POSTER ABSTRACTS - ISAKOS

Although softball has become one of the most
popular sports in recent years, more attention has
been directed to shoulder injuries in baseball
pitchers, focusing on the biomechanics and
muscle firing patterns associated with that sport.
Research on the overhand pitch has identified
critical instances during the pitching motion
where injuries occur, and with proper
intervention, may be prevented. However, there is
very little information pertaining to softball
pitchers and the biomechanics of the underhand
windmill pitch. Due to the paucity of literature
about the biomechanics of the windmill softball
pitch, phases and motions of the pitch have not
been standardized. By developing a better
understanding of the mechanics, we can identify
at-risk tissues leading to better diagnosis of
injuries and more specific rehabilitation and
conditioning programs. The purpose of this study
was to determine the kinematics of the windmill
softball pitch with video analysis. Digitizing
software was used to find shoulder position at
stride foot contact, elbow angle at ball release,
shoulder angular velocities through different
intervals, and ball speed at ball release, as these
variables have been associated with risks of
shoulder injury and performance.
Five healthy, female, high school student
athletes participated in this study. Kinematic
data was taken from 6 pitches from each of the 5
subjects with three digital camcorders. Reference
points were subjects’ bilateral feet, ankles, knees,
hips, shoulder, elbow, wrist, and hand, as well as
her chin, forehead and the ball. These landmarks
were used to calculate angular velocity and linear
displacement of different joints and/or segments
throughout the pitch. Data also helped us
establish different measurements per athlete,
averages, and standard deviation among athletes
in shoulder and knee position at stride foot
contact, elbow position at ball release, ball speed,
and angular velocity of the arm at each phase of
the pitch. A Pearson product moment correlation
was used to determine if there was any correlation
between these measurements and ball speed.
Only knee position at stride foot contact had a
significant correlation of -0.967 with ball speed.
The average stride length of the five subjects was
40.84 with a standard deviation of 1.88, with an
average body height to stride ratio of 63.5%.
Average shoulder angle and knee angle at stride
foot contact was 133 degrees and 32 degrees with
a standard deviation of 15 degrees and 5 degrees,
respectively. Elbow angle at ball release averaged
9 degrees with a standard deviation of 0.8
degrees. Ball speed averaged 54.88 mph with a
standard deviation of 6.5 mph.
As determined from our results, knee angle at
stride foot contact inversely influences ball speed.
Angular velocity may influence ball speed, but can
be affected by other variables.
E-poster w/ Standard #827
The Influence of Knee Replacement Type on
Joint Proprioception; Total versus
Unicompartmental Replacement
Sherif Mouneir Isaac, Oxford, UNITED KINGDOM,
Presenter
Karen Barker, Oxford, Oxon, UNITED KINGDOM
Irini Nabil Danial, Oxford, Oxon, UNITED
KINGDOM
David Beard, Headington, Oxford, UNITED
KINGDOM
Richie Gill, Oxford, Oxon, UNITED KINGDOM
Max Gibbons, Oxford, Oxon, UNITED KINGDOM
Christopher Dodd, Oxford, Oxfordshire, UNITED
KINGDOM
David Murray, Headington, Oxford, UNITED
KINGDOM
Nuffield Orthopaedic Centre NHS Trust, Oxford,
UNITED KINGDOM
Introduction:
Proprioception protects joints against injurious
movements and is critical for joint stability
maintenance under dynamic conditions. Knee
replacement effect on proprioception in general
remains elusive. This study aimed to evaluate the
changes in proprioceptive performance after knee
replacement; comparing Total (TKA) to
Unicompartmental Knee Arthroplasty (UKA).
Methods and Materials
Thirty-four patients with osteoarthritis were
recruited; 15 patients underwent TKA using the
AGC prosthesis and 19 patients underwent UKA
using the Oxford prosthesis. Both cruciate
ligaments were preserved in the UKA group, while
only the PCL was preserved in TKA patients.
Patients’ age was similar in both groups.
Joint Position Sense (JPS) and postural sway were
used as measures of proprioception. Both groups
were assessed pre- and 6 months post-operatively
in both limbs. JPS was measured as the error in
actively and passively reproducing five randomly
ordered knee flexion angles between 30 and 70
using an isokinetic dynamometer. Postural sway
(area and path) was measured during single leg
stance using a Balance Performance Monitor.