Thirty-five million children and young adults between the ages of 6 and 21 years participate in sports in the United States, and injuries related to their participation are common. There is general public concern that there is a high risk of injury when children play organized sports.1 Like many other injuries in children, most sports injuries are not "accidents" and are potentially preventable. Studies of sports injuries play an important role in preventing morbidity in childhood, providing team physicians, athletic trainers, and coaches with the impetus for rule changes and improvements in equipment that reduce the risk of injury during participation in sports.
Parents often seek advice from their pediatrician when their children are choosing sports. Is football too dangerous? Is gymnastics participation a good idea? This article reviews the epidemiology of sports injuries in children and adolescents to help the pediatrician discuss the relative risk of various sports with parents. The role of epidemiologic studies in the prevention of injuries also is presented.
THE STUDY OF SPORTS INJURIES
Fundamental to the epidemiology of sports injuries is the definition of an injury. Since every minor abrasion or bruise is not important, current studies only tally an injury if it produces time lost from at least a part of practice or competition. The severity of the injury can be defined by the degree of pathology found on the medical examination or by the number of days lost from the sports participation due to the injury. Because of the subjectivity in reporting the severity of injuries by physical examination, it is more practical to report the severity of injuries by days lost from practice or competition.
Unfortunately, there is no standard method of classification of injuries. One method classifies an injury as "mild" if the athlete was out less than 8 days and "significant" if greater than 8 days. "Moderately severe" injuries produce 8 to 21 days of disability and "major" injuries produce greater than 21 days of disability.2
Surveillance studies identify the number and types of injuries and when and where they occur. When a surveillance study identifies a large number of injuries, the mechanisms by which the injuries were sustained should be explored. For example, in football, the cluster of significant injuries occurring during kickofis and punts led to a study of the mechanisms of the injuries. When it was discovered that a preponderance of injuries occurred from blows below the waist, a rule was passed to penalize blocking below the waist during kickoffe and punts.
A standard method for reporting sports injuries does not exist. This makes comparisons of injuries occurring in the various sports difficult. The incidence of injury is usually reported as the percent of athletes who missed at least a part of a practice or a game during one season due to an injury.
Some studies report incidence density, which is the number of injuries per person during a specified duration of participation. The time of participation should be carefully monitored so that only those who participate count in the denominator and only the number of injuries per exposure or, better yet, per hour of exposure should be reported. If exposures are not monitored, the denominator (those who could be injured) changes during a season, leading to potential errors in the accuracy of reporting.
SAFETY OF VARIOUS SPORTS
Before discussing the specifics of injury risk in sports participation, parents should understand that the risk in any endeavor is never zero. It is impossible to make sports totally risk free. Fortunately, injury rates in youth sports are very low. Despite a parent's best efforts, children tend to self-select sports based on their own desire, peer pressure, and their own talent regardless of injury rates.
Some important questions about injury rates in various sports should be considered. Which injuries are important? Does it matter if one sport has more bruises than another? What sports have the largest number of injuries that are permanently disabling? What sports have the highest rates of catastrophic injury?
There are few studies on youth sports, but the overall injury rate in youth sports is very low. Despite the methodological concerns discussed previously, there is a predictable pattern of risk of injury in sports. The older and bigger the athlete, the greater the risk for injury. The more chance for contact and collision after puberty, the greater the severity of the injury.3
In 436 football players 9 to H years of age, Goldberg et al reported that 67 injuries occurred during one season with 63% of the injuries requiring less than 7 days' restriction.4 No known permanent disabilities occurred. Players in the heavier weight divisions (100 lbs to 130 lbs) had more injuries than the lighter weight division players (80 lbs to 115 lbs), with figures of 23.9% and 12.7%, respectively.
Backous et al5 reported an overall injury rate of 19% in boys and girls 6 to 17 years of age who participated in summer soccer camps. Only 3% of the injuries required the players to miss more than one day of playing.
In an older study of young hockey players, Sutherland6 reported 17 injuries occurring among 707 players during one season. The injury rate was 2.4%. This rose to 20% at the high school level and to 120% at the collegiate level (1.2 injuries per player per season on one collegiate hockey team).
Studies directed to high school and college sports are more numerous, but methodological flaws make comparisons among the various sports inaccurate. When studied prospectively by the same method, comparative injury rates between sports can be more accurately assessed. One of the best studies ever done on high school sports injuries was Garrick and Requa's 2-year evaluation of 3049 athletes from four high schools, using athletic trainers to identify injuries.7 The injury rate was highest in football (81%), followed by wrestling (75%) and girls' gymnastics (40%).
Similar results were reported by McLain and Reynolds more recently in a 1-year study of 1283 student athletes in one large high school.8 The highest injury rate was in football (61%), followed by girls' gymnastics (46%), boys' gymnastics (40%), and wrestling (40%). The injury rates for the various sports in the two studies are summarized in the Table.
Virtually none of the studies on sports injuries examine the potentially permanent disabling injuries, except those studies that address catastrophic injuries. For example, in their article on catastrophic injuries reported to the National Center for Catastrophic Sports Injury Research and the Sports Medicine Section of the American Association of Neurological Surgeons, Mueller and Cantu reported on the incidence of such injuries from the fell of 1982 through the spring of 1988 at the high school and collegiate levels.9 A catastrophic injury was defined as any injury in which there is permanent, severe functional neurological disability (nonfatal) or transient but not permanent functional neurological disability (serious).
Injury Rates In High School Sports*
As expected, football led the list of most reported catastrophic injuries with 187 injuries reported at the high school level and 50 at the collegiate level nationally. Seventy-three of these injuries were fetal. If the number of catastrophic injuries is calculated as a rate per 100 000 participants per year of this study, football at 3.3 shares the highest rates with ice hockey and gymnastics, which were 4.5 and 3.7, respectively. Wrestling was the fourth most dangerous sport with 1.5 catastrophic injuries per 100 000 participants per year. Almost every sport had at least one catastrophic injury reported during the study period. The data should be interpreted with caution because of the potential ascertainment bias due to the dependency on self-reporting by personnel associated with the sports. Underreporting of injuries is especially likely at the high school level where few full-time coaches exist.
There are countless examples of rule and equipment changes that reduce the risk of injuries during sports participation. One of the best examples of reduction of injuries related to injury data collection is the reduction of severe cervical spine injuries in football. Following the investigation of the mechanism of cervical injuries by Torg et al10 and others, and with the urging of physicians and athletic trainers, a rule change was implemented. "Spearing," the act of driving one's helmet into the body of another player along with any initial contact with the head while blocking and tackling was made illegal. Documentation of cervical spine injuries in football shewed that after the rule change was made in 1976, there was a dramatic reduction in the reports of quadriplegia.11 Although improvements were made in equipment over the same time period, the most dramatic decrease followed the rule change (Figure).
Figure. Yearly incidence of permanent cervical quadriplegia for all levels of participation demonstrate significant decrease in 1977, the first year after the rule change. (Reprinted with permission from Torg JS, Vegso JJ, Sennet B, Das M. The National Football Head and Neck Injury Registry: 14-year report on cervical quadriplegia, 1971-1984, JAMA. 1985; 254:3439-3443. Copyright ®1985, American Medical Association.)
A second exmple concerns eye injuries in ice hockey, which were common in Canada and the United States12 until helmets and fece masks were required. Pashby found a significant decrease in these injuries following the fece mask requirement.13
AREAS REQUIRING FURTHER STUDY
Surveillance of injuries in the sports described above was critical to identifying the need for changes and also in showing that the changes were effective. Further study is needed in other areas. The problem of sudden death in baseball and spinal injuries in ice hockey are two such issues that warrant further study.
There is concern about sudden death in youth baseball due to commotio cordis, the phenomenon of cardiac arrest due to blunt chest trauma.14 According to the United States Consumer Product Safety Commission, from 1973 to 1990, 56 baseball-related deaths occurred in 5- to 14-year-olds, with 24 of these deaths occurring as a result of blunt chest trauma (Goldberg B. Unpublished data. 1991). There has been no apparent increase in the number of deaths over the years of data collection. With an estimated 4-8 million participants in organized and recreational baseball, this makes the death rate 0.68/million participants per year, indeed a rare event. To keep this in perspective, football at the high school and college level with about 1 375 000 participants accounts for about 8.8 deaths/million participants annually.9 Death during participation in any sport is a rare event and probably should not influence sport selection for a youngster. Further studies are needed on the new softer baseballs, which might reduce the incidence of sudden death due to blunt chest trauma.
In an important study on spinal injuries to hockey players, Tator and Edmons reported 42 such injuries in Canada between 1976 and 1983. l5 The authors felt there had been a dramatic increase in the incidence of these injuries from previous years. There are no similar data from the United States. More striking was the finding that the most frequent injury mechanism was a blow to the head from a push or check into the boards. These occurred despite the feet that these blows were illegal; the rule was not always enforced. More recently, after a cervical spine injury occurred in competition, athletic trainers and physicians caring for American collegiate ice hockey players in the Western Collegiate Hockey Association expressed their concern.16 Enforcement of the rules against cross-checking and checking from behind would probably help prevent some of these injuries, especially if referees consistently penalized players for administering blows to the head and neck.
In addition to the concerns raised in ice hockey, Mueller and Cantu have suggested that wrestling and gymnastics also warrant further research related to potential changes in rules and their enforcement that would prevent injuries.9
Participation in youth sports is relatively safe. Injuries become more frequent as the child gets older, bigger, and achieves higher skill levels. At the high school and collegiate levels, football has the highest injury rate followed by wrestling and gymnastics. There is no risk-free sport, and children tend to select the sports they wish to participate in without considering injury rates. Pediatricians should take an active role in injury prevention when covering sporting events as team physicians and as spectators.
1 . Albright JP, Noyes FR. Role of the team physician in sports injury studies. Am J Sports Med. l988;16(suppl 1):l-4.
2. Risser WL. Epidemiology of sports injuries in adolescents. Adolescent Medicine: State of Art Reviews. 1991;2:109-124.
3. Micheli L]. The incidence of injuries in children's sports: a medical perspective. In: Brown EW. Brama CF, eds. Compentitive Sports for Children and Youth. Champaign, III: Human Kinetics; 1988:99-106.
4- Goldberg B, Rosenthal PF, Nicholas JA. Injuries in youth football. Phys Sportsmed. 1984;12:122-130.
5. Backous DD; Friedl KE, Smith NJ, Par TJ, Carpine WD Jr. Soccer injuries and their relation to physical maturity. Am J Dis CMd. 1988;142:839-842.
6. Sutherland GW. Fire on ice. Am J Sports Med. 1976;4:264-269.
7. Garrick JG, Requa RK. Injuries in high school sports. Pediatrics. 1978;61:465-469.
8. McLain LG, Reynolds S. Sports injuries in a high school. Pediatrics. 1989;84:446450.
9. Mueller FO Cantu RC Catastrophic injuries and fatalities in high school and college sports, fell 1982-spting 1988. Med Sri Sports Etere. 1990;22:737-741.
10. Torg JS, Quedenfeld TC, Burstein A, Spealman A, Nicholas C. National Football Head and Neck Injury Registry report on cervical quadriplegia 1971-1975. Am J Sports Med. 1977;7:127-132.
11. Torg JS, Vegso JJ, Sennet B. Das M. The National Football Head and Neck Injury Registry: 14-yearreport on cervical quadriplegia, 1971-1984 -MMA. 1985,254:34393443.
12. Sims FH, Simonet WT, Melton LJ HI, Lehn TA. Ice hockey injuries. Am j Sports Med. 1988;16(suppl 1):586-596.
13. Pashby TJ. Eye injuries in Canadian amateur hockey. AmJ Sports Med. 1979;7:254257.
14. Abunio TJ. Commotio cordis: the single, most common cause of traumatic death in youth baseball. Am I Dis ChM. 1991;145:1279-1282.
15. Tator CH, Edmons VE. National survey of spinal injuries in hockey players. Can Med Assoc J. 1984;130:875-880.
16. Proceedings of the Sports Medicine Committee of the Western Collegiate Hockey Association; March 10, 1991; Minneapolis, Minn.
Injury Rates In High School Sports*