Effects of movement for estimating the hip joint centre
Résumé
The determination of hip joint centre (HJC) with functional method requires various postures. The present study assesses the effect of the movement on the accuracy of HJC estimation. The type, the nature of the movement such as the number of cycles were tested with analytic and experimental approaches. Three-dimensional video data were collected for hip movements of seven athletes. Kinematic noise was modelled using data on the deformation of hip and thigh clusters, while perfect ball-and-socket movements (the reference) were computed from the movements of a subject. Virtual kinematic data allowed the implementation of 27 different tests for 500 virtual athletes. HJC location for each test was estimated using a sphere fitting algorithm. An error was defined as the euclidean distance between the estimated and the reference HJC. A nested ANOVA and a multiple comparison procedures were performed with all errors. Average error ranges between 4.0 and 7.9 mm. The accuracy is improved by a variety of postures obtained by dierent types of movement flexion-extension abduction-adduction and circumduction). A limited movement is better than larger range of motion, because the additional postures are too noisy. Lastly, it is interest- ing to acquire several cycles. To conclude, a test composed of 10 limited cycles of flexion-extension, abduction-adduction and circumduction guarantees the greatest accuracy in estimating HJC.