checking stays the primary cause of injury. (Mc Kay, Mosenthal, Todd)
Wilcox et. al analyzed the occurrence of head injuries in ice hockey players. In the study of 2013, they investigated the head impact by using an accelerometer device: the Head Impact Telemetry System measured the head impact during a match, more precisely the location, frequency and magnitude of impact. They concluded that there is still a high need to reduce the exposure of head impacts in order to lower the injury risk because that kind of trauma is a severe health problem. (Wilcox)
Thoughts were made to change the boards of the rings, as a cause of injuries, to decrease the injury rates.
Dasher boards in Switzerland
Raitasport Co. Ltd. is a company which supplies ice hockey arenas all over Europe with safe equipment since 1979. Dasher Board Systems are one of them which are even made for arenas where the Olympics and World Championship are held. HORNIUM and OPTIUM are modern flexible dasher boards made and sold by Raitasport and used in Switzerland.
Kaner-tec ag is another company who sells equipment for ice hockey arena since the seventies. A study by Touminen et. al found out that the risk to get injured is 29% lower in those arenas with the new flexible Engospond Flexboard PPS designs than in those arenas with traditional, stiff boards. (Touminen) Also, Kaner-tec supplies cities of Switzerland with dasher boards.
Prevention strategies
Prevention strategies are developed to reduce the prevalence of injuries to athletes, but the challenge is to avoid creating new risks by that. (Benson) Explorative studies should concentrate on twelve factors, when it is about verifying prevention strategies.
For example, in ice hockey, with the implementation of helmets it was proven that skull fractures and mild traumatic injuries became less. (Benson/Mc) Shoulder pads were made bigger and full facemasks and mouthguards made mandatory (Benson, Biasca) even though the full facemasks and mouthguards function is controversial. (Benson/Mc). They led to a reduction of dental, facial and ocular injuries (Benson, Biasca, Beson/Mc, Mosenthal) but did not protect the players adequate from severe head injuries such as concussions (Biasca, Mosenthal). Some studies even found out that trauma to the neck, brain and spinal cord were higher with the introduction of full facemasks. Therefore, only those under 18 need to wear full facemasks and mouthguards, otherwise the decision lies by the player. (Benson) Besides, safer equipment can result in aggressive behavior as stated in some literature because the athletes feel more protected. This compensating behavior of athletes is called the Peltzmann effect as mentioned in a study by Chong and Restrepo which can barely be avoided because it happens unconcious. (Chong) Also, nowadays, the players become stronger and bigger which can be further causes of the high prevalence of injuries. (Tedd) Besides, it is important that the equipment is worn correctly in order to avoid other trauma. Strict rules, controls and penalties were introduced to deal with these problems. (Biasca)
Because, as mentioned above, the injury prevention strategies focused on behavioral modifications are less effective, recently, concentration lies on contextual changes, such as environmental issues. But unfortunately, studies on equipment modifications for sport is rare. The Haddon matrix is a tool to identify and create intervention strategies. (Vriend) It is useful in the analysis of ice hockey injuries.
Benson et. al state that prevention in terms of rules enforcement, change of equipment and techniques is the best treatment for concussions. The aim of this study is the evaluation of a prevention strategy regarding the dasher boards used in ice hockey. There is the need to at least decrease the severity of body impacts if it cannot be avoided fully. (Benson) One prevention strategy is the change of the material from the dasher boards around the ice hockey rink. The aim is that the impact on the athletes body is reduced. A few tests were executed by different researchers. Therefore, this study summarizes the current evidence about dasher boards made out of a more flexible design.
Research on flexible dasher boards
The study by Cordis et. al from 2012 compared body checks against several boards made of different materials in real-life games and laboratory settings. According to the impact forces, there was a 25% difference between flexible boards and the most conventional dual base frames. The displacement of the most flexible board was 130% greater. Furthermore, they state that by replacing the glass with plastic shield, the impact forces were reduced. But it is important to mention that the plastic shield as well as metallic posts bear a high-risk even though the boards are more flexible. The injury risks could be reduced if the height of the board is lowered and metallic post removed because the player most likely hits the flexible part of the board and not the plastic shield or metallic post. (Cordis)
Poutiainin et. al evaluated 2012 the possible mechanism of injury rates caused by a player to board collision. Their goal was to compare three board designs and find which one has the lowest impact force by performing a case control experiment in a laboratory. A sand filled bag was used to simulate a collision with the board. They found out that single formed dasher boards are less stiff. The best results showed the dasher board made of acryl which was 15mm thick. The authors therefore recommend single framed, light and flexible protective shielding material without the metallic posts. (Poutiainin)
Touminen et. al observed 1.1 of 1000 players got injured when hitting a traditional board but only 0.2 of 1000 when flexible boards were used in ice hockey arenas. The incidence rate was measured during the international ice hockey World Championships and Olympic Winter Games between 2006 and 2015. The authors concluded that a flexible material can increase the impact energy resorption, decrease the peak forces, lead to greater stopping distances. (Poutiainin, Touminen) A bigger stopping distance results in a smaller force and injury risk. They recommend the use of glass and flexible boards to reduce concussions. (Touminen)
In 2016, Schmitt et. al compared six different boards designs and tested their collision impact with a dummy (representing a 78 kg heavy and 1.75 m tall person) as well as with a pendulum, cylindrical shaped. The reason for that was the statement that 20-40% of all injuries happened with the boards. In their experiments mainly the shoulder made the first contact with the flexible boards, the abdomen and thorax with the referenced ones. (Schmitt, bfu) Results showed that flexible boards were displaced four times more than traditional ones. However, although they did not absorb shock well enough, the displacement was increased what decreased the stiffness and effective mass, the rebound velocity was higher, and the impactor did not lead to a deformation. The study had a high repeatability. However, worth to mention is that a displacement is not sufficient enough to avoid biomechanical loading fully.
Later on, 2018, Schmitt et. al improved their own study design as well as the one executed by Touminen et. al. They have found some limitations regarding the used sand filled bag and testing environment. Therefore, they designed a new product which was standardized and tested in a laboratory as well as in an ice arena. The board in the arena showed a higher rebound velocity and lower displacement (20-30% compared to the laboratory) and curved boards were stiffer than straight ones.
Dasher boards in use
In North America, at the world champions league and in several northern Europe countries, flexible boards are already used. (Watson) Since 2018/19 it is an obligation for the national leagues in Switzerland to have impact limited boards in their ice arena. The cities Lausanne, Biel, Bern and Lugano started to implement these new designs in their stadiums and experienced positive results by that. One example are the numbers of an observation in Bern 2016: in the winter season the head impacts of ice hockey players were reduced because the lower part of the board was 15cm deeper and made of flexible design and the acrylic glass was higher. A mass of 60kg acted on the players head instead of 153kg with the old material. However, this shows that the total impact is still high enough, also with the new designs. Hansjürg Thüler, head of sports at the information desk for accident prevention (BfU), is satisfied with the results because 10% of the total injuries (30%), happened through body-checks against the boards, is expected to be prevented. Though, rule enforcements about hits against the heads needs to be strictly followed in the future. (Zeitung)
Conclusion and future research
Even though the new dasher boards which are currently improved in their designs reduce the overall injury rates of a collision between a player and board, there is still a high need of potential for development. Several advantages were outlined with the few researches which currently exists, but the ice hockey player is still put in jeopardy. It is not clear yet how severe an impact would be on different parts of the ice hockey rink and in how far the shear panels of the boards could be improved. Currently there are assessments running.
References
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