Graduation date: 2006

Objectives: To evaluate postural control in individuals with functional ankle instability using static, dynamic, and clinical balance tests. Also, to examine the relationships between the performances in each of these tests. Design: Postural control was evaluated with a single leg balance test, a balance test involving movement, and the star excursion balance test. Participants: A volunteer sample of 19 subjects with functional ankle instability and 19 uninjured control subjects. Main Outcome Measures: Center of pressure sway path length was calculated for the static and dynamic balance tests. Total reach distance was measured for the star excursion balance test. Results: Subjects with functional ankle instability demonstrated a significantly greater center of pressure sway path length in both the static and dynamic balance tests. Conclusions: Functional ankle instability may be associated with reduced postural control as demonstrated by decreased performance in static and dynamic balance tests. / Graduation date: 2003

Several recent studies have revealed that high caliber European professional soccer players often have diminished levels of neurological functioning, yet no study has been able to identify the specific aspect of soccer participation responsible for these decreases. In an effort to identify a source of mild traumatic brain injury present in everyday participation in soccer, this study investigated whether a single bout of heading a soccer ball would have acute detrimental, measurable effects on sensorimotor and neurocognitive functioning. We hypothesized that subjects would exhibit significant changes in postural stability, memory, and concentration immediately after an acute bout of repeated heading a soccer ball. Additionally, we evaluated the protective effect(s) associated with wearing a mouthguard while performing the acute bout of heading. Twenty-eight elite level soccer players (mean age, 20.9 �� 2.5 yrs) were randomly assigned to one of three experimental groups: Headers with mouthguard (n=10), Headers with no mouthguard (n=10), and Control (n=8). Subjects in the two treatment groups performed 12 headers of soccer balls projected at 40 km/hr from an electric soccer ball-launching machine. Postural stability was evaluated using a Biodex Stability System, while memory and concentration were assessed using Wechsler Digit Span (WDS) tests (digits forward and digits backward) in a 3 x 2 factorial ANOVA design (��=0.05). There were no significant main effects or interactions among the three measures of postural stability scores in the three groups (p>0.05). The WDS Forward group means ranged from 10.4 �� 1.8 to 13.5 �� 1.2 while the WDS Backward means ranged from 6.4 �� 1.1 to 7.7 �� 3.0, but were not different among the groups (p>0.05). We concluded that a single bout of 12 soccer headers approximating the number of headers performed during a typical NCAA Division I-A soccer practice did not produce significant deficits in postural stability, memory, or concentration. While our findings are similar to several recent studies, we suggest that more sensitive measurement tools such as ImPACT neurocognitive testing and functional magnetic resonance imaging be utilized to determine the effects of acute as well as chronic exposure to headers in soccer players. / Graduation date: 2003

Pedicle screw breakage and loosening remain as clinical complications of short segment instrumentation procedures for spinal stabilization. This study has directly visualized and measured elastic, plastic and total vertebral pedicle trabecular bone full-field strains in the regions immediately surrounding the pedicle screw during pedicle screw insertion by utilizing functional microCT imaging and digital volume correlation. Human, porcine and polyurethane foam samples were analyzed and compared. Analysis showed that when osteoporotic human, normal human and porcine pedicle trabecular bone samples were compared, osteoporotic samples showed higher peak plastic strains and greater variability of these strains from their means. This suggests that osteoporotic human samples are non-uniformly elastic and plastic, while normal human and porcine samples are more uniformly elastic and plastic throughout the trabecular structure. PU-foams are not appropriate as models for pedicle trabecular bone in the in vivo environment since strain results showed dissimilar plastic and elastic strain magnitudes than human and porcine pedicle trabecular bone. This study may aid in the development of performance criteria for new PU-foams and improved pedicle screw designs. / Graduation date: 2004

Ankle injuries comprise more than 15% of all sports injuries worldwide. The efficacy of the ankle taping for injury prevention has long been under scrutiny as numerous studies have shown that tape rapidly loses its ability to constrain ankle motion with exercise. Consequently, ankle braces (orthoses) are being used with increasing frequency for the prevention and functional management of ankle injuries. However, the motion restraining qualities of ankle orthoses have not been widely evaluated in closed kinetic chain environments under physiologic loads. The primary purpose of this study was to compare the abilities of four ankle orthoses (ankle taping, lace-up brace, semirigid orthosis and hybrid brace) against a control condition (no brace or tape) to control subtalar and talocrural motion during running on a laterally-tilted treadmill at 16.2 km/h before and after exercise. It has been hypothesized that ankle orthoses make a secondary contribution to injury prevention through enhanced proprioception. The secondary purpose of this study was to quantify the effects of the aforementioned ankle orthoses on postural stability during single-limb stance following a bout of exercise. Fifteen healthy university students (8 men and 7 women) with no history of significant ankle injuries (age, mean �� SD: 22.9 �� 3.9 years) volunteered to participate in this study. Three-dimensional kinematic data were captured with an active infrared digital camera system sampling at 120 Hz. To address the first question, data analyses were performed using 2way univariate (Ankle Orthoses x Pre/Post-Exercise x Subjects) (5 x 2 x 15) repeated measures analysis of variance (ANOVA) to determine the existence of differences among three closed and four open kinematic chain dependent measures before and after exercise. Maximum inversion angles (MAXINV) were similar for all ankle orthoses, with no orthosis limiting inversion during tilted treadmill running significantly more than another, or compared to the control condition, either before or after exercise (p>.05). Pre-exercise MAXINV group means and standard deviations during treadmill running ranged from 6.8 �� 3.4 deg with the Royce Medical Speed Brace to 9.5 �� 4.1 deg in the tape condition; post-exercise MAXINV mean values ranged from 7.6 �� 3.2 deg for the Aircast Sport Stirrup to 9.1 �� 4.6 deg with closed basketweave tape. While not statistically significant (p=0.10), ankle taping provided the least amount of inversion restraint, both before and after the exercise bout. The MAXINV angles measured during treadmill running (8.2 �� 4.0 deg) and open chain inversion AROM measured with a goniometer (34.5 �� 6.2 deg) were not related (r=-0.0003). The compressive forces present during closed kinetic chain activity are known to increase joint stability and thus may explain why MAXINV under dynamic varus loads was so much less in magnitude than inversion AROM measured under open kinetic chain conditions. The nonlinear relationship of these two variables supports our contention that reports of the motion controlling properties of ankle orthoses measured in open kinetic chain environments should not be used to infer the response characteristics of these same orthoses under dynamic, physiologic loads. To address the second question, data were analyzed using 3-way univariate (Ankle Orthoses x Pre/Post-Exercise x Eyes Open/Closed x Subjects) (5 x 2 x 2 x 15) repeated measures ANOVAs. Subjects' postural stability was assessed using a Biodex Balance System with eyes open and eyes closed conditions, before and after an exercise bout. The ankle orthoses evaluated did not influence postural stability as measured by mediolateral sway index, anteroposterior sway index, and overall sway index. Removal of visual perception via blindfolding resulted in significant decreases in all three measures of postural stability (p=.001). There was poor association among the closed chain postural stability parameters and the open chain AROM measures. These correlations ranged from r=.04 to .17, indicating minimal relationship between the amount of AROM permitted by the orthoses and postural stability as quantified by this method. / Graduation date: 2000

Graduation date: 1994

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Surgery / Master / Master of Research in Medicine

published_or_final_version / Surgery / Doctoral / Doctor of Philosophy