Proceedings of The Physiological Society
University of Bristol (2005) J Physiol 567P, C125
Decreased ankle joint eversion prior to and following initial ground contact during hopping in individuals with chronic ankle instability (CAI).
Delahunt, Eamonn; Monaghan, Kenneth; Caulfield, Brian;
1. School of Physiotherapy, University College Dublin, Dublin, Ireland.
Introduction: CAI, a subjective feeling of ankle instability or, recurrent symptomatic ankle sprains (or both), is the most serious residual disability following ankle sprains. To date, there have been no thorough investigations into the 3D kinematic patterns of subjects with CAI prior to and following initial ground contact during hopping. The purpose of this study was to undertake a comprehensive analysis, of the 3D kinematic patterns associated with hopping in a group of subjects with CAI, with the aim of determining whether changes in the neural control of movement and dynamic stability of the ankle joint exist in the these subjects. Methods: Thirteen subjects with unilateral CAI and 16 control subjects volunteered to participate. Inclusion criteria in the CAI group were based on the criteria used by Caulfield and Garrett (2004). CODA mpx 30 (Charnwood Dynamics Ltd.) infrared light emitting diodes were attached to the involved lower extremity in the CAI group and the left lower extremity in the control group and were used to provide information pertaining to 3D segment angular displacement and angular velocity. Subjects performed 10 single leg lateral hops onto a force platform from a distance of 30cm from the edge of the force platform. Average values for hip, knee and ankle joint 3D angular displacements and velocities were calculated for each subject. Group mean time averaged profiles (200ms pre initial contact (IC) to 200ms post initial contact) were calculated. Differences in CAI and control group time averaged profiles were tested for statistical significance using independent two-sided t-tests. Results and Discussion: CAI subjects exhibited a significant decrease in ankle joint eversion during the time period 10ms pre IC to 200ms post IC (p<0.05). A less everted position of the ankle joint will cause the subtalar joint axis to remain in a more lateral position. Consequently a greater external inversion load could be placed upon the ankle joint, thus increasing the potential for a hyperinversion injury. Conclusion: The disordered positioning of the ankle joint observed in subjects with CAI, manifests prior to and immediately following initial contact with the ground, rendering reflex correction impossible. Consequently this may result in repeated injury to the chronically unstable ankle, as a result of the potentially injurious external inversion load created by a less everted position of the ankle joint following initial ground contact.
Where applicable, experiments conform with Society ethical requirements