1st Joint ESMAC-GCMAS Meeting - Análise de Marcha

O-51
A COMPARISON OF METHODS FOR USING CENTER OF PRESSURE
PROGRESSION IN THE CLASSIFICATION OF FOOT DEFORMITY
Gene Jameson, MA, Jason Anderson, MS, Roy Davis, Ph.D.,
Jon Davids, MD, and Lisa Christopher, BS
Shriners Hospitals for Children, Greenville, SC, USA
Introduction
The pedobarograph, a system that measures plantar pressure, has been successfully applied to
patients with neuropathy where the information can be used to prevent pressure-related
problems 1,2 . In attempts to utilize the pedobarograph in the evaluation of children with
cerebral palsy and associated foot deformities, previous researchers used normalized plantar
pressure within different regions of the foot to classify the feet into varus or valgus
categories 3,4 . One recent method of pedobarograph analysis used the normal center of pressure
progression (COPP) during stance to establish medio-lateral divisions of the foot 5 . The COPP
for pathological feet could then be compared to COPP from a normal population. This method
required the longitudinal axis of the foot to be subjectively determined by the analyst so the
pedobabrograph output could be oriented consistently and comparisons made. The current
study expands on that method by introducing simultaneous motion capture to evaluate the
difference between subjective and objective methods of long axis determination.
Statement of Clinical Significance
This study reports a new pedobarograph analysis procedure as well as the results for a
population of pediatric individuals without gait impairment and compares it to previously
published data. This information can then be used in the evaluation and treatment of patients
with foot deformity.
Methods
Five successful walking trials were collected for each foot of 23 normal subjects (mean age
11.4 ± 3.3 years, range of 6 to 17 years). One representative trial was selected for each foot for
COPP analysis. Because the ultimate goal was to apply this technique to feet with pathology,
the custom software developed in our laboratory allows for the analysis of the COPP if the foot
shape is atypical and if the entire foot does not make contact with the floor surface. A
graphical computer interface allowed the four analysts to specify the long axis of each foot,
which was defined as a line connecting a point between the second and third metatarsal and the
midpoint of the heel. The medial and lateral borders of the foot were also identified. In
addition to this analysis, the 3D kinematic data was used to identify foot landmarks consistent
with standard gait analysis, i.e. medial and lateral malleoli, and the midline of the foot at the
base of the toes. The center point between the malleoli markers and the toe marker established
the long axis of the foot.
The length of the foot was divided into three regions longitudinally (Figure 1). One and two
standard deviations from the mean COPP were calculated (Figure 1). These fore/aft and
medio-lateral regions were numbered to facilitate classification (Figure 1). The time (% of
stance) and location of the COP within the heel, midfoot and forefoot regions were determined
so that the COPP could be described temporally as well as in both anteroposterior and
mediolateral directions (Figure 2). The rotation angles of the long axis as determined by the
two methods was compared, as well as the rotation angles between the four observers.
Results
The average COPP in normal individuals begins in the middle of the heel region at initial
contact then progresses forward for 23.8% of stance phase. It proceeds forward through the
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