Ultrasound Alpha Angles and Hip Pain and Function in Female Elite Adolescent Ballet Dancers

Abstract

Femoroacetabular impingement (FAI) is a common anatomical variant in ballet dancers. Cam morphology (a subtype of FAI) and increased alpha angles have been identified as risk factors for hip pain. Ultrasound has recently been used to measure alpha angles in the diagnosis of cam morphology, but its utility remains understudied. The purpose of this study was to investigate the effect of ultrasound measured alpha angles on hip pain and function scores in elite female adolescent ballet dancers. The alpha angles of 25 dancers (mean age: 15.9 years) were measured using ultrasound and calculated with ImageJ Software. Cam morphology was defined by alpha angles of 60° or greater. Participants rated their hip pain and function using the International Hip Outcome Tool 12 (iHOT-12) survey. For normally distributed variables, the independent t-test was performed, and for abnormally distributed variables, the Mann-Whitney U Test. Along with mean and standard deviation (SD) values, median score, interquartile range (IQR), and 95% confidence intervals (95% CIs) were also analyzed. Significantly lower iHOT-12 scores were found in dancers with alpha angles ≥ 60° (mean ± SD, 74.34 ± 13.01; 95% CIs, 58.18, 90.50, median 67.20; IQR, 18.55), compared to dancers with alpha angles < 60° (mean ± SD, 80.22 ± 15.65; 95% CIs, 72.90, 87.54; median, 81.60; IQR, 16.35; p = 0.001). It is concluded that: 1. elite female adolescent ballet dancers with alpha angles higher than 60° experienced worse hip pain and function; 2. alpha angles may impact hip pain and function in these dancers; and 3. further studies should use a prospective design to investigate the predictive ability of their findings.

Understanding hip pathology in ballet dancers

“…The presence of impingement‐type osseous morphology including cam and/or pincer morphology, low neck shaft angle (NSA < 125°) and acetabular version < 10° or > 20° also contributed to degenerative disease [56, 58, 59]. Hip pain was associated with reduced iliopsoas strength [22], low alpha angles [7], and female sex [72]. Increasing age was associated with ligamentum teres tears and degenerative hip disease, but also a lower rate of snapping hip.…”

Little or No Differences in Hip Morphology Between Professional Dancers and Controls: A Systematic Review

“…A total of 914 studies were excluded by examining their titles and/or abstracts. A further 8 studies were excluded after a full-text review because they did not report hip morphological parameters, 4,7,[23][24][25][26][27][28] and one study was excluded because it was on young female dancers who did not train at professional or competitive levels. 6 This left 12 studies [29][30][31][32][33][34][35][36][37][38][39][40] eligible for this systematic review, all of which were cohort or case-control studies (Table 1 and Figure 1).…”

“…1,2 Professional dancers train for 20 to 30 hours per week and also spend time performing, 2,3 which exposes them to injuries, with a reported annual incidence of 42% to 97% depending on the type and level of dance. 4,5 Although the foot and ankle are the most frequent sites of injury, the prevalence of hip injuries among professional dancers ranges from 4% to 27%, 5 possibly due to the extreme ranges of motion and high stresses exerted on the lower limbs. The intense training before skeletal maturity could even result in developmental, acquired, or adaptive anatomic anomalies at multiple joints.…”

Biomechanical Comparison of Pediatric Female Ballet Dancers With and Without Pain

“…These repetitive movements can lead to injuries including ankle/foot sprains, hip impingement, low back injuries and pain, and subsequent time away from activity. 7,8 Overall, there is a paucity of research looking specifically at the biomechanics of pediatric ballet dancers, specifically quantifying lower extremity movement patterns and muscle activity at peak growth times. However, more work in this area may contribute to the development of effective injury prevention programs geared specifically towards this high-risk population and may help contribute to a more standardized en pointe readiness assessment.…”