Recent 3D kinematic research has revealed foot abduction is the strongest predictor of standing functional and forced turnout postures.1 However, it is still unknown how the internal foot joints enable a large degree of foot abduction in turnout. The primary purpose of this study was to use a dance specific three-segment foot model to determine the lower leg and foot contributions to turnout.
Eighteen female dance students (mean age, 18.8 ± 1.6 years) volunteered for this study and signed a consent form prior to data collection. Retro-reflective markers were attached to the dancers’ dominant lower limb, hindfoot, midfoot, navicular, forefoot, hallux and pelvis. Each dancer performed three repetitions of functional turnout, forced turnout and ten consecutive sautés in first position. Repeated measures ANOVA with Bonferroni adjustments for the multiple comparisons were used to determine the kinematic adjustments between the first position tasks and natural stance.
Hindfoot eversion (4.6º, P < 0.001) and midfoot abduction (2.8º, P < 0.001) significantly increased in functional turnout compared to natural stance. Thirteen dancers demonstrated increased first MTPJ abduction in forced turnout, however no statistically significant increase was found. Navicular drop during sautés in first position significantly increased by 11 mm (P < 0.001) compared to natural stance.
Discussion and Clinical Relevance
Our findings suggest dancers do pronate, via hindfoot eversion, midfoot abduction and eversion in functional turnout, indicating foot pronation does play a role in achieving turnout. Dancers demonstrated strong static arches however this control may not necessarily extend to quick dynamic movement. No immediate association was found between forced turnout and first MTPJ abduction even though it increased in thirteen dancers. Anatomical structure of the first MTPJ and genetic factors 2-4 may be more important in the development of hallux valgus (HV). Motion analysis could be used in conjunction with visual and audible cues from dance educators to train the dancer from not collapsing through the feet upon landing as static arch height measurements do not reliably predict a dancers’ dynamic stability. Radiographic assessments of the first MTPJ may assist clinicians in determining a dancers’ risk of developing HV.