A Prospective Study of Kitesurfing Injuries

Transcription

1 DOI: / A Prospective Study of Kitesurfing Injuries Christoph Nickel,* MD, Oliver Zernial, MD, Volker Musahl, MD, Ute Hansen, MD, Thore Zantop, MD, and Wolf Petersen, MD From *Klinikum Elmshorn, Elmshorn, Germany, the Department of Orthopaedic Surgery, University Hospital Schleswig Holstein, Kiel, Germany, the Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, the Department of Abdominal Surgery, University Hospital Schleswig Holstein, Kiel, Germany, and the Department of Trauma, Hand, and Reconstructive Surgery, University Hospital Muenster, Muenster, Germany Background: To date, the pattern and rate of kitesurfing injuries are largely unclear. Hypothesis: The pattern and rate of kitesurfing injuries are comparable to that of contact sports such as football and soccer. Study Design: Prospective study. Methods: The study was conducted over a 6-month period of 1 season and included 235 kitesurfers. Results: The number of self-reported injuries was 124, for an overall self-reported injury rate of 7 per 1000 hours of practice. One fatal accident (polytrauma) and 11 severe injuries occurred during the study period (2 knee ligament injuries and 9 fractures at various sites). The most commonly injured sites were the foot and ankle (28%), skull (14%), chest (13%), and knee (13%). Fifty-six percent of the injuries were attributed to the inability to detach the kite from the harness in a situation involving loss of control over the kite. There was a tendency for athletes using a quick-release system to sustain fewer injuries than athletes without such a release system. Conclusion: Kitesurfing can be considered a high-risk sport. Clinical Relevance: The use of a quick-release system that enables the surfers to detach the kite in case of an accident might aid in the prevention of injuries. Keywords: kitesurfing; injury mechanism; polytrauma; prevention; knee Kitesurfing is a new water sport with rising popularity. 10,18 The athlete uses a small board and transfers the energy of the wind into speed by a large maneuverable kite (Figure 1A). The vertical lift of the kite enables the athlete to perform high jumps even in light surf conditions. The athlete can control the kite using a handlebar, which is connected to the kite via 4 small-diameter lines with lengths between 20 and 30 m (Figure 1B). The wrist or harness of the kitesurfer is connected to 1 of the 4 lines by a kite leash (Figures 1 and 3). This kite leash prevents the kite from blowing away in case the athlete loses control of the handle bar. The size of the kites varies between 5 and 20 m². Most commonly, kites between 9 and 16 m² are used. Address correspondence to Wolf Petersen, Department of Trauma, Hand, and Reconstructive Surgery, University Hospital Muenster, Muenster, Germany ( Wolf.Petersen@ukmuenster.de). No author or related institution has received financial benefit from research in this study. The American Journal of Sports Medicine, Vol. 32, No. 4 DOI: / American Orthopaedic Society for Sports Medicine The length of the boards varies between 120 and 200 cm, which means that the athlete will sink without the lift of the kite. In an emergency situation, however, the board may be used as a swimming support. Currently, 2 different types of boards are used: directionals and bidirectionals. Directionals are basically a miniature version of a windsurfing board with a nose and a tail. Drift-off is prevented by small fins mounted at the tail of the board. Bidirectionals are shorter than directionals, and they have fins at both ends of the board. This design enables the athlete to change direction without turning the board. The athlete is connected to the board by foot straps. Many kitesurfers use an elastic leash of approximately 200 cm in length to connect the ankle to the board. This leash should prevent the board from drifting off when the kitesurfer loses the board. Most commonly, the athlete has to enter and exit the kite while located on the beach (Figure 2). As the kite rises up with the wind, the athlete has to carry his or her board and move into the water. Because of the lift of the kite, the athlete is able to control the downwind drift to start. The kitesurfer is able to move downwind and upwind with a speed of approximately 30 to 40 mph. The most popular discipline in competition is freestyle, in which the 921

2 922 Nickel et al The American Journal of Sports Medicine Figure 1. A, a kitesurfer using a bidirectional 13 m² tube kite; B, the athlete can control the kite by a handlebar. The bar is connected to the kite by 4 small-diameter lines with lengths between 20 and 30 m. The black arrow indicates the depower lines; arrowheads, flying lines; white arrow, kite leash. kitesurfer has to show several moves and jumps and is judged by a jury. A second discipline is hang time. In this discipline, the athlete jumps while the time in the air is measured. Recent retrospective studies of kitesurfing have reported severe injuries such as a polytrauma 18 or tetraplegia due to a vertebral fracture. 10 These studies have shown that the rate of injury in kitesurfing is comparable to that reported for windsurfing. 7,8,17,19,20 Retrospective studies, however, are not suitable for evaluating sport-specific injury rates. Study participants tend to forget minor and mild injuries, and severe injuries may be underestimated because many athletes do not continue to perform the sport after a severe injury. To date, no prospective studies about the injury rate, pattern, and mechanism of kitesurfing are available. Figure 2. Most athletes start the kite on the beach. When the kite is in the sky, the athlete grasps his board and then moves into the water. The athletes should never launch upwind of people or hard objects and should give themselves at least 1 or 2 kite lines length distance from any obstacles. The purpose of this study was, therefore, to evaluate injuries in a kitesurfing population prospectively observed over the course of an entire season. The objective was to identify common injury patterns as well as potential areas in which prevention measures might be instituted. MATERIALS AND METHODS We surveyed a population of 235 kitesurfers in Schleswig- Holstein, Germany, over the course of the entire season from April 2002 to October A total of 225 athletes were male and 10 were female. Because the majority of athletes were not members of clubs or associations, the study participants were recruited via a local Web portal ( reports in the press, and personal contacts at the beach. In the beginning of the study, the participants completed an electronic questionnaire. Informed consent was obtained. This questionnaire evaluated name, gender, date of birth, phone number, address, equipment used, number of years of experience in

3 Vol. 32, No. 4, 2004 Kitesurfing Injuries 923 Figure 3. A quick release enables the athlete to depower the kite quickly in an emergency situation. The industry provides different systems: A, the release is mounted between the handlebar and the harness. When the athlete pulls the small line indicated by the black arrow, the kite collapses completely. White arrow, kite leash. B, this quick release is part of the depower system. The black arrow indicates the lever that activates the release. White arrow, kite leash. kitesurfing, previous injuries, and experience level. The experience level was assessed by the study participants according to the following scale: beginner, starting and landing the kite with help, downwind rides on the water; intermediate, easy maneuvers such as jibes, upwind rides, and small jumps; advanced, high jumps and transition jumps; expert, high jumps with rotation and foot-off jumps. Data concerning hours of sports participation or injury were collected on a prospective basis. At the end of each month, a questionnaire was mailed to all participating athletes. The first part of the questionnaire evaluated the number of practice hours and the number of competition hours to determine the injury exposure rates. The athletes were instructed to complete the first part of the report whether they were injured or not. Each issue of the German Kitesurfing Journal and the local kitesurfingspecific Web portals were checked for any reported fatal accidents of the study participants. Furthermore, the records of the German Society for Rescue of Lives (Deutsche Lebens Rettungs Gesellschaft, Kiel, Germany) were checked for any fatal kitesurfing accidents. The second part of the questionnaire collected information over the course of 1 month with respect to each injury sustained: type of injury, site of injury (beach, close to the beach, water), days of hospitalization, days off from kitesurfing, source of any treatment, time of restricted performance due to the injury, protective gear used (helmet, protective vest), cause of injury, weather conditions at the time of injury, maneuver that was performed when the injury occurred, and equipment used (board, kite, board leash). This investigation was not restricted by the extent of injury or whether the injury required treatment. Watson has stated that the significance of an injury to an athlete is a function of the disruption caused to training and competition, not the nature or complexity of the treatment obtained. 25 An injury was defined as the damage to an affection of body of sudden onset that occurred during kitesurfing training or competition and that resulted in incapacity to practice or compete as normal. To obtain the true injury rate, the number of injuries was divided by the number of hours spent practicing kitesurfing. For this study, the severity of the injury was classified according to Watson, 25 Seil et al, 22 and Baltzer et al. 2 Therefore, injuries leading to permanent disability or death were classified as catastrophic, injuries resulting in absence from kitesurfing for more than 6 weeks were classified as severe, injuries resulting in absence from kitesurfing for more than 1 day were classified as medium, and injuries resulting in incapacity to train or compete on a normal basis were classified as mild. In the case of a medium, severe, or catastrophic injury, the exact diagnosis was confirmed by an orthopaedic surgeon, primary care physician, or hospital charts. Statistics A Fisher exact test for count data was used for statistical comparison between injury rates. An alpha level of.05 was considered to be statistically significant. RESULTS Population Statistics and Response Rates For the population of kitesurfers in this study, there was a normal distribution of age ranging from 14 to 48 years, with a mean of 27.2 years. There was also a normal distribution in skill levels of the athletes (Figure 4). The average years of experience was 2.8 (±0.2). The majority of the 235

4 924 Nickel et al The American Journal of Sports Medicine TABLE 1 Types of Injuries in the Study Population Number of athletes Beginner Intermediate Advanced Expert All Injured athletes Injury Percentage n Contusion Abrasion Laceration Joint sprain Fracture ACL rupture PCL rupture Polytrauma Other Skill level Figure 4. Athletes categorized by skill level. The dark columns indicate the number of injured athletes in each group. athletes evaluated were men (225 men, 10 women). The response rate for the mail-in surveys decreased from 221 (94%) for the first month to 195 (83%) for the last month of the survey. Overall Injury Incidence and Rates A total of 124 injuries occurred during the 6-month season in the studied population. Twenty-five athletes had multiple injuries: 20 had 2 injuries, 3 had 3 injuries, and 2 had 4 injuries. During the 6-month season, a total of kitesurfing hours were recorded, with an overall injury rate of 7.0 injuries per 1000 hours of kitesurfing. There was a significantly higher rate of injuries during competition than during practice: 7 injuries occurred during competition (420 hours; 16.6 injuries per 1000 hours), and 117 injuries occurred during exercise or practice ( hours; 6.8 injuries per 1000 hours). The risk of injury during competition was 2.5 times higher than during training (95% confidence interval, ). Injury Patterns and Severity TABLE 2 Anatomical Regions of the Injured Body Region Percentage n Foot/ankle Calf Knee Thigh Hip Trunk Chest Shoulder Upper arm Elbow Forearm Hand/wrist Skull The most common injury types were contusions, followed by abrasions, lacerations, joint sprains, and fractures (Table 1). The most commonly injured regions were the foot and ankle (28%), followed by the head (14%), knee (13%), and thorax (13%) (Table 2). Injuries to the foot and ankle included 2 fractures (1 ankle fracture and 1 fracture of the fifth metatarsal) and 7 sprains of the ankle ligaments. Knee injuries included 1 tear each of the ACL and the PCL, as well as 3 medial collateral ligament sprains. Head injuries included 11 lacerations, 2 contusions with concussion, and 1 contusion with nasal hematoma. Thoracic injuries included contusions with 2 rib fractures. The majority of injuries were classified as mild (77%; 5.4 per 1000 kitesurfing hours), medium (19%; 1.4 per 1000 kitesurfing hours), and severe (3%; 0.2 per 1000 kitesurfing hours). There was 1 fatal accident in the study population (female athlete, 25 years of age). This athlete had an impact trauma against a mole, sustaining a polytrauma, which included a fatal rupture of the liver parenchyma. Site and Cause of Injury The majority of injured athletes (67 injuries, 54%) sustained their injuries on the water at a distance of >50 m to the beach, 32 injuries (26%) occurred on the water at a distance of <50 m to the beach, and 25 injuries (20%) occurred on the beach. Most of the injuries (15%) on the beach occurred while the athlete started the kite (Figures 3 and 5), with most injuries sustained due to a loss of control over the kite. Most of the contusions occurred because the uncontrolled kite pulled the athlete against an obstacle (stone, mole, sailing boat). The fatal accident occurred during competition, when a competitor during an extreme jump lost his kite, which subsequently got caught in the lines of the fatally injured competitor. This athlete could not release her own kite and was pulled against a mole. Thirty athletes reported that they have overestimated their expertise, and 19 reported misinterpretation of the weather conditions. Four athletes lost control over their

5 Vol. 32, No. 4, 2004 Kitesurfing Injuries 925 Injuries in percent % Water 26% Water (Close to the beach) 20% Beach Injuries per 1000 hours kitesurfing ,8 With quick release 7,6 Without quick release Figure 5. Site of injury. Close to the beach was defined as a distance of 50 m from the beach. This region was characterized by a low depth of water, reefs, moles, or anchored boats. Figure 6. Injury rates with and without the use of a quickrelease system. The difference between the injury rates was not statistically significant (P =.3). TABLE 3 Wind-Speed Units According to the World Meteorological Organization Beaufort m/s km/h Knot Description <1 <1 Calm, smoke rises vertically Light Gentle breeze Flags extended First whitecaps appear Trees begin to sway Sand blows on the beach Breaking waves blow in streaks Resistance felt when walking against wind High waves and large spray Severe storm Hurricane-like storm 12 >32.7 >118 >64 Hurricane kites because of incorrect mounting of the lines. Fifty-five kitesurfers attributed injury to a technical mistake. Thirty-eight of the injured athletes sustained their injuries while mislanding a jump, 13 athletes reported loss of control while surfing straight forward, and 11 injuries occurred while the athlete was starting the kite. Eight of 14 head injuries occurred because the board leash pulled a lost kiteboard against the head of the athlete. Five athletes reported lacerations caused by the sharp lines of the kite. Six athletes reported collisions with other kitesurfers, and 1 athlete reported a collision with a windsurfer. Environmental Factors The majority of injuries occurred at a wind speed between 11 and 18 knots at flat-water conditions (Table 3). These are the typical weather conditions at the Baltic Sea, and the vast majority of kitesurfers stated that they most frequently perform their sport under these conditions. Protective Equipment Only 21% of the athletes used protective devices. A helmet was used by only 7% of the study participants. None of these athletes sustained any kind of head injury. Forty-two athletes (18%) used a quick-release system, which enables the athlete to release the kite when he or she loses control of the kite. In this group, the injury rate (4.8 injuries per 1000 hours kitesurfing) was lower than in the group of athletes who refused the use of a quick-release system (7.6 injuries per 1000 hours kitesurfing) (Figure 6). There was a tendency toward lower injury rates for the athletes who used the quick-release system, but this tendency was not statistically significant (odds ratio, 0.69; 96% confidence interval, ; P =.3). Eleven of the 42 athletes who

6 926 Nickel et al The American Journal of Sports Medicine used a quick-release system were beginner-level athletes, 16 were intermediate-level athletes, and 15 were advancedlevel athletes. DISCUSSION This study investigated the incidence of injury in kitesurfing to gain a better understanding of associated injury mechanisms. The goal of the study was to provide objective data for physicians, officials, and athletes. In a previous retrospective study, it was found that the injury rate was 6.0 injuries per 1000 kitesurfing hours. 18 The present prospective study reports an injury rate of 7.0 per 1000 kitesurfing hours. This injury rate is lower than rates reported during games or tournaments in team handball, 22 basketball, 1 volleyball, 21 soccer, 5,13 ice hockey, 14 and American football. 2 However, it is known that the risk of injury often increases dramatically during competition. Therefore, the rates are not directly comparable to those obtained in the present study, in which the majority of study participants performed the sport at a noncompetitive level. Because a standardized definition of injury does not exist, it is difficult to compare injury rates among different studies. This investigation was not restricted by the extent of injury or whether the injury required treatment. An injury was defined as any damage to the body that resulted in incapacity to practice or compete normally. The justification of this approach was given in previous studies by Watson 25 because many sports injuries significantly degrade without totally preventing an athlete s performance. Such clinically minor injuries may prevent the athlete from practicing at the full intensity, or the athlete may be restricted in range of motion. 24 Failure to examine the consequences of the clinically less serious types of sports injuries may result in a significant underestimation of the true incidence of injury in sport. 24 It may also distort the picture from the most common cause of injury. This information, however, is critical for the development of prevention strategies because a specific type of accident might have different consequences in terms of the severity of the injury. In this study, blunt-impact trauma against obstacles caused mainly simple contusions; however, in 1 case it was the cause of a fatal accident. Watson 24 examined the incidence of injuries in 4 different types of sports in the following categories: endurance (running), contact (soccer, football), noncontact, and explosive sports. The highest rate of injury was found for contact sports, with 4.66 injuries per 1000 hours of sports participation. 24 This injury rate is much lower than the rate calculated for kitesurfing injuries using the same definition. Although the majority of injuries in the present study were classified as mild, and the number of intermediate and severe injuries was not greater than that reported for contact sports such as team handball 16,22 or American football, 2 there is concern about the fatal accident observed in this study. According to the literature, a fatal accident during sports participation is a rare event. Fatalities due to an impact trauma have been reported for alpine skiing, 11,15 American football, 4,6,23 and hang gliding and paragliding. 9,12 A recent study reported 2 fatal accidents due to windsurfing. 8 The occurrence of 1 fatal accident in a study population of 235 athletes allows no conclusions about the rate of fatalities; however, it allows the conclusion that kitesurfing accidents are of sufficient intensity to cause severe injury to the body. The data revealed a difference among the sites of injuries. The foot and ankle were found to be the most vulnerable parts of the body, followed by the knee, head, and thorax. These results are in accordance with previous reports about kitesurfing injuries. 10,18 Most foot/ankle and knee injuries could be attributed to mislanding a jump in flat water or close to the beach. These injuries could have been prevented if the athlete had performed the jumps in deep water and at a safe distance from the beach. Because nearly half of the injuries occurred on the water at a distance of <50 m from the beach or on the beach, a safe distance from the beach might help to prevent other injuries. The majority of head and thorax injuries resulted from blunt-impact trauma, which was overall the most frequent cause of injury in the present study. The most frequent situation resulting in an impact trauma was loss of control of the kite with inability to release the kite from the harness. As a result, the kitesurfer was pulled against an obstacle (stone, mole, boat). During the course of this study, several systems that enable the athlete to release the kite in such a situation have been developed; however, only a small number of athletes have used these systems. In this study, the difference between the rate of injury of athletes who used the quick-release system and those who did not was not statistically significant. However, there was a tendency toward a lower injury rate in the quick-release group. Because a large range of different systems is now provided by the industry, future research is needed to evaluate the effectiveness of these devices. Although this study was not designed to evaluate injuries of other water sport athletes, it was shown that an uncontrolled kite has the potential to injure not only the kitesurfer but also swimmers and other water sport athletes in the area. Therefore, we suggest that kitesurfing not be performed at beaches when many other people are present. Only 1 accident in this study has been attributed to a collision with a windsurfer. However, with the increasing number of kitesurfing enthusiasts, the risk of collision accidents will increase. To prevent collisions with windsurfers, surfers, and sailors, the local authorities or communities should be encouraged to assign specific areas for kitesurfing. Because the radius of a kitesurfer is much larger than that of a windsurfer, and because inexperienced kitesurfers have a tendency to drift off, these areas should be leeward of a windsurfing area. To prevent injuries to others when the kitesurfer loses the handlebar, strict use of a kite leash should be encouraged. A kite leash connects 1 of the 4 lines with the arm of the athlete so that when the athlete loses the handlebar, the kite collapses and cannot be blown away. A large number of head injuries was caused by a kiteboard that was pulled against the

7 Vol. 32, No. 4, 2004 Kitesurfing Injuries 927 head by the elastic board leash. Board leashes are useful for inexperienced kitesurfers. However, it is suggested that a helmet be worn when a board leash is used. In this study, only a small number of participants used specific helmets. In this group, no head injuries were observed. Limitations of this study include a small loss to follow-up (6% at 1- month and 17% at 6-month follow-up) and a subject population that consisted of 98% male athletes. In conclusion, kitesurfing can be considered a high-risk sport. The results from this study indicate that the injury rate might be decreased when prevention strategies are applied. These prevention strategies should include the use of protective equipment such as quick-release systems or helmets, athlete awareness of the distance to the beach, and regulations from authorities concerning assignment of specific areas for kitesurfing at the beach and on the water. Future research is needed to evaluate the impact of new protective equipment. REFERENCES 1. Arendt E, Dick R. Knee injury pattern among men and women in collegiate basketball and soccer: NCAA data and review of literature. Am J Sports Med. 1995;23: Baltzer AW, Ghadamgahi PD, Granrath M, Possel HJ. American football injuries in Germany: first results from Bundesliga football. Knee Surg Sports Traumatol Arthrosc. 1997;5: Bell M. Hang gliding injuries. Injury. 1976;8: Cantu RC, Mueller FO. Brain injury related fatalities in American football, Neurosurgery. 2003;52: Ekstrand J, Gillquist J, Liljedahl SO. Prevention of soccer injuries: supervision by doctor and physical therapist. Am J Sports Med. 1983;11: Floyd T. Alpine skiing, snowboarding, and spinal trauma. Arch Orthop Trauma Surg. 2001;121: Gosheger G, Jagersberg K, Linnenbecker S, et al. Injury patterns and prevention in world cup windsurfing [in German]. Sportverletz Sportschaden. 2001;15: Kalogeromitros A, Tsangaris H, Bilalis D, et al. Severe accidents due to windsurfing in the Aegean Sea. Eur J Emerg Med. 2002;9: Krissoff WB. Follow-up on hang gliding injuries in Colorado. Am J Sports Med. 1976;4: Kristen K, Kröner A. Kitesurfing Surfen mit Lenkdrachen: Präsentation und Risikoabschätzung einer neuen Trendsportart. Sportorthopädie Sporttraumatologie. 2001;17: Lang T, Biedermann H, Rothler G, et al. Collision injuries on ski slopes [in German]. Aktuelle Traumatol. 1980;10: Lautenschlager S, Karli U, Matter P. Multicenter paragliding accident study 1990 [in German]. Z Unfallchir Versicherungsmed. 1992;85: Lindenfeld TN, Schmitt DJ, Hendy MP, Mangine RE, Noyes FR. Incidence of injury in indoor soccer. Am J Sports Med. 1994;22: Lorentzon R, Wedren H, Pietila T. Incidence, nature, and causes of ice hockey injuries: a three-year prospective study of a Swedish elite ice hockey team. Am J Sports Med. 1988;16: Morrow PL, McQuillen EN, Eaton LA Jr, et al. Downhill ski fatalities: the Vermont experience. J Trauma. 1988;28: Myklebust G, Maehlum S, Holm I, et al. A prospective cohort study of anterior cruciate ligament injuries in elite Norwegian team handball. Scand J Med Sci Sports. 1998;8: Nathanson AT, Reinert SE. Windsurfing injuries: results of a paperand Internet-based survey. Wilderness Environ Med. 1999;10: Petersen W, Hansen U, Zernial O, et al. Mechanisms and prevention of kitesurfing injuries [in German]. Sportverletz Sportschaden. 2002;16: Petersen W, Rau J, Hansen U, et al. Mechanisms and prevention of windsurfing injuries [in German]. Sportverletz Sportschaden. 2003;17: Prymka M, Plotz GM, Jerosch J. Injury mechanisms in windsurfing regatta [in German]. Sportverletz Sportschaden. 1999;13: Schafle MD, Requa RK, Patton WL, et al. Injuries in the 1987 national amateur volleyball tournament. Am J Sports Med. 1990;18: Seil R, Rupp S, Tempelhof S, et al. Sports injuries in team handball: a one-year prospective study of sixteen men s senior teams of a superior nonprofessional level. Am J Sports Med. 1998;26: Varga M, Takacs P. A fatal accident on the football field. Int J Legal Med. 1990;104: Watson AW. Incidence and nature of sports injuries in Ireland: analysis of four types of sport. Am J Sports Med. 1993;21: Watson AW. Sports injuries in the game of hurling: a one-year prospective study. Am J Sports Med. 1996;24: