Article

Hierarchical biomechanical models (conventional gait model, CGM) are attractive
because of simple data collection demands, yet they are susceptible to errors
that are theoretically better controlled using six degree-of-freedom models that
track body segments independently (OPT1). We wished to compare gait variables
obtained with these models. Twenty-five normal children walked while wearing a
hybrid marker configuration, permitting identical strides to be analyzed using
CGM and OPT1. Kinematics and ground reaction forces were obtained using a common
motion capture system. CGM and OPT1 were implemented in Visual3D software, where
inverse dynamics provided 20 clinically relevant gait variables (joint angles,
moments and powers). These were compared between models using dependent t-tests
(Bonferroni-adjusted alpha of 0.0025), and ensemble averages. We hypothesized
that OPT1 would provide data similar to CGM in the sagittal plane, and different
from CGM in coronal and transverse planes. Six variables were significantly
different in the sagittal plane, suggesting that CGM produced a more extended
lower extremity; this was explained by a posterior bias to the lateral knee
marker during knee flexion, as a result of skin movement artifact. No significant
differences were found in coronal plane variables. Four variables were
significantly different in the transverse plane. Ensemble averages were
comparable between models. For normal children, biomechanical interpretations
based upon these tested variables are unlikely to change due to independent
segment tracking alone (CGM vs. OPT1). Additional differences may appear due to
pathology, and when segment reference frames are changed from those used in CGM
to reflect individual anatomy.

Langue : ANGLAIS