Measurement of turnout in dance research a critical review.
Turnout measurement procedures, results, and reporting formats vary in dance medicine and science research, making comparisons difficult. It is agreed that turnout results from summative contributions of the hip, knee, lower-leg, and the foot-ankle complex. However, the most frequently reported measurement is hip external rotation, and even this is measured in incompatible ways. No normative data exist for component and summative measures or for different categories of dancers, making screening, clinical assessment, and research problematic. Thus, there is a need to standardize component measurements, develop an inclusive measurement procedure for total turnout, and establish normative data for each measurement and for different categories of dancers. This review evaluates the 24 published articles that have reported original data for turnout assessment in dancers. Results are summarized and displayed for each article. In conclusion, recommendations are made for: use of selected hip external range of motion and tibial version measurements as the most important components of turnout; a procedure for assessing total turnout; adoption of conventions for reporting data in compatible forms; and the development of normative data sets for different categories of dancers.
The term "turnout" (TO) is commonly used in dance to denote external rotation of the lower extremities; in particular, ballet uses a foundation of five turned out positions of the feet: first, second, third, fourth, and fifth positions. (1,2) However, the term has many associations, and an operational definition has yet to be established. Some researchers define TO as external rotation of the legs such that the longitudinal axes of the feet establish a 180[degrees] angle. (1-10) One study further defines three distinct subcategories: "technically correct," "functional," and "compensated" TO. (1) "Technically correct" TO is the position, as determined by dance instructors, in which the hips are maximally rotated externally and weight is centered through the knee and ankle. "Functional" TO is the position assumed by the dancer, and "compensated" TO is determined by the difference between "functional" TO and bilateral passive hip external rotation.
Dance aesthetics often demand what is considered "perfect TO," without regard to anatomical capabilities and limitations. Perfect turnout requires 90[degrees] of external rotation of each extremity, establishing a 180[degrees] angle between the longitudinal axes of the feet. (1,3,5,8,11,12) This is a phenomenon that is anatomically and biomechanically uncommon. (1,12,15) Of the desired 90[degrees] of perfect unilateral external rotation, the research suggests that a range of 60[degrees] to 70[degrees] is contributed by the hip, while the distal aspects of the lower extremity contribute approximately 10[degrees] to 35[degrees]. (2,4,12,16-18) Findings by Hamilton and colleagues (19) and Khan and associates (6) support the concept of distal contributions by reporting that approximately 40% of TO originates from below the knee. These findings emphasize the need for a total TO measurement inclusive of all components.
The degree of total turnout (TTO) accessible during functional movement is different between individuals, and is affected by several factors, including soft tissue and skeletal anatomy. (2,5-7,15) While soft tissue characteristics (including ligamentous laxity, muscle stretch, and muscle strength) influence TO, the scope of this review is limited to skeletal influences. Skeletal features influential in TTO include the following: orientation and depth of the acetabulum; shape of the femoral neck; degree of femoral version; and degree of tibial version.
The hip is a ball and socket joint, the "ball" referring to the head of the femur and the "socket" to the acetabulum. Orientation and depth of the acetabulum influence the degree of available TTO. (2,10,15) A retro-oriented acetabulum results in greater appearance of TTO, while an ante-oriented acetabulum limits the appearance of TTO. A shallow acetabulum allows for greater hip joint mobility, while a deep acetabulum provides greater hip joint stability and limits external rotation.
The length and shape of the femoral neck influences hip range of motion (ROM) by determining the point at which the neck contacts the acetabulum during external rotation. (20) Long concave femoral necks permit increased external rotation ROM of the lower extremity before bony contact with the rim of the acetabulum occurs. Conversely, shorter and less concave necks decrease external rotation of the lower extremity by allowing less TO before contact occurs with the acetabular rim.
Femoral version is a normal twist in the shaft of the femur. The typical adult human femur is anteverted 6[degrees] to 15[degrees] along the longitudinal axis. (2,4,10,12,21,22) Decreased femoral anteversion, or the unusual presence of femoral retroversion, increases the appearance of TTO. (7,12,20)
Tibial version (TV) is a normal twist in the shaft of the tibia along the longitudinal axis in a retroverted direction. (21,23-28) Average values as reported for samples of the general population range from 10[degrees] to 42[degrees]. (21,22,24,26-31) Average values of 10[degrees] to 28[degrees] have been reported for samples of dancers. (19,32,33) However, normal values ranging from 0[degrees] to 20[degrees] have been referenced in the dance literature. (4,12,15,16,18,20)
This review was initiated in response to an interactive panel at the 2005 International Association for Dance Medicine and Science annual conference in Stockholm, Sweden. (34) On that occasion the panel of experts determined that there was less agreement with regards to the assessment of turnout than anticipated. It was presumed that this would be an opportunity for the international dance medicine and science community to reach a consensus on the measurement of turnout, with the goal of standardizing assessment in the near future. It was quickly determined, however, that this was too large an endeavor to be completed at the time.
Ultimately, the task of performing a detailed and critical review of related literature evolved to the current authors. Searches were conducted of internet databases, bibliographies, and reference lists for related research that generated and published original data on TO measurement in dancers. Relevant studies of dance screening and the assessment of tibial version in non-dancers were also referenced.
Various methods used to assess TO have unfortunately provided incompatible and sometimes non-applicable data. While it is generally agreed that TO results from summative contributions of the hip, knee, lower-leg, and the foot-ankle complex, (7,8,11,12,19,20,35) clinical measurements of TO often assess only external rotation of the hip, (36-38) despite research indicating significant contributions of non-hip components ranging between 30% to 48%. (6,19,39)
The purpose of this review is threefold: to catalogue published reports on TO in dancers and describe methods of measurement; to evaluate and display the results; and to make recommendations for future assessment and research.
At the time of this review, 24 articles that generated original data on the measurement of TO in dancers were located (additional procedural articles were found, but are not evaluated because they did not report original data). A template was devised during the review process to record specific information and to manage inconsistencies in the literature (Fig. 1). Results were sorted by measurement, and are displayed in Tables 1, 2, and 3. Hip external rotation (HER) data reported by 17 dance-specific studies are listed in Table 1. Table 2 lists data reported by the 12 studies that assessed non-hip components of turnout (NHCTO). Table 3 lists data generated by the 15 studies that reported measurements of TTO, a measurement inclusive of both hip and non-hip components. The names of authors, the year of publication, and a brief description of the sample, measurement procedure (including type of motion, testing position, and instrumentation or calculation), sorting variables, and results are included in each table. Studies are catalogued in more than one table if values for more than one measurement were reported. Evaluation of these reports will proceed through a brief description of each measurement procedure.
Hip External Rotation: Table 1
Methods of assessing HER varied. Three positions were used: 1. prone with hip extension and knee flexion, 2. supine with hip extension and knee flexion, 3. sitting with hip and knee flexion. In addition, one study described a unique calculation for active "external rotation lag." A brief description of measurement methods and results follows.
Prone: Hip Extension and Knee Flexion
Nine studies assessed passive HER (PaHER) in the prone position, with hip extension and knee flexion, while none assessed active HER (AHER) in this position. Variable instrumentation was used: 1. standard goniometer, as suggested by the American Academy of Orthopaedic Surgeons; 2. standard goniometer, modified with a level; or 3. inclinometer. Four studies are described in further detail below: the two studies that reported the lowest and highest values using a goniometer, the one study that used a modified goniometer, and the one study that used an inclinometer.
Standard goniometers were used in seven studies to measure PaHER in the prone position. (1,14,19,36-38,40) Subjects ranged from young ballet students to professional ballet dancers. Results varied from means of 38[degrees] to 61[degrees] in unilateral measurement. (36,38)
Figure 1 Article review template. Author(s): Title: Source [Journal Volume(Issue): Pages, Date.]: Objective: Relevant Assessment: HER -- NHER -- TTO -- Definition(s) of Turnout: Subjects: N: -- Genre: Level: Students -- Pre-Prof Students -- University -- Professional -- Age: Range -- Mean -- Gender: Female -- Male -- Mixed -- Age at training inception: -- Dance Experience: -- Dance Hours / Week: -- Protocol: Investigators: # Administrators-- # Assistants --_ Trials: -- Time of day: -- Warm-up: yes -- no -- NP -- Description: HER: Type: Passive -- Active -- NP -- Positions: (F: Flexed, E: Extended, 90: measured at 90[degrees]) Prone -- Hip -- Knee -- Supine -- Hip -- Knee -- Sitting -- Hip -- Knee -- NP -- Extremities: Right -- Left -- Dominant -- RL -- NP -- Instrumentation: Standard Goniometer -- Adapted Goniometer -- Inclinometer -- Other -- NP --_ Procedure: Method Cited: -- Corrective / Stabilization Measures: Yes -- No -- NP -- Description: Results: NHCTO: Type: Passive -- Active -- NP -- Positions: (H: Hips, K: Knees, F: Flexed, E: Extended, 90: measured at 90[degrees]) Prone --_ Supine --_ Calculated --(equation: -- -- --_) NP -- Extremities: Right -- Left -- Dominant -- RL -- NP -- Instrumentation: Standard Goniometer -- Adapted Goniometer -- Inclinometer -- Other -- NP -- Procedure: Method Cited: -- Corrective / Stabilization Measures: Yes -- No -- NP -- Description: Results: TTO: Measurement: Passive -- Active -- NP -- Positions: (H: Hips, K: Knees, F: Flexed, E: Extended, 90: measured at 90[degrees]) Supine -- Standing 1st -- 2nd -- R3rd -- R4th -- R5th -- Calculated --_(equation: --) Other: -- NP -- Extremities: Right -- Left -- Dominant -- RL -- NP -- Instrumentation: Standard Goniometer -- TO Protractor -- Tracing --_ Calculated -- NP -- Procedure: Method Cited: Corrective / Stabilization Measures: Yes -- No -- NP -- Results: Conclusions: Notes / Literature Review: Comments:
DiTullio and coworkers evaluated PaHER in dominant lower extremities. (36) Thirty female ballet students (14 to 18 years of age, mean age and standard deviation not reported) were measured. Data were not explicitly noted. A bar graph indicated an average value of 38[degrees] for PaHER in the prone position, a value lower than those reported in other studies. Limited description of methods prevents speculation on factors contributing to the relatively low values obtained.
LiGrecci-Mangini assessed passive hip ROM in a sample of 15 professional female ballet dancers. (38) Mean age of subjects was 24 [+ or -] 1.5 years. Relatively high results, means of 61[degrees] and 59[degrees] for right and left sides, were reported.
Using a standard goniometer modified with a level, Gilbert and colleagues assessed 20 female ballet students. (3) The stationary arm of the goniometer was vertically aligned with the bubble level, and the moveable arm of the goniometer was placed along the tibial shaft. Subjects were 11 to 14 years old, with a mean age of 12.35 [+ or -] 1.18 years. A mean right and left summed value of 79.4[degrees] of PaHER was reported.
Using a digital inclinometer attached to the tibia, Hamilton and colleagues evaluated 64 female ballet dancers. (42) Subjects were between 14 and 25 years of age, with a mean age of 18.16 [+ or -] 1.80 years. These researchers reported mean values of 48.8[degrees], 49.9[degrees], and 98.7[degrees] for right, left, and summed measurements.
Supine: Hip Extension and Knee Flexion
Five studies measured HER in the supine position with hips extended and knees flexed 90[degrees] over the table edge. (5,6,8,44,45) PaHER and AHER were assessed using one of the following instruments: 1. a standard goniometer; 2. a standard goniometer modified with a level; or 3. an inclinometer. Mean unilateral measures across these five studies for PaHER ranged between 41[degrees] and 49[degrees], while mean AHER measures ranged from 30[degrees] to 45[degrees]. (8,45)
In the only study to assess both PaHER and AHER, Negus and associates used a standard goniometer while measuring subjects in the supine position with hip extension and 90[degrees] of knee flexion. (8) A total of 29 subjects were assessed, 24 female and 5 male. All subjects were described as pre-professional ballet students, 15 to 22 years of age, with a sample mean of 18 years (no standard deviation reported). Passive and active measures were assessed with the axis of the standard goniometer placed on the tibial tuberosity, the moving arm aligned with the longitudinal axis of the lower leg, and the stationary arm vertically aligned with the table leg. The authors reported right, left, and summative (bilateral) means for AHER and PaHER found in female, male, and both (group mean) samples. Mean AHER values ranged between 30[degrees] and 36[degrees]. Mean PaHER values (the only values reported in this review for PaHER assessment in the supine position) ranged between 41[degrees] and 49[degrees].
Two studies reported using a standard goniometer that was modified with a level, in supine position, with hip extension and knee flexion. (6,44) Khan and colleagues measured AHER in right and left hips. (6,44) The moving arm of a standard goniometer was placed on the anterolateral margin of the tibia below the tibial tuberosity. It was reported that the addition of a level was advantageous when paired with the goniometer to better establish true vertical. The angle between the anterolateral margin of the tibia and vertical was measured while subjects performed maximal AHER. Results ranged from a mean of 39[degrees] in the initial study to a mean of 43[degrees] in the follow-up study on the same subjects.
Bennell and coworkers published two studies on the measurement of AHER assessed in the same position as Khan and colleagues, using an inclinometer. (5,45) Their first study assessed the right hip of 77 female ballet students ages 8 to 11 with a mean age of 9.6 [+ or -] 0.8 years. (5) In that study an AHER mean of 32.3[degrees] [+ or -] 12.5[degrees] was noted. The second study aimed to evaluate change in AHER over time. (45) These authors recorded a mean value of 45[degrees] for right AHER from a sample of 53 dancers, mean age of 10.7 [+ or -] 0.8 years, who had participated in the previous study.
Sitting: Hip and Knee Flexion
A third method used to measure HER assessed subjects in the seated position with 90[degrees] of hip and knee flexion. Four studies used this method with either a standard goniometer or a goniometer modified with a level. (36,38,46,47) Both PaHER and AHER were assessed. Mean unilateral PaHER results ranged from 35[degrees] to 45[degrees], while a mean of 45[degrees] was reported for AHER. (38,46,47)
Reporting the lowest value for PaHER measurement, LiGrecciMangini evaluated 15 professional female dancers in the seated position using a standard goniometer. (38) The mean age for subjects in this study was 24.4 [+ or -] 4.45 years. A unilateral value of 35[degrees] was reported from the average of right and left mean PaHER values.
Reid and associates reported values from a level-adapted goniometer to better establish true horizontal and vertical positions of the stationary arm. (46) Subjects were 13 to 19 years old, with a mean age of 15.4 years. These researchers reported mean values of 76[degrees] [+ or -] 20.1[degrees] for 13 to 14 year old subjects, 89[degrees] [+ or -] 5.9[degrees] for 17 to 19 year old subjects, and a combined mean of 84[degrees] [+ or -] 16.2[degrees] for all 30 dancers in their study.
In a study designed to evaluate the effects of classical ballet training on the lumbar region of the spine, Livanelioglu and coworkers were the only group to report AHER measures. (47) Measurement procedures were not described; however, it is known that a standard goniometer was used. These researchers referenced techniques used by Reid and colleagues (46) and noted one difference: Reid assessed PaHER. It was determined that Reid and colleagues assessed HER in the seated position. Thus, it is inferred that Livanelioglu and coworkers assessed subjects in the same position. Livanelioglu and coworkers measured AHER in 40 female students, 12 to 19 years of age, with a mean age of 15 [+ or -] 2 years. A mean of 44.97[degrees] of AHER was reported.
Active External Rotation Lag
Negus and colleagues calculated three TO variables in an effort to relate values to function. (8) They termed the first value "active external rotation lag" (ER lag), and defined it as the difference between active and passive measurements of HER. Their second variable was termed "compensated TO," and the third was termed "functional TO." The second and third measurements are not directly related to HER, and are discussed under the sub-headings "Non-Hip Components of Turnout" and "Total Turnout."
Unique to the Negus study is the concept of "active ER lag." This variable determines the difference produced by passive and active HER methods of measurement as the difference between summed right/left supine PaHER measurements and summed right/left supine AHER measurements [Active ER lag = (R + L PaHER) - (R + L AHER)].
A value of 29.6[degrees] was reported for this sample. These findings indicate that bilateral AHER was approximately 30[degrees] less than bilateral PaHER. Therefore, a unilateral AHER lag of approximately 15[degrees] was reported.
Non-Hip Components of Turnout: Table 2
Researchers (1,6,8,9,19,20,33,44) suggest the need for evaluating TO in dancers by including measurements of TO components, such as hip external rotation and tibial version (TV). Of the studies evaluated in this review, 10 assessed various components of TO not derived from the hip. (1,5,6,8,19,32,33,40,44,48) Non-hip components of turnout (NHCTO) data were obtained from direct measurement, indirect measurement, or calculations.
Three studies measured NHCTO directly using a version of the goniometer. (19,32,33) Ballet students, professional ballet dancers, and university dancers were assessed. Mean results across the studies ranged from 7[degrees] to 33[degrees]. (32,33) The studies that reported the lowest and highest values are described below.
Baillon and colleagues assessed TV in female dancers, both students and professionals, using a dupuis tropometer. (32) Subjects were between 15 and 40 years of age (mean or standard deviation of age not provided). Three samples were evaluated and means were reported as follows: 25.20[degrees], 23.46[degrees], and 33.33[degrees]. The first sample was comprised of dance students, the second and third of professional dancers. These results are almost triple those reported by Hamilton and colleagues.
Nemecek and Chatfield briefly discussed data collected from a Dance Kinesiology flexibility laboratory in the Proceedings of the 14th Annual IADMS conference. (33) During this lab 22 female university dancers (age data not provided) assessed their own flexibility and the flexibility of their colleagues via an array of methods, which were not described. Mean values of 12[degrees] and 7[degrees] for respective R and L TV were reported.
In the only study of foot progression angle (FPA), Solomon and coworkers assessed a sample of 103 female dancers between 7 and 19 years of age (mean and standard deviation not provided).48 FPA is often defined as the difference between the long axis of the foot and the line of progression. This measurement includes contributions of the femur and tibial version during gait. (22,31,41,49,50) A mean of 16.14[degrees] [+ or -] 4.32[degrees] was reported, a value consistent with the afore-mentioned TV measures and with the normal FPA range of 0[degrees] to 20[degrees]. (22,31,41,49)
Six studies derived NHCTO from original equations. (1,5,6,8,40,44) NHCTO was calculated in each study by subtracting HER from a standing TTO measurement. Calculations were termed "below-hip ER" (NHER), "non-hip ER" (NHER), and "compensated TO" (CTO). Mean bilateral results across the studies were 5[degrees] to 90[degrees]. (1,8)
While investigating the relationship between TO and injury, Coplan assessed CTO among 3 male and 27 female university instructors and students. 1 Subjects were 16 to 50 years of age, with a mean age of 22 years (injured men 20 [+ or -] 0, range 20 to 20; non-injured men 27 [+ or -] 7, range 20 to 34; injured women 19.7 [+ or -] 1.6, range 16 to 22; and non-injured women 23.8 [+ or -] 8.7, range 16 to 50). CTO was calculated as the difference between the active functional TO angle (FTO, a bilateral TTO measurement acquired by tracing the feet while standing in first position) and bilateral PaHER (CTO = FTO - RL Sum PaHER). In this study, 21 of the 30 subjects were found to demonstrate CTO. Mean values of 25[degrees] in the injured dancers and 5[degrees] in the non-injured dancers were reported for CTO. These results suggest a positive correlation between CTO and injury.
Negus and associates used a variation of the CTO equation provided by Coplan in their study to investigate the relationship between TO and lower extremity injuries in 29 pre-professional ballet students. (8) Subjects included 24 female and 5 male dancers who were 15 to 22 years old, with a mean age of 18 years (standard deviation not provided). Contrary to Coplan's method of subtracting passive HER from active FTO, Negus and associates considered active HER measurements (i.e., CTO = FTO angle - combined AHER). They assessed dancers in first, R fifth, and L fifth positions. Mean values across different stance positions included a range of 57.8[degrees] to 89.5[degrees] of CTO. The lowest value represented males standing in first position and the highest females standing in R fifth.
Total Turnout: Table 3
Total turnout (TTO) is a measurement inclusive of contributions by the hip, knee, lower-leg, and the foot-ankle complex. (20,34) This measurement has also been referred to as "turnout" (TO), (39,42,51) "turnout angle" (TO angle), (3,9) "turnout range" (TO range), (5,45) "lower-limb external rotation" (LLER), (6,44) and "functional TO angle" (FTO angle). (1,8) In addition, some studies have reported inclusive TTO measurements as "hip external rotation" (52,53) and "hip external rotation flexibility." (40)
Across these studies TTO has been assessed in several ways, including: 1. subjects standing in first position on an original protractor; (5,6,44,45) 2. measuring lines constructed on tracings of feet in different ballet positions, including first, first demiplie, first after landing from jumping, second, third, fourth, R/L fifth, and R/L fifth after landing from jumping; (1,3,8,9,42,51,52) 3. measurements of TTO from photographs of subjects standing on friction-free foot pedals; (39) 4. the Nicholas lower extremity torque flexibility test; (40) and 5. using the Leighton Flexometer with the subjects in the seated position. (53)
The first four in the above list measured active TTO, while it is unknown whether the fifth measured passive or active TTO. Of the studies included in this review, 13 reported original data on active TTO, (1,3,5,6,8,9,39,40,42,44,45,51,52) one study reported original data on passive TTO, (33) and one study was undetermined. 53 Reported mean values ranged from 25[degrees] to 174[degrees] for assessment of active TTO, while passive TTO results had a much narrower range of 86[degrees] to 106[degrees]. (33,40,51) Six studies are described in greater detail below. Included are the studies that: 1. reported the lowest TTO measure, 2. reported the highest TTO measure, 3. assessed passive TTO, 4. investigated static and dynamic discrepancies, 5. used friction-free foot pedals, and 6. used the Leighton Flexometer.
Winslow and Yoder randomly selected 10 subjects (age not provided) from the 24 females in their study to measure the angle of TO. (51) The angle between the frontal plane and a longitudinal line through the dancer's foot was established, but the procedure for doing this was not described. A unilateral sample mean of 25[degrees] was reported using a coronal reference line. To make this value comparable to all of the other studies in Table 3, this value is converted to a comparable unilateral mean of 65[degrees] using a sagittal rather than coronal reference.
Kadel and colleagues applied two methods for assessing hip external rotation. (40) The first qualified as HER, the second as TTO assessment. The second measurement, originally used by Nicholas, assessed externally rotated stance in the ballet first position. (54) Nicholas defined this flexibility test as a measurement of total leg TO. Subjects stood heel to heel, externally rotated both lower extremities to the maximal degree, and the angle created by the feet was recorded. (54) Kadel and colleagues used a goniometer to measure the angle between the long axes of the two feet. A bilateral mean of 174.09[degrees] [+ or -] 4.65[degrees] was reported for the sample of 43 female pre-professional ballet students with an average age of 10 years. These findings represent the greatest TTO measures in this review.
The only study of passive TTO, by Nemecek and Chatfield, reported R/L measures of 53[degrees] and 43[degrees] degrees. (33) A variety of approaches were used to assess TTO; however, no methods were described in the publication.
In a unique study, Negus and coworkers evaluated static, dynamic, and static-dynamic TO discrepancies. (8) These researchers approached the assessment of TO through tracing the feet. Functional TO angle (FTO) was determined for 24 female and 5 male pre-professional dancers (age 15 to 22 years, mean 18 years) utilizing the following protocol: feet were traced in first, R fifth, and L fifth positions (static); subjects were instructed to perform three jumps, and the feet were retraced (dynamic); lines from the heel midpoint through the second toe were used to establish longitudinal axes of the feet, and the angle created by the intersection of longitudinal axes was measured. Mean static measures ranged from 123.8[degrees] (first position, males) to 151.2[degrees] (right fifth, females). Mean dynamic measures ranged from 114.3[degrees] (first position, males) to 148.4[degrees] (R fifth, females). Considering the dynamic aspects of dance, the authors also calculated the difference between static (St) and dynamic (Dy) functional TO angle (StDy difference = St FTO angle - Dy FTO angle), yielding a mean difference of 2.6[degrees] (first position, females) to 9.5[degrees] (first position, males).
Meinel and Atwater presented a brief description of their investigation intended to quantify component contributions to TTO. (39) At the time of our review, this represented the only study to investigate TTO with subjects standing on friction-free discs, thus eliminating friction coupling. The thighs, shanks, and feet of 21 female ballet dancers (10 beginning and 11 advanced; age data not provided) were attached with fins to allow measurement of each segment using aerial photographs. The dancers were photographed standing in first position on the friction-free discs, first in demiplie with hips and knees flexed, then with hips and knees extended. Joint rotations were measured and averaged for three trials in both positions. Statistical analysis determined greater TTO among both sample groups in plie compared with standing. Means of 130.8[degrees] [+ or -] 17.7[degrees] versus 108.1[degrees] [+ or -] 17.1[degrees] (beginning dancers standing in plie versus standing straight) and 158.7[degrees] [+ or -] 18.0[degrees] versus 135.7[degrees] [+ or -] 15.9[degrees] (advanced dancers standing in plie versus standing straight) were found, indicating a 23[degrees] increase in both groups while in plie.
The Leighton flexometer was used by Micheli and associates to evaluate hip external rotation in 25 pre-professional ballet dancers (gender not specified). (53) A mean age of 16 years (range and standard deviation not provided) was reported. Measurement procedures were not described in this report. The investigators cited an original article by Leighton, which includes the following protocol for hip external rotation assessment: subject in the seated position on a bench in hip flexion with knees extended; flexometer attached to the foot; contralateral foot may rest on the floor; dial is locked when the leg is externally rotated to the end range and the pointer is locked at the end range of inward rotation; the position of the pointer on the dial measures the arc through which the movement has passed; knee and ankle joints remain locked and hips should not shift. (55) Based on information provided by Micheli and Leighton, it is unknown whether this procedure assessed passive or active TTO. Data were catalogued accordingly and an average of 48.1[degrees] [+ or -] 6.5[degrees] was reported.
Discussion and Recommendations
TO is assessed by approximately 95% of practitioners during initial screens and injury evaluations, and it is one of the most frequently researched subjects in dance medicine and science. (56,57) However, some researchers have concluded that "the 'ultimate truth' concerning turnout and ballet remains elusive." (37) Much of this can be attributed to the absence of a standardized measurement, not only for TTO (a measurement inclusive of all components) but also for the components of TO.
Various methods for measuring TO have been devised. One of the primary differences among these methods is the definition of TO. Some researchers define and measure TO as hip external rotation, while others define and measure it as the sum of lower extremity external rotation. As demonstrated by this review, these methodological differences produce different results, making comparisons difficult. On the other hand, standardizing the assessment of TO would enable us to: better screen and assess dancers; understand TO and its relationships to training, performance, and injury; and more accurately interpret and compare TO research. (20,34,58,59)
Hip External Rotation
Hip external rotation (HER) is the most common TO measurement reported in research. Approximately 70% of the studies included in this review assessed HER. The methods referenced in this review for measuring HER reflect standard methods recommended by the American Academy of Orthopaedic Surgeons (AAOS), (43) or slight variations thereof. In 1965, the AAOS published Joint Motion: Method of Measuring and Recording, (43) which was approved by several international orthopaedic associations. This project initiated the fulfillment of requests to standardize methods of measuring joint motion. These requests parallel our call for standardization of the measurement of TO. As a result of efforts made by the AAOS, HER measurement protocol has been standardized, and few variations of the recommended methods were noted in this review.
HER measurement is affected by many factors. (8) Each factor should be considered during assessment, reporting, comparison, and analysis. These factors include: 1. type of procedure: active or passive; 2. testing position: prone, supine, sitting, or standing; 3. pelvic position: degree of pelvic tilt, stabilization, and correction; 4. hip position: degree of flexion or extension; 5. position of the contralateral limb: neutral or abducted, and the presence of knee flexion or knee extension; and 6. warm-up status of the dancer. We agree with other researchers that HER should be measured in the prone position with hips in extension and knees in 90[degrees] flexion. (15,20,58,60) This position allows for both passive and active assessment of HER. It is important for HER to be measured while the hips are extended, as this best reflects the functional stance position of the dancer and hip placement during TTO measurement. In addition, warm-up status should be reported.
Non-Hip Components of Turnout / Tibial Version
When comparing HER and TTO measures a discrepancy exists: the former results are consistently less than the latter. This difference is accounted for in non-hip components of turnout (NHCTO). Approximately half of the studies in this review reported values for NHCTO measurements. A variety of terms and definitions were noted. Tibial version, non-hip external rotation, compensated turnout, below-hip external rotation, active non-hip TO, and FPA were all used to denote a TO measurement not inclusive of the hip component. Tibial version is the primary non-hip component of TTO, as it can contribute up to 20[degrees] to TTO without inducing rotational stress at the knee. (12,15) Of the 24 studies reviewed, only three included original TV data. (19,32,33) Absence of research on TV indicates that it is often overlooked in the assessment of dancers.
A standardized procedure for TV measurement in the general population and in dancers has yet to be established. Naturally, different measurement procedures produce different results. (20,22,25-27,30,33,58,61-65) Two studies of non-dancers assessed TV using different measurement procedures. (62,63) The first reported a range of 19[degrees] to 34[degrees], and the second a range of 14[degrees]to 46[degrees]. Tibial version measurement procedure also affected calculations of TTO in a sample of collegiate modern dancers. Depending on the TV measurement procedure used, the calculated TTO measurements varied from 97[degrees] to 116[degrees]. Findings from the above studies emphasize the need for standardization.
Several measurement procedures have been reported for TV. (19-22,25-31,41,49,61-65) One method, the "thigh-foot angle" (TFA), is an accessible and noninvasive approach. This procedure has been discussed and recommended by researchers for the assessment of TV in dancers. (18,20) TFA has been described as the angular difference between the long axis of the foot and the long axis of the thigh, and can be measured with a goniometer in the prone position with hip extension and 90[degrees] knee flexion. (41,49) One arm of the goniometer is placed along the second metatarsal shaft and the other arm is aligned with the tibial tuberosity.
Although researchers agree that TTO is summative, this review identifies HER, a component measurement, as the primary measurement in the evaluation of TO. This review supports previous findings that HER measurement is not a predictor of total or functional TO. (3,8) A TTO measurement procedure, one that is inclusive of all contributions [hip, knee, lower-leg (e.g., tibial version), and the foot-ankle complex], not only is an efficient assessment approach for clinicians and researchers, but better reflects the concept of TO as it relates to dance. (10,20) While we acknowledge the paucity of reliable and valid methods, we emphasize the importance of using an inclusive TTO measurement in the assessment of TO.
Grossman (20) proposes an effective measurement procedure for passive TTO assessment. This procedure was adapted from an inclusive HER measurement procedure previously discussed by Clippinger, (10,15) Hoppenfield, (66) and the AAOS. (43) It is described as follows: the subject is supine with hips and knees extended; the foot and ankle complexes are locked in dorsiflexion, limiting pronation; the entire lower extremity is externally rotated; measurement is taken at the foot using a goniometer, one arm vertically aligned and the other aligned with the center of the heel and along the shaft of the second metatarsal. (20) This method is easily accessible and allows for comparison of data from passive HER and TV measurements. Although it warrants further investigation and testing, we recommended that it be used in the assessment of passive TTO.
To date there are no methods of active TTO measurement that have been tested for validity and reliability. However, several approaches have been investigated. As previously noted, some researchers have used rotational discs to assess active TTO in dancers while eliminating friction coupling. This method should be further investigated and eventually tested for reliability and validity.
Important Considerations for Measurement
Until further research is conducted and measurement procedures are standardized, important considerations in the assessment of TO are: 1. type of motion: active or passive; 2. testing position: standing, prone or supine; 3. pelvic position and degree of stabilization; 4. alignment: natural or corrected via verbal cues or physical manipulation; 5. friction coupling: increased TO by using friction from the floor when standing (except when standing on rotational discs); (58) 6. warm-up status of the dancer: activity and duration.
Data Collection, Handling and Reporting
Many methods described in this evaluation of the literature have not been tested for reliability and validity. To reduce measurement and reporting error it is recommended that future studies use one trained and experienced administrator and report averages from a minimum of three trials. (9,19,27,33,63) Clinicians and researchers should use goniometeric measurement rather than visual estimates to increase reliability. (67) Not only are goniometers reliable, but they are affordable, easy to obtain, and non-invasive. (67)
As should be abundantly clear, measurement procedures and formats for reporting TO measures vary tremendously. These inconsistencies make comparisons across studies difficult or even impossible. The following principles are adapted from a list provided by the AAOS (43) and are recommended for the measurement and reporting of TO in dancers: 1. motions should be calculated from a defined zero starting position, adding the degrees of joint motion in the direction the joint moves; 2. to eliminate possible confusion as a result of measuring joint motions from different starting positions, the extended "anatomical position" of an extremity is accepted as 0[degrees], rather than 180[degrees]; 3. motions should be listed as either passive or active; 4. hip and knee positions should be described as either flexed or extended; and 5. terminology should be clearly defined.
Normative values for NHCTO and TTO do not exist. This makes screening and clinical assessment problematic. Norms cannot be established until measurements are consistent and standard. Standardized methods of measuring HER, NHCTO, and TTO among dancers should be simple, inexpensive, objective, time efficient, and reliable. Upon standardization, norms can be established for dancers that take into consideration age, gender, level of training, and genre. Dance-specific normative values will enable the dance medicine and science community, in particular researchers and clinicians, to better compare data and literature. In addition, this will allow dance medicine and science professionals to better screen for, assess, and ultimately prevent injuries among dancers.
It is recommended that the dance medicine and science community determine and acknowledge all components of TO to allow for more thorough and accurate assessment. This crucial area of work and its applicability to proper training, performance, injury assessment and prevention will benefit greatly from the development of standardized and systematic procedures for the measurement and reporting of HER, NHCTO, and TTO.
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Lowry M. Champion, M.F.A., is at Stanford University, Palo Alto, California. Steven J. Chatfield Ph.D. is in the School of Music and Dance, University of Oregon, Eugene, Oregon.
Correspondence: Lowry M. Champion, M.F.A., P.O. Box 311 Burlingame, California 94011; email@example.com.
Table 1 Hip External Rotation Study Sample: Measurement N; Level; Gender; Age Bauman et al. 1994 14; Professional; HER Female; 31 Bennell et al. 1999 77; Student; Female; 10 HER Bennell et al. 2001 53; Student; Female; 11 HER Coplan 2002 30; University Instructor HER & Student; Mixed; 16-50 DiTullio et al. 1989 30; Student; Female; 14-18 HER Garrick & Requa 1994 591; Pre-Professional; HER Female; 9-19 Gilbert et al. 1998 20; Student; Female; 11-14 HER Hamilton, D. 64; Pre-Professional; HER et al. 2006 Female ; 14-25 Hamilton, W. 28; Professional; HER et al. 1992 Mixed; 22-41 Kadel et al. 2005 43; Pre-Professional; HER Female; 10 Khan et al. 1997 66; Pre-Professional; HER Mixed; 18 Khan et al. 2000 48; Pre-Professional; HER Mixed; 18 LiGreci-Mangini 1993 15; Professional; HER Female; 24 Livanelioglu 40; Student; Female; 15 HER et al. 1998 Meinel & 21; Beginning H TO Atwater 1988 & Advanced; Female;NP contributions Negus et al. 2005 29; Pre-Professional; ER ROM Mixed; 18-22 ER Lag Reid et al. 1987 30; Pre-Professional; HER Female; 15.4 Study Intrumentation/ Side Motion Position calculation (A/Pa) Bauman et al. 1994 G R, L Pa Pr Bennell et al. 1999 I R A Su Bennell et al. 2001 I R A Su Coplan 2002 G R, L Pa Pr DiTullio et al. 1989 G Do Pa Si & Pr Garrick & Requa 1994 G RL Pa Pr Mean Gilbert et al. 1998 AdG RL Sum Pa Pr Hamilton, D. I R, L, Pa Pr et al. 2006 RL Sum Hamilton, W. G RL NP Pr et al. 1992 Mean Kadel et al. 2005 G R, L Pa Pr Khan et al. 1997 AdG R, L A Su Khan et al. 2000 AdG R, L, A Su RL Sum LiGreci-Mangini 1993 G R, L P Si & Pr Livanelioglu G RL Mean A NP et al. 1998 Meinel & Protractor, NP A Sg Atwater 1988 Photographs, Rotating Disks Negus et al. 2005 G R Pa Su L R A L RL Sum Pa RL Sum A NA / Pa HER RL Sum NA NA -A HER Reid et al. 1987 AdG NP Pa Si Study Sorting Results: Mean Variable Degrees (rounded) Bauman et al. 1994 Right 46 Left 45 Bennell et al. 1999 NA 32 Bennell et al. 2001 NA 45 Coplan 2002 Injured, Right 47 Injured, Left 47 Non-injured, Right 49 Non-injured, Left 47 DiTullio et al. 1989 Sitting 43 * Prone 38 * Garrick & Requa 1994 Age 9 45 Age 10 43 Age 11 45 Age 12 47 Age 13 47 Age 14 49 Age 15 49 Age 16 53 Age 17 50 Age 18 51 Age 19 47 Gilbert et al. 1998 NA 79 Hamilton, D. Right 49 et al. 2006 Left 50 RL Sum 99 Hamilton, W. Male 52 et al. 1992 Female 52 Kadel et al. 2005 Right 49 Left 49 Khan et al. 1997 Female, Right 39 Female, Left 39 Male, Right 39 Male, Left 41 Khan et al. 2000 Right 43 Left 41 RL Sum 84 LiGreci-Mangini 1993 Sitting, Right 35 Sitting, Left 35 Prone, Right 61 Prone, Left 59 Livanelioglu NA 45 et al. 1998 Meinel & Beginner Dancers, 70% of 131 Atwater 1988 Demi-plie Advanced Dancers, 68% of 159 Demi-plie Beginner Dancers, 55% of 108 Straight Leg Advanced Dancers, 52% of 136 Straight Leg Negus et al. 2005 Total Sample 45 Female 45 Male 41 Total Sample 47 Female 47 Male 49 Total Sample 31 Female 31 Male 30 Total Sample 32 Female 31 Male 36 Total Sample 92 Female 92 Male 91 Total Sample 63 Female 62 Male 66 Total Sample 30 Female 31 Male 25 Reid et al. 1987 Age 13-14 76 Age 17-19 89 Total Sample 84 * Data extrapolated from figures. A (Active); AdG (Adapted Goniometer); Do (Dominant); ER (External Rotation); ER Lag (Active External Rotation Lag); G (Goniometer); HER (Hip External Rotation); I (Inclinometer); L (Left); NA (Not Applicable); NP (Not Provided); Pa (Passive); Pr (Prone); R (Right); ROM (Range of Motion); Sg (Standing); Si (Sitting); Su (Supine); Turnout (TO) Table 2 Non-Hip Components of Turnout Study Sample: Measurement N; Level; Gender; Age Baillon et al. 1983 15, Student, 15-20 TV 14, Professional, 18-40 21, Professional, 18-30 Bennell et al. 1999 77; Student; Female; 10 NHER Bennell et al. 2001 53; Student; Female; 11 NHER Coplan 2002 30; University Instructor CTO & Student; Mixed; 16-50 Gilbert et al. 1998 20; Student; Female; 11-14 NP Hamilton W et al. 28; Professional; Mixed; TV 1992 22-41 Khan et al. 1997 66; Pre-Professional; 18 BHER Mixed; 18 Khan et al. 2000 48; Pre-Professional; BHER Mixed; Meinel & Atwater 21; Beginning & Advanced; A NH TO 1988 Female; NP contributions Negus et al. 2005 29; Pre-Professional; CTO Mixed; 18-22 Nemeck & Chatfield 22; University; Female; NP TV 2004 Solomon et al. 1994 103; Student; Female; 7-19 FPA Study Intrumentation/ Side Position calculation (Pr/Su; H E/f; K E/F Baillon et al. 1983 Dupuis RL NA tropometer Mean Bennell et al. 1999 R ATO--R AHER R NA Bennell et al. 2001 R ATO--R AHER R NA Coplan 2002 FTO-RL Pa HER RLSum NA Gilbert et al. 1998 ATO angle- RL Sum RL Sum RL Pa HER Hamilton W et al. G RL Mean NP 1992 Khan et al. 1997 LLER-(R+L A HER) RL Sum NA Khan et al. 2000 LLER-(R+L A HER) RL Sum NA Meinel & Atwater Quantified from RL Sum Standing 1988 Photographs, (HE; KF) Protractor, Friction-free Foot Pedals Negus et al. 2005 First St FTO RL Sum NA angle-A HER (R+L) R Fifth St FTO angle-A HER (R+L) L Fifth St FTO angle-A HER (R+L) Nemeck & Chatfield NP R, L NA 2004 Solomon et al. 1994 Quantified from RL Mean Gait Footprints, Protractor Study Sorting Results: Mean/ Variable Range(rounded) Baillon et al. 1983 Group 111 25 Group IV 23 Group V 33 Bennell et al. 1999 NA 18 Bennell et al. 2001 NA 8 Coplan 2002 Injured 25 Non-injured 5 Gilbert et al. 1998 NA 13-17 Hamilton W et al. Male 11 1992 Female 10 Khan et al. 1997 Female 46 Male 37 Khan et al. 2000 NA 37 Meinel & Atwater Beginner Dancers, 30% of 131 * 1988 Demi-plie Advanced Dancers, 32% of 159 * Demi-plie Beginner Dancers, 45% of 108 * Straight Leg Advanced Dancers, 48% of 136 * Straight Leg Negus et al. 2005 Total Sample 69 Female 71 Male 58 Total Sample 87 Female 90 Male 74 Total Sample 86 Female 89 Male 72 Nemeck & Chatfield Right 12 2004 Left 7 Solomon et al. 1994 Total Sample 16 Ages 7 & 8 9 Age 9 11 Age 10 19 Age 11 18 Age 12 19 Age 13 19 Age 14 18 Age 15 18 Age 16 14 Ages 17 & 19 14 * Derived from data provided for hip contributions; A (Active); BHER (Below Hip External Rotation); CTO (Compensated Turnout); ER (External Rotation); FPA (Foot Progression Angle); FTO (Functional Turnout); G (Goniometer); HE (Hip Extension); HER (Hip External Rotation); HF (Hip Flexion); KE (Knee Extension); KF (Knee Flexion); L (Left); LLER (Lower Leg External Rotation); NA (Not Applicable); NHCTO (Non-Hip Components of Turnout); NHER (Non-Hip External Rotation); NP (Not Provided); Pa (Passive); Pr (Prone); R (Right); ROM (Range of Motion); Sg (Standing); Si (Sitting); Su (Supine); TO (Turnout); TV (Tibial Version) Table 3 Total Turnout Study Sample: Measurement/ N; Level; Description Gender; Age Bennell et al. 1999 77; Student; Turnout Female; 10 Range Bennell et al. 2001 53; Student; Turnout Female; 11 Range Coplan 2002 30; University Functional Instructor Turnout Angle & Student Mixed; 22 Gilbert et al. 1998 20; Student; Turnout Angle Female; 11-41 Hamilton, D. et al. 64; Turnout et al. 2006 Preprofessional; Female; 14-25 Kadel et al. 2005 43; HER Pre-Professional; Flexibility * Female; 10 Khan et al. 1997 66; LLER Pre-Professional; Mixed; 18 Khan et al. 2000 48; LLER Pre-Professional; Mixed; 18 Martin et al. 1998 6; Professional; HER * Female; NP Meinel & 21; Beginning Turnout Atwater 1988 & Advanced Female; NP Micheli 1984 25; HER * Pre-Professional; Female; 16 Negus et al. 2005 29; Functional Pre-Professional; Turnout Mixed; 18-2 Angle Nemeck 22; University; TTO & Chatfield 2004 Female; NP Watkins 1989 350; Young, Turnout Preprofessional, Angle University, Professional; Mixes; 11-25 Winslow 10; University; Turnout Angle & Yoder 1995 Female; NP Study Intrumentation/ Side Motion Method (A/Pa, St/Dy) Bennell et al. 1999 Turnout R, L, A Protractor RL Sum Bennell et al. 2001 Turnout R, L, A Protractor RL Sum Coplan 2002 NP; Measurement RL Sum A of angle of longitudinal bisection on paper tracing of feet Gilbert et al. 1998 Goniometer; RL Sum A angle of longitudinal bisection of feet on paper tracing Hamilton, D. et al. Goniometer; RL Sum A et al. 2006 Measurement of angle of longitudinal bisection on paper tracing of feet Kadel et al. 2005 Goniometer; RL Sum A degrees of external rotation demonstrated by the long axis of the foot Khan et al. 1997 Turnout protractor R, L A Khan et al. 2000 Turnout protractor R, L, A RL Sume Martin et al. 1998 Goniometer Do A Meinel & Quantified RL Sum A Atwater 1988 from Photographs, Protractor, Friction-free Foot Pedals Micheli 1984 Leighton R, L NP flexometer; NP Negus et al. 2005 Goniometer; RL Sum A, St Bisection of longitudinal axes of feet on paper A, Dy tracing of feet A, St A, Dy A, St A, Dy Nemeck NP R, L A & Chatfield 2004 A Pa Pa Watkins 1989 NP; Angle of RL Sum A reference lines of feet measured on a paper tracing of both feet in the ballet position Winslow NP; Angle NP A & Yoder 1995 between the frontal plane and a longitudinal line through the foot Study Position Sorting Results: (H: E/F; Variable Mean K: E/F) Degrees (rounded) Bennell et al. 1999 Standing: R 46 First L 47 (HE; KE) RL Sum 93 Bennell et al. 2001 Standing: R 53 First L 52 (HE; KE) RL Sum 105 Coplan 2002 Standing: Injured 119 First Dancers (HE; KE) Non-Injuried 100 Dancers Gilbert et al. 1998 Standing: First Position 94 First, Second Second Position 97 Third, Fourth Third Position, 93 (HE; KE) RF Fourth Position, 94 RF Fifth Position, 95 RF Hamilton, D. et al. Standing First Position 136 et al. 2006 First (HE; KE) Kadel et al. 2005 Standing First Position 136 First (HE; KE) Khan et al. 1997 Standing: Female Right 63 First Female Left 62 (HE; KE) Male Right 59 Male Left 55 Khan et al. 2000 Standing: Right 62 First Left 60 (HE; KE) RL Sum 122 Martin et al. 1998 Standing: Subject 1 82 First Subject 2 83 (HE; KE) Subject 3 71 Subject 4 93 Subject 5 81 Subject 6 62 Meinel & Standing: Beginning 31 Atwater 1988 Dancer; Plie Advanced 159 Dancer; Plie Beginning 180 Dancer; Straight Leg Advance Dancer; 136 Straight Leg Micheli 1984 NP NA 48 Negus et al. 2005 Standing: Total sample 131 First Female 133 (HE; KE) Male 124 Standing: Total sample 128 First Female 130 (HE; KE) Male 114 Standing: Total sample 149 R Fifth Female 151 (HE; KE) Male 140 Standing: Total sample 146 R Fifth Female 148 (HE; KE) Male 134 Standing: Total sample 149 L Fifth Female 151 (HE; KE) Male, Static 138 Standing: Total sample 143 L Fifth Female 146 (HE; KE) Male 130 Nemeck NP Right 50 & Chatfield 2004 Left 49 Right 53 Left 43 Watkins 1989 Standing Plie: R Fifth 147 R Fifth (HE; KF) Standing Plie: L Fifth 146 L Fifth (He; KF) Winslow Standing: NA 65 ([dagger]) & Yoder 1995 * Referenced as HER in study, follows TTO criteria; ([dagger]) this value has been converted from 25[degrees] with reference to a coronal measurement; A (Active); Do (Dominant); Dy (Dynamic); ER (External Rotation); G (Goniometer); HE (Hip Extension); HER (Hip External Rotation); HF (Hip Flexion); KE (Knee Extension); KF (Knee Flexion); L (Left); NA (Not Applicable); NP (Not Provided); Pa (Passive); R (Right); ROM (Range of Motion); St (Static); TO (Turnout); TTO (Total Turnout)
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|Author:||Champion, Lowry M.; Chatfield, Steven J.|
|Publication:||Journal of Dance Medicine & Science|
|Date:||Oct 1, 2008|
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