Biomedical subjects

Dorsey S Williams

Publications and source records attributed to Dorsey S Williams.

5 recordsLinked to original sources

PubMed2005

Effect of foot orthotics on rearfoot and tibia joint coupling patterns and variability.

The purpose of this study was to compare joint coupling patterns and variability of the rearfoot and tibia during running in subjects who were treated with two types of orthotic devices to that of controls. Eleven subjects with various lower extremity injuries were treated unsuccessfully with a standard orthotic, and then successfully with an inverted orthotic. Three-dimensional kinematic data were collected while subjects ran without orthoses and then in standard and inverted orthoses. Eleven healthy subjects ran without orthoses for comparison. The rearfoot inversion/eversion and tibial internal/external rotation joint coupling pattern and variability relationship was assessed using a vector coding technique. It was hypothesized that when the treated runners ran without orthotic devices, they would exhibit lower joint coupling angles and lower joint coupling variability compared to the controls. In addition, it was hypothesized that there would be no difference in the coupling angle or coupling variability between the standard and no orthotic conditions of the treated runners. Finally, it was hypothesized that coupling angle would decrease and variability would increase in the inverted versus the standard and non-orthotic conditions. No significant differences in joint coupling pattern or variability were observed between the treated and control subjects. In addition, no significant differences were noted between the orthotic conditions in the treated group. These results suggest that foot orthotic devices do not produce significant changes in rearfoot-tibial coupling. Therefore, the relief experienced with the inverted orthotic is likely due to factors other than alterations in this coupling.

Adolescent↗

PubMed2004

High-arched runners exhibit increased leg stiffness compared to low-arched runners.

Leg stiffness between high-arched (HA) and low-arched (LA) runners was compared. It was hypothesized that high-arched runners would exhibit increased leg stiffness, increased sagittal plane support moment, greater vertical loading rates, decreased knee flexion excursion and increased activation of the knee extensor musculature. Twenty high-arched and 20 low-arched subjects were included in this study. Leg stiffness, knee stiffness, vertical loading rate and lower extremity support moment were compared between groups. Electromyographic data were collected in an attempt to explain differences in leg stiffness between groups. High-arched subjects were found to have increased leg stiffness and vertical loading rate compared to low-arched runners. Support moment at the impact peak of the vertical ground reaction force was related to leg stiffness across all subjects. High-arched subjects demonstrated decreased knee flexion excursion during stance. Finally, high-arched subjects exhibited a significantly earlier onset of the vastus lateralis (VL) than the low-arched runners. Differences exist in leg stiffness and vertical loading rate between runners with different foot types. Differences in lower extremity kinetics in individuals with different foot types may have implications for new treatment strategies or preventative measures.

Adolescent↗

PubMed2003

Gender differences in lower extremity mechanics during running.

OBJECTIVE: To compare differences in hip and knee kinematics and kinetics in male and female recreational runners. DESIGN: Gait analysis of 20 men and 20 women recreational runners. BACKGROUND: Female runners are reported to be more likely to sustain certain lower extremity injuries compared to their male counterparts. This has been attributed, in part, to differences in their structure and it has been postulated that these structural differences may lead to differences in running mechanics. It was hypothesized that females would exhibit greater peak hip adduction, hip internal rotation, knee abduction and decreased knee internal rotation compared to their male counterparts. It was also hypothesized that females would exhibit greater hip and knee negative work in the frontal and transverse planes compared to males. METHODS: Comparisons of hip and knee three-dimentional joint angles and negative work during the stance phase of running gait were made between genders. RESULTS: Female recreational runners demonstrated a significantly greater peak hip adduction, hip internal rotation and knee abduction angle compared to men. Female recreational runners also demonstrated significantly greater hip frontal and transverse plane negative work compared to male recreational runners. CONCLUSION: Female recreational runners exhibit significantly different lower extremity mechanics in the frontal and transverse planes at the hip and knee during running compared to male recreational runners. RELEVANCE: Understanding the differences in running mechanics between male and female runners may lend insight into the etiology of different injury patterns seen between genders. In addition, these results suggest that care should be taken to account for gender when studying groups of male and female recreational runners.

Adolescent↗

PubMed2003

Effect of inverted orthoses on lower-extremity mechanics in runners.

INTRODUCTION: Foot orthoses are recommended for individuals with injuries associated with abnormal lower-extremity mechanics. However, the biomechanical effect of these devices is not completely understood. Most clinicians and researchers believe that foot orthoses are effective in reducing some aspect of rearfoot motion. This is important as many injuries are suggested to be the result of increased pronation. Inverted orthoses are a more aggressive treatment in those whose symptoms do not respond to standard orthotics. They are likely to alter motion in all planes. However, no three-dimensional studies have assessed lower-extremity mechanics in individuals wearing inverted orthotics. PURPOSE: The purpose of this study was to compare the three-dimensional kinematics and kinetics of the rearfoot and knee during running while varying orthotic intervention. METHODS: Eleven subjects were initially fitted with standard foot orthoses and then with inverted orthoses. Three-dimensional kinematic and kinetic data were collected for conditions of no orthoses, standard orthoses, and inverted orthoses. RESULTS: There were no differences between conditions in peak rearfoot eversion or rearfoot eversion excursion. Peak rearfoot inversion moment and work were significantly reduced (P = 0.045 and P < 0.001, respectively) in the inverted orthotic condition suggesting a decreased demand on the soft tissue structures that control eversion. Significant differences were seen in tibial rotation (P = 0.043), knee adduction (P = 0.035), and knee abduction moment (P < 0.001) in the inverted orthotic condition, suggesting alterations were made further up the kinetic chain. CONCLUSIONS: The differences in kinetic parameters at the rearfoot may result in fewer injuries of the rearfoot soft tissue structures when using inverted orthotics. These alterations in lower-extremity mechanics associated with inverted orthoses provide clinicians some evidence for prescribing this device.

Adult↗

PubMed2002

A comparison of four methods of obtaining a negative impression of the foot.

Four methods are currently available for taking a negative impression of the foot for the purpose of fabricating an orthotic device: nonweightbearing plaster casting, partial-weightbearing foam impressions, and partial-weightbearing and nonweightbearing laser scanning. This study compares the reliability and accuracy of these methods. Each impression method was performed three times on each foot of 15 subjects. Measures of rearfoot and forefoot width, forefoot-to-rearfoot relationship, and arch height were obtained from the negative impressions. Additionally, rearfoot and forefoot width and forefoot-to-rearfoot relationship were measured clinically for each subject. This study found that 1) foot measures are significantly influenced by the method used to obtain a negative foot impression; 2) the methods differ in reliability; and 3) plaster casting may be preferable to the other three methods when it is important to capture the forefoot-to-rearfoot relationship, as in fabricating a functional orthosis.

Analysis of Variance↗