POSTER ABSTRACTS - ISAKOS

Female soccer players sustained 115 contact
injuries compared to 161 non-contact injuries. The
magnitude of the difference in injury rates
between male and female basketball players (.32-
.21, p=.93) remained constant while the
magnitude of the difference in the rate of injuries
between male and female soccer players (.16-.21,
p=.08) widened. Comparing injury within gender
by sport, soccer players consistently sustained
more ACL injuries than basketball players. The
rate of ACL injury for male soccer players was .11
compared to .08 for male basketball players
(p=.002). The rate of ACL for female soccer players
was .33 and for female basketball players was .29
(p=.04). The rates for all ACL injuries for females
were statistically significantly higher (p < .01) than
the rates for all ACL injuries for male regardless of
the sport. In soccer, the rate of all ACL injuries
across the thirteen years for male soccer players
significantly decreased (p = .02) while remaining
constant for female.
Conclusions: In this sample of NCAA schools, the
rate of ACL injury regardless of mechanism of
injury, continues to be significantly higher for
female collegiate athletes than for male collegiate
athletes in both soccer and basketball. Despite
vast attention to the discrepancy between ACL
injury rates between men and women, collegiate
basketball and soccer players continue to exist.
Additionally, although the rate of injury for
women is higher than for men, the actual rate of
injury remains low and should not be a deterrent
to participation in sports.
E-poster w/ Standard #424
How Does the ACL Deficient Knee Behave in
Different Walking Speeds?
Tina Moraiti, Ioannina, GREECE, Presenter
Nick Stergiou, Omaha, USA
Giannis Giakas, Trikala, GREECE
Argyris Mitsou, Athens, GREECE
Anastasios Georgoulis, Ioannina, GREECE
Orthopeadic Sports Medicine Center, Medical
School, Ioannina, GREECE
Introduction
Modern mathematics can estimate whether a
system is periodic, random, or chaotic. Chaotic
systems are complex but flexible and therefore,
they can cope with an unpredictable and everchanging
environment. It has been demonstrated
that variability in human gait exhibits such
chaotic properties, which seem to diminish with
pathology. The purpose of this study was to
investigate the effect of ACL deficiency on
locomotion variability under different walking
speeds using chaotic dynamics.
Methods
Ten subjects with unilateral ACL deficiency,
walked on a treadmill at self-selected speed, 20%
faster, and 20% slower. Two minutes (120
footfalls) of continuous data were recorded in
each speed with 6-camera video (50Hz). Chaotic
dynamics analysis consisted of using the
Surrogation method and the calculation of the
Lyapunov Exponent (LyE) of the knee flexionextension
time series. Surrogation is a phaserandomization
technique that determines if the
fluctuations in a system’s (i.e. knee during
locomotion) behavior are deterministic and it was
performed on all time series. LyE measures the
amount of fluctuations present in the trajectories
of the time series under investigation. Small LyE
means that the amount and the rate of the
fluctuations within the system are also small and
thus, the system is more stable. The LyE for the
original time series and their surrogated
counterparts were compared using Student T-
tests. Two-way (Side X Speed) fully-repeated
ANOVAs were also performed on group means for
the LYE.
Results
We found significant differences for LyE values
between the original time series and their
surrogate counterparts for all subject-conditions.
We also found that the ACL deficient knee
exhibits significantly larger LyE than the
contralateral intact knee, regardless of the walking
speed. No significant differences were found for
the LyE values among the three speeds. No
significant interaction was present.
Discussion
Our surrogation results showed that the
deterministic nature of human walking is
maintained despite the absence of the ACL. Thus,
the deterministic nature of locomotion is
controlled not at the periphery but by the central
nervous system (i.e. spinal cord). However,
according to our LyE results, the loss of ACL
resulted in a less stable knee when compared with
the contralateral intact knee, regardless of the
walking speed. These results indicated that ACL
rupture may reduce the ability of the knee to resist
to perturbations and therefore render it less able
to adjust to the unpredictable and changing
environmental demands. This could probably
explain the increased amount of future pathology
(osteoarthriris and meniscal damage) found in