Ultrasound Observation of Hip Translational Motion in Adolescent Dancers

Hip microinstability, characterized by supraphysiologic movement of the femoroacetabular joint, has recently been recognized as a clinically relevant pathology. The potentially detrimental effects of its presence on joint health make identifying microinstability important; however, due to its multifaceted nature, screening for microinstability presents challenges. Musculoskeletal ultrasound offers an opportunity to visualize the arthrokinematics of the femoroacetabular joint on dynamic evaluation. Dancers may be particularly afflicted by microinstability due to the unique demands of their discipline. This study describes a method for evaluating femoral translation using dynamic ultrasound in adolescent dancers. One hundred forty-two dancers (117 females and 25 males) were recruited from a northeast high school dance program. Females mean age was 16.02 ± 1.06 years, mean BMI 20.35 ± 2.30 kg/m², and mean years of dance experience 10.91 ± 2.84 years. Males mean age was 15.84 ± 1.26 years, mean BMI 21.78 ± 2.84 kg/m², and mean years of dance experience 7.96 ± 2.82 years. Two hundred eighty-four hips were visualized under ultrasound imaging with the participants in both a neutral position and with the hip extended and externally rotated. The distance (mm) the femoral head was positioned anterior to the acetabulum was recorded for both these positions. The calculated difference in these values represented anterior translation. For female hips, the total mean anterior translation was 1.23 ± 2.01mm (-4.8 to 9.30 mm); for male hips, the mean of anterior translation was 1.39 ± 2.22 mm (-7.90 to 5.90 mm). This study identified a normative value range for hip anterior translational motion under dynamic ultrasound among a healthy population of adolescent dancers.