Sheila Gibbs

A method to calculate the centre of the ankle joint: a comparison with the Vicon Plug-in-Gait model.

BACKGROUND In gait analysis, calculation of the ankle joint centre is a difficult task. The conventional way to calculate the ankle joint centre is using the Vicon Plug-in-Gait model. The present study proposes a new model, which calculates the joint centre from two markers positioned over the medial and lateral malleoli (i.e. Two-marker-model). METHODS In order to compare the proposed model with Plug-in-Gait model, gait data from healthy and patient subjects were captured using a motion capture system. The ankle joint centres were calculated by the two models. A test-retest experiment was carried out to check reliability and repeatability for Two-marker-model. FINDINGS Two ankle joint centres produced by two models were significantly different. The distances between two ankle joint centres were approximately 16.8 (mm), and the differences in the posterior-anterior, medial-lateral and inferior-superior directions were approximately 6.3, 7.7 and 8.2 (mm). Further error analysis highlighted that the probability of producing errors in Two-marker-model is lower than that in Plug-in-Gait model due to the Two-marker-models simple and reliable marker positioning. The reliability and repeatability coefficients for the new model were greater than 0.9. INTERPRETATION In principle, the Plug-in-Gait model is more likely to produce errors than the Two-marker-model, because the former employs multiple markers from the pelvis to calf to define the ankle joint centre with marker positions being very user-dependent. The results suggest that the Two-marker-model can be considered an alternative to Plug-in-Gait model for calculating ankle joint centre.

Analysis of knee joint kinematics during walking in patients with cerebral palsy through human motion capture and gait model-based measurement

Cerebral palsy is leading cause of physical disability in childhood. This interferes with normal ambulation. Rectus femoris muscle spasticity has been reported to be a cause of stiff knee gait in the patients with cerebral palsy. This study aimed to analyse changes in sagittal knee joint kinematic parameters following botulinum toxin injection to the rectus femoris. Fifteen patients were included in the study. A Vicon Motion capture system with Plug-in-Gait model was used for the pre- and post-treatment gait analysis of knee joint angles as well as knee joint flexion velocity. The results from statistical analysis revealed that there were no significant differences in the knee joint range of motion as well as velocity of knee joint flexion in the pre-swing and early swing phase of gait cycle. Although statistical results did not show any significant improvement, it was noted that there was variation in the outcomes for individual patients, with some showing improvements.