Author Identifier

Sarah Louise Carter

https://orcid.org/0000-0001-5781-1822

Date of Award

2018

Document Type

Thesis - ECU Access Only

Publisher

Edith Cowan University

Degree Name

Doctor of Philosophy

School

Western Australian Academy of Performing Arts (WAAPA) / University of Western Australia

First Supervisor

Dr Luke S. Hopper

Second Supervisor

Professor Alan Bryant

Third Supervisor

Professor Barry Iacopetta

Abstract

Turnout, the act of externally rotating the legs, is produced through the summation of joint structure characteristics and ranges of motion at the hip, knee, ankle and foot. The hip joint’s contribution to functional turnout, a dancer’s preferred turnout stance, has received extensive examination, whereas little is known about below-the-hip contributions. Dancers with limited hip external rotation (HER) are associated with an increased risk of overuse lower limb injury. These injuries have been attributed to forcing turnout via additional external tibiofemoral rotation (TFR) and foot pronation. Yet knowledge of these compensatory mechanisms is based on biomechanical theories and clinical observations rather than quantitative clinical assessments or 3D motion analysis. The principal aim of this research was to investigate the lower leg and foot contributions to turnout in university-level female dancers using quantitative clinical assessments and 3D motion analysis, as well as the compensations mechanisms dancers use to increase turnout.

The first study focused on assessing the lower leg and foot contributions to turnout using the clinical assessments of passive TFR and active measures of foot pronation in turnout. The results showed dancers assumed a more pronated posture in turnout, and those with a greater passive TFR demonstrated a less pronated position in turnout providing new insight into the mechanical coupling between the foot and the tibiofemoral joint in dancers.

The purpose of the second study was to use 3D kinematic analyses to determine the lower leg and foot compensations that dancers use to accentuate their turnout. Active and passive TFR of the dancers was also measured. The results demonstrated foot abduction was the strongest predictor of functional and forced turnout, compared to both the hip and knee external rotation. A moderate-strong negative relationship was observed between HER and foot abduction in all turnout conditions. A moderate negative relationship was found between the passive TFR and foot abduction in all turnout conditions. These findings indicate clinical measures of external tibiofemoral rotation can predict the total below-hip compensation mechanisms a dancer uses to achieve turnout. Suggesting, dancers are more likely to pronate about the foot/ankle complex, than rotate at the knee to compensate for limited HER. Whereas dancers with less foot mobility may force additional rotation via the knee which may contribute to rotational knee joint laxity.

The previous study provided the rational for an in-depth analysis of the foot/ankle complex such as that provided by three-dimensional multi-segment foot models (3DMFMs). The lack of an appropriate model for ballet dancers led to the modification of the Rizzoli Foot Model. Kinematic repeatability of the model was determined from analysing ballet dancers performing the following movements; parallel stance, turnout plié, turnout stance, turnout rise and flex-point-flex. First metatarsophalangeal joint (MTPJ) in the sagittal plane demonstrated excellent intra and inter-assessor repeatability across all movements. All inter-segmental angles except for the tibia-hindfoot and hindfoot-midfoot frontal planes demonstrated excellent intra-assessor repeatability during flex-point-flex movements. Providing a reliable method to measure 3D foot/ankle complex can enable a deeper understanding of the foot/ankle complex contribution to turnout. Previous 3DMFM used in dance science consisted of only two foot segments, hindfoot and forefoot whereas this model includes a midfoot segment which is important as forefoot abduction has been suggested to give the illusion of a larger turnout angle.

The final study aimed to examine the lower leg and foot compensations that dancers use to accentuate their turnout using a dance specific 3DMFM. Hindfoot abduction and eversion were the strongest predictors of foot abduction in turnout. Midfoot abduction was significantly greater in forced turnout compared to functional turnout. No significant differences were found for forefoot abduction, first MTPJ abduction and navicular drop in functional or forced turnout, compared to natural stance. Foot pronation does play a role in achieving turnout and there may be a safe range of pronation. However, the amount of detrimental pronation for a dancer is unknown. The overall results from these studies offer compelling evidence that the foot/ankle complex plays a more important role in achieving turnout, than previously thought. Further prospective research on in situ measures of the lower leg and foot in turnout and injury surveillance are required to improve our understanding of the normal and abnormal dance biomechanics.

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