© Springer International Publishing AG 2017Ruth Solomon, John Solomon and Lyle J. Micheli (eds.)Prevention of Injuries in the Young DancerContemporary Pediatric and Adolescent Sports Medicine10.1007/978-3-319-55047-3_1
1. Epidemiology of Injury in the Young Dancer
Physical Medicine and Rehabilitation, Rehabilitation Institute of Chicago, 345 E. Superior Street, Chicago, IL 60611, USA
Department of Orthopedics, Podiatry, and Sports Medicine, Kaiser Permanente San Leandro Medical Center, 2500 Merced Street, San Leandro, CA 94577, USA
KeywordsPediatric dancersAdolescent dancersDance injuriesGrowth processRisk factorsInjury incidenceInjury locationInjury typeDiagnosisTreatmentPrevention
Pediatric: The term pediatric is used to describe pre-pubertal (skeletally immature) and pubertal (approaching skeletal maturity) dancers. Studies referenced in this chapter include patients aged 3–20 years. In this chapter the term “child” typically refers to the pre-pubertal group, while the term “adolescent” typically refers to the peri-pubertal or pubertal group.
Airplane test: A functional test for pointe readiness. The trunk is pitched forward and the non-supporting leg is raised straight in extension, bringing the trunk and non-supporting leg into a line parallel to the floor with the pelvis square to the ground. The dancer passes if he/she performs 4 of 5 pliés with arms moving from second position to the floor while maintaining lower extremity alignment.
Sauté test: A functional test for pointe readiness. The dancer passes if he/she performs at least 8 of 16 consecutive single-leg sauté jumps while maintaining neutral pelvis and lower extremity alignment, stable trunk, toe-heel landing, and fully extended knee with pointed foot in the air.
Topple test: A functional test for pointe readiness. The dancer passes if she performs a pirouette en dehors from fourth position with the gesture leg in full retiré and the support leg fully extended while maintaining a vertical trunk and demonstrating a controlled landing.
Soft tissue injury: Damage to muscles, tendons, or ligaments throughout the body.
Strain: An injury to muscles or tendons that causes fibers to be stretched and/or torn.
Sprain: An injury to one or more of the ligaments that support a joint.
Tendon injury: Includes tendinitis (acute inflammatory tendon injury), tendinosis (chronic tendon injury with cellular degeneration and no inflammation), and tendinopathy (chronic tendon injury of any etiology). Specific examples in this chapter include groin, ankle, and foot (pedis) tendon injury.
Jumper’s knee: Patellar tendon injury resulting in pain at the anterior, inferior knee.
Bony injury: Injury to bone or cartilage.
Growth plate or physis: A hyaline cartilage plate in the metaphysis of long bones that is responsible for the longitudinal growth. Growth plates close as the child ages and are not present in mature, adult bone.
Physeal injury: Injury to the growth plate, or physis.
Apophysis: A secondary ossification center in bone that acts as an insertion site for a tendon.
Apophysitis: Injury, irritation, or inflammation of the apophysis.
Chondromalacia patella: Damage to the cartilage on the undersurface of the patella.
Patellofemoral pain: Anterior knee pain arising from the patella subchondral bone.
Spondylolysis: Bony defect or fracture within the pars interarticularis of the vertebral arch in the spinal column, typically lumbar.
Ankle impingement: Painful mechanical limitation of ankle range of motion due to osseous or soft tissue abnormality.
Dancing requires a unique blend of artistry and athleticism. It is studied by individuals of all ages and comes in many forms. Given the variability of its participants and its demands, it can be associated with a broad profile of injuries. For young dancers, while some enjoy it as a form of recreation, others undergo intense and prolonged training starting at an early age with the hope of embarking on a professional career. Some researchers consider the intensity of dance second only to football . Because of its high physical demand, the risk of injury can be significant. Furthermore, young dancers may be more vulnerable to such injuries due to the physiological growth process [1, 2]. Here, we highlight some important factors to be considered in assessing and managing injuries in this special population.
The Young Dancer Population
A substantial portion of American youth participate in dance. Approximately 3.5 million children receive dance instruction from dance specialists across 32,000 private dance schools in the USA . A recent national survey of adolescents showed a 20% prevalence of dance participation, ranging from 8% for males to 38.4% for females .
Young Dancer Injury Statistics
The self-reported rate of injury among adolescent pre-professional dancers has been cited as high as 4.7 injuries per 1000 dance hours . This injury rate is similar to that reported in other adolescent sports—comparable to youth indoor soccer (4.5 injuries/1000 h)  and higher than elite adolescent gymnastics (2.6 injuries/1000 h)  and figure skating (1.4/1000 h) . In addition, dance injuries can be quite severe, and often require urgent evaluation. Between 1991 and 2007, 113,084 children and adolescents aged 3–19 years were reportedly treated in US emergency departments due to dance injuries .
Studies have shown that pre-professional dancers, aged 9–18 years, report higher rates of injury (0.77–4.71/100 h) [10–12] than adult professional ballet and modern dancers, aged 17–55 years (0.51–4.4/1000 h) [13–16]. Between 42.1 and 77% of ballet students aged 9–20 years have reported being injured at least once during their training [10–12]. For pre-professional dancers, these injuries can have significant effects throughout their dance careers.
Injuries do not plague only elite dancers; reported injury rates among recreational dancers are also high. A 2013 study of 569 injured recreational dancers, aged 8–16 years, found that 42.4% had reported a prior dance-related injury .
Given the high rate of dance participation, in conjunction with the high rate of injury among young dancers, it is critical to understand risk factors, injury patterns, and prevention and treatment strategies for dance injuries in the pediatric population.
Risk Factors for Dance Injuries
Risk factors for dance injury are commonly classified as intrinsic or extrinsic. Intrinsic factors are characteristics of the individual, while extrinsic factors are related to the environment or training.
Among the intrinsic risk factors, age is of particular interest, as the prevalence and type of injuries reported have been shown to vary by age . Dance involves repetitive movements in non-physiologic positions and requires significant neuromuscular control and balance, which places heavy loads on the joints and their supporting structures [9, 14]. It has been theorized that pediatric dancers are vulnerable to such stressors due to maturing growth plates and the growth process itself [1, 2, 18]. There is evidence to suggest that young dancers may be at particular risk of injury during the peri-pubertal period and its associated growth spurt. While determination of pubertal onset for males can be difficult as there is no one defining characteristic, puberty typically occurs around age 12 in females, usually marked by the onset of menarche . Recent research has shown that cartilage active throughout the pubertal growth spurt may be more susceptible to injury than immature or mature bone . The loss of flexibility that occurs during this time period, as bones grow faster than ligaments and tendons, has also been theorized to increase injury risk [20, 21]. Overall, the intensive and specialized training required of dancers may create conditions that cause the growth process to predispose the adolescent dancer to injury. However, there is no clear consensus based on the current literature confirming the relationship between age, growth, and injury.
While other intrinsic risk factors have been studied extensively, few high-quality studies have emerged. A recent systematic review evaluated the current evidence regarding risk factors for musculoskeletal injury in pre-professional ballet and modern dancers, aged 18 years or younger, but, due to the lack of studies worthy of full consideration in the review, no definitive conclusions could be reached . There was low-level evidence suggesting that previous injury, insufficient psychological coping skills, low body mass index, poor aerobic capacity, abnormal lower extremity alignment in turnout, and perfectionism may be associated with increased risk of injury in pre-professional young dancers . Studies on additional intrinsic risk factors in young dancers have shown inconsistent results.
Extrinsic risk factors hypothesized as contributors to dance injury include poor technique, improper training, inappropriate scheduling to prevent fatigue, lack of strengthening to prevent muscular imbalances, and suboptimal equipment, including footwear and floor type . These are areas of particular interest, as they are modifiable aspects of training. In the aforementioned systematic review, only jump landing technique and fatigue had low-level evidence to suggest an association with injuries in young dancers . In a study by Liederbach et al., adult professional dancers were shown to have different landing kinetics/kinematics and increased resistance to fatigue-induced changes compared to other female athletes, who incur higher rates of ACL injuries. Prevention of fatigue and proper jump technique were therefore proposed as protective mechanisms against specific injuries, including ACL injuries [24, 25]. These results have been echoed in studies that have linked training intensity with increased injury incidence among adolescent dancers . However, despite the vast quantity of studies examining extrinsic risk factors, insufficient high-quality data exist to make definitive conclusions regarding extrinsic risk factors for musculoskeletal injury in young dancers.
Injuries by Dancer Demographics
For reasons previously described, age and growth have been hypothesized to be risk factors for dance injuries. Studies have shown that young dancers in the peri-pubertal period have a higher rate of injury than young dancers at other ages [10, 21, 26]. In a 2014 survey-based study of 806 young dancers, 11–12 year olds were found to have a higher rate of injury (1.55/1000 h) than 13–18 year olds (1.17–1.24/1000 h) . This was consistent with prior studies showing that dancers ≤10 years or 14–16 years of age had lower injury rates than dancers aged 11–13 years [10, 26].
Injury location has been shown to differ among age groups. The lower extremity has consistently been identified as the most common site of injury in pediatric dancers of all ages and all dance styles [17, 20, 21, 26]. However, younger dancers, aged 8–11 years, have shown high rates of injury to the foot and ankle [17, 20, 26], while older dancers, aged 12–18 years, have shown increased rates of injury to the knee and hip [17, 20, 21, 26]. Results regarding the distribution of injury at the spine and upper extremities among age ranges are conflicting [17, 20, 21, 26].
The type of tissue injured has also been shown to differ among age groups [17, 20, 21, 26]. A recent study of young dancers of any discipline showed that pediatric dancers, aged 8–11 years, more commonly injured bony structures, while adolescent dancers, aged 12–18 years, had similar rates of bony and soft tissue injuries, suggesting that soft tissue injuries increase in frequency as the young dancer grows . Similarly, Steinberg et al.  found that ligament and tendon injuries increased in frequency with increasing age (from 4% in 8–10-year olds to 13.7% in 16–18-year olds) among young dancers of all disciplines.
Gender-specific research is limited in young dancers. The majority of dance research has been performed in ballet and has largely focused on females, likely due to their increased participation compared to males . In a 2002 prospective study of 39 adolescent dancers of various disciplines, aged 14–18 years, males reported injuries twice as frequently as females (8.4 vs. 4.1 injuries/1000 dance hours) . However, in a recent study of 266 pre-professional ballet dancers, aged 15–19 years, no significant difference in the rate of injury was found between sexes . Likewise, in a recent systematic review, the rate of injury in adolescent male ballet dancers (1.08 injuries/1000 dance hours) was similar to that of adolescent female ballet dancers (0.99 injuries/1000 dance hours). These findings suggest that adolescent male ballet dancers have equivalent injury rates to females, while male dancers of other disciplines may have an increased risk for injury compared to females. Further research for causation and replicability is needed. Of note, these results somewhat contrast with the literature in adults, which suggests that professional male ballet dancers have a higher rate of injury than their female counterparts [16, 27].