User guide

Charnwood Dynamics Ltd. Coda cx1 User Guide - Gait Analysis II - 1
CX1 USER GUIDE - COMPLETE.doc 26/04/04 59/162
SEGMENTAL GAIT ANALYSIS (3-D)
Overview
Codamotion Analysis software includes functions for calculating 3-dimensional segmental
gait analysis data.
By using a special marker set which includes a pelvic frame, thigh wands and shank
wands (see Marker placement & naming), data may be acquired unilaterally or bilaterally
for the calculation of internal joint centres for the Hip, Knee, and Ankle joints, and their 3D
internal rotations. The 3D orientations of the Pelvis and Foot are also calculated.
If force-plate data is acquired for the ground reaction force of a foot during stance, 3D
moments are calculated for the Hip, Knee and Ankle joints during the swing and stance
phases using inverse dynamics modelling of each leg segment. The total power
dissipated in each joint is also calculated.
Additional data required for the calculation of internal joint centres and for the inverse
dynamics calculation of joint moments and powers is entered through a Patient Data
dialogue. This data includes Patient age and weight, joint widths, and leg-segment data
(segment length, mass-ratio, centre-of-mass position, radii of gyration). The segment
data may be defined from standard reference data or entered manually. The Patient Data
is stored in the Movement Data File and may be stored to and retrieved from a Patient
Data file.
The calculation of internal joint centres and rotations is invoked automatically when the
appropriate set of marker names is defined in the Setup and when data has been
acquired for those markers. The data configurations for the Pelvis, Right Leg, and Left
Leg are independent of each other - rotation data is calculated automatically for whatever
combination of limb data there is present in the acquired data or data file. Moments and
Powers are calculated if ground reaction force data is available for either leg; the force
data is automatically assigned to the appropriate leg.
All segmental analysis data may be plotted on-screen as user-configurable graphs and
saved in the movement data file. The Motion Database application program is used to
generate hard-copy Gait Analysis reports in a standard format.
Marker Names
Codamotion Analysis recognizes the gait analysis data configuration by the names of
markers assigned (by the user) in the Setup. (The marker numbers are not important.)
The presence of data for the Pelvis and for each leg is detected separately, and for
unilateral data the body side (left/right) is detected automatically from the direction of
travel. Pelvis data must be present for gait analysis on either or both legs, but Leg data
need not be present if only Pelvic rotations are required.