Background: Female ballet dancers require extreme ankle motion. The objective of this study was to quantify the relative contributions of the ankle and various foot joints to extreme plantarflexion (PF) and dorsiflexion (DF) in female ballet dancers using an X-ray superimposition technique and digital graphics software.
Materials and methods: One asymptomatic ankle was studied in each of seven experienced female ballet dancers. Three lateral weightbearing X-rays were taken of each ballet dancer's ankle: en pointe (maximum PF), in neutral position, and in demi-plié (maximum DF). Using graphics software, a subject's three X-ray images were superimposed and the tali were aligned. On each image the tibia, navicular, intermediate cuneiform, and first metatarsal were marked. Positional differences of a bone's line among the three images demonstrated angular movement of the bone in degrees. The neutral position was the reference from which PF and DF of the bones were calculated.
Results: The talocrural joint contributed the most motion of any pair of bones evaluated for both PF and DF, with mean movements of 57.6 ± 5.2 degrees en pointe and 24.6 ± 9.6 degrees in demi-plié. Approximately 70% of total PF and DF were attributable to the talocrural joint, with the remaining 30% coming from motion between adjacent pairs of the studied foot bones.
Conclusion: Superimposed X-rays for assessing ankle and foot contributions to the extreme positions required of female ballet dancers offer insight into how these positions are attained that is not available via goniometry.
Clinical relevance: Functional information gained from this study may assist clinicians in assessing ankle and foot pain in these individuals.