Comprehensive Surveillance of Dance Injuries A Proposal for Uniform Reporting Guidelines for...

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Original Article

Shaw Bronner, P.T., Ph.D., O.C.S., Director, ADAM Center at Long Island University, Brooklyn, New York, and Director, Therapy Services at Alvin Ailey, New York, New York. Sheyi Ojofeitimi, M.P.T, Research Associate, ADAM Center at Long Island University, Brooklyn, New York, and Physical Therapist, Therapy Services at Alvin Ailey, New York, New York. Lester Mayers, M.D., Director, Sports Medicine, Pace University, Pleasantville, New York.

Correspondence: Shaw Bronner, P.T., Ph.D., O.C.S., Adam Center at Long Island University, 122 Ashland Place, Suite 1A, Brooklyn, New York 11201.

AbstractVarying methods of injury definition, data collection and interpretation of findings complicate analysis of results from epidemiological studies of sport and dance injuries. Comparison be-tween studies is therefore difficult. Researchers have suggested adoption of uniform methodology for injury definition and reporting. This paper outlines a suggested comprehensive injury reporting system for professional dance companies. Components of a comprehensive injury surveillance system include: 1. pre-season screening of intrinsic risk factors, 2. extrinsic risk factor track-ing, and 3. injury occurrence reporting system. Dance screens provide healthy baseline data, uncover existing pathol-ogy, and help define population char-acteristics. Extrinsic risk factor tracking includes quantification of exposure to specific environment, equipment, and technique demands. Exposure may be delineated as activity (number of per-formance, class, and rehearsal events) or time (hours of participation in dance activities) based. These exposure measures are then incorporated into incidence calculations, enabling injury rate comparison between populations.

Standardized injury definitions are proposed to facilitate the comparison of injury rates. We propose defining “injury” as any physical complaint sustained by a dancer resulting from performance, rehearsal, or technique class. Injury is further delineated in the following ways: 1. physical complaint injury, 2. medical injury, 3. time-loss injury, and 4. financial injury. Coding by severity, injury type, location, tissue, activity, and style of dance and chore-ography is also included. We hope this may ultimately result in uniform injury registration for dancers of all ages and levels. Adoption of a common system should result in improved understand-ing of injury incidence and risk factors with potential to increase the effective-ness of injury prevention interventions and rehabilitation.

Injuries occur with all physical activities, including dance. Com-prehensive injury surveillance

and risk assessment are required to help direct injury prevention ef-forts. Injury surveillance involves the ongoing collection of data related to the occurrence of and factors as-sociated with injury.1 Occupational

and sports medicine researchers have developed surveillance systems that reveal changes in patterns, rates, and severity of injury, identify risk factors, and assess the effectiveness of injury prevention strategies.2,3 Although many systems are used, sports epidemiologists have reiterated the need for uniform reporting stan-dards and methodologies.2,4-14 Dance medicine researchers have echoed this call for a uniform standard.15-17 The dance community may learn from discussions among sports medi-cine researchers about injury surveil-lance. No consensus exists in dance medicine concerning injury definition and reporting. Meaningful com-parisons of injury across groups of dancers require uniform definitions, data collection methods, and study designs. This paper outlines a suggested comprehensive injury reporting system for professional dance companies. These tools were derived from our comprehensive injury management and surveillance program developed over the last eight years at a modern dance organization, Alvin Ailey, which includes two companies and a large dance school. Following an extensive literature review, we attempted to incorporate the recommendations of sports medicine researchers,1,2,4-14,18 while making dance-specific modifi-cations to reflect this population. This system has enabled us to ascertain the effectiveness of our program in reduc-ing new Workers Compensation cases

Comprehensive Surveillance of Dance InjuriesA Proposal for Uniform Reporting Guidelines for Professional Companies

Shaw Bronner, P.T., Ph.D., O.C.S., Sheyi Ojofeitimi, M.P.T, and Lester Mayers, M.D.

70 Volume 10, Numbers 3 & 4, 2006 • Journal of Dance Medicine & Science

and to calculate the financial savings re-sulting from our program. It is impera-tive that the medical teams working with dance companies recognize the importance of controlling costs while providing the highest quality care. We hope that these guidelines may ultimately result in standardized injury registration for dancers of all ages and ability levels. This will en-able implementation of a common surveillance system facilitating risk identification, prevention, and inter-ventions.

Components of an Injury Surveillance SystemSince the 1970s, sports organizations have developed and implemented injury reporting systems. In North America, one of the most extensive is

the National Collegiate Athletic As-sociation Injury Surveillance System (NCAA® ISS), established in 1982 and now in electronic form.2,18 However, this instrument tracks injury occur-rence only. Missing components in many in-jury reporting systems are pre-season intrinsic risk factor assessment19 and tracking of extrinsic risk factors. A comprehensive injury surveillance system should possess three compo-nents: 1. pre-season intrinsic risk factor

screening of healthy participants, 2. extrinsic risk factor assessment,

and 3. injury occurrence reporting sys-

tem.Risk factors are attributes or ele-ments that predispose an individual

to injury and can be classified as either intrinsic or extrinsic.20 Pre-season screening permits assessment of intrinsic risk factors, which are individual-specific physical char-acteristics. Extrinsic risk factors include type of work, exposure or duration of workload, equipment, and environmental conditions. An injury occurrence reporting system documents the circumstances sur-rounding injuries as well as the results of medical triage. A conceptual model of the multi-factorial interactions of risk factors to injury in dancers is presented in Figure 1. This model also delineates the interaction of prevention and intervention measures such as joint protection, work modification, and modified duty.

Pre-Season Screening of Intrinsic Risk FactorsCausal associations between risk factors and injury cannot be demon-strated from injury reporting alone. Information is necessary concern-ing uninjured participants as well. This emphasizes the importance of pre-participation screening of potential intrinsic risk factors for all participants. Pre-season screening permits assessment of intrinsic risk factors or individual-specific physi-cal characteristics such as structural (skeletal) asymmetries, joint laxity, muscle flexibility, physical fitness (strength, aerobic conditioning), age, gender-specific factors (e.g., factors related to the female athlete triad: disordered eating, dysmenor-rhea and amenorrhea, osteopenia, and osteoporosis), psychological factors, professional experience, and previous history of injury, that may or may not be modifiable (Table 1 and Fig. 1). Through the development of large screening da-tabases from different age groups, sports medicine researchers have developed sport-specific normative profiles for healthy professional, college, and other age athletes.21-24 By correlating screening results with injury patterns, hypotheses about the contribution of intrinsic risk

Figure 1 Conceptual paradigm: A multi-factorial model of dance injury and preven-tion-intervention.

71Journal of Dance Medicine & Science • Volume 10, Numbers 3 & 4, 2006

factors to injury are developed and theories about interventions may be tested. Preventative measures can then be initiated to decrease risk factors. Dance screens provide healthy baseline data, may uncover pathol-ogy, and help define population characteristics at a given level of performance. To date, screening has been performed on professional and student dancers for comparisons with non-dancers.25,26 If a dancer lies outside dance “norms,” then practitioners recommend corrective programs. While this information is valuable, dance medicine must move beyond descriptive reports of screenings to an understanding of injury risk factors and, ultimately, injury prevention. This can be ac-complished through the combined use of intrinsic injury risk factor screening, tracking extrinsic risk factors, and injury surveillance.

Extrinsic Risk Factor TrackingAs with intrinsic risk factors, po-tential extrinsic risk factors must be identified for all participants for correlation with injury occur-rence. Extrinsic risk factor tracking requires time-based quantification of exposure to specific environ-ment (e.g., type of sprung or other floor, floor covering, temperature, humidity, rake, in or out of doors, and so forth), equipment (including props, costumes, masks, headpieces, footwear), technique demands (cho-reography with and without lifts, repetitive foot pounding, squatting, and so forth), or activity of interest to the researcher. For example, if one believes that dancing in char-acter shoes with 4-inch heels may contribute to injury, it is necessary to track time exposure dancing in those shoes versus other footwear. Many sports researchers record overall sport exposure only while

most dance publications have not reported exposure at all.

Exposure“Exposure” is defined as the time or number of events during which the participants are at risk of injury (e.g., while they are participating in their sport-specific practice or game). Reporting exposure dura-tion relates injury to time on task (risk). Sport exposure is delineated in two ways: activity-based and time-based. “Activity-based exposure” defines an athlete exposure as one athlete participating in one game or practice.18 The number of weekly events are calculated per athlete, with specification of game events and practice events. This is the unit of risk adopted by the NCAA, with injury rates calculated as the num-ber of injuries per sum of all events. “Time-based exposure” is defined as

Table 1 Comprehensive Dance Injury Surveillance System for Professional CompaniesA. Pre-season Screening of Intrinsic Risk Factors Year (of data collection) # years of dance training Name # years professional Gender # years in company Gender-specific variables Company status (principal, soloist) (e.g., female athlete triad) Previous injury history Age Other intrinsic risk factors (screening results) Summary group characteristics (range of: age, years of training, years of professional experience, years in current company)

B. Extrinsic Risk Factor Tracking Name of company # touring weeks Year (of collection) # rehearsal weeks Style of company (ballet, modern: # performance weeks specify) # hours dance / week # dancers # contract weeks # performances (total & per week) Environmental conditions (in / outdoors, raked # rehearsals (total & per week) / non-raked stage, temperature, floor # technique classes (total & per week) surface & hardness) Technique / choreography Equipment (props, footwear, costumes) Organizational & social factors

C. Injury Occurrence Report Date of Injury Choreography (name of piece / style) Diagnosis Activity (rehearsal, performance, class, other) Body region # performance days missed Classification (trauma / overuse / recurrent) # work days missed Severity of injury: (minor <1 wk, Workers compensation case moderate 1-4 wks, severe >4 wks) Medical expenses Mechanism of Injury (lift, fall, Disability expenses slip, jump, collision, etc) Environmental conditions Injury outcome (full return, Equipment recurrence, retirement from performance)


hours of participation in practice or competition. Weekly exposure hours are calculated per athlete, with specification of practice hours and competition hours. Injury rates are then calculated as the number of injuries per 1,000 hours of sports participation.3,4,6,7,10,12,14,27-32 This is the unit of risk adopted by many European researchers in sports such as football (soccer) and rugby. For dance, “activity-based expo-sure” is one dancer exposure (DE), with 1-DE defined as one dancer participating in one event. A dancer participating in five performances, five rehearsals, and five technique classes in a week therefore experiences 15-DE. Alternatively, “time-based expo-sure” is calculated in hours of par-ticipation in dance activities (class, re-hearsal, and performance). If a dancer has class from 10:30am to noon, rehearsal from noon to 7:00pm, with a one-hour break for lunch on Monday through Friday, she is dancing for 7.5 hours/day for 5 days/week or 37.5 hours/week during this period. Hours may differ during performance weeks. Missed time for vacation or illness is subtracted from total exposure. Ideally, the exposure record should be individual-based, however this is impractical for many dance organiza-tions. In large ballet companies, the individual dancer’s scheduled hours of rehearsal and performance may be far too time-consuming to record. Although individual-based exposure is the best way to determine differing injury rates by company rank (i.e., principal, soloist, or corps), average exposure calculation based on group data is an acceptable solution.

Annual and Weekly Extrinsic Risk Factor TrackingSports researchers recommend the study of injury incidence in year blocks that include pre-season train-ing.35 Dance medicine researchers may calculate annual dance exposure for professionals by recording the number of contracted employment weeks, hours of dancing per week, number of performance or rehearsal

weeks, total number of performances and rehearsals, and number of tour-ing weeks (Table 1). For example, a company of 50 dancers performing, rehearsing, and taking class for 35 hours/week for 40 weeks experi-ences total annual exposure hours of 50 X 35 X 40 = 70,000 hours. However, estimating exposure hours for dancers as a group neglects to account for absences. Thus, absences must be tracked on a weekly basis to achieve more precise computa-tions. Only dance workdays should be recorded (e.g., days that included performance, rehearsal, or class). Layoff days during which dancers at-tended class (outside work), days off while on tour, and travel days are not included. In addition, if a company has a 52-week contract including 4-weeks of vacation, those 4-weeks are not included. Non-dance classes and gym workouts for cross training, or other outside work commitments are also excluded. These non-work activities may contribute to overuse stressors, which is a limitation of this reporting system. However, based on the definitions of sports8,35 and occu-pational36 injury and what is covered by company Workers Compensation insurance, we have followed the guidelines set forth by these groups. A weekly company manager summa-ry of dancer absences due to vacation, illness, or injury allows more precise computation of specific exposure per employee and a cross check of the days lost due to injury.

Injury Occurrence ReportingThe third component of a comprehen-sive injury surveillance system is the injury occurrence reporting system. This is the area where the greatest con-fusion lies due to the lack of precise, standardized definitions.

Definition of InjuryThe lack of standardized and clearly defined terminology has complicated comparison of injury rates within sports and dance medicine. Currently there is no widely accepted definition of what constitutes an injury. The U.S. National Athletic Injury Registration

System (NAIRS) defined report-able injury as limiting participation for at least one day following the injury.3,10 In some sports, the defini-tion is more stringent, specifying one or more criteria including: absence from training or game(s), need for medical treatment, and diagnosis of tissue damage (requiring x-ray, MRI, or other diagnostic tests).35 Injury definition involving activity time-loss and medical referral is used in the United States Occupational Safety and Health Administration (OSHA) definition of recordable occupational injury.36 The NCAA® ISS defines injury similarly: requiring medical attention (physician, team trainer, or other professional) and resulting in restriction of the athlete beyond the day of injury.18 In dance, a “time-loss” definition of injury may underestimate injuries in organizations with fewer classes, rehearsals, or performances and un-der-report minor injuries that do not result in lost time. At the elite level, a problem may restrict performance without requiring medical atten-tion. Watson14 noted that time-loss injury reporting is conducted from the perspective of the professional treating an injury rather than the athlete suffering it. Since dancers and athletes frequently have aches and pains from unaccustomed activity or eccentric overloading, defining the “reportable” level of discomfort is problematic. The recent consensus document on injury definitions and standards for football (soccer) resolves some of these problems.8 “Injury” is defined as any “physical complaint resulting from a football match or training, irrespec-tive of the need for medical attention or time-loss from football activities.” Injuries are then specified as medical-attention injury or time-loss injury depending on the specifics. For dance, we propose defining “injury” as any physical complaint sustained by a dancer resulting from company performance, rehearsal, or technique class, irrespective of the need for medical attention or time-loss from dance activities (Table 2).


Injury is further delineated in the following ways: 1. physical complaint injury, 2. medical injury, 3. time-loss injury, and 4. financial injury. Injury that results in a dancer reporting for triage, while able to

perform full activity but feeling restricted, is referred to as a “physi-cal complaint injury.” Injury that requires medical attention beyond triage (evaluation by an onsite health-care provider to ascertain need for further referral or curtailment of activities) is referred to as a “medical

injury.” Injury that results in a dancer being unable to participate in future performance, rehearsal, or class is referred to as a “time-loss injury.” A medical injury that results in finan-cial outlay (e.g., physician expenses, diagnostic testing, etc.) is categorized as a “financial injury.” Financial

Table 2 Dance Injury Surveillance System DefinitionsActivity-based exposure: the activity event during which the participants are at risk of injury. One dancer exposure (1-DE)

is defined as one dancer participating in one event. If a dancer participates in five performances, five rehearsals, and five technique classes over a week’s time, that is counted as 15-DE.

Activity-based injury incidence rate: the risk of injury per activity event is calculated as:(# new injuries during the year) / (# participants in the company) (sum of all performance, rehearsal, and technique class

events)Financial injury: an injury resulting in financial outlay for medical treatment. This may include opening workers compensa-

tion case or a company “self-insurance” case.Injury: any physical complaint sustained by a dancer resulting from company performance, rehearsal, or technique class and

resulting in a dancer injury report and triage, irrespective of the need for medical attention or time-loss from dance activi-ties. Injuries are delineated in the following ways: physical complaint injury, medical injury, time-loss injury, and financial injury,

Injury incidence: the number of new cases (dance injuries) that occur during a given time period, divided by the total number of cases at risk (e.g., number of participants in the group).

Injury incidence rate: the number of new cases (dance injuries) that occur during a given time period, divided by the total exposure (either activity-based event or time-based 1,000 hours depending on which exposure definition being used) of all the cases (dancers in the group) at risk.

Injury outcome: does the outcome of the injury result in full return, recurrence, or retirement from performance?Injury prevalence: the number of existing cases divided by the total population at a given point in time.Injury report classifications: The following injury classifications are recommended: by type (overuse or trauma), location by

region, by tissue, type of activity when injury occurred, and mechanism of injury (see Fig. 2 and Tables 3 and 4).Injury severity: defined by time lost (e.g., the number of days elapsed from the date of injury until the date of dancer’s return

to full participation). The day on which the injury occurs is counted as day zero. If the dancer cannot participate for the rest of the dance day they were injured, but is able to return the next day, this is recorded as zero time-loss days. The following groupings are suggested:

Set A Set B Slight (0 days) Minor (1 to 7 days) Minimal (1 to 3 days) Mild (4 to 7 days) Moderate (8 to 28 days) Moderate (8 to 28 days) Severe (greater than 28 days) Severe (greater than 28 days)If a dancer retires from dance performance as a direct consequence of injury sustained during the study and before returning

to participation, the injury is reported as “career-ending.” Medical injury: an injury resulting in medical attention beyond triage alone.Overuse injury: injury occurring as the consequence of repetitive micro-trauma. Period of study: minimum of one calendar year.Physical complaint injury: an injury resulting in a dancer injury report and triage, able to perform full activities, but feeling

they are restricted. Recurrent injury: an injury with the same diagnosis as a previously recorded injury and that occurs within 2-months after the

dancer’s return to participation. Contusions, lacerations, and concussions are not included in this definition.Study group: describe eligibility criteria. Time-based exposure: the time during which the participants are at risk of injury (e.g., hours spent participating in company

performance, rehearsal, or class). Injuries are reported per exposure time (e.g., per 1,000 hours of dance participation). Time-based injury incidence rate: the risk of injury per 1,000 hours exposure is calculated as:(# new injuries during the year X 1,000) / (# dancers in the company) (total hours participation in company class, rehearsal,

and performance activities over the year)Time-loss injury: an injury resulting in a dancer being unable to participate in future activities. The day of the injury is not

counted.Triage: evaluation by an onsite healthcare provider to ascertain need for further referral or curtailment of activities.Trauma: injury resulting from a specific macro-traumatic event.


injury may be classified further as a new Workers Compensation case, or, in a case management program, a self-insurance case, paid for by the company.33,37-39 With utilization of diagnostic tests, a case designated as a medical injury and financial injury, may be a zero time-loss injury if the test is negative. Injuries unrelated to performance, rehearsal, or class should not be recorded in studies of dance injuries. This multi-level injury definition allows flexibility to capture injury data that might be missed us-ing time-loss definition alone.

For calculation of time-loss injury, absences are counted from the day following the injury until the day preceding the dancer’s return. If a dancer reports an injury but never ceases participation in dance activities that day, then an injury is reported as a physical complaint injury and a zero time-loss injury. Multiple injuries sus-tained by a dancer in a single event are recorded as one injury with multiple diagnoses. Similar to calculations for exposure, only dance workdays are recorded for time-loss (e.g., days that included performance, rehearsal, or

class). Layoff days, days off while on tour, and travel days are not included. If a dancer retires from performing as a direct consequence of injury sustained during the study, the injury is reported as “career ending.”8 If the dancer sub-sequently becomes a choreographer or dance educator, that is considered a new career. A recurrent injury can be prob-lematic in any reporting system and must be clearly defined. “Recurrent injury” is defined as an injury with the same or closely related diagnosis and occurring at the same anatomical

InjURy OCCURREnCE REPORT Today’s Date: __________________________

Please fill in or circle the relevant information.

name:_______________________________ Date/Time of Injury:____________________Injury (specify): Left / Right _____________________________Activity Injury Occurred: Rehearsal Performance Class Non-dance Other (specify):______________________________________________________________________Mechanism of Injury: Overuse Collision Lift Jump LandingSlip Fall Partnering Stretching Twisting Turning AlignmentShoes: none heels soft ballet pointe other________________________________Floor surface / hardness / raked stage Other (specify): _______________________________Specify Choreography: _____________________________________________________________Injury Location: (name of Theater / Address) ____________________________________________________________________________________________________________________________

To be Completed by Trained Medical Staff:Dancer triaged by (circle and provide name): PT / ATC / MD ________________________ house MD________________________ MD office ___________________________ ER______________________________Diagnosis:_____________________________________________________________________Level of Injury: Physical complaint Medical Time-loss FinancialRecommendations: Emergency Room MD office PT office Chiropractor office Rest Ice Massage None Other:____________Treatment Recommendations:____________________________________________________

Signature:____________________________________________________

Follow Up:Company Expenses (out of pocket): $_______________Dancer Expenses (out of pocket): $_________________Dates of Missed Performances:__________________________________________________Dates of Missed Rehearsals:____________________________________________________Return to Work Date:____________________________

Figure 2 Injury occurrence report form (Adapted from Alvin Ailey Injury Report form).


location.8 A defined time frame is key to delineating this type of injury. The soccer consensus group designated three types of recurrent injury: early (within 2 months of return), late (oc-curring 2 to 12 months of return), and delayed (occurring more than 12 months after full return).8 However, contusions, lacerations, and concus-sions were never considered to be recurrent injuries. To avoid recall bias,

the soccer consensus group chose only to record a recurrent injury as one occurring within 2 months following full return.9 We also recommend that if a dancer returns to full activities and re-injures the same tissue (with the same diagnosis) within 2 months, it is designated as a recurrent injury and not counted as a separate new injury. Injury to the same tissue oc-curring after 2 months is counted as

a new injury. If a dancer continues rehabilitation but has returned to full participation in all activities, the 2 month period begins at return to work.

Definition of Injury Severity“Injury severity” is often defined by time lost (e.g., the number of days elapsed from the date of injury until the date of the participant’s return to

Table 3 Injury by Anatomical RegionMain Category Tissue

Head & neck Head / face Neck / cervical upper trapezius levator scapulae

Upper extremity Shoulder / clavicle / scapula middle & lower trapezius rotator cuff tear / tendinosus / tendinopathy shoulder dislocation/subluxation/ impingement proximal biceps tendinosus / tendinopathy rhomboid, pectoralis strain Upper arm biceps / triceps muscle strain Elbow Forearm Wrist Hand / fingers / thumb

Trunk Sternum / ribs / upper back (thoracic) Abdomen Low back / pelvis / sacrum lumbar stress fracture / sacroiliac joint dysfunction gluteus maximus / medius / minimus strain

Lower extremity Hip / groin iliopsoas proximal & distal proximal adductor / hamstring / rectus femoris tendinosus /

tendinopathy Thigh hamstring / quadriceps / adductor muscle strain Knee patella subluxation / dislocation / tendinosus / tendinopathy

/ dysfunction quadriceps tendinosus / tendinopathy Baker’s cyst meniscus tear ACL / PCL / LCL / MCL sprain / rupture pes anserine bursitis distal hamstring / adductor strain ITB syndrome Lower leg / Achilles tendon Achilles tendinosus / tendinopathy peroneal tendinosus / tendinopathy shin splints (medial tibial stress syndrome) gastrocnemius or soleus strain Ankle ankle sprain anterior / posterior ankle impingements Foot/toe FHL tendinosus / tendinopathy hallux valgus / rigidus metatarsalgia Lisfranc sprain cuboid subluxation plantar fascitis sesamoiditis fifth metatarsal fracture


full participation).2,8-10,33,35 Researchers have generally designated injury time lost as “minor” (1 to 7 days), “moder-ate” (8 to 28 days), or “severe” (greater than 28 days) (Table 2).9,10,16,29-31,33 Some researchers have added a fourth and fifth designation by dividing the minor category into “slight” (0 days), “minimal” (1 to 3 days), and “mild” (4 to 7 days).8,9 By adding the slight (0 days) category, researchers are able to include zero time-loss injuries within the severity categories. Injury severity may also be catego-rized by tissue damage, (e.g., grade 1 to 3 ligament sprain).7,11 However, this may confer a level of diagnosis beyond the capability of the staff that triages an injury or require testing to confirm the diagnosis. Finally, “injury severity” may be defined by the level of treatment provided (e.g., first aid, emergency care, or hospital admis-sion).5

Injury Occurrence and CodingWhen an injury is sustained that may warrant triage, we recommend that the dancer complete an Injury Oc-currence Report (Fig. 2). This permits

tracking of valuable extrinsic risk factor and biomechanical stressor information such as the activity, cho-reography, venue, and mechanism of injury (see Fig. 1). For analysis of injury patterns and trends, injury classifications are crucial for dealing with large amounts of data. The following injury classifications are recommended: type (overuse or trauma), location by anatomical re-gion, tissue, activity and movement when injury occurred, style of dance, and choreography (Fig. 2 and Table 2). Injury type defines an “overuse injury” as the consequence of repeti-tive micro-trauma and “trauma” if it is the result of a specific macro-trau-matic event.33,40 Stress fractures and osteochondral dissecans are catego-rized as overuse. Activity designates whether the injury was sustained during performance (with name and style of choreography), rehearsal (with name and style of choreography), or technique class (specify type). Increasingly, the “environment” in which athletes perform is acknowl-edged to influence the frequency and nature of injuries. The environment

may be defined by air temperature and humidity in marathons,41 type of field (natural or artificial) in soccer and football,42,43 field surfaces and weather in rugby,44 and snow quality, visibility, and temperature in skiing events.45 Furthermore, studies on ski bindings,46 break away bases,47 and metal bats48 demonstrate the relation-ship between equipment use, design, and materials and injury. Accordingly, we recommend that the specifics of the dance environment at the time of injury are also tracked. These include the mechanism of injury (collision, lift, jump take-off, landing, slip, fall, partnering, stretching, twisting, turn-ing, or alignment), type of shoes or flooring, or other relevant data (see Fig. 2). To code injury by “anatomical location,” 17 categories are listed un-der four main headings (head-neck, upper extremity, trunk, and lower extremity), with specific examples for each (Table 3). To code injury by “tissue pathology,” there are seven categories (fracture and bone stress, joint-ligament, muscle and tendon, contusion, laceration or skin lesion,

Table 4 Pathologic Mechanism: Type of Injury by TissueCategory Pathology

Fractures & bone stress acute fracture stress fracture stress-reaction / bone edema avulsion fracture avascular necrosis apophysitis (Osgood Schlatter’s, Sever’s)Joint (non-bone) & ligament dislocation / subluxation impingement, loose body sprain / tear ligament or capsule (plantar fascitis) cartilage – meniscus tear, osteochondritis, disc herniation degeneration, synovitis mechanical joint dysfunctionMuscle & tendon strain / tear / rupture tendinitis / tendinosis / tendinopathy bursitis spasm / cramp myositis ossificans compartment syndromeContusions contusion / bruise / hematomaLaceration or skin lesion abrasion / laceration / blisterCNS / PNS concussion nerve injury / neuroma / radiculopathy (sciatica)Other dental, dehydration, hyperthermia, hyponatremia (overhydration), infection

Note: effusions are listed with the related tissue.


central nervous system/peripheral ner-vous system (CNS/PNS), and other) (Table 4). Examples are given for each. Other types of coding include the World Health Organization’s Interna-tional Classification of Diseases, 9th Revision codes, otherwise known as the ICD-9 codes.49 The ICD-9 is the official system of assigning codes to diagnoses and procedures associated with hospital utilization in the United States.

Calculating Injury numbers “Injury prevalence” is a snapshot calculation of the number of existing cases divided by the total population at a given point in time (Table 2). Currently, we do not have sufficient dance population estimates to calcu-late injury prevalence numbers. “Injury incidence” refers to the number of new cases that develop over a given time period, divided by the total number of cases at risk (e.g., number of participants in the group or company) (Table 2). For example, Company A has 12 dancers who sustained 6 injuries over one year, for an annual injury incidence of 50%.

Company B has 24 dancers who sus-tained 12 injuries over one year, for an injury incidence of 50% (Table 5). Injury incidence rate, on the other hand, provides a more precise estimate of injury based on exposure (either “activity-based” events or “time-based” hours). It is the number of new cases (dance injuries) that develop during a specified period of time, di-vided by the total exposure of all the cases (dancers in the group) at risk. Unless there is a common denomina-tor based on exposure, it is impossible to compare the two companies. Dance injury reports have not traditionally delineated exposure rates. A literature search found only two dance studies reporting injury rates per 1,000 hours exposure.33,34 Annual injuries over a six-year period ranged from 0.57 to 0.18 injuries per 1,000 dance hours at the Alvin Ailey modern dance companies.33 A mean of 0.62 injuries per 1,000 dance hours over a five-year period were reported at the Swedish Ballet.34 In their 1996 review chapter, Caine and Garrick were unable to find or calculate injury rates per 1,000

hours of exposure from the existing literature.17 Instead, they estimated a rate based on 100 hours of exposure from information provided in various published reports. The annual injury rate per 1,000 exposure hours is defined as the number of new injuries divided by the time all dancers spent in company dance activities (sum of performance, rehearsal, and technique class hours) in one year, reflected in the formula show in Figure 3. The annual injury rate per dancer exposure is defined as the number of new injuries divided by the total number of exposures all dancers spent in company dance activities (sum of performance, rehearsal, and technique classes) in one-year, reflected in the formula shown in Figure 4. Although Company A and B (Table 5) had the same injury incidence (50%), their injury incidence rate per 1,000 hours exposure differed. If Company B danced only 10 weeks (35 hr/wk) and Company A danced 20 weeks (35 hr/wk), then Company B’s injury rate per 1,000 hours exposure (1.4) was twice that for Company A (0.7). Alternatively, we calculated injury incidence rate per activity-based ex-posure using the same two companies (Table 6). Company A participated in 5 rehearsals per week for 10 weeks (50 DE) and 4 performances and 2 rehearsals for 10 weeks (60 DE). Company B participated in 5 rehears-als per week for 5 weeks (25 DE) and 5 performances and 5 rehearsals for 5 weeks (50 DE). Using the activity-based calcu-lation, the injury incidence rate per exposure event of Company B

Table 5 Example of Injury Incidence Calculation for Two Dance Companies

Number of Number of Dance Exposure Injuires Per Company #Dancers Injuries Weeks Hours 1,000 hours

A 12 6 (50%) 20 8400 0.7 B 24 12 (50%) 10 8400 1.4

Table 6 Calculation of Injury Incidence Rate Per Activity-Based Exposure Number of Number of Dance Exposure Injuries Per Company Dancers Injuries Weeks Events Dance Exposure

A 12 6 (50%) 20 110 0.0045 B 24 12 (50%) 10 75 0.0067

Figure 4 Calculation of the annual injury rate per dancer exposure.

Figure 3 Calculation of injury rates per 1,000 hours of exposure.

(# new injuries during the year)

(# participants in the company) (sum of all performance, rehearsal, and technique class events)

(# new injuries during the year) (1,000)

(# participants in the company) (annual hours participation in class, rehearsal, and performance)


(0.0067) was about 1.5 times that of Company A (0.0045) (Table 6). Using the time-based calculation, the injury incidence rate per 1,000 hours expo-sure of Company B was twice that of Company A (Table 5). One concern in using activity-based exposure calculations is how to capture large differences in length of the activities. For example, if one com-pany rehearses for 6 hours per day and another for only 3 hours per day, and each day is one “rehearsal” exposure, comparison at the level of activity (DE) masks the time on task inequity. Tracking activity-based exposure is ap-pealing to allow comparisons between dance and NCAA sports. However, this may mask important information. If an athletic team plays 3 games per week but those games run 4 hours per game and a dance company dances 4 performances per week but perfor-mances last 3 hours per performance, the total number of exposures differ (3 versus 4) but the total number of hours (12) are similar. Tracking activity-based exposure events is relatively simple in sports: on any given day, players have either a game or a practice. In a dance com-pany, dancers may participate in addi-tional activities besides rehearsal, class, and performance. These may include lecture-demonstrations, “mini-perfor-mances,” and teaching master classes. Additionally, many of these may occur on the same day. The answer may be to track dance injury incidence both ways. One cannot, however compare injury incidence rate per DE to injury inci-dent rate per 1,000 hours of exposure because the denominators differ.

Epidemiologic Study Design and Sample Optimally, epidemiologic studies of dance injury should have a prospec-tive cohort design, enrolling a group (cohort) at the beginning of a study and following them over time. With pre-season screening to assess group characteristics at the beginning of each year, differences between uninjured and subsequently injured dancers may be determined. This type of study

permits analysis of injury risks as well as rates. We recommend that designated, on-site medical personnel triage and report injury. Who reports the injury (dancer versus medical personnel) and when the injury is reported (retrospec-tive versus prospective report) affects the calculation of injury incidence. At one dance academy, dancers’ self-report of injury was twice the rate recorded by a physical therapist.50 A dancer’s self-report may include trivial aches that still allow them to dance, which inflates injury reports. Retro-spective designs are associated with the risk of recall bias. Retrospective questionnaires were shown to deflate the true incidence compared to pro-spective weekly surveillance systems in athletes.35 Less than one third of moderate and 10% of minor injuries were remembered retrospectively in a comparison of data collection meth-ods. A description of the eligibility crite-ria is key to understanding the group being studied. Are apprentices or students participating in special per-formances (for example, Nutcracker) included? One definition of eligibility criteria might be time based: employ-ment greater than a designated period of time (e.g., more than 30 days).33

Finally, the study period should include one full year (the entire an-nual contract period) at a minimum to reflect injury patterns with respect to rehearsal and performance. Optimally, multiple years are included. In addi-tion, the privacy and confidentiality of each participant must be protected at all times, according to current health-care regulations.

next StepsThe sports and dance communities continue to struggle with these issues. In 1992, van Mechelen’s “sequence of prevention model for sports” proposed four steps to further sports injury reduction.40 1. Establish the extent of sports

injury (incidence and severity), 2. Establish the etiology and mecha-

nism of sports injury (e.g., intrin-sic and extrinsic risk factors),

3. Introduce prevention measures, and

4. Assess the effectiveness of those prevention measures by repeating step 1.

These goals have been discussed and refined by our sports medicine predecessors and require only slight modifications to apply to dancers. If the dance medicine community accomplishes standardization in our definitions, data collection methods, and reporting, information about injury mechanisms combined with currently available screening tools will allow us to move on to van Mechelen’s Step 2 to identify risk factors for injury, and so on. To optimize these efforts, we must collaborate with our colleagues across disciplines.

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