Automobile racing

A retrospective study over six seasons at the Indianapolis Raceway Park identified neurologic injuries in drivers during 61 open-wheel racing events. Four drivers required hospital admission, and two of these required admission to the ICU for head injuries. Head trauma comprises 29% of all injuries in professional automobile racing, and open head injuries occur in 5% of these cases. Closed head injuries rarely include intracranial hemorrhages, resulting instead in diffuse axonal injury. Although exposure to emissions of carbon monoxide and vehicle fires certainly occurs in race car drivers (in one race an increased carboxyhemoglobin concentration was found in all race car drivers), no correlation has been demonstrated between carbon monoxide level and driver symptomatology. Heat stroke has been reported rarely in automobile racing drivers. Spinal injuries comprise 20% of sports-related injuries in professional automobile drivers and occur most often during a vehicular rollover; cervical spine or spinal cord injury seems to be the most common spinal injury. One innovation that may improve the safety of race car drivers or racing motorcyclists is the introduction of additional chicanes, or turns placed in the fastest part of the racetrack. Their use on one racetrack decreased the risk of severe injury from 0.1% to 0.03%.

Baseball and softball

Baseball and softball

Basketball

Injury rates generally are lower in basketball than in other popular team sports. For high school basketball players in an observational cohort study, injury rates per 100 high school player-seasons were 1.04 for girls’ basketball and 0.75 for boys’ basketball. The incidence of MTBIs in high school basketball players is lower than in other organized sports, such as football, wrestling, and soccer. In a United States national survey, basketball injuries leading to ambulatory clinic visits were more common in male participants (5.7/1000) than in female participants (0.9/1000), with neurologic injuries occurring rarely. In collegiate women basketball players, injury rates during a game (7.68/1000 AEs) are double those in practice (3.99/1000 AEs). Likewise, male collegiate basketball players have more injuries in games (9.9/1000 AEs) than during practice (4.3/1000 AEs). In Olympian basketball players, male injuries occur at a rate of 64 per 1000 athlete-matches, and female injuries occur at a rate of 67 per 1000 athlete-matches with no indication of the rate of neurologic injuries in either group. In professional basketball players, the injury rates are 24.9 per 1000 AEs for women and 19.3 per 1000 AEs for men.

Most basketball injuries are musculoskeletal injuries affecting the lower extremity. Concussion rates are estimated to be 0.3 to 0.5 per 1000 AEs. Multiple studies have found that women collegiate basketball players are more subject to concussion, which represents 9% of all injuries in women compared with only 5% in male collegiate basketball players. In one study in trauma center hospitals, basketball injuries capable of causing head injuries in 10- to 19-year-olds usually were related to striking the basketball pole or rim or being struck by a falling pole or backboard.

Bicycling

Although the incidence of injuries caused by bicycling accidents is largely unknown, some studies have provided estimates. In Norway, all bicycle injuries and fatalities are expected to be recorded but probably remain underreported (eg, single-bicycle accidents seem to be almost completely unreported in Norway, whereas in Canadian reports isolated crashes are the most common mode of injury). Among Canadian recreational bicyclists, collision with vehicles accounts for 64% of bicycle-related deaths. Although anecdotally suggested, there is no evidence that bicycle accidents are more common with bicycle motocross (BMX) style bikes than with non-BMX bikes. In fact, it remains unclear which forms of bicycling may be more injury prone, and BMX bicycle riders have a lower proportion of serious injuries than bicycle racers, including fewer head injuries. Most accidents occurring in BMX riders are related to performing stunts or to poor cycling technique. Approximately 7% of the injuries caused by BMX riding are concussions. Although most injuries occurring in off-road bicycle racing are musculoskeletal in nature, a small incidence of concussion (< 1%) occurs, about 40% less than in other forms of cycling. This low incidence may relate to a significantly higher rate of helmet use in bikers going off road. Women seemed to be much more likely than men to sustain an serious injury while off-road biking, although males have higher numbers of injuries, including cervical spinal cord injuries, because of their more frequent participation.

Children are subject to bicycling injuries, but it is unclear as to whether they suffer more injuries than older riders. Among pediatric admissions to a trauma center, 6% of injuries were related to bicycling. Sixty-four percent of cycling-related injuries presenting to a pediatric emergency department were head and neck injuries. Potentially avoidable head injuries resulting from bicycling accidents in which the participants were not wearing helmets have received media and political attention. In Canada, helmet use was associated with less likelihood of hospital admission following injury, a lower incidence of head and facial injury, and a lower incidence of concussion. In the United States, the use of bicycle safety helmets for children led to a 88% risk reduction in intracranial injury and prevented skull fractures and possibly death caused by head injuries, end results possible in helmet-less children.

Boxing

Boxing is perhaps the most controversial sport for physicians because of the degree of neurologic injury, questions about long-term sequelae, and the occurrence of death during a competition that is intended to injure the opponent. Both the American Medical Association and the American Academy of Pediatrics have stated opposition to both amateur and professional boxing. A major problem with determining the rates of injury in boxing is the regulatory policy–induced minimization of injuries. Nonetheless, the incidence of serious acute head injury in amateur boxing and noncompetitive boxing is believed to be lower than in the professional ranks, perhaps because of the greater degrees of regulation and reporting of injuries at the amateur level. In one study of instructional boxing in the United States Marine Corps, only one serious head injury occurred per 60,000 participants, only 0.3% of all boxing-related injuries during the study period. Amateur boxing participants suffered a severe concussion or multiple knockouts in 0.58% of competitions. Again, these studies may be subject to underreporting. In professional boxers, most early studies examining the sport in New York State demonstrated knockout rates of 3% per participant in the 1950s, and about three head injuries per 10 boxers in the 1980s. A more recent study of professional boxing from Nevada has documented an overall injury rate of of 17.1 per 100 boxer-matches. Male professional boxers are more likely to be injured than are female professional boxers. Boxers who lose by knockout have twice the risk of injury as those boxers who do not. Although the incidence of intracranial hemorrhage in boxers is unknown, acute subdural hematomas are the major cause of boxing-related mortality. Despite these deaths related to acute injury, there is no evidence that boxers had a shorter life span than participants in other sports when data from the late nineteenth century and early to mid-twentieth century were assessed. Assessment of neurologic injuries caused by boxing must be categorized to illuminate two important points. First, acute neurologic injuries must be distinguished from chronic brain injuries. Second, the level of competitive boxing, amateur versus professional, must be considered because of different regulations and protective gear. Obviously, acute neurologic injuries such as concussion, postconcussion syndrome, and intracranial hemorrhage are more easily identified than chronic neurologic injuries because of their immediate impact and obvious relationship to recently inflicted trauma. Serious acute intracranial injuries caused by boxing are recognized but are said by some to be rare. In the case of a knockout, the boxer has sustained a concussion, which is easily recognizable.

Amateur boxing differs from professional boxing in the duration of fights, the nature of rules and regulatory policies, the degree of medical evaluation, and the use of protective devices (ie, headgear). The incidence of serious acute head injury in amateur boxing and noncompetitive boxing is thought to be lower than in the professional ranks, perhaps because of more regulation and greater reporting of injuries. In amateur boxing, studies have reported the incidence of concussion or other head injury to be between 6.5% and 51.6% of all injuries. For professional boxers, concussion and head injury rates may be higher, estimated to be between 16% and 70% of all injuries. Concussion rates for both amateur and professional boxing are substantially higher than in other sports, ranging between 14 and 45 per 100 AEs.

Chronic neurologic injuries from boxing are insidious in onset and often do not present until after the boxing career has ended. Among former professional boxers who had participated in the sport for at least 3 years, 17% were found to have clinical evidence of CNS deficit considered to be attributable to boxing. Measures of more chronic effects of boxing and neuropsychologic and cognitive effects have been studied many times with varying results. In fact, a systematic review has determined that there is no strong evidence associating chronic traumatic brain injury with participation in amateur boxing, although much of the available evidence is of poor quality. The most severe abnormalities of neurologic functioning can be identified in the most severe cases of retired boxers who have post-boxing encephalopathy; these abnormalities, which include cerebellar, extrapyramidal, and intellectual impairments, have been termed “dementia pugilistica.” Other clinical features in patients who have dementia pugilistica can include tremor, dysarthria, and psychiatric changes such as explosive behavior and paranoid and jealous delusions. Risk factors for a persistent CNS deficit have been varied and remain controversial. Some of the more consistent risk factors include a long boxing career with many bouts and the presence of the apolipoprotein E4 phenotype, a risk factor for other causes of neurodegeneration, including Alzheimer’s disease.

Neuropathologic abnormalities reported in former professional boxers include scarring of cerebellar folia with loss of cerebellar Purkinje cells, degeneration of the substantia nigra, the presence of neurofibrillary tangles in limbic gray matter, and the presence of cavum septum pellucidum. Neurofibrillary tangles in dementia pugilistica brains are concentrated in the superficial neocortical layers, in contrast to Alzheimer’s disease, where they predominate in deep layers. As well, tau pathology in patients who have chronic traumatic injury, including boxers who have dementia pugilistica, possess the same tau epitopes found in filamentous tau inclusions in Alzheimer’s disease brains, suggesting that pathologic mechanisms similar to those in Alzheimer’s disease may be present. Serum glial protein S-100B, postulated to have a relationship to cognitive deficits, increases immediately after boxing matches and correlates significantly with the number and severity of head blows. These are all nonspecific markers of dysfunction, but their co-presence is strongly suggestive of boxing-induced encephalopathic changes.

Cheerleading

Cheerleading involves many high-risk maneuvers, including high team throws and daring aerial drills, frequently leading to accidents, particularly during pyramid building. Severe head injuries including skull fractures, hematomas, or cerebral edema have occurred. Mortality at the time of or within days of a head injury has occurred in two cheerleaders. The number of injuries caused by cheerleading per 1000 participants per year ranges from 8.1 for 12- to 17-year-olds to 1.2 for 6- to 11-year-olds. Concussion comprises 7% of all injuries (9.36/100,000 AEs) in high school cheerleaders, but catastrophic head injuries have not been reported. In one study of concussion rates in high school athletes, cheerleading was the only sport for which the concussion rate was greater for practices than for games.

Cricket

Mean match injury incidences are quite low in cricket, ranging from 48.7 per 10,000 player-hours in test matches to 40.6 per 10,000 player-hours in 1-day international cricket, with injury prevalences of 11.3% and 8.1%, respectively. In domestic cricket matches, the incidence rates of match injury are 13.9 per 10,000 player-hours for first-class cricket, and 25.4 per 10,000 player-hours in 1-day domestic competitions. Batsmen and fast bowlers are most likely to be injured. Neurologic injuries seem to be very rare.

Diving

The most common mechanism of injury associated with water activities is diving, with ervical spinal cord injury comprising 4.9% of all water-related accidents in children. Cervical spinal cord injury is so common in divers that one large, retrospective study reported all spinal cord injuries associated with diving were at the cervical level and led almost uniformly to quadriplegia. No further epidemiologic studies have been attempted to determine the prevalence of diving-related injuries, however.

Equestrian sports

Surprisingly, injuries in equestrian sports are very common, perhaps 20 times more common than in motorcycling. Closed head injuries are a common cause of injury in riders because of falls. Sixty percent of equestrian-related injuries are caused by falls from the horse; 40% result from being kicked by a horse. More females than males are injured in equestrian events because of the female predominance in this activity. Helmet use reduces the risk and severity of head injuries, but most riders are helmetless; only about 9% of riders involved in equestrian trauma were wearing helmets.

Field hockey and lacrosse

Despite the use of a hard ball and sticks by aggressive players, injury rates in lacrosse and field hockey tend to be much lower than other major sports. Neurologic injuries are extremely rare. Field hockey was the least likely sport of 10 sports studied to cause head injury (1.1% of all MTBIs). Most head injuries in field hockey are caused by ball contact. The rate of concussion has increased during the last decade (0.5/1000 AEs); again, concussion rates are much higher during competition than during practice.

In Olympian field hockey players, injury rates of 55 and 8 per 1000 player-matches occur in males and females, respectively. For collegiate women field hockey players the injury rate during games is twice that during practice (7.9 versus 3.7 injuries/1000 AEs). The most common mechanisms for injury affecting female field hockey players were falls while ball handling or contact with a stick while ball handling. Ankle sprains are most common injuries in both female and male field hockey players.

Lacrosse-related trauma is more common among male players (81% of all cases in a male-dominated sport) and is most common among teenaged players (mean age, 16.9 years). Male lacrosse players at the collegiate level also are much more likely to sustain injuries in games than during practice (12.6 versus 3.2 injuries/1000 AEs).

Of all major women’s collegiate sports, lacrosse seems to have the highest percentage of injuries as concussions (14%), higher than in male lacrosse players (10%). Females are more likely to suffer head or face injury (30%, versus 18% in males), perhaps because female lacrosse players are less likely to wear helmets, although concussion rates seem to be slightly higher in male players. One case of epidural intracranial hematoma was reported after the player was hit by a lacrosse stick. Closed head injuries comprise 6% of all lacrosse-related injuries. These statistics have led to recommendations for the use of protective head/face gear.

Football

Golf

Most golf injuries that occur independently of a golf cart–related accident result from the golf swing. The 1-year incidence rate of golf injury is 0.36 to 0.60 injuries per 1000 participant-hours, although neurologic injuries are distinctly uncommon. Nearly all golf-related injuries affecting the head and spine are related to golf cart accidents, often involving inebriated passengers and drivers.

Gymnastics

In some studies the prevalence of injuries to the cervical spine among gymnasts is next to that in football and wrestling, with most of the spinal cord lesions occurring at the mid-cervical levels. For collegiate female gymnasts, the rate of injury in competition (15.2/1000 AEs) is double that in practice (6.1 /1000 AEs). High school and college gymnasts are also at greater risk of death than are participants in other sports.

In recent years the trampoline has been identified as a common cause of injury and of spinal cord injuries in particular. Trampolines have been held responsible for more than 6500 pediatric cervical spine injuries in 1998 in the United States, a fivefold increase in reported injuries compared with the previous 10 years. Trampoline-related injuries occur equally in females and males, with a median age of 7 years.

Hockey

Ice hockey is associated with high rates of injury in both amateur and professional leagues, although good epidemiologic studies of hockey-related injuries have been completed only recently. In children aged 9 to 16 years, overall injury rates are 30 injuries per 100 players per season or 4.13 injuries per 1000 player-hours, with injury rates rising with increasing age in general. For high school hockey players, total injury rates of 75 cases per 100 players, or 5 injuries per 1000 player-hours, have been reported. Of these injuries, 12% were concussions experienced by 9% of the players. In collegiate female hockey players, the rate of injury in games (12.6/1000 AEs) is more than five times higher than the rate in practice (2.5/1000 AEs). Unlike male hockey players, concussions are the most common injury for female hockey players both in games (21.6%) and in practices (13.2%). In collegiate men’s hockey the injury rate is more than eight times higher in games (16.3/1000 AEs) than in practice (2.0/000 AEs). A Danish study of adult hockey players found an equally high injury rate, 90 cases per 100 players per season, or 4.7 injuries per 1000 exposure-hours. Female and male hockey players have similar overall injury rates (9.19/1000 AEs for males versus 7.77/1000 AEs for females), even though intentional body checking is not allowed in women’s hockey. Injury rates in ice hockey are much higher in males under the age of 18 years (9:1), however.

Most hockey injuries affect the head and neck. Peak accelerations inside the helmet, which probably contribute to the risk of head injury, are significantly higher for hockey players than for football players. Body checking remains the most common cause of injury in hockey, because children and teenaged players in contact leagues are four times more likely to be injured and are 12 times more likely to receive a fracture than players of the same age in noncontact leagues. Some of the other risk factors for injury in ice hockey are distinct from those in other sports: more experienced players are significantly more likely to sustain injury; the older, taller, and heavier a player is, the greater is the risk of injury as well. Particular events associated with injury include forechecking and breakout plays (head injury) and backchecking. Illegal activities such as elbowing and high sticking were responsible for 26% of hockey injuries.

Concussion rates are high at every level of hockey play. Every season, 10% to 12% of minor league hockey players 9 years to 17 years old suffer a head injury, usually concussive in nature. The rate of concussion has a positive correlation with the age of the player: youth players aged 5 to 17 years suffer 2.8 concussions per 1000 player-hours; college hockey players have a rate of 4.2 per 1000 player-hours; and elite amateur players have a rate of 6.6 per 1000 player-hours. This positive association with increasing age is probably related to higher rates of body checking. At the professional level, concussion rates are even higher, 20 to 30 concussions per 1000 player-hours or 3.7 per athlete-season. Of even greater concern is the continuing rise in the concussion rates in professional ice hockey players in recent seasons. Again in contrast to other sports, the incidence of concussion increases with higher levels of play and greater player experience. Although this increase may reflect greater rates of recognition and reporting, other factors, such as larger and faster players, harder boards, and the presence of glass over the boards may contribute also.

Since 1981, hockey-related spinal injuries have been on the rise, although reporting bias, increasing numbers of hockey players, and better diagnostic and reporting skills may contribute to the increase. An average of 17 major spinal injuries occurs annually in Canada, and there have been six deaths in Canada caused by spinal injury during this period. Most of the athletes suffering major spinal injuries were males aged 16 to 20 years. A Canadian registry of hockey-related spinal injuries has been created to capture spinal injury cases from 1966 to 1996.