Faculty Bibliography

BACKGROUND: Ballet and modern dance are jump-intensive activities, but little is known about the incidence of anterior cruciate ligament (ACL) injuries among dancers. HYPOTHESIS: Rigorous jump and balance training has been shown in some prospective studies to significantly reduce ACL injury rates among athletes. Dancers advance to the professional level only after having achieved virtuosic jump and balance technique. Therefore, dancers on the elite level may be at relatively low risk for ACL injury. STUDY DESIGN: Descriptive epidemiology study. METHODS: Dance exposure, injuries, and injury conditions were systematically recorded at 4 dance organizations over 5 years. Select neuromuscular and psychometric variables were compared between and within ACL-injured and noninjured dancers. RESULTS: Of 298 dancers, 12 experienced an ACL injury over the 5-year period. The incidence of ACL injury was 0.009 per 1000 exposures. Landing from a jump onto 1 leg was the mechanism of injury in 92% of cases. Incidence was not statistically different between gender or dance groups, although women modern dancers had a 3 to 5 times greater relative risk than women ballet dancers and men dancers. No difference between ACL-injured and noninjured dancers emerged with regard to race, oral contraceptive use, or select musculoskeletal measures. CONCLUSION: Dancers suffer considerably fewer ACL injuries than athletes participating in team ball sports. The training dancers undertake to perfect lower extremity alignment, jump, and balance skills may serve to protect them against ACL injury. Anterior cruciate ligament injuries happened most often late in the day and season, suggesting an effect of fatigue

STUDY DESIGN: Case report. BACKGROUND: Tendon lacerations of the hallux are potentially devastating to a dancer. Strength of the hallux musculature is necessary to attain and maintain balance, push-off in multiple turns, and decelerate in jumps and hops. The purpose of this paper is to report on the repair and rehabilitation of extensor hallucis longus and extensor hallucis brevis tendon lacerations in a professional dancer. CASE DESCRIPTION: A 30-year-old dancer sustained complete laceration of her extensor hallucis longus and extensor hallucis brevis tendons, and partial laceration of the dorsal aspect of the hallux metatarsophalangeal (MTP) joint capsule. Following primary repair, at 9 weeks postsurgery, hallux MTP joint active dorsiflexion was limited to 5 degrees and passive dorsiflexion to 70 degrees . First toe dorsiflexion and plantar flexion strength was 4/5 at the MTP and 3+/5 at the interphalangeal joint. Rehabilitation included functional electrical stimulation to address considerable calf atrophy, strengthening exercises, functional retraining, and progressive return to dance. OUTCOME: The dancer returned to her previous level of dancing in 18 weeks, with 73 degrees and 85 degrees of hallux MTP joint active and passive dorsiflexion, and 30 degrees and 35 degrees of active and passive plantar flexion, respectively. Hallux MTP and interphalangeal joint muscle strength were 5/5 and 4+/5, respectively. Improvement, manifested in her SF-36 and Dance Functional Outcome System scores, accompanied her full functional recovery. DISCUSSION: Hallux stability provided by coactivation of the great toe extensors and flexors is crucial to accomplish the demands of bipedal and unipedal balances and activities in dance. This report demonstrates the success of primary surgical repair and rehabilitation in a dancer/athlete experiencing this injury

Disseration, Ph.D. New York Universiyt, 2008

Modern dancers are a unique group of artists, performing a diverse repertoire in dance companies of various sizes. In this study, 184 professional modern dancers in the United States (males N=49, females N=135), including members of large and small companies as well as freelance dancers, were surveyed regarding their demographics and training characteristics. The mean age of the dancers was 30.1 +/- 7.3 years, and they had danced professionally for 8.9 +/- 7.2 years. The average Body Mass Index (BMI) was 23.6 +/- 2.4 for males and 20.5 +/- 1.7 for females. Females had started taking dance class earlier (age 6.5 +/- 4.2 years) as compared to males (age 15.6 +/- 6.2 years). Females were more likely to have begun their training in ballet, while males more often began with modern classes (55% and 51% respectively, p < 0.0001). The professional modern dancers surveyed spent 8.3 +/- 6.0 hours in class and 17.2 +/- 12.6 hours in rehearsal each week. Eighty percent took modern technique class and 67% reported that they took ballet technique class. The dancers who specified what modern technique they studied (N=84) reported between two and four different techniques. The dancers also participated in a multitude of additional exercise regimens for a total of 8.2 +/- 6.6 hours per week, with the most common types being Pilates, yoga, and upper body weightlifting. The dancers wore many different types of footwear, depending on the style of dance being performed. For modern dance alone, dancers wore 12 different types of footwear. Reflecting the diversity of the dancers and companies surveyed, females reported performing for 23.3 +/- 14.0 weeks (range: 2-52 weeks) per year; males reported performing 20.4 +/- 13.9 weeks (range: 1-40) per year. Only 18% of the dancers did not have any health insurance, with 54% having some type of insurance provided by their employer. However, 23% of the dancers purchased their own insurance, and 22% had insurance provided by their families. Only 16% of dancers reported that they had Workers' Compensation coverage, despite the fact that they were all professionals, including many employed by major modern dance companies across the United States. It is concluded that understanding the training profile of the professional modern dancer should assist healthcare providers in supplying appropriate medical care for these performers

OBJECTIVE: To determine the effect of landing type (unilateral vs. bilateral) and gender on the biomechanics of drop landings in recreational athletes. DESIGN: This study used a repeated measures design to compare bilateral and unilateral landings in male and female athletes. A repeated measures multivariate analysis of variance (type of landing*gender) was performed on select variables. SETTING: Biomechanics laboratory. PARTICIPANTS: Sixteen female and 16 male recreational athletes. MAIN OUTCOME MEASURES: Kinetic, kinematic, and electromyographic (EMG) data were collected on participants while performing bilateral and unilateral landings from a 40-cm platform. RESULTS: Compared to bilateral landings, subjects performed unilateral landings with increased knee valgus, decreased knee flexion at initial contact, decreased peak knee flexion, decreased relative hip adduction, and increased normalized EMG of the rectus femoris, medial hamstrings, lateral hamstrings, and medial gastrocnemius (P < 0.005). During both types of landing, females landed with increased knee valgus and normalized vertical ground reaction force (VGRF) compared to males (P < 0.009), however, the interaction of landing type*gender was not significant (P = 0.29). CONCLUSIONS: Compared to bilateral landings, male and female recreational athletes performed unilateral landings with significant differences in knee kinematic and EMG variables. Female athletes landed with increased knee valgus and VGRF compared to males during both types of landing