Kinematic analysis of a multi-segment foot model for research and clinical applications: a repeatability analysis
Introduction
In gait analysis, the clinical biomechanical models usually represent the foot as a single rigid vector, permitting only foot progression angle and net dorsi/plantarflexion to be determined. In the research literature, there is no standard nor reliable method for dynamic in vivo measurement and it is recognised that this is very difficult to achieve due to the foot's complex structure. This paper describes a multi-segment approach to measuring foot kinematics during gait and a repeatability analysis on healthy feet.
In the last decade a few groups have presented multi-segment in vivo studies of the foot (DeLozier et al., 1991; D’Andrea et al., 1993; Kidder et al., 1996; Leardini et al., 1999), with others looking at the ankle/subtalar complex in vivo (Moseley et al., 1996; Liu et al., 1997). However, the means of marking and describing the segment fixed anatomical axes have varied between authors so that comparability of the results of these studies are limited (Leardini et al., 1999). There is a need for a standardised protocol which requires thorough testing and validation (Kidder et al., 1996). The objectives of the present study were:
Section snippets
Foot model
The foot model simplifies the complex anatomical structure of the 28 bones of the foot. We selected a three segment foot model (hindfoot, forefoot and hallux), plus a tibial segment (Fig. 1) based on rigid body assumptions. Here, interest in the mid-foot focussed on its role as a mechanism transmitting motion between the hindfoot and forefoot. Relative motion is described without inter-segment constraints, that is with six possible degrees of freedom between any pair of segments.
Subjects and strategy
The method was
Inter-segment motion
Twelve inter-segment angles plotted against stance time for every test run, θ(τ), show distinct patterns of motion. Fig. 5 gives one example of the median result from one subject. The hindfoot dorsiflexes with respect to the tibia through mid-stance and plantar flexes at push off (Fig. 5d). It also progresses into inversion and internal rotation in late stance (Figs. 5e and f), a movement known to occur mostly in the subtalar joint complex (Perry, 1992). The forefoot dorsiflexes with respect to
Kinematic analysis of a multi-segment foot model
Several previous multi-segment models have been presented (DeLozier et al., 1991; D’Andrea et al., 1993; Kidder et al., 1996; Liu et al., 1997; Leardini et al., 1999). The marker set described here is most similar to that of Kidder et al. (1996) although there are important differences. Two additional markers are introduced (CPEG, D2MT), the proximal first MT marker is attached to the dorsal side of the foot, and a reduction of the marker set is proposed between the static and dynamic
Acknowledgments
We would like to thank Kathryn Kirby and Nick Annetts for their invaluable time in the gait lab. We would also like to acknowledge and thank the Arthritis Research Campaign for the project grant supporting this work.
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