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Author
Wai-Po Tang, Vol.1, n.4, 2000. Webpublish Dec 2001. (Abstract
and Introduction only)
Two
Dimensional Analysis and Three Dimensional Analysis of the Rearfoot
Motion
ABSTRACT
This
report investigated the comparison between two dimensional analysis
and the three dimensional analysis on rearfoot motion. The difficulty
in determining accurate measurements of the foot motions has been
hampered by the complexities and use of a two-dimensional data collection
protocol (Nigg & Bahlsen, 1988). Bartlett (1989) stated, 'The advantage
of two dimensional cinematography or videography is simplicity,
but requires the movement to be in a pre-selected movement plane
and introduces perspective error for non-planar movements; however,
it yield acceptable results for essentially planar movements'.
One
subject ran on a treadmill (Woodway PPS 55) at a speed of 3.5m.
-1 for a short period of 10 seconds, and three footfalls' data were
collated. The results showed that there was significant differences
difference (F5,17 = 2.60; p < 0.05) between the 2D and 3D protocols,
and this lead to the assumption that the 2D data collection was
not accurate. The gait intraclass correlation was significant between
the two methodologies r = 0.98, (F2,17 = 55.69; p < 0.01), and this
suggested that 2D analysis was acceptable to establish common pattern
of movements.
The findings of the present study supports past research that 3D
analysis is superior to 2D analysis with regards to assessing the
rearfoot motion or other rotational movements. Therefore, rearfoot
motion analysis must adopt the three dimensional videography or
cinematography to accurately measure eversion or inversion of the
foot.
INTRODUCTION
Sports injuries to the lower extremities of the human body are often
the resultant of excessive stresses. The ankle joints are no exception
to the excessive stresses of repetitive sports such as squash, boxing
and running. Common injuries like shin splints and achilles tendonitis
are assumed to be related to the instability of the rear foot joint
at the subtalar (Nigg & Bahlsen, 1988). Souas-Little, Beavis,
Verstraete and Markus (1987) stated, 'The amount and rate of pronation
and supination have been the subject of interest to runners for
some time.' Past researches (Bates, Osternig, Mason & James,
1979; Clarke, Frederick, & Hamil, 1984; Clement, Taunton, Smart,
& McNicol, 1981; Fredericket., et. al., 1983; Nigg, Eberle,
Frey, Segesser, & Weber, 1977; Schuster, 1978; Segesser, Nigg,&
Morell, 1980; Stacoff, & Kaelin, 1983) speculated that the anterior
medial compartment syndrome (shin splints) and illiotibial band
syndrome are caused by excessive motion about the subtalar axis.
Furthermore, injuries to the achilles tendons are also speculated
to occur during the take-off phase whereby the foot over-supinates
(Nigg & Leuthi, 1980; Nigg & Morlock, 1987). It is the initial
impact phase and the take-off phase of the foot that are often investigated
via kinematics and kinetic analyses.
Due
the structure and the movements of the foot - fast and subtle motions
are somewhat difficult to measure accurately. Hall (1991) described,
'The structure of the subtalar joint is located at the anterior
and posterior facets on the inferior side of the talus that articulates
with the superior calcaneous to form the subtalar joint. Four talocalcaneal
ligaments join the talus and the calcaneous. The joint is essentially
uniaxial, with an alignment slightly oblique to the conventional
descriptive planes of motion.' The difficulty in determining accurate
measurements of the foot motions has been hampered by the complexities
and use of a two-dimensional data collection protocol (Nigg &
Bahlsen, 1988). The multi-directional movement of the foot would
require three-dimensional (3D) data collection to ensure accurate
measurement any curvilinear trajectory.
Souas-Little,
and et. al (1987) found that two-dimensional (2D) analysis via video
projection are liable to errors. These errors are compounded during
plantar and dorsiflexion and medial and lateral foot rotation. Nigg
& Morlock, (1987) supports the argument against the 2D method
by claiming the rotation around the ankle or subtalar joint cannot
be accuarately determined. Bartlett (1989) stated, 'The advantage
of two dimensional cinematography or videography is simplicity,
but requires the movement to be in a pre-selected movement plane
and introduces perspective error for non-planar movements; however,
it yield acceptable results for essentially planar movements'.
The
objective of the present study was to compare the 2D and 3D methodology
of rearfoot motion (eversion and inversion displacement). Also,
to compare the findings to that of the past researches on the eversion
of the foot.
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