Abstract
BackgroundIn 3D gait analysis, the knee joint is usually described by the Eulerian way. It consists in breaking down the motion between the articulating bones of the knee into three rotations around three axes: flexion/extension, abduction/adduction and internal/external rotation. However, the definition of these axes is prone to error, such as the “cross-talk” effect, due to difficult positioning of anatomical landmarks. This paper proposes a correction method, principal component analysis (PCA), based on an objective kinematic criterion for standardization, in order to improve knee joint kinematic analysis.MethodsThe method was applied to the 3D gait data of two different groups (twenty healthy subjects and four with knee osteoarthritis). Then, this method was evaluated with respect to three main criteria: (1) the deletion of knee joint angle cross-talk (2) the reduction of variance in the varus/valgus kinematic profile (3) the posture trial varus/valgus deformation matching the X-ray value for patients with knee osteoarthritis. The effect of the correction method was tested statistically on variabilities and cross-talk during gait.ResultsCross-talk was lower (p<0.05) after correction (the correlation between the flexion-extension and varus-valgus kinematic profiles being annihilated). Additionally, the variance in the kinematic profile for knee varus/valgus and knee flexion/extension was found to be lower and higher (p<0.05), respectively, after correction for both the left and right side. Moreover, after correction, the posture trial varus/valgus angles were much closer to x-ray grading.ConclusionThe results show that the PCA correction applied to the knee joint eliminates the cross-talk effect, and does not alter the radiological varus/valgus deformation for patients with knee osteoarthritis. These findings suggest that the proposed correction method produces new rotational axes that better fit true knee motion.
Highlights
This technique has to rely on the palpation of external anatomical landmarks, which is an experimental problem [10]
These results are consistent with previous studies [2,12,23.] They demonstrated that the more misaligned the defined coordinate systems (CS), the more sensitive to change in flexion/extension the knee varus/valgus became
The correction method eliminated the presence of knee joint angle cross-talk, as proved by mean r2 values close to 0 for the left and right side after correction
Summary
This technique has to rely on the palpation of external anatomical landmarks, which is an experimental problem [10]. Minor changes of marker placements modify the orientation of the coordinate systems and thereafter lead to significant errors in abduction/adduction and internal/external rotation angle curves [11,12,13,14] This error is known as the kinematic ‘‘cross-talk’’ effect [15,16,17,18], which affects the kinematics of joints that articulate principally around one major component, e.g. the knee joint [19]. In 3D gait analysis, the knee joint is usually described by the Eulerian way It consists in breaking down the motion between the articulating bones of the knee into three rotations around three axes: flexion/extension, abduction/ adduction and internal/external rotation. This paper proposes a correction method, principal component analysis (PCA), based on an objective kinematic criterion for standardization, in order to improve knee joint kinematic analysis
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