Relationships between Foot Type and Dynamic Rearfoot Frontal Plane Motion
of the variation in maximum eversion angle.
This is in contrast to initial investigations of
the relationship between FPI and dynamic
foot function which demonstrate a weaker
relationship between both dynamic midfoot
and ankle joint complex motion and static
FPI scores [9,10] . One previous study evaluated
ankle joint complex motion and the FPI score
in manipulated positions [9] . The method of
measuring maximum rearfoot eversion in
unmodified gait and in a larger sample may
explain the increased strength of relationship
found in this study. Furthermore, in this study
FPI scores Were correlated with maximum
rearfoot eversion whenever this occurred during
stance phase allowing for an inter-relationship
between the midfoot and forefoot to be included.
This allowed for delayed or prolonged rearfoot
eversion, both recently identified as distinct
patterns of rearfoot motion [16] to be included in
the statistical tests.
Investigation of the relationship between the
FPI frontal plane score of the rearfoot and
maximum eversion angle demonstrated a strong,
statistically significant relationship between
the two variables for both the pronated foot
type group and the normal foot type group.
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The pronated group demonstrated the stronger
correlation with rearfoot motion, most likely
due to greater range of pronation providing
measurable differences in the individual planar
components of rearfoot pronation. The presence
of a positive relationship in a relatively small
cohort suggests that further investigations
are required, particularly relating to a highly
pronated foot type (FPI 10+) which is more likely
to demonstrate significant differences across
the three planes of motion making up subtalar
pronation. Correct identification of dominant
planar components of rearfoot motion may
potentially assist with orthotic prescription,
specifically in relation to the position of the
point of correction and the style of the device,
with frontal plane dominance suggesting
increased calcaneal motion control is required.
Modern three-dimensional motion analysis
techniques used for collection of rearfoot
data from participants in this study may also
have contributed to findings of much stronger
predictive ability of the FPI than in results for
midfoot dynamic motion captured with Video
Sequence Analysis as published previously [10] .
Similarly, isolation of this study to the rearfoot
ensured movement from multiple joints in the