This study aims to identify kinematic differences between children with Ponseti treated clubfoot and age-mat- ched healthy controls during gait, using the Oxford Foot Model. This pilot is part of a large project comparing gait kinematics between children with Ponseti treated clubfoot with and without relapse and healthy controls. Final results could identify relevant gait parameters which will allow for early detection of a relapse clubfoot.
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A clubfoot is characterized by a three-dimensional deformity with an equinus, varus, cavus and adduction component. Nowadays the Ponseti method is the preferred treatment for clubfeet, aiming to achieve a normal appearing, functional and painless foot. The reoccurrence of clubfoot components in treated clubfeet, a relapse, is a known problem in clubfoot patients. 3Dgait analysis can be used in assessment of foot function and residual deviations in gait or possible relapses. Gait analysis is frequently used to analyse differences in gait between clubfoot and healthy controls. However, the usage of multisegment foot models is, although of importance considering the characteristics of the clubfoot, rare. In order to capture the full multi-planar and multi-joint nature of a clubfoot, it is highly important to implement multi-segment foot models in gait analysis. In order to improve treatment of individual relapse clubfoot kinematics differences in clinical relevant functional outcomes should be known.
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Inertial measurement units (IMUs) allow for measurements of kinematic movements outside the laboratory, persevering the athlete-environment relationship. To use IMUs in a sport-specific setting, it is necessary to validate sport-specific movements. The aim of this study was to assess the concurrent validity of the Xsens IMU system by comparing it to the Vicon optoelectronic motion system for lower-limb joint angle measurements during jump-landing and change-of-direction tasks. Ten recreational athletes performed four tasks; single-leg hop and landing, running double-leg vertical jump landing, single-leg deceleration and push off, and sidestep cut, while kinematics were recorded by 17 IMUs (Xsens Technologies B.V.) and eight motion capture cameras (Vicon Motion Systems, Ltd). Validity of lower-body joint kinematics was assessed using measures of agreement (cross-correlation: XCORR) and error (root mean square deviation and amplitude difference). Excellent agreement was found in the sagittal plane for all joints and tasks (XCORR > 0.92). Highly variable agreement was found for knee and ankle in transverse and frontal plane. Relatively high error rates were found in all joints. In conclusion, this study shows that the Xsens IMU system provides highly comparable waveforms of sagittal lower-body joint kinematics in sport-specific movements. Caution is advised interpreting frontal and transverse plane kinematics as between-system agreement highly varied.
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