Epidemiological Review of Injury in Pre‑Professional Ballet Dancers Dennis Caine, Ph.D., Brett J. Goodwin, Ph.D., Caroline G. Caine, Ph.D., and Glen Bergeron, Ph.D., C.A.T.(C.)

Abstract The objective of this study was to provide an epidemiological review of the literature concerning ballet injuries affecting preprofessional ballet dancers. The literature search was limited to published peerreviewed reports and involved an extensive examination of Scopus, SPORTDiscus, and CINAHL. The following search terms were used in various combinations: ballet, injury, epidemiology, risk factor, pre-professional, and intervention. Additional citations were located using the ancestry approach. Unlike some other athletic activities that have been the focus of recent intervention research, there is a paucity of intervention and translational research in pre-professional ballet, and sample sizes have often been small and have not accounted for the multivariate nature of ballet injury. Exposure-based injury rates in this population appear similar to those reported for professional ballet dancers and female gymnasts. A preponderance of injuries affect the lower extremity of these dancers, with sprains and strains being the most frequent type of injury reported. The majority of injuries appear to be overuse in nature. Injury risk factors have been tested

in multiple studies and indicate a variety of potential injury predictors that may provide useful guidance for future research.

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t is estimated that there are 32,000 private dance schools and studios in the USA, and 3.5 million children receive dance instruction from dance specialists.1 These numbers include dance-in-education settings as well as countless dance studios and schools and therefore do not accurately describe ballet participation specifically. The results of a recent survey of a nationally representative sample of USA adolescents indicated a 20% prevalence of dance participation (95% CI, 18.2 to 22.9) in 2011.2 A significantly greater proportion of girls (34.8%; 95% CI: 30.8% to 38.8%) reported dancing during this period than boys (8%: 95% CI: 6.8% to 10%).2 Clearly, dancing is a popular activity for adolescents in the USA, especially among girls. Children often enroll first in ballet class before exploring other types of

Dennis Caine, Ph.D., Professor Emeritus, Department of Kinesiology and Public Health Education, University of North Dakota, Grand Forks, North Dakota. Brett J. Goodwin, Ph.D., Associate Professor and Chair, Department of Biology, University of North Dakota, Grand Forks, North Dakota. Caroline G. Caine, Ph.D., retired dance professor and Department Head, Department of Dance, University of Oregon, Eugene, Oregon. Glen Bergeron, Ph.D., C.A.T.(C.), Associate Dean and Professor, Faculty of Kinesiology and Applied Health, The University of Winnipeg, Winnipeg, Manitoba, Canada. Correspondence: Dennis Caine, Ph.D., Department of Kinesiology and Public Health Education, University of North Dakota, Grand Forks, North Dakota 58502; [email protected].

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dance later in their career.3 Ballet is a theatrical pursuit that is well known for its high volume and intensity of training and relatively young starting age of participants. Those participants who choose a level of training for a professional career in ballet, usually affiliated with a professional ballet company, are typically regarded as “pre-professional.” There are multiple well-known preprofessional ballet schools in North America, for example the School of American Ballet (New York City Ballet) and Canada’s Royal Winnipeg Ballet School (Canada’s Royal Winnipeg Ballet), which are associated with professional ballet companies.4 These ballet schools provide a level of training that includes a rigorous physical and academic dance training schedule. Pre-professional ballet training typically involves youth and young adults, ages 11 to 21 years,5 although girls may begin as early as age 8 to 10 years. These programs are designed to progressively replicate both the technical demands and intensity of the professional setting.6 Pre-professional ballet training places increasing demands on the student, often requiring up to 5 or 6 days a week of training as the dancer approaches the professional level.7-9 Weekly hours of preparation range from 6 to 45 hours per week during the academic year in pre-professional schools, depending on age and technique level.5,6,10,11 In children and adolescents, physical activity increases both cardio-respiCopyright © 2015 J. Michael Ryan Publishing, Inc. http://dx.doi.org/10.12678/1089-313X.19.4.140

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ratory fitness and muscular strength, reduces body fat, improves cardiovascular and metabolic disease risk profiles, enhances bone health, and reduces symptoms of depression and anxiety.12 Similar health benefits have been attributed to dancing during these formative years.2 However, ballet involves repetitive, rotational movements and pointe work, which are physically demanding and can lead to injuries.13 Young ballet dancers may be particularly vulnerable to injury due to the presence of still maturing growth plates and the growth process itself.8,14 They might also be at risk because of underdeveloped coordination, technical skills, and spatial perception.15 The frequent and intensive training and performance of pre-professional ballet dancers may create conditions under which these potential risk factors exert their influence. It is perhaps not surprising that concern has been raised regarding the incidence rate, severity, and long-term effects of injury sustained in ballet. For example, early signs of osteoarthritis of the knee, hip, and first metatarsophalangeal joint were present in a cohort of professional ballet dancers, ages 19 to 36 years,16 and a high prevalence of osteoarthritis has been found in retired ballet dancers.17,18 In one published report, retired professional ballet dancers suffered from a significant increase in walking difficulty or limping because of hip or knee pain compared to nondancers.19 Epidemiological studies report that 42.1% to 77% of pre-professional ballet students were injured at least once during the study period.5,6,10,20 Some ballet students incur multiple injuries.21 Injury has also been linked to cause for dropping out of preprofessional training. In one study, for example, 55% of pre-professional students dropped out of training over a period of 4 years.22 Those who discontinued training had a higher injury rate (50% versus 13%; p < 0.05) than those who continued. In addition to the immediate healthcare costs, these injuries may have long-term consequences on the musculoskeletal system, resulting in

reduced levels of physical activity and therefore reduction in wellness. Although there are few published reviews of musculoskeletal injury in dance,23-25 there are no reviews of the epidemiology of injury specifically addressing the pre-professional ballet dancer. Therefore, the purpose of this article is to provide an epidemiological review of ballet injuries affecting preprofessional ballet dancers as reported in the literature.

Methods

Literature Search The primary reference sources for this study were the electronic database SCOPUS, the world’s largest database of peer-reviewed coverage of Medline, SPORTDiscus, and CINAHL. The literature search was limited to published, peer-reviewed reports and involved the following search terms as well as extensive cross-referencing: ballet, injury, pre-professional, injury risk factors, and injury prevention. Additionally, a search of the Dance Medicine & Science Bibliography was conducted.26 In this regard, the following subject indices were searched and cross-referenced for published articles related to “ballet injury,” “epidemiology,” and “injury survey.” Published studies arising from descriptive and analytical studies (including cross-sectional, cohort, and intervention designs) related to pre-professional ballet injuries were reviewed by two of the investigators, DC and CC, for possible inclusion. All published studies that included data related to the research question were included. Although there were two intervention studies, there were no case-control or randomized control trials involving pre-professional ballet dancers available at the time of our search. Conclusions regarding the epidemiology of injury affecting pre-professional ballet dancers were linked primarily to data arising from cross-sectional and cohort studies. Methodological Limitations In reviewing the existing literature, several methodological limitations arose as follows:

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• Diversity of study populations with respect to age, technique level, and type of training environment. • Relatively short study duration in most cases. • Use of self-report questionnaires that may not capture accurate details of the diagnosis and exact nature of injury. Such reports may also be prone to recall bias if dancers are prompted to recall past injuries. Typically, less severe injuries, particularly those that occurred months earlier, are forgotten. • In the absence of detailed injury records, retrospectively collected data are susceptible to dancer and teacher recall bias and tend to miss relatively minor injuries, thereby resulting in an underestimation of overall injury rates. • Variability in injury definition across studies, resulting in different approaches to “counting” injuries. • Lack of uniformity in reporting anatomical location, type, and severity of injury across studies. • Non-random selection of ballet programs, resulting in the possibility that those programs most concerned with injury will be over-represented in the published literature. • Failure of many of the studies that investigated risk factors to account for the multi-factorial nature of injury risk. • Limited information on exposure of the population from which the injured dancers came (i.e., denominator data). In spite of these limitations, it is the intent of this article to find the best answers possible at this point in time by presenting the various properties and findings of the studies in an integrative way to provide a global picture of pre-professional ballet injuries.

Epidemiology of Injury Participants in ballet and everyone who works with them, whether they are parents, sports medicine personnel, ballet governing bodies, or ballet

*Overuse injuries only; †One dance exposure equals one dancer participating in a training or performance session; SRI, self-reported injuries; RI-PT, injuries reported by a physical therapist.

4.7 (SRIs) 3.8 - 4.6 2.9 (RI-PT) 2.2 - 3.6 n/a n/a 112 SRIs n/a 71 RI-PT n/a Liberal Arts High School Dance Program (mostly classical ballet) Prosp. Total = 39 15.8 ± 1.0 9 mos. 34 F 5M Luke, et al.20

Self-reported and by a physical therapist or health professional

n/a 1.77 n/a 1.09 198 Elite American ballet school Retros. Total = 359 14.7 ± 1.9 5 yrs. 288 F 71 M Gamboa, et al.10

Physical therapist

n/a n/a n/a 0.80 0.80 F 0.80 M n/a n/a Orthopaedic consultant Royal Swedish Ballet School Retros. Total = 476 n/a 7 yrs. 297 F 179 M Leanderson, et al.5

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1.24 - 1.52 1.18 - 1.54 F 1.19 - 1.62 M 1.68-2.06 1.38 1.61-2.10 F 1.36 F 1.60-2.18 M 1.40 M 1.87 1.85 F 1.89 M 3 elite pre-prof. Physiotherapist Australian ballet schools Prosp. Total = 266 17.2 ± 1.21 1 yr. 154 F 112 M Ekegren, et al.6

378 218 F 160 M

2.40 2.19 F 2.81 M n/a n/a n/a 3.52 3.21 F 4.12 M 59 24 F 35 M Australian Ballet Physical therapist School Prosp. Total = 46 16.0 ± 1.58 6 mos 30 F 16 M

Subjects Study

Bowerman, et al.27,*

Affiliation

Individual Who Recorded Injuries Age Mean ± SD (years)

A summary of cohort studies reporting on the incidence of injury affecting young ballet dancers is shown in Table 1.5,6,10,20,27 Perusal of this table reveals that the majority of participants in these studies were female (range: 57.9% to 87.2%); however, male ballet dancers were also included (range: 12.8% to 42.1%). Studies were both prospective and retrospective in nature and ranged in follow-up from 6 months to 7 years. Mean age of participants ranged from 14.7 to 17.2 years. Injury data were collected by a physical therapist in most studies,6,10,20,27 although an orthopaedic consultant was employed in one study5 and self-report of injury included in another.20 Ballet injury cannot be defined easily as “missing practice or class” because dancers often train through injuries.10,20 The cohort studies in Table 1 utilize somewhat differing definitions of injury, which limits comparability of injury rates across studies. Injury definitions in these studies include the following: • Any physical issue resulting in pain or discomfort that required a dancer to modify his or her dance activity during one or more classes or which required a dancer to cease all dance-related activity.27 • “An anatomic tissue-level impairment as diagnosed by a licensed healthcare practitioner that results in full-time loss of activity for one or more days beyond the day of onset.”6

Table 1 Cohort Studies of Injuries Rates in Pre-Professional Female and Male Ballet Dancers

Incidence of Injury

Number of Injuries

Number of Injuries per 1,000 DEs†

95% Confidence Interval

Number of Injuries per 1,000 hours

95% Confidence Interval

teachers and choreographers, need to know answers to important research questions, such as: What is the risk of injury, and does the risk vary relative to technique level? When and where are injuries most likely to occur? What is the anticipated outcome of any given injury? What factors are associated with an increased risk of injury? These are all questions that need to be answered through scientific investigation. Providing this information is an important objective of epidemiological research related to pre-professional ballet.

n/a n/a n/a

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Study Design

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• “Any dance-related medical problem which required orthopaedic consultation.”5 • “An injury was considered to have occurred when a dancer sought at least one treatment session from a physical therapist.”10 • Luke and coworkers20 used two definitions of injury: 1. selfreported injury during bi-weekly survey and 2. injuries reported by a physical therapist in the school clinic. Overall injury rates (including acute and overuse injuries) were reported across all studies as number of injuries per 1,000 hours of exposure. Several studies also reported the number of injuries per 1,000 danceexposures,6,10 where one dance exposure equals one dancer participating in a training or performance session. There was no standard methodology for capturing workload exposure (i.e., number of actual hours spent dancing) in the studies reviewed, which affects the comparability of injury rates reported. Bowerman and colleagues27 used the timetables for each year level at the ballet school to estimate exposure. Ekegren and associates6 collected precise group data on a weekly basis from the students’ weekly timetables. Similarly, Leanderson and coworkers5 determined exposure from data provided by the school board regarding daily registered attendance at dance training. Gamboa and colleagues 10 did not report how exposure data were gathered in their study; however, since the study was retrospective, the precision of the exposure data would depend on the nature of the records available. Luke and coworkers20 summed the average reported hours of dance per 2-week blocks. Overall injury rates for female and male dancers ranged from 1.09 to 3.52 injuries per 1,000 dance exposures (DEs) and from 0.8 to 2.9 injuries per 1,000 hours training. In contrast, Luke and coworkers20 reported rate of self-reported injuries of 4.7/1,000 hours. Injury rates of 4.4 injuries per 1,000 hours28 and 0.6 injuries per 1,000 hours29 have been reported for

USA and Swedish professional ballet dancers, respectively. By comparison, injury rates for competitive female gymnasts reportedly range from 0.5 to 5.3 injuries/1,000 hours.30 Results from the National High School Sports-Related Injury Surveillance Study (High School RIO),31 for all years studied (2005 to 2014), indicate a range in overall injury rates from 0.21 (swim and dive) to 4.5 (football) injuries per 1,000 athletic-exposures (AEs) for boys’ sports and from 0.32 (swim and dive) to 2.42 AEs (soccer) for girls’ sports. However, higher injury rates have been recorded for full contact sports, especially during competition.31 With the exception of Luke and coworkers20 none of the studies in Table 1 tested for gender differences in injury rates. Luke and coworkers reported significantly higher selfreported injury rates (SRIs) in males compared to females (p = 0.02), in spite of the fact that the female ballet dancers reported dancing significantly more hours per day than the males.

Recurrent Injury A recurrent injury is one of the same type and location as a previous injury32-34 and would be considered a re-injury if it occurred after the initial injury had fully healed. It is generally recognized that unresolved residual symptoms from a previous injury predispose the athlete to reinjury at the same and different sites.30 However, there are surprisingly few data that illuminate the proportion or incidence rate of recurrent injury in pre-professional ballet. Percentage estimates for reinjury in two studies of pre-professional ballet dancers range from 14% to 43.7%.5

Injury Location Understanding the anatomical location of injury is important for instructors and healthcare professionals who work with young ballet dancers. Such information identifies the body parts most likely to be injured and therefore those that should be the focus of attention for possible preventive measures. The percent dis-

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tribution of injury by anatomical location among pre-professional female and male ballet students is addressed in multiple studies.5,6,10,11,20,21,27,35 As reported in these studies, the lower extremity is the body region where the majority of ballet injuries occur (range: 69.0% to 91.1%), followed by the head, spine, and trunk (range: 4.6% to 24.0%). In the lower extremity, the foot and toes (combined) are the most common site of injury reported (range: 13.1% to 33.0%),5,6,10,11,20,27 followed by the hip (range: 7.1% to 30%),6,21,35 ankle (range: 8.4% to 50.0%),6,11,20,28 and knee (range: 7.0% to 22.0%).5,6,10,11,20,28,36 The neck is the most commonly reported injury site in the head, spine, and trunk region (range: 4.6% to 24%).5,10,20,27 Garrick21 reported that the foot and toes were the most common site of injury (28.2%), followed by the ankle (19.9%), and knee (16.1%) in his study of 194 injuries affecting 38 of 59 ballet students, ages 13 to 18 years, seen at his clinic from November 1996 through June 1998. Similarly, Negus and associates36 found that the most common injury locations in their cross-sectional study of pre-professional ballet dancers were the hip (25.6%) and ankle (25.6%), followed by the lower leg (19.5%) and foot (11%). This anatomical distribution is similar to that reported for professional ballet dancers. For example, in the study by Nilsson and colleagues, the ankle and foot (54%), low back and gluteal region (17.9%), and knee (11%) were the most common anatomical locations of injury in a 5-year survey of injuries in a Swedish ballet company.29

Injury Type Information on injury types sustained highlights common injuries that may be the focus of preventive efforts. Data on injury types vary across studies; however, it is evident that pre-professional ballet dancers most commonly incur sprains and strains, as well as overuse injuries, such as tendonitis.5,20,21 Ekegren and coworkers reported that the three most common

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injury types in their study were lower leg overuse (10.3%), ankle tendinopathy (6.0%), and ankle impingement (5%).6 In contrast, the most frequent injuries reported by Leanderson and associates were tendinosis (22.2%), ankle sprain (11.4%), and low back pain (10.3%).5 Luke and coworkers reported that the most common ankle injury in their study was Achilles tendinopathy, and that the most common back injury was mechanical low back pain.20 Wiesler and colleagues reported that the most common injuries sustained by pre-professional ballet (N = 101) and modern (N = 47) dancers in their study were tendinitis (24.0%), ankle sprain (13.8%), and knee strain (13.8%). 37 Notably, sprain (ankle and foot; 18.7%) was the most common diagnosis among dancers in the Swedish professional ballet company mentioned above.29 Head, Spine, and Trunk As recorded in the cohort studies reviewed, head, spine, and trunk injuries comprised from 9.8% to 24% of injuries among young ballet dancers. Most of these injuries involved the spine, including low back strain and other soft tissue injuries.5,21 In two cohort studies, low back injury ranged from 10.3% to 29.6% of all reported injuries.5,21 It has been estimated that from 60% to 80% of ballet dancers have some history of back injury.38 The repetitive flexion or combined flexion and extension of the spine required in ballet dancing, with or without rotation, appears to contribute to fatigue fracture of the posterior elements, usually the pars interarticularis.39-41 However, these lesions may also, infrequently, occur through the pedicles. Although in the immature spine the weakest portion of the lamina is the pars interarticularis, in the physically mature spine it may be the pedicle.39 In one study,42 stress fractures of the lumbar spine were documented in 10% of all stress fractures affecting pre-professional ballet dancers, ages 15 to 19 years. Sport-related concussion affecting young athletes is a topic of increasing public and media attention, yet there

is a paucity of information on this injury type in the dance literature. In a recent study, Stein and coworkers43 reported that 3,011 new concussion visits were conducted in an established concussion clinic over 5.5 years. Of these, only 11 involved dancers aged 12 to 20 years, including two pre-professionals. One cohort study of pre-professional dancers reported that 4.6% of all injuries involved the head and neck, although frequency of concussion was not reported.11 In contrast, concussions represented 8.9% of all high school athletic injuries in the 2005 to 2006 High School Sports Injury Surveillance Study.44 Upper Extremity Three cohort studies reported upper extremity (UE) injuries, and these ranged from 3% to 9.5% of all injuries.5,6,11 Nilsson and associates29 found that 7.2% of all injuries involved the upper extremity in their 5-year report of injuries affecting Swedish professional female and male ballet dancers (e.g., rotator cuff problems). Notably, these conditions were more common in males than females (p < 0.05), most likely because they lift their female partners while dancing.29 Lower Extremity Lower extremity (LE) injuries comprise from 69% to 91% of injuries among pre-professional ballet dancers.5,6,10,11,20,21,27,35 These results are not surprising given the repetitive nature of ballet training, and that the lower extremities are under continuous stress while dancing. Few studies reviewed reported the distribution of lower extremity injury types. Leanderson and colleagues5 found that the three most common lower extremity injuries were tendinosis of the feet and groin (22.2%), ankle sprain (11.4%), and jumper’s knee (7.1%). Luke and coworkers20 reported that 31% of all reportable injuries (physical therapist) were ankle injuries, and that among these the most common were tendinopathy and strain (10 of 22 cases) and ankle sprain (4 of 22 cases). Notably, stress-related injury of the lower leg and foot of young ballet

dancers, including stress fracture,45-49 posterior ankle impingement,7,8,50,51 and tendinopathy,7,52-54 are commonly reported.

Injury Onset As a great number of training hours are required for high-level performance in ballet, it is to be expected that both traumatic and overuse injuries will occur. Overuse injuries are thought to result from exposure to repeated sub-maximal loads without adequate recovery time.55 Studies reporting on injury onset in young ballet dancers indicate a range of 53.6% to 85% for overuse injuries and from 12% to 45% for traumatic injuries.5,6,10,20 Bowerman and associates reported a rate of 2.4 overuse injuries per 1,000 exposure hours.27 Two cross-sectional studies of adolescent ballet dancers reported a prevalence of overuse versus traumatic injuries. McNeal and colleagues reported that among 171 pre-professional ballet dancers, ages 13 to 21 years, 75% of knee injuries, 63% of ankle injuries, and 51% of foot injuries were the result of overuse.56 Negus and coworkers discovered that 86.2% of 29 pre-professional ballet students in their study currently had overuse injuries.36 By way of comparison, Nilsson and associates attributed the majority of injuries (57%) in their prospective study of Swedish professional ballet dancers to overuse.29 Similarly, Allen and coworkers reported that 64% of injuries were overuse in their study of adult ballet dancers. The predominance of overuse injuries among young ballet dancers is a concern given that up to 50% of these injuries may be preventable.57

Injury Severity In pre-professional ballet dancers epidemiologic data concerning absence from training due to injury and treatment of injury are scarce. In the study by Ekegren and colleagues,6 a mean of 28.7 days were lost from full participation due to injury, suggesting that many of those injuries were relatively severe in nature. In that study, female participants took longer (Mean: 32.54

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days) to return to full participation than males (Mean: 21.59 days) pursuant to injury (p = 0.005). Additionally, bone injuries required significantly more recovery time per injury than muscle (p = 0.001) and joint (p = 0.011) injuries. 6 Similarly, Leanderson and coworkers reported that tibial stress fractures (N = 5) in their study required the greatest amount of time to recover; however, foot stress reaction and stress fractures (N = 15) required the greatest time off in total.5 Ekegren and colleagues also reported a mean of 7.02 (95% CI: 6.19 to 7.86) physiotherapy treatments per injury over the academic year (approximately 10 treatments per dancer).6 Over one school year, there was a total of 145 injuries requiring medical referral, 226 injuries requiring medical investigation (e.g., x-ray, MRI scan, and so forth), and 23 injuries (6.1%) requiring surgery. Two studies included time loss and treatment related to injuries. Of 16 ballet dancers (ages 12 to 18 years) in one study,35 94% experienced at least one injury during their dance career. Almost one-third of injuries (29%) required 3 to 7 days of training modification, 47% required from 1 to 4 weeks, 6% 1 to 3 months, and 18% required more than 3 months of reduced training. More than half (58%) of the ballet dancers sought treatment from physical therapists and 19% consulted physicians. Thomas and associates reported that 125 of 239 (52.3%) adolescent ballet dancers attending intensive summer ballet programs had a lifetime history of injury (stress fracture, broken bone, or medically treated tendonitis).58 More than two thirds (71.2%) of injured dancers in that study took, on average, 14 days off from ballet to recuperate from injury.

Injury Risk Factors Injury risk factors have been tested in multiple studies of injuries affecting young ballet dancers. The following factors were significantly associated with injury5,10,22,27,37,59: • Rate of growth was associated with increased risk of lumbar and

lower extremity overuse injury (RR = 1.41, CI = 0.53 to 0.98).27 Additionally, superior right extremity alignment was associated with a reduction in rate of overuse injuries.27 • Overall injury rates were significantly lower for younger girls (≤ 10 years old) versus older girls, both 11 to 14 year olds (p = 0.04) and 15 to 21 year olds (p = 0.005), and for boys less than or equal to 10 years old versus 15 to 21 year olds (p = 0.03) and for 11 to 14 year olds versus 15 to 21 year olds (p = 0.0006).5 • Previous sprain of the contralateral ankle emerged as a significant predictor of lateral ankle sprains (HR = 3.90; CI = 1.49 to 10.22; p = 0.006).59 Injury history (lower limb) was also a significant predictor (p = 0.02) of lower extremity injury in ballet and modern dancers.37 • The following screening variables distinguished injured from noninjured dancers: current disability score based on flexibility and strength tests (p = 0.007), history of low back pain (p = 0.017), right foot pronation (p = 0.005), insufficient right-ankle plantar flexion (p = 0.037), and lower extremity strength (p = 0045).10 • Deficits in an orthopaedic screening exam predicted dancers who dropped out of training at the advanced level from those who became professionals.22 Eleven cross-sectional studies analyzed injury risk factors in preprofessional ballet dancers.11,35,36,58,60-66 Although the results of these analyses indicate factors that may relate to increased risk of injury, they provide only limited evidence for a causeand-effect relationship because they provide no direct evidence of the sequence of events.67 Several studies compared injured to non-injured dancers60,61 or ballet dancers versus non- or other-dancers11,35 to identify possible predisposing factors to injury. The following factors significantly distinguished between the groups: • Increased landing foot eversion

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and inefficient muscle activations from foot to hip during landing in ankle-injured ballet dancers protecting against re-injuries (p < 0.05).60 • Proprioceptive deficits after sprained ankle may contribute to inferior postural stability in the medial-lateral direction during single-leg standing and ballet postures for the ankle-injured ballet dancers compared to healthy dancers and non-dancers (p < 0.05).61 With or without vision assistance, ballet dancers who suffered from ankle sprains demonstrated inferior postural stability. • A greater frequency of lateral hip and knee problems than nonballet students. Passive hip adduction was significantly reduced in the dancers with a history of lateral pain or snapping (p < 0.001).11 Several cross-sectional studies analyzed potential injury risk factors among samples of pre-professional ballet students.36,58,62,63,65,66 Significant injury risk factors that emerged from these analyses included greater number of lifetime disordered eating behaviors (p = 0.01) and history of vomiting (p = 0.04),58 insufficient functional turnout,36 gender (females having a higher occurrence of hamstring injury than males, p < 0.05),65 number of double heel strikes during jump landing and a history of shin splint pain (p = 0.02),66 and ballet dancers with longer second toes had more callosities than ballet dancers with equal length or shorter second toes (p = 0.003).64 In one study,63 low levels of aerobic fitness (r = .590; p = 0.034) and percent body fat (r = -.614; p = 0.026) were associated with the length of time a dancer was forced to modify activity due to injury.

Inciting Factors for Injury Few studies noted inciting event or activity at the time of injury. Hiller and coworkers followed 115 dance and ballet students of a performing arts secondary school and local dance school (N = 115 M/F; M = 14.2 ± 1.8 years of age) for 13 months to

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describe the incidence, mechanisms, and intrinsic predictors of lateral ankle sprains.59 During the study period, 38 ankle sprains were sustained by 33 dancers (28.9% of participants). Among sprains sustained while dancing, 43.8% occurred from landing after a jump or hop and 37.5% while moving on demi-pointe. A review of accident reports from six Berlin theatres and one state ballet school68 revealed that the most common activity at the time of injury in both professional dancers and dance students was “slipping,” due to dirt, liquid, props, and parts of costumes on the flooring. “Getting caught” or “stumbling” on “too sticky” or uneven flooring was the second most frequent problem for professional dancers and students.

Injury Prevention Ballet injuries may cause significant discomfort and disability, reduce productivity, and are responsible for substantial medical expenses. Although it is impossible to eliminate all injuries, attempts to reduce them are obviously warranted. The results of research in youth sports that were designed to determine the effects of injury prevention countermeasures are promising and demonstrate the potential for balance and proprioceptive training, strength conditioning, and fall and recovery training programs to reduce the risk, particularly of lower extremity injury, among young athletes.69-71 Our search procedures produced only two injury prevention studies in relation to pre-professional ballet dancers. Noh and colleagues72 examined the effects of two psychological interventions designed to reduce injury by enhancing coping skills. Thirty-five pre-professional ballet dancers were assigned to one of three conditions for 12 weeks training and 12 weeks practice (3 times weekly): control (N = 12), autogenic training (N = 12), and a broad-based coping skills condition (N = 11). Study results indicated that participants in the broad-based coping skills condition spent significantly less time injured than those in the control group (p < 0.05). The investigators concluded

that interventions that reduce stress or increase coping skills or both can reduce the likelihood of injury. Kaufman and associates73 conducted a 2-year non-randomized intervention study involving 39 dancers from an elite ballet school to determine if education, in the form of counseling, could decrease the incidence of reproductive dysfunction and injury, particularly stress fractures. Comparison of subjects who completed (N = 8) versus those who dropped out of the study and training (N = 31) were not significant. However, subjects who completed the study were naturally thinner, more premenarcheal, manifested less dieting behavior at baseline, and were further from their ideal weight than those who dropped out of the study and training. Notably, early recognition of injury through pre-participation screening and subsequent management of injuries has been recommended at both the pre-professional and professional levels of ballet training to decrease the number of problems advancing to the stage where formal medical care is required.21,74-76 In one ballet company, this type of intervention resulted in decreased annual percentage of injuries from 94% to 75% over a 5-year period.38 Allen and coworkers74 tested such an intervention in a study of professional ballet dancers ranging in number from 52 to 58 over a 3-year period. Incidence of injury was significantly reduced (p < 0.001) in years 2 and 3 compared to year 1 in both female and male dancers.

Study Relevance This is the first epidemiological review of the pre-professional ballet injury literature and is designed to serve as a basis for further epidemiological research on injuries affecting this population, including injury prevention. The objective of this line of research is, ultimately, to reduce the incidence and severity of injury experienced by young ballet dancers and to provide direction for further research.

Conclusions There is a dearth of epidemiological research on dance injuries. None-

theless, in this review of the limited research we aimed to provide insight into the incidence and distribution of injury affecting pre-professional ballet dancers and to elucidate possible injury risk factors. However, many of these studies suffer from methodological shortcomings and do not account for the multivariate nature of ballet injury. Intervention research is surprisingly lacking in comparison with the abundance of research that has been published on young female and male participants in other athletic endeavors such as soccer, team handball, and ice hockey.69-71 This finding is a matter of concern given the rigorous training demands of dance and the life-changing impact injury can have on young ballet dancers. The importance of establishing denominatorbased injury surveillance programs in obtaining an accurate picture of injury risk and severity and as a basis of testing for modifiable risk factors and preventive measures cannot be overemphasized.

References 1. Organization NDE. Statistics. General U.S. Education and Dance Education, 2014: http://www.ndeo.org/ content.aspx?page_id=22&club_ id=893257&module_id=55774. Accessed July 24, 2014. 2. O’Neill JR, Pate RR, Leise AD. Descriptive epidemiology of dance participation in adolescents. Res Q Exerc Sport. 2011 Sep;82(3):373-80. 3. Weiss DS, Shah S, Burchette RJ. A profile of the demographics and training characteristics of professional modern dancers. J Dance Med Sci. 2008;12(2):41-6. 4. http://deballet.com/schools. Accessed March 15, 2015. 5. Leanderson C, Leanderson J, Wykman A, et al. Musculoskeletal injuries in young ballet dancers. Knee Surg Sports Traumatol Arthrosc. 2011 Sep;19:1531-5. 6. Ekegren CL, Quested R, Brodrick A. Injuries in pre-professional ballet dancers: incidence, characteristics and consequences. J Sci Med Sport. 2014 May;17:271-5. 7. Albisetti W, Ometti M, Pascale V, De Bartolomeo O. Clinical evaluation and treatment of posterior impinge-

Journal of Dance Medicine & Science • Volume 19, Number 4, 2015 ment in dancers. Am J Phys Med Rehabil. 2009 May;88(5):349-54. 8. Poggini L, Losasso S, Iannone S. Injuries during the dancer’s growth spurt: etiology, prevention, and treatment. J Dance Med Sci. 1999;3(2):73-9. 9. Kadel NJ, Teitz CC, Kronmal RA. Stress fractures in ballet dancers. Am J Sports Med. 1992 JulAug;20(4):445-9. 10. Gamboa JM, Roberts LA, Maring J, Fergus A. Injury patterns in elite preprofessional ballet dancers and the utility of screening programs to identify risk characteristics. J Ortho Sports Phys Ther. 2008 Mar;38(3):126-36. 11. Reid DC, Burnham RS, Saboe LA, Kushner SF. Lower extremity flexibility patterns in classical ballet dancers and their correlation to lateral hip and knee injuries. Am J Sports Med. 1987 Jul-Aug;15(4):347-52. 12. US Department of Health and Human Services. Physical activity advisory committee report. Washington, DC: US Department of Health and Human Services, 2008. Available at http://health.gov/paguidelines/ report/pdf/committeereport.pdf. Accessed October 5, 2015. 13. Roberts KJ, Nelson NG, McKenzie L. Dance-related injuries in children and adolescents treated in US emergency departments in 1991-2007. J Phys Act Health. 2013 Feb;10(2):143-50. 14. Micheli L, Solomon R. Training the young dancer. In: Ryan AJ, Stephens RE (eds): Dance Medicine: A Comprehensive Guide. Chicago, Il: Plurius Press, 1983; pp. 51-72. 15. National Center for Injury Prevention and Control. CDC Injury Research Agenda 2009–2018.Atlanta (GA): Centers for Disease Control and Prevention, 2009. http://www. cdc.gov/injury/ResearchAgenda. Accessed June 29, 2014. 16. Angioi M, Maffulli GD, McCormack M, et al. Early signs of osteoarthritis in professional ballet dancers: a preliminary study. Clin J Sport Med. 2014 Sep;24(5):435-7. 17. Van Dijk CN, Lim LS, Poortman A, et al. Degenerative joint disease in female ballet dancers. Am J Sports Med. 1995 May-Jun;23(3):295-300. 18. Andersson S, Nillson B, Hessel T, et al. Degenerative joint disease in ballet dancers. Clin Orthop Relat Res. 1989 Jan;(238);233-6. 19. Rönkkö R, Heliövarra M, Malmi-

vaara A, et al. Musculoskeletal pain, disability and quality of life among retired dancers. J Dance Med Sci. 2007;11(4):105-9. 20. Luke AC, Kinney SA, D’Hemecourt PA, et al. Determinants of injuries in young dancers. Med Probl Perform Art. 2002;17(3):105-12. 21. Garrick JG. Early identification of musculoskeletal complaints and injuries among female ballet students. J Dance Med Sci. 1999;3(2):80-3. 22. Hamilton LH, Hamilton WC, Warren MP, et al. Factors contributing to the attrition rate in elite ballet students. J Dance Med Sci. 1997;1(4):131-8. 23. Jacobs CL, Hincapié CA, Cassidy DL. Musculoskeletal injuries and pain in dancers: a systematic review update. J Dance Med Sci. 2012;16(2):74-84. 24. Hincapié CA, Morton E, Cassidy JD. Musculoskeletal injuries and pain in dancers: a systematic review. Arch Phys Med Rehabil. 2008 Sep;89(9):1819-29. 25. Caine CG, Garrick JG. Dance. In: Caine DJ, Caine CG, Lindner KJ (eds): Epidemiology of Sports Injuries. Champaign, IL: Human Kinetics Publishers, 1996, pp. 124-160. 26. Solomon R, Solomon J. Dance Medicine and Science Bibliography (6 ed). Eugene, OR: International Association for Dance Medicine and Science, 2014. 27. Bowerman E, Whatman C, Harris N, et al. Are maturation, growth and lower extremity alignment associated with overuse injury in elite adolescent ballet dancers? Phys Ther Sport. 2014 Nov;15(4):234-41. 28. Allen N, Nevill A, Brooks J, et al. Ballet injuries: injury incidence and severity over 1 year. J Orthop Sports Phys Ther. 2012 Sep;42(9):781-90. 29. Nilsson C, Leanderson J, Wykman A, Strender LE. The injury panorama in a Swedish professional ballet company. Knee Surg Sports Traumatol Arthrosc. 2001 Jul;9(4):242-6. 30. Caine D, Harringe ML. Epidemiology of injury in gymnastics. In: Caine D, Russell K, Lim L (eds): Gymnastics Handbook of Sports Medicine and Science. Hoboken, NJ: Wiley-Blackwell Publishers, 2013, pp. 111-124. 31. Comstock RD, Dahab KS, James, DA. Epidemiology of injury in high school sports. In: Caine D, Purcell L (eds): Injury in Pediatric and Adolescent Sports: Epidemiology, Treatment

147

and Prevention. New York: Springer, 2016, pp 51-57. 32. Fuller CW, Ekstrand J, Junge A, et al. Consensus station on injury definitions and data collection procedures in studies of football (soccer) injuries. Clin J Sports Med. 2006 Mar;16(2):97-106. 33. Fuller CW, Malloy MG, Bagate C, et al. Consensus statement on injury definitions and data collection procedures for studies of injuries in rugby union. Clin J Sports Med. 2007 May;17(3):177-81. 34. Caine D, Cochrane B, Caine C, et al. An epidemiologic investigation of injuries affecting young competitive female gymnasts. Am J Sports Med. 1989 Nov-Dec;17(6):811-20. 35. Krasnow D, Mainwaring L, Kerr G. Injury, stress, and perfectionism in young dancers and gymnasts. J Dance Med Sci. 1999;3(2):51-8. 36. Negus V, Hopper D, Briffa NK. Associations between turnout and lower extremity injuries in classical ballet dancers. J Orthop Sports Phys Ther. 2005 May;35(5):307-18. 37. Wiesler ER, Hunter DM, Martin DF, et al. Ankle flexibility and injury patterns in dancers. Am J Sports Med. 1996 Nov-Dec;24(6):754-7. 38. Solomon R, Solomon J, Micheli LJ, et al. The “cost” of injuries in a professional ballet company. A fiveyear study. Med Probl Perform Art. 1999;14:164-9. 39. Amari R, Sakai T, Katoh S, et al. Fresh stress fracture of lumbar pedicles in an adolescent male ballet dancer: case report and literature review. Arch Orthop Trauma Surg. 2009 Mar;129(3):397-401. 40. Ireland ML, Micheli LJ. Bilateral stress fracture of the lumbar pedicles in a ballet dancer. J. Bone Joint Surg Am. 1987 Jan;69(1):140-2. 41. Abel MS. Jogger’s fracture and other stress fractures of the lumbo-sacral spine. Skeletal Radiol. 1985;13(3):221-7. 42. Lunden K, Melcher L, Bray K. Stress fractures in ballet: a twentyfive year review. J Dance Med Sci. 1999;3(3):101-7. 43. Stein CJ, Kinney SA, McCrystal T, et al. Dance-related concussion: a case series. J Dance Med Sci. 2014;18(2):53-61. 44. Gessel LM, Fields SK, Collins CL, et al. Concussions among United States high school and collegiate athletes. J Athl Train. 2007 Oct-

148

Volume 19, Number 4, 2015 • Journal of Dance Medicine & Science

Dec;42(4):495-503. 45. Albesetti W, Ometti M, Pascale V, De Bartolomeo O. Clinical evaluation and treatment of posterior impingement in dancers. Am J Phys Med Rehabil. 2009 May;88(5):349-54. 46. O’Malley MJ, Hamilton WG, Munyak J, DeFranco MJ. Stress fractures at the base of the second metatarsal in ballet dancers. Foot Ankle Int. 1996 Feb;17(2):89-94. 47. Burton EM, Amaker BH. Stress fracture of the great toe sesamoid in a ballerina: MRI appearance. Pediatr Radiol. 1994;24(1):37-8. 48. Harrington T, Crichton KJ, Anderson IF. Overuse ballet injury of the base of the second metatarsal. A diagnostic problem. Am J Sports Med. 1993 Jul-Aug;21(4):591-8. 49. Micheli LJ, Sohn RS, Solomon R. Stress fractures of the second metatarsal involving Lisfranc’s joint in ballet dancers. J Bone Joint Surg Am. 1985 Dec;67(9):1372-75. 50. Bureau NJ, Cardinal E, Hobden R, et al. Posterior ankle impingement syndrome: MR imaging findings in seven patients. Radiology. 2000;215(2):497-503. 51. Marotta JJ, Micheli LJ. Os trigonum impingement in dancers. Am J Sports Med. 1992Sep-Oct;20(5):533-6. 52. Porter EB, Dubois MS, Raasch WG. A 17-year-old ballet dancer with medial ankle pain. Curr Sports Med Rep. 2010 Sep-Oct;9(5):290-1. 53. Kolettis GJ, Micheli LJ, Klein JD. Release of the flexor hallucis longus tendon in ballet dancers. J Bone Joint Surg Am. 1996 Sep;78(9):1386-90. 54. Cowell HR, Elener V, Lawhon SM. Bilateral tendonitis of the flexor hallucis longus in a ballet dancer. J Pediatr Orthop. 1982;2(5):582-6. 55. Brenner JS. American Academy of Pediatrics Council on Sports Medicine and Fitness. Overuse injuries, overtraining, and burnout in child and adolescent athletes. Pediatrics. 2007 Jun;119(6):1242-5. 56. McNeal AP, Watkins A, Clarkson PM, et al. Lower extremity alignment

and Injury in young, preprofessional, college and professional ballet dancers. Part II: Dancer-reported injuries. Med Probl Perform Art. 1990:5:83-8. 57. DiFiori JP, Benjamin HJ, Brenner J, et al. Overuse injuries and burnout in youth sports: a position statement from the American Medical Society for Sports Medicine. Clin J Sport Med. 2014 Jan;24(3):3-20. 58. Thomas JJ, Keel PK, Heatherton TF. Disordered eating and injuries among adolescent ballet dancers. Eat Weight Disord. 2011 Sep;16(3):e216-22. 59. Hiller CE, Refshauge KM, Herbert RD, Kilbreath SL. Intrinsic predictors of lateral ankle sprain in adolescent dancers: a prospective cohort study. Clin J Sport Med. 2008 Jan;18(1):44-8. 60. Lee HH, Lin CW, Wu HW, et al. Changes in biomechanics and muscle activation in injured ballet dancers during a jump-land task with turnout (Sissonne Fermée). J Sports Sci. 2012;30(7):689-97. 61. Lin CF, Lee IJ, Liao JH, et al. Comparison of postural stability between injured and uninjured ballet dancers. Am J Sports Med. 2011 Jan;39(6):1324-31. 62. Ducher G, Kukuljan S, Hill B, et al. Vitamin D status and musculoskeletal health in adolescent male ballet dancers: a pilot study. J Dance Med Sci. 2011 Sep;15(3):99-107. 63. Twitchett E, Brodrick A, Nevill AM, et al. Does physical fitness affect injury occurrence and time loss due to injury in elite vocational ballet students? J Dance Med Sci. 2010;14(1):26-31. 64. Oztekin HH, Boya H, Nalcakan M, Ozcan O. Second-toe length and forefoot disorders in ballet and folk dancers. J Am Podiatr Med Assoc. 2007 Sep-Oct:97(5):385-8. 65. Askling C, Lund H, Saartok T, Thorstensson A. Self-reported hamstring injuries in student-dancers. Scand J Med Sci Sports. 2002 Aug;12(4):230-5. 66. Gans A. The relationship of heel

contact in ascent and descent from jumps to the incidence of shin splints in ballet dancers. Phys Ther. 1985 Aug;65(8):1192-6. 67. Gordis L. Epidemiology (4th ed). Philadelphia: Saunders, 2009. 68. Wanke EM, Mill H, Wanke A, et al. Dance floors as injury risk. Analysis and evaluation of acute injuries caused by dance floors in professional dance with regard to preventive aspects. Med Probl Perform Art. 2012 Sep;273):137-42. 69. Emery CA, Thierry-Oliver R, Hagel B, et al. Injury prevention in youth sports. In: Caine D, Purcell L (eds): Injury in Pediatric and Adolescent Sports: Epidemiology, Treatment and Prevention. Bern: Springer International Publishing, 2016, pp 205-229. 70. Caine D, Maffulli N. Caine C. Epidemiology of pediatric and adolescent sports injuries. Clin Sports Med. 2008 Jan;27(1):19-50. 71. Schiff M, Caine D, O’Halleron R. Injury prevention in sports. Am J Lifestyle Med. 2010;4:42-64. 72. Noh YE, Morris T, Andersen MB. Psychological intervention programs for reduction of injury in ballet dancers. Res Sports Med. 2007 JanMar;15(1):13-32. 73. Kaufman BA, Warren MP, Hamilton L. Intervention in an elite ballet school: an attempt at decreasing eating disorders and injury. Women’s Study International Forum. 1996;19(5):545-9. 74. Allen N, Nevill AM, Brooks JHM, et al. The effect of a comprehensive injury audit program on injury incidence in ballet: a 3-year prospective study. Clin J Sport Med. 2013 Sep;23(5):373-8. 75. Molnar M, Esterson J. Screening students in a pre-professional ballet school. J Dance Med Sci. 1997;1(3):118-21. 76. Solomon R. A pro-active screening program for addressing injury prevention in a professional ballet company. J Dance Med Sci. 1997;1(3):113-17.