Elsevier

Physical Therapy in Sport

Volume 15, Issue 4, November 2014, Pages 234-241
Physical Therapy in Sport

Original research
Are maturation, growth and lower extremity alignment associated with overuse injury in elite adolescent ballet dancers?

https://doi.org/10.1016/j.ptsp.2013.12.014Get rights and content

Abstract

Objective

To identify growth, maturation and biomechanical risk factors for overuse injury in elite adolescent ballet dancers.

Methods

Maturation (Tanner scale), growth (foot length change) and age at onset of menarche were recorded in elite adolescent ballet dancers. A modified knee valgus angle and lateral tilt of the pelvis were measured using 2D video during two dance movements (fondu, temps levé) to quantify lower extremity alignment. Overuse dance injuries were recorded by a physiotherapist. The injury rate ratio (RR) associated with each variable was estimated using over-dispersed Poisson regression modelling.

Results

Changes in right foot length (RR = 1.41, CI = 0.93–2.13), right knee angles during the fondu (RR = 0.68, CI = 0.45–1.03) and temps levé (RR = 0.72, CI = 0.53–0.98), and pelvic angles during the temps levé on the left (RR = 0.52, CI = 0.30–0.90) and fondu on the right (RR = 1.28, CI = 0.91–1.80) were associated with substantial changes in injury risk.

Conclusions

Rate of growth in elite adolescent ballet dancers is likely associated with an increase in risk of lower extremity overuse injury and better right lower extremity alignment is likely associated with a reduction in risk of right lower extremity overuse injury.

Introduction

It is well documented that there is a high incidence of injury among elite adolescent and professional ballet dancers. Overuse injuries of the spine and lower extremities are particularly common in this population (Allen et al., 2012, Bowling, 1989, Ekegren et al., 2011, Gamboa et al., 2008, Garrick, 1999, Krasnow et al., 1999, Leanderson et al., 2011, Nilsson et al., 2001, Steinberg et al., 2011). Recent research has begun to highlight key risk factors for these injuries with particular reference to adolescent dancer populations (Fournier et al., 1997, Gamboa et al., 2008, Phillips, 1999a, Steinberg et al., 2011) due to a sharp increase in the incidence of injuries observed at the onset of, and during pubertal development. The adolescent growth spurt and the period of maturation that follows, including the age at onset of menarche in females, have been suggested as two key risk factors for injury in elite adolescent dancers and athletes (Ford et al., 2010, Hewett et al., 2004, Matthews et al., 2006, Poggini et al., 1999, Steinberg et al., 2008).

Maturation, or the development of secondary sexual characteristics, occurs during adolescence with significant variation between individuals in the timing and tempo of growth (Matthews et al., 2006, Phillips, 1999a). Several studies of female athletes have highlighted how maturation can lead to an increased risk of injury. Following the onset of maturation, female athletes demonstrated increased peak knee abduction angle when landing from a vertical drop jump (Ford et al., 2010, Hewett et al., 2004). A number of studies have highlighted a relationship between poor dynamic alignment of the lower extremity on landing and increased risk of lower extremity injury (Levinger et al., 2007, Willson and Davis, 2008). Poor alignment is commonly reported as the appearance of excessive knee valgus (femur angle inward, tibia angle outward) likely resulting from various combinations of altered hip and knee transverse and frontal plane kinematics (Willson & Davis, 2008). Currently, no research has assessed this period of maturation as a risk factor for injury in elite adolescent ballet dancers, nor specifically the possible link with poor dynamic lower extremity alignment.

Due to the variation in timing of maturation, chronological age is not necessarily an accurate indicator of the level of injury risk for a young dancer exposed to high levels of training (Helsen et al., 2005, Matthews et al., 2006). Instead, measures of maturation such as the Tanner scale (Marshall & Tanner, 1969) may offer a more accurate guide, and therefore provide guidance when determining desirable training loads during certain growth and maturation phases. Although the use of Tanner scales may improve specificity in training loads and assist in reducing injuries, few studies with adolescent dancers have used them. Age at onset of menarche is further associated with the period of maturation, although there is general agreement among the literature that this milestone is often delayed among female ballet dancers putting them at greater risk for injury (Brooks-Gunn et al., 1988, Kadel et al., 2005, Kadel et al., 1992, Klentrou and Plyley, 2003, Torstveit and Sundgot-Borgen, 2005, Vadocz et al., 2002, Warren et al., 1986). While numerous studies have demonstrated a link between delayed onset of menarche or menstrual irregularity with high volume advanced dancers (Brooks-Gunn et al., 1988, Kadel et al., 2005, Steinberg et al., 2008, Torstveit and Sundgot-Borgen, 2005), this delay has not been successfully demonstrated to coincide with an increase in injuries aside from stress fractures, specifically in elite adolescent populations.

An increase in injury incidence has reportedly been observed in dancers both at the beginning, and throughout the adolescent growth spurt (Burckhardt et al., 2011, Daniels et al., 2001, Krasnow et al., 1999, Leanderson et al., 2011, Phillips, 1999b, Stacey, 1999, Steinberg et al., 2011). However it is difficult to ascertain the exact cause for this observed increase given adolescence is often when students also begin to increase the intensity of dance training (Daniels et al., 2001). Several studies assessing injury incidence have reported a higher injury frequency in adolescent dancers (Leanderson et al., 2011, Steinberg et al., 2011), noting that the observed increase could be explained by an amplified rate of bone growth in comparison to the ligaments and tendons, thereby exposing the soft tissue to a higher risk of injury (Hamilton, Hamilton, Marshall, & Molnar, 1992). However, there was no clear evidence for this being the cause of injury as opposed to increased exposure. Although there are some biomechanical and physiological underpinnings suggesting a rapid increase in growth may lead to an increased risk of injury (Daniels et al., 2001, Phillips, 1999b, Stacey, 1999), there is currently a lack of evidence supporting this cause–effect relationship, specifically in elite adolescent dancers.

Poor alignment of the hip, knee and ankle has been identified as a further risk factor for lower extremity injury (Murphy et al., 2003, Poggini et al., 1999, Whatman et al., 2012, Willson et al., 2006). In athletes, poor frontal and/or transverse plane control of the pelvis, hip, knee and foot is considered less than ideal, and it is thought that identifying this may help detect those athletes most at risk for injury (Stensrud et al., 2011, Whatman et al., 2012). This pattern of lower extremity dynamic alignment is also considered important in dancers (Clippinger, 2007). A number of studies have been conducted in athlete populations to assess for poor lower extremity alignment with several studies demonstrating a link between poor dynamic alignment and injury (Levinger et al., 2007, Willson and Davis, 2008). However, to date no research has assessed elite adolescent ballet dancers for lower extremity alignment during functional dance movement with regard to injury risk.

Currently a paucity of information exists around key risk factors for injury, including growth, maturation and lower extremity alignment in elite adolescent dancers. To date, little research supports the cause–effect relationship between rapid growth and injury, while there is also no evidence assessing the effects of maturation on dance technique and its potential risk for injury. Furthermore, lower extremity alignment in dancers has yet to be assessed during dance movement with regard to injury risk. Therefore the aim of this study was to identify growth, maturation and biomechanical risk factors for overuse injury in elite adolescent ballet dancers.

Section snippets

Methods

Forty-six (Female = 30, Male = 16) adolescent ballet dancers (mean ± SD, age 16 ± 1.58 years) were recruited from the Australian Ballet School (ABS) in Melbourne and prospectively followed over six months. All dancers were full-time ballet students at the school. Ethical consent was granted for the study by the AUT University Ethics Committee (AUTEC) and the Australian Catholic University Ethics Committee. The dancers and their guardians provided written assent/consent prior to participation.

Results

A summary of baseline dancer characteristics are presented in Table 1. Over the six month follow-up period change in foot length (cm) was; mean ± SD, left foot 0.34 ± 0.25; right foot 0.34 ± 0.32 (based on 42 dancers). A total of 59 injuries were reported for 29 dancers over the follow-up period of six months. Sixteen of those 29 dancers suffered from multiple injuries. Table 2 presents the injury counts and injury rates for all dancers, males and females, right and left legs, and lumbar spine.

Discussion

The purpose of this study was to determine whether growth, stage of maturation, and lower extremity alignment were associated with overuse injury risk in elite adolescent ballet dancers. A total of 59 injuries were recorded for 46 dancers over a six month period with an injury rate of 3.52 injuries per 1000 dance exposures and 2.40 injuries per 1000 dance hours. These injury rates are higher than those reported in previous studies of elite adolescent dancers but lower than rates reported for

Conclusion

Rate of growth in elite adolescent ballet dancers is likely associated with a small to moderate increase in risk of lumbar and lower extremity overuse injury. Conversely, improved right lower extremity alignment is likely associated with a reduction in risk of right lower extremity overuse injury. While the effects were unclear, there were observed changes in risk associated with several other factors and these warrant further investigation. Monitoring growth and screening lower extremity

Conflict of interest

The authors declare no conflict of interest in submitting this article.

Ethical approval

Ethical approval for this research was granted by the Auckland University of Technology Ethics Committee (AUTEC) and the Australian Catholic University Ethics Committee (ACUEC). The AUTEC reference was 12/175, with approval granted originally on 31st of July 2012. Registration of external ethics approval was granted by the ACUEC on the 13 December 2012 with a reference identification of 2012 320V.

Funding

None declared.

Acknowledgements

The authors gratefully acknowledge the assistance of Dr. Vicki Higgins and Physiotherapist Sarah Way from the Australian Ballet School.

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